From f6dd332820f802ff346ad5937580c952532df718 Mon Sep 17 00:00:00 2001
From: hi-rustin <rustin.liu@gmail.com>
Date: Fri, 7 May 2021 10:41:04 +0800
Subject: [PATCH 01/26] shrinking the deprecated method span

---
 compiler/rustc_middle/src/middle/stability.rs | 25 ++++-
 compiler/rustc_passes/src/stability.rs        |  6 +-
 compiler/rustc_typeck/src/astconv/mod.rs      |  7 +-
 compiler/rustc_typeck/src/check/expr.rs       |  4 +-
 compiler/rustc_typeck/src/check/method/mod.rs |  6 +-
 .../rustc_typeck/src/check/method/probe.rs    |  2 +-
 compiler/rustc_typeck/src/check/pat.rs        |  9 +-
 .../ui/deprecation/deprecation-lint.stderr    | 64 ++++++-------
 ...84637-deprecated-associated-function.fixed |  9 ++
 ...ue-84637-deprecated-associated-function.rs |  9 ++
 ...4637-deprecated-associated-function.stderr | 20 ++++
 .../ui/lint/lint-stability-deprecated.stderr  | 96 +++++++++----------
 12 files changed, 159 insertions(+), 98 deletions(-)
 create mode 100644 src/test/ui/deprecation/issue-84637-deprecated-associated-function.fixed
 create mode 100644 src/test/ui/deprecation/issue-84637-deprecated-associated-function.rs
 create mode 100644 src/test/ui/deprecation/issue-84637-deprecated-associated-function.stderr

diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index fc9a2970e00ae..1bb427d8a675d 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -281,7 +281,13 @@ impl<'tcx> TyCtxt<'tcx> {
     /// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
     /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
     /// `id`.
-    pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
+    pub fn eval_stability(
+        self,
+        def_id: DefId,
+        id: Option<HirId>,
+        span: Span,
+        method_span: Option<Span>,
+    ) -> EvalResult {
         // Deprecated attributes apply in-crate and cross-crate.
         if let Some(id) = id {
             if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
@@ -300,6 +306,10 @@ impl<'tcx> TyCtxt<'tcx> {
                     let path = &with_no_trimmed_paths(|| self.def_path_str(def_id));
                     let kind = self.def_kind(def_id).descr(def_id);
                     let (message, lint) = deprecation_message(&depr_entry.attr, kind, path);
+                    let span = match method_span {
+                        None => span,
+                        Some(method_span) => method_span,
+                    };
                     late_report_deprecation(
                         self,
                         &message,
@@ -382,8 +392,14 @@ impl<'tcx> TyCtxt<'tcx> {
     ///
     /// This function will also check if the item is deprecated.
     /// If so, and `id` is not `None`, a deprecated lint attached to `id` will be emitted.
-    pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
-        self.check_optional_stability(def_id, id, span, |span, def_id| {
+    pub fn check_stability(
+        self,
+        def_id: DefId,
+        id: Option<HirId>,
+        span: Span,
+        method_span: Option<Span>,
+    ) {
+        self.check_optional_stability(def_id, id, span, method_span, |span, def_id| {
             // The API could be uncallable for other reasons, for example when a private module
             // was referenced.
             self.sess.delay_span_bug(span, &format!("encountered unmarked API: {:?}", def_id));
@@ -399,6 +415,7 @@ impl<'tcx> TyCtxt<'tcx> {
         def_id: DefId,
         id: Option<HirId>,
         span: Span,
+        method_span: Option<Span>,
         unmarked: impl FnOnce(Span, DefId),
     ) {
         let soft_handler = |lint, span, msg: &_| {
@@ -406,7 +423,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 lint.build(msg).emit()
             })
         };
-        match self.eval_stability(def_id, id, span) {
+        match self.eval_stability(def_id, id, span, method_span) {
             EvalResult::Allow => {}
             EvalResult::Deny { feature, reason, issue, is_soft } => {
                 report_unstable(self.sess, feature, reason, issue, is_soft, span, soft_handler)
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 9c4f9b1198cf2..6b1813fba7600 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -739,7 +739,7 @@ impl Visitor<'tcx> for Checker<'tcx> {
                     None => return,
                 };
                 let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
-                self.tcx.check_stability(def_id, Some(item.hir_id()), item.span);
+                self.tcx.check_stability(def_id, Some(item.hir_id()), item.span, None);
             }
 
             // For implementations of traits, check the stability of each item
@@ -783,7 +783,7 @@ impl Visitor<'tcx> for Checker<'tcx> {
                             .map(|item| item.def_id);
                         if let Some(def_id) = trait_item_def_id {
                             // Pass `None` to skip deprecation warnings.
-                            self.tcx.check_stability(def_id, None, impl_item.span);
+                            self.tcx.check_stability(def_id, None, impl_item.span, None);
                         }
                     }
                 }
@@ -832,7 +832,7 @@ impl Visitor<'tcx> for Checker<'tcx> {
 
     fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
         if let Some(def_id) = path.res.opt_def_id() {
-            self.tcx.check_stability(def_id, Some(id), path.span)
+            self.tcx.check_stability(def_id, Some(id), path.span, None)
         }
         intravisit::walk_path(self, path)
     }
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index 2f2e90e4bd66f..fcae995b8d484 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -431,6 +431,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 param.def_id,
                                 Some(arg.id()),
                                 arg.span(),
+                                None,
                                 |_, _| {
                                     // Default generic parameters may not be marked
                                     // with stability attributes, i.e. when the
@@ -1053,7 +1054,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 .span_label(binding.span, "private associated type")
                 .emit();
         }
-        tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span);
+        tcx.check_stability(assoc_ty.def_id, Some(hir_ref_id), binding.span, None);
 
         if !speculative {
             dup_bindings
@@ -1659,7 +1660,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     .find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident, adt_def.did));
                 if let Some(variant_def) = variant_def {
                     if permit_variants {
-                        tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span);
+                        tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span, None);
                         self.prohibit_generics(slice::from_ref(assoc_segment));
                         return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
                     } else {
@@ -1779,7 +1780,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 .span_label(span, &format!("private {}", kind))
                 .emit();
         }
-        tcx.check_stability(item.def_id, Some(hir_ref_id), span);
+        tcx.check_stability(item.def_id, Some(hir_ref_id), span, None);
 
         if let Some(variant_def_id) = variant_resolution {
             tcx.struct_span_lint_hir(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| {
diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs
index 991c2ba693d69..d0cbb58fb10eb 100644
--- a/compiler/rustc_typeck/src/check/expr.rs
+++ b/compiler/rustc_typeck/src/check/expr.rs
@@ -1230,7 +1230,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // struct-like enums (yet...), but it's definitely not
                 // a bug to have constructed one.
                 if adt_kind != AdtKind::Enum {
-                    tcx.check_stability(v_field.did, Some(expr_id), field.span);
+                    tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
                 }
 
                 self.field_ty(field.span, v_field, substs)
@@ -1571,7 +1571,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             self.apply_adjustments(base, adjustments);
                             self.register_predicates(autoderef.into_obligations());
 
-                            self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
+                            self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
                             return field_ty;
                         }
                         private_candidate = Some((base_def.did, field_ty));
diff --git a/compiler/rustc_typeck/src/check/method/mod.rs b/compiler/rustc_typeck/src/check/method/mod.rs
index bd7ffd057b466..0b1129a631249 100644
--- a/compiler/rustc_typeck/src/check/method/mod.rs
+++ b/compiler/rustc_typeck/src/check/method/mod.rs
@@ -205,7 +205,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .insert(*import_id);
         }
 
-        self.tcx.check_stability(pick.item.def_id, Some(call_expr.hir_id), span);
+        self.tcx.check_stability(pick.item.def_id, Some(call_expr.hir_id), span, None);
 
         let result =
             self.confirm_method(span, self_expr, call_expr, self_ty, pick.clone(), segment);
@@ -445,7 +445,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // them as well. It's ok to use the variant's id as a ctor id since an
                     // error will be reported on any use of such resolution anyway.
                     let ctor_def_id = variant_def.ctor_def_id.unwrap_or(variant_def.def_id);
-                    tcx.check_stability(ctor_def_id, Some(expr_id), span);
+                    tcx.check_stability(ctor_def_id, Some(expr_id), span, Some(method_name.span));
                     return Ok((
                         DefKind::Ctor(CtorOf::Variant, variant_def.ctor_kind),
                         ctor_def_id,
@@ -475,7 +475,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let def_kind = pick.item.kind.as_def_kind();
         debug!("resolve_ufcs: def_kind={:?}, def_id={:?}", def_kind, pick.item.def_id);
-        tcx.check_stability(pick.item.def_id, Some(expr_id), span);
+        tcx.check_stability(pick.item.def_id, Some(expr_id), span, Some(method_name.span));
         Ok((def_kind, pick.item.def_id))
     }
 
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index c79743f2d7363..440e0f4e1a2ac 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -1286,7 +1286,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         if let Some(uc) = unstable_candidates {
             applicable_candidates.retain(|&(p, _)| {
                 if let stability::EvalResult::Deny { feature, .. } =
-                    self.tcx.eval_stability(p.item.def_id, None, self.span)
+                    self.tcx.eval_stability(p.item.def_id, None, self.span, None)
                 {
                     uc.push((p, feature));
                     return false;
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index 53593b9bab4b8..3ac760e23634e 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -958,7 +958,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let field_ty = self.field_ty(subpat.span, &variant.fields[i], substs);
                 self.check_pat(&subpat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
 
-                self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span);
+                self.tcx.check_stability(
+                    variant.fields[i].did,
+                    Some(pat.hir_id),
+                    subpat.span,
+                    None,
+                );
             }
         } else {
             // Pattern has wrong number of fields.
@@ -1192,7 +1197,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .get(&ident)
                         .map(|(i, f)| {
                             self.write_field_index(field.hir_id, *i);
-                            self.tcx.check_stability(f.did, Some(pat.hir_id), span);
+                            self.tcx.check_stability(f.did, Some(pat.hir_id), span, None);
                             self.field_ty(span, f, substs)
                         })
                         .unwrap_or_else(|| {
diff --git a/src/test/ui/deprecation/deprecation-lint.stderr b/src/test/ui/deprecation/deprecation-lint.stderr
index 959cf93bac053..3699a939e2788 100644
--- a/src/test/ui/deprecation/deprecation-lint.stderr
+++ b/src/test/ui/deprecation/deprecation-lint.stderr
@@ -359,16 +359,16 @@ LL |         foo.method_deprecated();
    |             ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::MethodTester::method_deprecated`: text
-  --> $DIR/deprecation-lint.rs:18:9
+  --> $DIR/deprecation-lint.rs:18:14
    |
 LL |         Foo::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::MethodTester::method_deprecated`: text
-  --> $DIR/deprecation-lint.rs:19:9
+  --> $DIR/deprecation-lint.rs:19:16
    |
 LL |         <Foo>::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated`: text
   --> $DIR/deprecation-lint.rs:20:13
@@ -377,10 +377,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated`: text
-  --> $DIR/deprecation-lint.rs:22:9
+  --> $DIR/deprecation-lint.rs:22:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::MethodTester::method_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:26:13
@@ -389,16 +389,16 @@ LL | ...   foo.method_deprecated_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::MethodTester::method_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:27:9
+  --> $DIR/deprecation-lint.rs:27:14
    |
 LL | ...   Foo::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::MethodTester::method_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:28:9
+  --> $DIR/deprecation-lint.rs:28:16
    |
 LL | ...   <Foo>::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:29:13
@@ -407,10 +407,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:31:9
+  --> $DIR/deprecation-lint.rs:31:16
    |
 LL | ...   <Foo>::trait_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated field `deprecation_lint::DeprecatedStruct::i`: text
   --> $DIR/deprecation-lint.rs:35:13
@@ -431,10 +431,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated`: text
-  --> $DIR/deprecation-lint.rs:66:9
+  --> $DIR/deprecation-lint.rs:66:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:68:13
@@ -443,10 +443,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:70:9
+  --> $DIR/deprecation-lint.rs:70:16
    |
 LL | ...   <Foo>::trait_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `deprecation_lint::Trait::trait_deprecated`: text
   --> $DIR/deprecation-lint.rs:75:13
@@ -551,16 +551,16 @@ LL |         foo.method_deprecated();
    |             ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::MethodTester::method_deprecated`: text
-  --> $DIR/deprecation-lint.rs:247:9
+  --> $DIR/deprecation-lint.rs:247:14
    |
 LL |         Foo::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::MethodTester::method_deprecated`: text
-  --> $DIR/deprecation-lint.rs:248:9
+  --> $DIR/deprecation-lint.rs:248:16
    |
 LL |         <Foo>::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
   --> $DIR/deprecation-lint.rs:249:13
@@ -569,10 +569,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
-  --> $DIR/deprecation-lint.rs:251:9
+  --> $DIR/deprecation-lint.rs:251:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:255:13
@@ -581,16 +581,16 @@ LL | ...   foo.method_deprecated_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:256:9
+  --> $DIR/deprecation-lint.rs:256:14
    |
 LL | ...   Foo::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:257:9
+  --> $DIR/deprecation-lint.rs:257:16
    |
 LL | ...   <Foo>::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:258:13
@@ -599,10 +599,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:260:9
+  --> $DIR/deprecation-lint.rs:260:16
    |
 LL |         <Foo>::trait_deprecated_text(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated field `this_crate::DeprecatedStruct::i`: text
   --> $DIR/deprecation-lint.rs:269:13
@@ -623,10 +623,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
-  --> $DIR/deprecation-lint.rs:293:9
+  --> $DIR/deprecation-lint.rs:293:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
   --> $DIR/deprecation-lint.rs:295:13
@@ -635,10 +635,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
-  --> $DIR/deprecation-lint.rs:297:9
+  --> $DIR/deprecation-lint.rs:297:16
    |
 LL |         <Foo>::trait_deprecated_text(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^^^^^
 
 error: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
   --> $DIR/deprecation-lint.rs:302:13
diff --git a/src/test/ui/deprecation/issue-84637-deprecated-associated-function.fixed b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.fixed
new file mode 100644
index 0000000000000..99a2b09614fd9
--- /dev/null
+++ b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.fixed
@@ -0,0 +1,9 @@
+// run-rustfix
+
+#![deny(deprecated)]
+
+fn main() {
+    let _foo = str::trim_start("   aoeu"); //~ ERROR use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start` [deprecated]
+
+    let _bar = "   aoeu".trim_start(); //~ ERROR use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start` [deprecated]
+}
diff --git a/src/test/ui/deprecation/issue-84637-deprecated-associated-function.rs b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.rs
new file mode 100644
index 0000000000000..62bf84aa3ea28
--- /dev/null
+++ b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.rs
@@ -0,0 +1,9 @@
+// run-rustfix
+
+#![deny(deprecated)]
+
+fn main() {
+    let _foo = str::trim_left("   aoeu"); //~ ERROR use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start` [deprecated]
+
+    let _bar = "   aoeu".trim_left(); //~ ERROR use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start` [deprecated]
+}
diff --git a/src/test/ui/deprecation/issue-84637-deprecated-associated-function.stderr b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.stderr
new file mode 100644
index 0000000000000..e65d21bb09bbe
--- /dev/null
+++ b/src/test/ui/deprecation/issue-84637-deprecated-associated-function.stderr
@@ -0,0 +1,20 @@
+error: use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start`
+  --> $DIR/issue-84637-deprecated-associated-function.rs:6:21
+   |
+LL |     let _foo = str::trim_left("   aoeu");
+   |                     ^^^^^^^^^ help: replace the use of the deprecated associated function: `trim_start`
+   |
+note: the lint level is defined here
+  --> $DIR/issue-84637-deprecated-associated-function.rs:3:9
+   |
+LL | #![deny(deprecated)]
+   |         ^^^^^^^^^^
+
+error: use of deprecated associated function `core::str::<impl str>::trim_left`: superseded by `trim_start`
+  --> $DIR/issue-84637-deprecated-associated-function.rs:8:26
+   |
+LL |     let _bar = "   aoeu".trim_left();
+   |                          ^^^^^^^^^ help: replace the use of the deprecated associated function: `trim_start`
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/lint/lint-stability-deprecated.stderr b/src/test/ui/lint/lint-stability-deprecated.stderr
index 47dc8e4a63c07..94fc1a7b46dba 100644
--- a/src/test/ui/lint/lint-stability-deprecated.stderr
+++ b/src/test/ui/lint/lint-stability-deprecated.stderr
@@ -335,16 +335,16 @@ LL |         foo.method_deprecated();
    |             ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:26:9
+  --> $DIR/lint-stability-deprecated.rs:26:14
    |
 LL |         Foo::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:27:9
+  --> $DIR/lint-stability-deprecated.rs:27:16
    |
 LL |         <Foo>::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated`: text
   --> $DIR/lint-stability-deprecated.rs:28:13
@@ -353,10 +353,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:30:9
+  --> $DIR/lint-stability-deprecated.rs:30:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:34:13
@@ -365,16 +365,16 @@ LL | ...   foo.method_deprecated_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:35:9
+  --> $DIR/lint-stability-deprecated.rs:35:14
    |
 LL | ...   Foo::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:36:9
+  --> $DIR/lint-stability-deprecated.rs:36:16
    |
 LL | ...   <Foo>::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:37:13
@@ -383,10 +383,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:39:9
+  --> $DIR/lint-stability-deprecated.rs:39:16
    |
 LL | ...   <Foo>::trait_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable`: text
   --> $DIR/lint-stability-deprecated.rs:43:13
@@ -395,16 +395,16 @@ LL | ...   foo.method_deprecated_unstable();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable`: text
-  --> $DIR/lint-stability-deprecated.rs:44:9
+  --> $DIR/lint-stability-deprecated.rs:44:14
    |
 LL | ...   Foo::method_deprecated_unstable(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable`: text
-  --> $DIR/lint-stability-deprecated.rs:45:9
+  --> $DIR/lint-stability-deprecated.rs:45:16
    |
 LL | ...   <Foo>::method_deprecated_unstable(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable`: text
   --> $DIR/lint-stability-deprecated.rs:46:13
@@ -413,10 +413,10 @@ LL |         foo.trait_deprecated_unstable();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable`: text
-  --> $DIR/lint-stability-deprecated.rs:48:9
+  --> $DIR/lint-stability-deprecated.rs:48:16
    |
 LL | ...   <Foo>::trait_deprecated_unstable(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable_text`: text
   --> $DIR/lint-stability-deprecated.rs:52:13
@@ -425,16 +425,16 @@ LL | ...   foo.method_deprecated_unstable_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable_text`: text
-  --> $DIR/lint-stability-deprecated.rs:53:9
+  --> $DIR/lint-stability-deprecated.rs:53:14
    |
 LL | ...   Foo::method_deprecated_unstable_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::MethodTester::method_deprecated_unstable_text`: text
-  --> $DIR/lint-stability-deprecated.rs:54:9
+  --> $DIR/lint-stability-deprecated.rs:54:16
    |
 LL | ...   <Foo>::method_deprecated_unstable_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable_text`: text
   --> $DIR/lint-stability-deprecated.rs:55:13
@@ -443,10 +443,10 @@ LL | ...   foo.trait_deprecated_unstable_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable_text`: text
-  --> $DIR/lint-stability-deprecated.rs:57:9
+  --> $DIR/lint-stability-deprecated.rs:57:16
    |
 LL | ...   <Foo>::trait_deprecated_unstable_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated field `lint_stability::DeprecatedStruct::i`: text
   --> $DIR/lint-stability-deprecated.rs:109:13
@@ -467,10 +467,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:146:9
+  --> $DIR/lint-stability-deprecated.rs:146:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:148:13
@@ -479,10 +479,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:150:9
+  --> $DIR/lint-stability-deprecated.rs:150:16
    |
 LL | ...   <Foo>::trait_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable`: text
   --> $DIR/lint-stability-deprecated.rs:152:13
@@ -491,10 +491,10 @@ LL |         foo.trait_deprecated_unstable();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable`: text
-  --> $DIR/lint-stability-deprecated.rs:154:9
+  --> $DIR/lint-stability-deprecated.rs:154:16
    |
 LL | ...   <Foo>::trait_deprecated_unstable(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable_text`: text
   --> $DIR/lint-stability-deprecated.rs:156:13
@@ -503,10 +503,10 @@ LL | ...   foo.trait_deprecated_unstable_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated_unstable_text`: text
-  --> $DIR/lint-stability-deprecated.rs:158:9
+  --> $DIR/lint-stability-deprecated.rs:158:16
    |
 LL | ...   <Foo>::trait_deprecated_unstable_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `lint_stability::Trait::trait_deprecated`: text
   --> $DIR/lint-stability-deprecated.rs:175:13
@@ -539,16 +539,16 @@ LL |         foo.method_deprecated();
    |             ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::MethodTester::method_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:332:9
+  --> $DIR/lint-stability-deprecated.rs:332:14
    |
 LL |         Foo::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::MethodTester::method_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:333:9
+  --> $DIR/lint-stability-deprecated.rs:333:16
    |
 LL |         <Foo>::method_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
   --> $DIR/lint-stability-deprecated.rs:334:13
@@ -557,10 +557,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:336:9
+  --> $DIR/lint-stability-deprecated.rs:336:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:340:13
@@ -569,16 +569,16 @@ LL | ...   foo.method_deprecated_text();
    |           ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:341:9
+  --> $DIR/lint-stability-deprecated.rs:341:14
    |
 LL | ...   Foo::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::MethodTester::method_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:342:9
+  --> $DIR/lint-stability-deprecated.rs:342:16
    |
 LL | ...   <Foo>::method_deprecated_text(&foo);
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:343:13
@@ -587,10 +587,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:345:9
+  --> $DIR/lint-stability-deprecated.rs:345:16
    |
 LL |         <Foo>::trait_deprecated_text(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated field `this_crate::DeprecatedStruct::i`: text
   --> $DIR/lint-stability-deprecated.rs:386:13
@@ -605,10 +605,10 @@ LL |         foo.trait_deprecated();
    |             ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
-  --> $DIR/lint-stability-deprecated.rs:407:9
+  --> $DIR/lint-stability-deprecated.rs:407:16
    |
 LL |         <Foo>::trait_deprecated(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
   --> $DIR/lint-stability-deprecated.rs:409:13
@@ -617,10 +617,10 @@ LL |         foo.trait_deprecated_text();
    |             ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated_text`: text
-  --> $DIR/lint-stability-deprecated.rs:411:9
+  --> $DIR/lint-stability-deprecated.rs:411:16
    |
 LL |         <Foo>::trait_deprecated_text(&foo);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                ^^^^^^^^^^^^^^^^^^^^^
 
 warning: use of deprecated associated function `this_crate::Trait::trait_deprecated`: text
   --> $DIR/lint-stability-deprecated.rs:428:13

From 7c5bc204fa8cbfdbfe3a560aa3a3acc3b44ca116 Mon Sep 17 00:00:00 2001
From: hi-rustin <rustin.liu@gmail.com>
Date: Sat, 8 May 2021 09:02:22 +0800
Subject: [PATCH 02/26] Address comments

---
 compiler/rustc_middle/src/middle/stability.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 1bb427d8a675d..aa0f18846d154 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -306,10 +306,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     let path = &with_no_trimmed_paths(|| self.def_path_str(def_id));
                     let kind = self.def_kind(def_id).descr(def_id);
                     let (message, lint) = deprecation_message(&depr_entry.attr, kind, path);
-                    let span = match method_span {
-                        None => span,
-                        Some(method_span) => method_span,
-                    };
+                    let span = method_span.unwrap_or(span);
                     late_report_deprecation(
                         self,
                         &message,

From 0778e8dcb8842add101787fbf0e751009b073977 Mon Sep 17 00:00:00 2001
From: shirshak55 <shirshak55@pm.me>
Date: Mon, 10 May 2021 19:31:09 +0800
Subject: [PATCH 03/26] change k to key and v to v in std::env mod

---
 library/std/src/env.rs | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 11d052dae9e90..4403280efc11b 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -324,13 +324,13 @@ impl Error for VarError {
 /// assert_eq!(env::var(key), Ok("VALUE".to_string()));
 /// ```
 #[stable(feature = "env", since = "1.0.0")]
-pub fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(k: K, v: V) {
-    _set_var(k.as_ref(), v.as_ref())
+pub fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
+    _set_var(key.as_ref(), value.as_ref())
 }
 
-fn _set_var(k: &OsStr, v: &OsStr) {
-    os_imp::setenv(k, v).unwrap_or_else(|e| {
-        panic!("failed to set environment variable `{:?}` to `{:?}`: {}", k, v, e)
+fn _set_var(key: &OsStr, value: &OsStr) {
+    os_imp::setenv(key, value).unwrap_or_else(|e| {
+        panic!("failed to set environment variable `{:?}` to `{:?}`: {}", key, value, e)
     })
 }
 
@@ -366,13 +366,13 @@ fn _set_var(k: &OsStr, v: &OsStr) {
 /// assert!(env::var(key).is_err());
 /// ```
 #[stable(feature = "env", since = "1.0.0")]
-pub fn remove_var<K: AsRef<OsStr>>(k: K) {
-    _remove_var(k.as_ref())
+pub fn remove_var<K: AsRef<OsStr>>(key: K) {
+    _remove_var(key.as_ref())
 }
 
-fn _remove_var(k: &OsStr) {
-    os_imp::unsetenv(k)
-        .unwrap_or_else(|e| panic!("failed to remove environment variable `{:?}`: {}", k, e))
+fn _remove_var(key: &OsStr) {
+    os_imp::unsetenv(key)
+        .unwrap_or_else(|e| panic!("failed to remove environment variable `{:?}`: {}", key, e))
 }
 
 /// An iterator that splits an environment variable into paths according to

From 41779f60ecdc96bddc88cd0d7184fa67e411b894 Mon Sep 17 00:00:00 2001
From: LingMan <LingMan@users.noreply.github.com>
Date: Tue, 11 May 2021 01:17:08 +0200
Subject: [PATCH 04/26] Fix typo in variable name

All other sibling functions call this variable "slot", so "slote" was most likely a typo.
---
 compiler/rustc_session/src/options.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 10e195f4f2548..ca8bb3af2ba69 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -621,9 +621,9 @@ mod parse {
         true
     }
 
-    crate fn parse_linker_flavor(slote: &mut Option<LinkerFlavor>, v: Option<&str>) -> bool {
+    crate fn parse_linker_flavor(slot: &mut Option<LinkerFlavor>, v: Option<&str>) -> bool {
         match v.and_then(LinkerFlavor::from_str) {
-            Some(lf) => *slote = Some(lf),
+            Some(lf) => *slot = Some(lf),
             _ => return false,
         }
         true

From f740923b8cd984b5aa5d8e6af46b87c61b7ddc4d Mon Sep 17 00:00:00 2001
From: Fabian Wolff <fabi.wolff@arcor.de>
Date: Tue, 11 May 2021 18:12:36 +0200
Subject: [PATCH 05/26] Use .name_str() to format primitive types in error
 messages

---
 compiler/rustc_middle/src/ty/error.rs         | 17 ++++++++++--
 src/test/ui/mismatched_types/issue-84976.rs   | 21 +++++++++++++++
 .../ui/mismatched_types/issue-84976.stderr    | 27 +++++++++++++++++++
 3 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/mismatched_types/issue-84976.rs
 create mode 100644 src/test/ui/mismatched_types/issue-84976.stderr

diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 008e6d015e879..96aae3bd70cd2 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -159,10 +159,23 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                 )
             }),
             IntMismatch(ref values) => {
-                write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found)
+                let expected = match values.expected {
+                    ty::IntVarValue::IntType(ty) => ty.name_str(),
+                    ty::IntVarValue::UintType(ty) => ty.name_str(),
+                };
+                let found = match values.found {
+                    ty::IntVarValue::IntType(ty) => ty.name_str(),
+                    ty::IntVarValue::UintType(ty) => ty.name_str(),
+                };
+                write!(f, "expected `{}`, found `{}`", expected, found)
             }
             FloatMismatch(ref values) => {
-                write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found)
+                write!(
+                    f,
+                    "expected `{}`, found `{}`",
+                    values.expected.name_str(),
+                    values.found.name_str()
+                )
             }
             VariadicMismatch(ref values) => write!(
                 f,
diff --git a/src/test/ui/mismatched_types/issue-84976.rs b/src/test/ui/mismatched_types/issue-84976.rs
new file mode 100644
index 0000000000000..b4ea872979ada
--- /dev/null
+++ b/src/test/ui/mismatched_types/issue-84976.rs
@@ -0,0 +1,21 @@
+fn foo(length: &u32) -> i32 {
+    0
+}
+
+fn bar(length: &f32) -> f64 {
+    0.0
+}
+
+fn main() {
+    let mut length = 0;
+    length = { foo(&length) };
+    //~^ ERROR mismatched types [E0308]
+    length = foo(&length);
+    //~^ ERROR mismatched types [E0308]
+
+    let mut float_length = 0.0;
+    float_length = { bar(&float_length) };
+    //~^ ERROR mismatched types [E0308]
+    float_length = bar(&float_length);
+    //~^ ERROR mismatched types [E0308]
+}
diff --git a/src/test/ui/mismatched_types/issue-84976.stderr b/src/test/ui/mismatched_types/issue-84976.stderr
new file mode 100644
index 0000000000000..b9f6954dbbb25
--- /dev/null
+++ b/src/test/ui/mismatched_types/issue-84976.stderr
@@ -0,0 +1,27 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-84976.rs:11:16
+   |
+LL |     length = { foo(&length) };
+   |                ^^^^^^^^^^^^ expected `u32`, found `i32`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-84976.rs:13:14
+   |
+LL |     length = foo(&length);
+   |              ^^^^^^^^^^^^ expected `u32`, found `i32`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-84976.rs:17:22
+   |
+LL |     float_length = { bar(&float_length) };
+   |                      ^^^^^^^^^^^^^^^^^^ expected `f32`, found `f64`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-84976.rs:19:20
+   |
+LL |     float_length = bar(&float_length);
+   |                    ^^^^^^^^^^^^^^^^^^ expected `f32`, found `f64`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

From 001f0dd5a1a544ac9373f0d18e13014ec18dff94 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Sun, 21 Mar 2021 19:21:45 -0700
Subject: [PATCH 06/26] rustdoc: Show basic type layout information

Right now it just shows the size.
---
 src/librustdoc/html/render/print_item.rs | 39 ++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 7ccc313cc5905..9b7006150b7f1 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -846,6 +846,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
     });
 
     document(w, cx, it, None);
+
     let mut fields = s
         .fields
         .iter()
@@ -880,7 +881,9 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
             document(w, cx, field, Some(it));
         }
     }
-    render_assoc_items(w, cx, it, it.def_id.expect_real(), AssocItemRender::All)
+    let def_id = it.def_id.expect_real();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_ty_layout(w, cx, def_id);
 }
 
 fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum) {
@@ -940,6 +943,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
     });
 
     document(w, cx, it, None);
+
     if !e.variants.is_empty() {
         write!(
             w,
@@ -1014,7 +1018,9 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
             render_stability_since(w, variant, it, cx.tcx());
         }
     }
-    render_assoc_items(w, cx, it, it.def_id.expect_real(), AssocItemRender::All)
+    let def_id = it.def_id.expect_real();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_ty_layout(w, cx, def_id);
 }
 
 fn item_macro(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Macro) {
@@ -1114,6 +1120,7 @@ fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
     });
 
     document(w, cx, it, None);
+
     let mut fields = s
         .fields
         .iter()
@@ -1152,7 +1159,9 @@ fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
             }
         }
     }
-    render_assoc_items(w, cx, it, it.def_id.expect_real(), AssocItemRender::All)
+    let def_id = it.def_id.expect_real();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_ty_layout(w, cx, def_id);
 }
 
 fn item_static(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Static) {
@@ -1522,3 +1531,27 @@ fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
         w.write_str("</div></details>");
     }
 }
+
+fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
+    let param_env = cx.tcx().param_env(ty_def_id);
+    let ty = cx.tcx().type_of(ty_def_id);
+    match cx.tcx().layout_of(param_env.and(ty)) {
+        Ok(ty_layout) => {
+            writeln!(w, r#"<h2 class="small-section-header">Layout</h2>"#);
+            writeln!(w, "<div>");
+            if ty_layout.layout.abi.is_unsized() {
+                writeln!(w, "<strong>Sized:</strong> (unsized)");
+            } else {
+                writeln!(
+                    w,
+                    "<strong>Size:</strong> {size} byte{pl}",
+                    size = ty_layout.layout.size.bytes(),
+                    pl = if ty_layout.layout.size.bytes() == 1 { "" } else { "s" },
+                );
+            }
+            writeln!(w, "</div>");
+        }
+        // FIXME: should we crash instead? or report an error?
+        Err(_layout_err) => {}
+    }
+}

From 5859c5d333465fe91be46196e2b47bff9fc48ece Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Wed, 7 Apr 2021 20:55:37 -0700
Subject: [PATCH 07/26] Remove FIXME

Layout errors can occur with valid code, e.g. generic types.
---
 src/librustdoc/html/render/print_item.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 9b7006150b7f1..1f7b317a45b8d 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -1551,7 +1551,9 @@ fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
             }
             writeln!(w, "</div>");
         }
-        // FIXME: should we crash instead? or report an error?
-        Err(_layout_err) => {}
+        // Layout errors can occur with valid code, e.g. if you try to get the layout
+        // of a generic type such as `Vec<T>`. In case of a layout error, we just
+        // don't show any layout information.
+        Err(_) => {}
     }
 }

From 20b30acfa856309857e8914fb2bb5f831e991d0b Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Thu, 8 Apr 2021 16:04:21 -0700
Subject: [PATCH 08/26] Include a warning in the layout docs that layout is
 unstable

---
 src/librustdoc/html/render/print_item.rs | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 1f7b317a45b8d..41565019c6b19 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -1537,10 +1537,19 @@ fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
     let ty = cx.tcx().type_of(ty_def_id);
     match cx.tcx().layout_of(param_env.and(ty)) {
         Ok(ty_layout) => {
-            writeln!(w, r#"<h2 class="small-section-header">Layout</h2>"#);
-            writeln!(w, "<div>");
+            writeln!(w, "<h2 class=\"small-section-header\">Layout</h2>");
+            writeln!(w, "<div class=\"docblock\">");
+            writeln!(
+                w,
+                "<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
+                 completely unstable and may be different between compiler versions. \
+                 The only exception is types with certain <code>repr(...)</code> attributes. \
+                 Please see the Rust Reference’s \
+                 <a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
+                 chapter for details on type layout guarantees.</p></div>"
+            );
             if ty_layout.layout.abi.is_unsized() {
-                writeln!(w, "<strong>Sized:</strong> (unsized)");
+                writeln!(w, "<p><strong>Size:</strong> (unsized)</p>");
             } else {
                 writeln!(
                     w,

From 9859e2b01d2498ea0465a36bf4055d45e1f96f5b Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Mon, 12 Apr 2021 19:06:15 -0700
Subject: [PATCH 09/26] Add test for memory layout information

---
 src/test/rustdoc/type-layout.rs | 43 +++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 src/test/rustdoc/type-layout.rs

diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
new file mode 100644
index 0000000000000..261f407a9063b
--- /dev/null
+++ b/src/test/rustdoc/type-layout.rs
@@ -0,0 +1,43 @@
+// @has type_layout/struct.Foo.html 'Size: '
+// @has - ' bytes'
+pub struct Foo {
+    pub a: usize,
+    b: Vec<String>,
+}
+
+// @has type_layout/enum.Bar.html 'Size: '
+// @has - ' bytes'
+pub enum Bar<'a> {
+    A(String),
+    B(&'a str, (std::collections::HashMap<String, usize>, Foo)),
+}
+
+// @has type_layout/union.Baz.html 'Size: '
+// @has - ' bytes'
+pub union Baz {
+    a: &'static str,
+    b: usize,
+    c: &'static [u8],
+}
+
+// @has type_layout/struct.X.html 'Size: '
+// @has - ' bytes'
+pub struct X(usize);
+
+// @has type_layout/struct.Y.html 'Size: '
+// @has - ' byte'
+// @!has - ' bytes'
+pub struct Y(u8);
+
+// @!has type_layout/struct.Generic.html 'Size: '
+pub struct Generic<T>(T);
+
+// @has type_layout/struct.Unsized.html 'Size: '
+// @has - '(unsized)'
+pub struct Unsized([u8]);
+
+// @!has type_layout/type.TypeAlias.html 'Size: '
+pub type TypeAlias = X;
+
+// @!has type_layout/trait.MyTrait.html 'Size: '
+pub trait MyTrait {}

From 48da66f28f078c0dc31068a30977e9079c876d90 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Mon, 12 Apr 2021 19:23:49 -0700
Subject: [PATCH 10/26] Show memory layout for type aliases

At first you might think "why not just click through to the aliased
type?", but if a type alias instantiates all of the generic parameters
of the aliased type, then it can show layout info even though the
aliased type cannot (because we can't compute the layout of a generic
type). So I think it's still useful to show layout info for type
aliases.
---
 src/librustdoc/html/render/print_item.rs | 5 ++++-
 src/test/rustdoc/type-layout.rs          | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 41565019c6b19..9ac9ee66f6a86 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -830,11 +830,14 @@ fn item_typedef(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::T
 
     document(w, cx, it, None);
 
+    let def_id = it.def_id.expect_real();
     // Render any items associated directly to this alias, as otherwise they
     // won't be visible anywhere in the docs. It would be nice to also show
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
-    render_assoc_items(w, cx, it, it.def_id.expect_real(), AssocItemRender::All)
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+
+    document_ty_layout(w, cx, def_id);
 }
 
 fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Union) {
diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index 261f407a9063b..e18bdeba91352 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -36,7 +36,8 @@ pub struct Generic<T>(T);
 // @has - '(unsized)'
 pub struct Unsized([u8]);
 
-// @!has type_layout/type.TypeAlias.html 'Size: '
+// @has type_layout/type.TypeAlias.html 'Size: '
+// @has - ' bytes'
 pub type TypeAlias = X;
 
 // @!has type_layout/trait.MyTrait.html 'Size: '

From 12ee920a7c3aa237eb7e207e128120f5a639743a Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Mon, 12 Apr 2021 19:42:26 -0700
Subject: [PATCH 11/26] Only show type layout info if `--show-type-layout` is
 passed

---
 src/librustdoc/config.rs                      | 4 ++++
 src/librustdoc/html/render/context.rs         | 4 ++++
 src/librustdoc/html/render/print_item.rs      | 4 ++++
 src/librustdoc/lib.rs                         | 3 +++
 src/test/rustdoc/type-layout-flag-required.rs | 4 ++++
 src/test/rustdoc/type-layout.rs               | 2 ++
 6 files changed, 21 insertions(+)
 create mode 100644 src/test/rustdoc/type-layout-flag-required.rs

diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 045b42d0dcaf7..b75e98ae16c16 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -267,6 +267,8 @@ crate struct RenderOptions {
     crate document_hidden: bool,
     /// If `true`, generate a JSON file in the crate folder instead of HTML redirection files.
     crate generate_redirect_map: bool,
+    /// Show the memory layout of types in the docs.
+    crate show_type_layout: bool,
     crate unstable_features: rustc_feature::UnstableFeatures,
     crate emit: Vec<EmitType>,
 }
@@ -636,6 +638,7 @@ impl Options {
         let document_hidden = matches.opt_present("document-hidden-items");
         let run_check = matches.opt_present("check");
         let generate_redirect_map = matches.opt_present("generate-redirect-map");
+        let show_type_layout = matches.opt_present("show-type-layout");
 
         let (lint_opts, describe_lints, lint_cap) = get_cmd_lint_options(matches, error_format);
 
@@ -695,6 +698,7 @@ impl Options {
                 document_private,
                 document_hidden,
                 generate_redirect_map,
+                show_type_layout,
                 unstable_features: rustc_feature::UnstableFeatures::from_environment(
                     crate_name.as_deref(),
                 ),
diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index 4e17dc8d3a7d0..666d9dfc3e9e4 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -91,6 +91,8 @@ crate struct SharedContext<'tcx> {
     crate include_sources: bool,
     /// The local file sources we've emitted and their respective url-paths.
     crate local_sources: FxHashMap<PathBuf, String>,
+    /// Show the memory layout of types in the docs.
+    pub(super) show_type_layout: bool,
     /// Whether the collapsed pass ran
     collapsed: bool,
     /// The base-URL of the issue tracker for when an item has been tagged with
@@ -373,6 +375,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             generate_search_filter,
             unstable_features,
             generate_redirect_map,
+            show_type_layout,
             ..
         } = options;
 
@@ -446,6 +449,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             all: RefCell::new(AllTypes::new()),
             errors: receiver,
             redirections: if generate_redirect_map { Some(Default::default()) } else { None },
+            show_type_layout,
         };
 
         // Add the default themes to the `Vec` of stylepaths
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 9ac9ee66f6a86..2de1a2226f5c2 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -1536,6 +1536,10 @@ fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
 }
 
 fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
+    if !cx.shared.show_type_layout {
+        return;
+    }
+
     let param_env = cx.tcx().param_env(ty_def_id);
     let ty = cx.tcx().type_of(ty_def_id);
     match cx.tcx().layout_of(param_env.and(ty)) {
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 169ef015fa88c..5ede3780e87ae 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -594,6 +594,9 @@ fn opts() -> Vec<RustcOptGroup> {
             )
         }),
         unstable("no-run", |o| o.optflag("", "no-run", "Compile doctests without running them")),
+        unstable("show-type-layout", |o| {
+            o.optflag("", "show-type-layout", "Include the memory layout of types in the docs")
+        }),
     ]
 }
 
diff --git a/src/test/rustdoc/type-layout-flag-required.rs b/src/test/rustdoc/type-layout-flag-required.rs
new file mode 100644
index 0000000000000..a01fbd229508b
--- /dev/null
+++ b/src/test/rustdoc/type-layout-flag-required.rs
@@ -0,0 +1,4 @@
+// Tests that `--show-type-layout` is required in order to show layout info.
+
+// @!has type_layout_flag_required/struct.Foo.html 'Size: '
+pub struct Foo(usize);
diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index e18bdeba91352..9fd8f92aeb976 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -1,3 +1,5 @@
+// compile-flags: --show-type-layout -Z unstable-options
+
 // @has type_layout/struct.Foo.html 'Size: '
 // @has - ' bytes'
 pub struct Foo {

From 9615d6dd48489a4700b31b301fe1a45cfa3e536e Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Mon, 12 Apr 2021 19:43:55 -0700
Subject: [PATCH 12/26] Enable `--show-type-layout` for the rustc API docs

---
 src/bootstrap/doc.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index a32b92ef1af83..e42d4fcd8647c 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -549,6 +549,7 @@ impl Step for Rustc {
         cargo.rustdocflag("--enable-index-page");
         cargo.rustdocflag("-Zunstable-options");
         cargo.rustdocflag("-Znormalize-docs");
+        cargo.rustdocflag("--show-type-layout");
         compile::rustc_cargo(builder, &mut cargo, target);
 
         // Only include compiler crates, no dependencies of those, such as `libc`.

From db3a06d01eb517448954ec0eaccd68f88be988e0 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Mon, 12 Apr 2021 20:13:19 -0700
Subject: [PATCH 13/26] Fix a few small things

---
 src/librustdoc/html/render/print_item.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 2de1a2226f5c2..1fe445b2ea1ba 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -837,7 +837,7 @@ fn item_typedef(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::T
     // we need #14072 to make sense of the generics.
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
 
-    document_ty_layout(w, cx, def_id);
+    document_type_layout(w, cx, def_id);
 }
 
 fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Union) {
@@ -886,7 +886,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
     }
     let def_id = it.def_id.expect_real();
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
-    document_ty_layout(w, cx, def_id);
+    document_type_layout(w, cx, def_id);
 }
 
 fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum) {
@@ -1023,7 +1023,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
     }
     let def_id = it.def_id.expect_real();
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
-    document_ty_layout(w, cx, def_id);
+    document_type_layout(w, cx, def_id);
 }
 
 fn item_macro(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Macro) {
@@ -1164,7 +1164,7 @@ fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
     }
     let def_id = it.def_id.expect_real();
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
-    document_ty_layout(w, cx, def_id);
+    document_type_layout(w, cx, def_id);
 }
 
 fn item_static(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Static) {
@@ -1535,7 +1535,7 @@ fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
     }
 }
 
-fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
+fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
     if !cx.shared.show_type_layout {
         return;
     }
@@ -1560,7 +1560,7 @@ fn document_ty_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
             } else {
                 writeln!(
                     w,
-                    "<strong>Size:</strong> {size} byte{pl}",
+                    "<p><strong>Size:</strong> {size} byte{pl}</p>",
                     size = ty_layout.layout.size.bytes(),
                     pl = if ty_layout.layout.size.bytes() == 1 { "" } else { "s" },
                 );

From 8048c705688fbd0822fe134210556f9af79e8f85 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Tue, 13 Apr 2021 18:33:25 -0700
Subject: [PATCH 14/26] Add `tcx` local variable

---
 src/librustdoc/html/render/print_item.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index 1fe445b2ea1ba..a2d1a6a23c63b 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -1540,9 +1540,10 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
         return;
     }
 
-    let param_env = cx.tcx().param_env(ty_def_id);
-    let ty = cx.tcx().type_of(ty_def_id);
-    match cx.tcx().layout_of(param_env.and(ty)) {
+    let tcx = cx.tcx();
+    let param_env = tcx.param_env(ty_def_id);
+    let ty = tcx.type_of(ty_def_id);
+    match tcx.layout_of(param_env.and(ty)) {
         Ok(ty_layout) => {
             writeln!(w, "<h2 class=\"small-section-header\">Layout</h2>");
             writeln!(w, "<div class=\"docblock\">");

From bcbc72767288ac2723213d0b02dfe1f98cc27948 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Fri, 23 Apr 2021 14:01:00 -0700
Subject: [PATCH 15/26] Apply suggestions from code review

Co-authored-by: Ivan Tham <pickfire@riseup.net>
---
 src/librustdoc/html/render/print_item.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index a2d1a6a23c63b..af7745d6126c9 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -1550,7 +1550,7 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
             writeln!(
                 w,
                 "<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
-                 completely unstable and may be different between compiler versions. \
+                 completely unstable and may be different between compiler versions and platforms. \
                  The only exception is types with certain <code>repr(...)</code> attributes. \
                  Please see the Rust Reference’s \
                  <a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
@@ -1559,11 +1559,12 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
             if ty_layout.layout.abi.is_unsized() {
                 writeln!(w, "<p><strong>Size:</strong> (unsized)</p>");
             } else {
+                let bytes = ty_layout.layout.size.bytes();
                 writeln!(
                     w,
                     "<p><strong>Size:</strong> {size} byte{pl}</p>",
-                    size = ty_layout.layout.size.bytes(),
-                    pl = if ty_layout.layout.size.bytes() == 1 { "" } else { "s" },
+                    size = bytes,
+                    pl = if bytes == 1 { "" } else { "s" },
                 );
             }
             writeln!(w, "</div>");

From 61a84794726c94dd297a7b0fd0321a1d4a6d08dd Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Fri, 23 Apr 2021 14:10:51 -0700
Subject: [PATCH 16/26] Make test more specific

---
 src/test/rustdoc/type-layout.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index 9fd8f92aeb976..72e2830040524 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -27,7 +27,7 @@ pub union Baz {
 pub struct X(usize);
 
 // @has type_layout/struct.Y.html 'Size: '
-// @has - ' byte'
+// @has - '1 byte'
 // @!has - ' bytes'
 pub struct Y(u8);
 

From 879a914eea7d8d10bf865822e76a165938e41544 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Tue, 27 Apr 2021 10:38:12 -0700
Subject: [PATCH 17/26] Add test case for zero-sized types

---
 src/test/rustdoc/type-layout.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index 72e2830040524..cb6e354f7df54 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -31,6 +31,10 @@ pub struct X(usize);
 // @!has - ' bytes'
 pub struct Y(u8);
 
+// @has type_layout/struct.Z.html 'Size: '
+// @has - '0 bytes'
+pub struct Z;
+
 // @!has type_layout/struct.Generic.html 'Size: '
 pub struct Generic<T>(T);
 

From 8b9298bbaaa1e1803f1ca4040c3200ed3373a210 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Tue, 27 Apr 2021 17:11:58 -0700
Subject: [PATCH 18/26] Add note to docs when layout cannot be computed

This should prevent confusion about why generic types don't have layout
docs.
---
 src/librustdoc/html/render/print_item.rs | 33 +++++++++++++++++++-----
 src/test/rustdoc/type-layout.rs          | 10 ++++++-
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index af7745d6126c9..bde42371713ca 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -7,6 +7,7 @@ use rustc_hir as hir;
 use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::stability;
+use rustc_middle::ty::layout::LayoutError;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Symbol};
@@ -1540,13 +1541,14 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
         return;
     }
 
+    writeln!(w, "<h2 class=\"small-section-header\">Layout</h2>");
+    writeln!(w, "<div class=\"docblock\">");
+
     let tcx = cx.tcx();
     let param_env = tcx.param_env(ty_def_id);
     let ty = tcx.type_of(ty_def_id);
     match tcx.layout_of(param_env.and(ty)) {
         Ok(ty_layout) => {
-            writeln!(w, "<h2 class=\"small-section-header\">Layout</h2>");
-            writeln!(w, "<div class=\"docblock\">");
             writeln!(
                 w,
                 "<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
@@ -1567,11 +1569,28 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
                     pl = if bytes == 1 { "" } else { "s" },
                 );
             }
-            writeln!(w, "</div>");
         }
-        // Layout errors can occur with valid code, e.g. if you try to get the layout
-        // of a generic type such as `Vec<T>`. In case of a layout error, we just
-        // don't show any layout information.
-        Err(_) => {}
+        // This kind of layout error can occur with valid code, e.g. if you try to
+        // get the layout of a generic type such as `Vec<T>`.
+        Err(LayoutError::Unknown(_)) => {
+            writeln!(
+                w,
+                "<p><strong>Note:</strong> Unable to compute type layout, \
+                 possibly due to this type having generic parameters. \
+                 Layout can only be computed for concrete, fully-instantiated types.</p>"
+            );
+        }
+        // This kind of error probably can't happen with valid code, but we don't
+        // want to panic and prevent the docs from building, so we just let the
+        // user know that we couldn't compute the layout.
+        Err(LayoutError::SizeOverflow(_)) => {
+            writeln!(
+                w,
+                "<p><strong>Note:</strong> Encountered an error during type layout; \
+                 the type was too big.</p>"
+            );
+        }
     }
+
+    writeln!(w, "</div>");
 }
diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index cb6e354f7df54..637e4aef3d61c 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -35,9 +35,17 @@ pub struct Y(u8);
 // @has - '0 bytes'
 pub struct Z;
 
-// @!has type_layout/struct.Generic.html 'Size: '
+// We can't compute layout for generic types.
+// @has type_layout/struct.Generic.html 'Unable to compute type layout, possibly due to this type having generic parameters'
+// @!has - 'Size: '
 pub struct Generic<T>(T);
 
+// We *can*, however, compute layout for types that are only generic over lifetimes,
+// because lifetimes are a type-system construct.
+// @has type_layout/struct.GenericLifetimes.html 'Size: '
+// @has - ' bytes'
+pub struct GenericLifetimes<'a>(&'a str);
+
 // @has type_layout/struct.Unsized.html 'Size: '
 // @has - '(unsized)'
 pub struct Unsized([u8]);

From 9b89d01bbbc674f19a69838d2eb2e17ba4a84899 Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Sun, 9 May 2021 13:15:33 -0700
Subject: [PATCH 19/26] Enable `--show-type-layout` for the rustdoc API docs

---
 src/bootstrap/doc.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index e42d4fcd8647c..326a6fdaa80ff 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -649,6 +649,7 @@ impl Step for Rustdoc {
 
         cargo.rustdocflag("--document-private-items");
         cargo.rustdocflag("--enable-index-page");
+        cargo.rustdocflag("--show-type-layout");
         cargo.rustdocflag("-Zunstable-options");
         builder.run(&mut cargo.into());
     }

From d43701caa01003d9e0386fbd7a61d530e830564b Mon Sep 17 00:00:00 2001
From: Camelid <camelidcamel@gmail.com>
Date: Sun, 9 May 2021 13:18:28 -0700
Subject: [PATCH 20/26] Disable layout docs for type aliases for now

There are issues with computing layout for type aliases; see #85103.
Once the issues are fixed, we should re-enable layout docs for them.
---
 src/librustdoc/html/render/print_item.rs | 2 --
 src/test/rustdoc/type-layout.rs          | 4 ----
 2 files changed, 6 deletions(-)

diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index bde42371713ca..f0ca24b8f0221 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -837,8 +837,6 @@ fn item_typedef(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::T
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
-
-    document_type_layout(w, cx, def_id);
 }
 
 fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Union) {
diff --git a/src/test/rustdoc/type-layout.rs b/src/test/rustdoc/type-layout.rs
index 637e4aef3d61c..272911de6815b 100644
--- a/src/test/rustdoc/type-layout.rs
+++ b/src/test/rustdoc/type-layout.rs
@@ -50,9 +50,5 @@ pub struct GenericLifetimes<'a>(&'a str);
 // @has - '(unsized)'
 pub struct Unsized([u8]);
 
-// @has type_layout/type.TypeAlias.html 'Size: '
-// @has - ' bytes'
-pub type TypeAlias = X;
-
 // @!has type_layout/trait.MyTrait.html 'Size: '
 pub trait MyTrait {}

From f510e412e93958e099334de22de375d26264e767 Mon Sep 17 00:00:00 2001
From: Jacob Hoffman-Andrews <github@hoffman-andrews.com>
Date: Sun, 9 May 2021 13:49:22 -0700
Subject: [PATCH 21/26] rustdoc: remove explicit boolean comparisons.

For boolean variables it's shorter and more readable to check the value
directly, or negate it with `!`.

In a couple of cases I reordered an if/else pair because it made the
initial `if` statement simpler.

Removed unused isType parameter from two functions.
---
 src/librustdoc/html/static/main.js          | 36 +++++-----
 src/librustdoc/html/static/search.js        | 74 ++++++++++-----------
 src/librustdoc/html/static/source-script.js |  9 ++-
 src/librustdoc/html/static/storage.js       | 14 ++--
 4 files changed, 64 insertions(+), 69 deletions(-)

diff --git a/src/librustdoc/html/static/main.js b/src/librustdoc/html/static/main.js
index dc65e14ab37b8..04dc25341f4d3 100644
--- a/src/librustdoc/html/static/main.js
+++ b/src/librustdoc/html/static/main.js
@@ -448,14 +448,14 @@ function hideThemeButtonState() {
     }
 
     function getHelpElement(build) {
-        if (build !== false) {
+        if (build) {
             buildHelperPopup();
         }
         return document.getElementById("help");
     }
 
     function displayHelp(display, ev, help) {
-        if (display === true) {
+        if (display) {
             help = help ? help : getHelpElement(true);
             if (hasClass(help, "hidden")) {
                 ev.preventDefault();
@@ -466,7 +466,7 @@ function hideThemeButtonState() {
             // No need to build the help popup if we want to hide it in case it hasn't been
             // built yet...
             help = help ? help : getHelpElement(false);
-            if (help && hasClass(help, "hidden") === false) {
+            if (help && !hasClass(help, "hidden")) {
                 ev.preventDefault();
                 addClass(help, "hidden");
                 removeClass(document.body, "blur");
@@ -477,9 +477,9 @@ function hideThemeButtonState() {
     function handleEscape(ev) {
         var help = getHelpElement(false);
         var search = searchState.outputElement();
-        if (hasClass(help, "hidden") === false) {
+        if (!hasClass(help, "hidden")) {
             displayHelp(false, ev, help);
-        } else if (hasClass(search, "hidden") === false) {
+        } else if (!hasClass(search, "hidden")) {
             searchState.clearInputTimeout();
             ev.preventDefault();
             searchState.hideResults(search);
@@ -491,7 +491,7 @@ function hideThemeButtonState() {
     var disableShortcuts = getSettingValue("disable-shortcuts") === "true";
     function handleShortcut(ev) {
         // Don't interfere with browser shortcuts
-        if (ev.ctrlKey || ev.altKey || ev.metaKey || disableShortcuts === true) {
+        if (ev.ctrlKey || ev.altKey || ev.metaKey || disableShortcuts) {
             return;
         }
 
@@ -908,11 +908,11 @@ function hideThemeButtonState() {
         function implHider(addOrRemove, fullHide) {
             return function(n) {
                 var shouldHide =
-                    fullHide === true ||
-                    hasClass(n, "method") === true ||
-                    hasClass(n, "associatedconstant") === true;
-                if (shouldHide === true || hasClass(n, "type") === true) {
-                    if (shouldHide === true) {
+                    fullHide ||
+                    hasClass(n, "method") ||
+                    hasClass(n, "associatedconstant");
+                if (shouldHide || hasClass(n, "type")) {
+                    if (shouldHide) {
                         if (addOrRemove) {
                             addClass(n, "hidden-by-impl-hider");
                         } else {
@@ -934,7 +934,7 @@ function hideThemeButtonState() {
 
         var relatedDoc;
         var action = mode;
-        if (hasClass(toggle.parentNode, "impl") === false) {
+        if (!hasClass(toggle.parentNode, "impl")) {
             relatedDoc = toggle.parentNode.nextElementSibling;
             if (hasClass(relatedDoc, "item-info")) {
                 relatedDoc = relatedDoc.nextElementSibling;
@@ -964,11 +964,11 @@ function hideThemeButtonState() {
             relatedDoc = parentElem;
             var docblock = relatedDoc.nextElementSibling;
 
-            while (hasClass(relatedDoc, "impl-items") === false) {
+            while (!hasClass(relatedDoc, "impl-items")) {
                 relatedDoc = relatedDoc.nextElementSibling;
             }
 
-            if (!relatedDoc && hasClass(docblock, "docblock") === false) {
+            if (!relatedDoc && !hasClass(docblock, "docblock")) {
                 return;
             }
 
@@ -987,7 +987,7 @@ function hideThemeButtonState() {
             if (action === "show") {
                 removeClass(relatedDoc, "fns-now-collapsed");
                 // Stability/deprecation/portability information is never hidden.
-                if (hasClass(docblock, "item-info") === false) {
+                if (!hasClass(docblock, "item-info")) {
                     removeClass(docblock, "hidden-by-usual-hider");
                 }
                 onEachLazy(toggle.childNodes, adjustToggle(false, dontApplyBlockRule));
@@ -996,7 +996,7 @@ function hideThemeButtonState() {
                 addClass(relatedDoc, "fns-now-collapsed");
                 // Stability/deprecation/portability information should be shown even when detailed
                 // info is hidden.
-                if (hasClass(docblock, "item-info") === false) {
+                if (!hasClass(docblock, "item-info")) {
                     addClass(docblock, "hidden-by-usual-hider");
                 }
                 onEachLazy(toggle.childNodes, adjustToggle(true, dontApplyBlockRule));
@@ -1045,7 +1045,7 @@ function hideThemeButtonState() {
             });
         }
 
-        if (hideMethodDocs === true) {
+        if (hideMethodDocs) {
             onEachLazy(document.getElementsByClassName("method"), function(e) {
                 var toggle = e.parentNode;
                 if (toggle) {
@@ -1132,7 +1132,7 @@ function hideThemeButtonState() {
     if (sidebar_menu) {
         sidebar_menu.onclick = function() {
             var sidebar = document.getElementsByClassName("sidebar")[0];
-            if (hasClass(sidebar, "mobile") === true) {
+            if (hasClass(sidebar, "mobile")) {
                 hideSidebar();
             } else {
                 showSidebar();
diff --git a/src/librustdoc/html/static/search.js b/src/librustdoc/html/static/search.js
index 9fab435de49c8..b4f9d7b374052 100644
--- a/src/librustdoc/html/static/search.js
+++ b/src/librustdoc/html/static/search.js
@@ -146,23 +146,21 @@ window.initSearch = function(rawSearchIndex) {
 
         removeEmptyStringsFromArray(split);
 
-        function transformResults(results, isType) {
+        function transformResults(results) {
             var out = [];
             for (var i = 0, len = results.length; i < len; ++i) {
                 if (results[i].id > -1) {
                     var obj = searchIndex[results[i].id];
                     obj.lev = results[i].lev;
-                    if (isType !== true || obj.type) {
-                        var res = buildHrefAndPath(obj);
-                        obj.displayPath = pathSplitter(res[0]);
-                        obj.fullPath = obj.displayPath + obj.name;
-                        // To be sure than it some items aren't considered as duplicate.
-                        obj.fullPath += "|" + obj.ty;
-                        obj.href = res[1];
-                        out.push(obj);
-                        if (out.length >= MAX_RESULTS) {
-                            break;
-                        }
+                    var res = buildHrefAndPath(obj);
+                    obj.displayPath = pathSplitter(res[0]);
+                    obj.fullPath = obj.displayPath + obj.name;
+                    // To be sure than it some items aren't considered as duplicate.
+                    obj.fullPath += "|" + obj.ty;
+                    obj.href = res[1];
+                    out.push(obj);
+                    if (out.length >= MAX_RESULTS) {
+                        break;
                     }
                 }
             }
@@ -266,9 +264,7 @@ window.initSearch = function(rawSearchIndex) {
                     path = result.item.path.toLowerCase(),
                     parent = result.item.parent;
 
-                if (isType !== true &&
-                    validateResult(name, path, split, parent) === false)
-                {
+                if (!isType && !validateResult(name, path, split, parent)) {
                     result.id = -1;
                 }
             }
@@ -352,7 +348,7 @@ window.initSearch = function(rawSearchIndex) {
             var lev_distance = MAX_LEV_DISTANCE + 1;
             var len, x, firstGeneric;
             if (obj[NAME] === val.name) {
-                if (literalSearch === true) {
+                if (literalSearch) {
                     if (val.generics && val.generics.length !== 0) {
                         if (obj.length > GENERICS_DATA &&
                               obj[GENERICS_DATA].length >= val.generics.length) {
@@ -373,7 +369,7 @@ window.initSearch = function(rawSearchIndex) {
                                     break;
                                 }
                             }
-                            if (allFound === true) {
+                            if (allFound) {
                                 return true;
                             }
                         } else {
@@ -394,7 +390,7 @@ window.initSearch = function(rawSearchIndex) {
                 }
             }
             // Names didn't match so let's check if one of the generic types could.
-            if (literalSearch === true) {
+            if (literalSearch) {
                  if (obj.length > GENERICS_DATA && obj[GENERICS_DATA].length > 0) {
                     return obj[GENERICS_DATA].some(
                         function(name) {
@@ -429,12 +425,12 @@ window.initSearch = function(rawSearchIndex) {
                 var length = obj.type[INPUTS_DATA].length;
                 for (var i = 0; i < length; i++) {
                     var tmp = obj.type[INPUTS_DATA][i];
-                    if (typePassesFilter(typeFilter, tmp[1]) === false) {
+                    if (!typePassesFilter(typeFilter, tmp[1])) {
                         continue;
                     }
                     tmp = checkType(tmp, val, literalSearch);
-                    if (literalSearch === true) {
-                        if (tmp === true) {
+                    if (literalSearch) {
+                        if (tmp) {
                             return true;
                         }
                         continue;
@@ -445,7 +441,7 @@ window.initSearch = function(rawSearchIndex) {
                     }
                 }
             }
-            return literalSearch === true ? false : lev_distance;
+            return literalSearch ? false : lev_distance;
         }
 
         function checkReturned(obj, val, literalSearch, typeFilter) {
@@ -458,12 +454,12 @@ window.initSearch = function(rawSearchIndex) {
                 }
                 for (var x = 0, len = ret.length; x < len; ++x) {
                     var tmp = ret[x];
-                    if (typePassesFilter(typeFilter, tmp[1]) === false) {
+                    if (!typePassesFilter(typeFilter, tmp[1])) {
                         continue;
                     }
                     tmp = checkType(tmp, val, literalSearch);
-                    if (literalSearch === true) {
-                        if (tmp === true) {
+                    if (literalSearch) {
+                        if (tmp) {
                             return true;
                         }
                         continue;
@@ -474,7 +470,7 @@ window.initSearch = function(rawSearchIndex) {
                     }
                 }
             }
-            return literalSearch === true ? false : lev_distance;
+            return literalSearch ? false : lev_distance;
         }
 
         function checkPath(contains, lastElem, ty) {
@@ -507,7 +503,7 @@ window.initSearch = function(rawSearchIndex) {
                     }
                     lev_total += lev;
                 }
-                if (aborted === false) {
+                if (!aborted) {
                     ret_lev = Math.min(ret_lev, Math.round(lev_total / clength));
                 }
             }
@@ -634,14 +630,14 @@ window.initSearch = function(rawSearchIndex) {
                         dontValidate: true,
                     };
                 }
-                if (in_args === true && results_in_args[fullId] === undefined) {
+                if (in_args && results_in_args[fullId] === undefined) {
                     results_in_args[fullId] = {
                         id: i,
                         index: -1,
                         dontValidate: true,
                     };
                 }
-                if (returned === true && results_returned[fullId] === undefined) {
+                if (returned && results_returned[fullId] === undefined) {
                     results_returned[fullId] = {
                         id: i,
                         index: -1,
@@ -676,7 +672,7 @@ window.initSearch = function(rawSearchIndex) {
                 fullId = ty.id;
 
                 returned = checkReturned(ty, output, true, NO_TYPE_FILTER);
-                if (output.name === "*" || returned === true) {
+                if (output.name === "*" || returned) {
                     in_args = false;
                     var is_module = false;
 
@@ -684,26 +680,26 @@ window.initSearch = function(rawSearchIndex) {
                         is_module = true;
                     } else {
                         var allFound = true;
-                        for (it = 0, len = inputs.length; allFound === true && it < len; it++) {
+                        for (it = 0, len = inputs.length; allFound && it < len; it++) {
                             allFound = checkType(type, inputs[it], true);
                         }
                         in_args = allFound;
                     }
-                    if (in_args === true) {
+                    if (in_args) {
                         results_in_args[fullId] = {
                             id: i,
                             index: -1,
                             dontValidate: true,
                         };
                     }
-                    if (returned === true) {
+                    if (returned) {
                         results_returned[fullId] = {
                             id: i,
                             index: -1,
                             dontValidate: true,
                         };
                     }
-                    if (is_module === true) {
+                    if (is_module) {
                         results[fullId] = {
                             id: i,
                             index: -1,
@@ -763,10 +759,10 @@ window.initSearch = function(rawSearchIndex) {
                     }
                 }
                 if ((lev = levenshtein(searchWords[j], val)) <= MAX_LEV_DISTANCE) {
-                    if (typePassesFilter(typeFilter, ty.ty) === false) {
-                        lev = MAX_LEV_DISTANCE + 1;
-                    } else {
+                    if (typePassesFilter(typeFilter, ty.ty)) {
                         lev += 1;
+                    } else {
+                        lev = MAX_LEV_DISTANCE + 1;
                     }
                 }
                 in_args = findArg(ty, valGenerics, false, typeFilter);
@@ -821,7 +817,7 @@ window.initSearch = function(rawSearchIndex) {
         var ret = {
             "in_args": sortResults(results_in_args, true),
             "returned": sortResults(results_returned, true),
-            "others": sortResults(results),
+            "others": sortResults(results, false),
         };
         handleAliases(ret, query, filterCrates);
         return ret;
@@ -1263,7 +1259,7 @@ window.initSearch = function(rawSearchIndex) {
         if (query.query.length === 0) {
             return;
         }
-        if (forced !== true && query.id === currentResults) {
+        if (!forced && query.id === currentResults) {
             if (query.query.length > 0) {
                 searchState.putBackSearch(searchState.input);
             }
diff --git a/src/librustdoc/html/static/source-script.js b/src/librustdoc/html/static/source-script.js
index 42b54e4cc1e46..81df541189681 100644
--- a/src/librustdoc/html/static/source-script.js
+++ b/src/librustdoc/html/static/source-script.js
@@ -44,7 +44,7 @@ function createDirEntry(elem, parent, fullPath, currentFile, hasFoundFile) {
     if (elem.dirs) {
         for (i = 0, len = elem.dirs.length; i < len; ++i) {
             if (createDirEntry(elem.dirs[i], folders, fullPath, currentFile,
-                               hasFoundFile) === true) {
+                               hasFoundFile)) {
                 addClass(name, "expand");
                 hasFoundFile = true;
             }
@@ -59,8 +59,7 @@ function createDirEntry(elem, parent, fullPath, currentFile, hasFoundFile) {
             var file = document.createElement("a");
             file.innerText = elem.files[i];
             file.href = window.rootPath + "src/" + fullPath + elem.files[i] + ".html";
-            if (hasFoundFile === false &&
-                    currentFile === fullPath + elem.files[i]) {
+            if (!hasFoundFile && currentFile === fullPath + elem.files[i]) {
                 file.className = "selected";
                 addClass(name, "expand");
                 hasFoundFile = true;
@@ -72,7 +71,7 @@ function createDirEntry(elem, parent, fullPath, currentFile, hasFoundFile) {
     children.appendChild(files);
     parent.appendChild(name);
     parent.appendChild(children);
-    return hasFoundFile === true && currentFile.startsWith(fullPath);
+    return hasFoundFile && currentFile.startsWith(fullPath);
 }
 
 function toggleSidebar() {
@@ -116,7 +115,7 @@ function createSidebarToggle() {
 // This function is called from "source-files.js", generated in `html/render/mod.rs`.
 // eslint-disable-next-line no-unused-vars
 function createSourceSidebar() {
-    if (window.rootPath.endsWith("/") === false) {
+    if (!window.rootPath.endsWith("/")) {
         window.rootPath += "/";
     }
     var main = document.getElementById("main");
diff --git a/src/librustdoc/html/static/storage.js b/src/librustdoc/html/static/storage.js
index 2ed87fdedaec6..208afd2e732dd 100644
--- a/src/librustdoc/html/static/storage.js
+++ b/src/librustdoc/html/static/storage.js
@@ -59,15 +59,15 @@ function onEach(arr, func, reversed) {
     if (arr && arr.length > 0 && func) {
         var length = arr.length;
         var i;
-        if (reversed !== true) {
-            for (i = 0; i < length; ++i) {
-                if (func(arr[i]) === true) {
+        if (reversed) {
+            for (i = length - 1; i >= 0; --i) {
+                if (func(arr[i])) {
                     return true;
                 }
             }
         } else {
-            for (i = length - 1; i >= 0; --i) {
-                if (func(arr[i]) === true) {
+            for (i = 0; i < length; ++i) {
+                if (func(arr[i])) {
                     return true;
                 }
             }
@@ -111,7 +111,7 @@ function switchTheme(styleElem, mainStyleElem, newTheme, saveTheme) {
 
     // If this new value comes from a system setting or from the previously
     // saved theme, no need to save it.
-    if (saveTheme === true) {
+    if (saveTheme) {
         updateLocalStorage("rustdoc-theme", newTheme);
     }
 
@@ -131,7 +131,7 @@ function switchTheme(styleElem, mainStyleElem, newTheme, saveTheme) {
             return true;
         }
     });
-    if (found === true) {
+    if (found) {
         styleElem.href = newHref;
     }
 }

From d5a24b0a33bccb69e8ba19da42a15b5a69639e22 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sun, 2 May 2021 16:50:14 +0200
Subject: [PATCH 22/26] Move rustdoc-gui rust libraries into their own folder
 and prepare the field for more libraries

---
 src/bootstrap/test.rs                         | 21 +++++++++++++++----
 src/test/rustdoc-gui/basic-code.goml          |  2 +-
 src/test/rustdoc-gui/basic.goml               |  2 +-
 .../rustdoc-gui/check_info_sign_position.goml |  2 +-
 src/test/rustdoc-gui/code-sidebar-toggle.goml |  2 +-
 src/test/rustdoc-gui/hash-item-expansion.goml |  2 +-
 .../rustdoc-gui/impl-default-expansion.goml   |  2 +-
 src/test/rustdoc-gui/list_code_block.goml     |  2 +-
 src/test/rustdoc-gui/search-input-mobile.goml |  2 +-
 ...rch-tab-selection-if-current-is-empty.goml |  6 +++---
 src/test/rustdoc-gui/shortcuts.goml           |  2 +-
 src/test/rustdoc-gui/source-code-page.goml    |  4 ++--
 src/test/rustdoc-gui/{ => src}/lib.rs         |  0
 src/test/rustdoc-gui/theme-change.goml        |  2 +-
 src/test/rustdoc-gui/toggle-docs.goml         |  2 +-
 .../rustdoc-gui/trait-sidebar-item-order.goml |  2 +-
 16 files changed, 34 insertions(+), 21 deletions(-)
 rename src/test/rustdoc-gui/{ => src}/lib.rs (100%)

diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 78163651158ed..de5eb7a2800e5 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -827,15 +827,28 @@ impl Step for RustdocGUI {
             }
 
             let out_dir = builder.test_out(self.target).join("rustdoc-gui");
-            let mut command = builder.rustdoc_cmd(self.compiler);
-            command.arg("src/test/rustdoc-gui/lib.rs").arg("-o").arg(&out_dir);
-            builder.run(&mut command);
 
+            // We remove existing folder to be sure there won't be artifacts remaining.
+            let _ = fs::remove_dir_all(&out_dir);
+
+            // We generate docs for the libraries present in the rustdoc-gui's src folder.
+            let libs_dir = Path::new("src/test/rustdoc-gui/src");
+            for entry in libs_dir.read_dir().expect("read_dir call failed") {
+                let entry = entry.expect("invalid entry");
+                let path = entry.path();
+                if path.extension().map(|e| e == "rs").unwrap_or(false) {
+                    let mut command = builder.rustdoc_cmd(self.compiler);
+                    command.arg(path).arg("-o").arg(&out_dir);
+                    builder.run(&mut command);
+                }
+            }
+
+            // We now run GUI tests.
             let mut command = Command::new(&nodejs);
             command
                 .arg("src/tools/rustdoc-gui/tester.js")
                 .arg("--doc-folder")
-                .arg(out_dir.join("test_docs"))
+                .arg(out_dir)
                 .arg("--tests-folder")
                 .arg("src/test/rustdoc-gui");
             builder.run(&mut command);
diff --git a/src/test/rustdoc-gui/basic-code.goml b/src/test/rustdoc-gui/basic-code.goml
index 8da465662547a..d014ed60eb039 100644
--- a/src/test/rustdoc-gui/basic-code.goml
+++ b/src/test/rustdoc-gui/basic-code.goml
@@ -1,3 +1,3 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 click: ".srclink"
 assert: (".line-numbers", 1)
diff --git a/src/test/rustdoc-gui/basic.goml b/src/test/rustdoc-gui/basic.goml
index ed23300860b70..44fcec3393744 100644
--- a/src/test/rustdoc-gui/basic.goml
+++ b/src/test/rustdoc-gui/basic.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 assert: ("#functions")
 goto: ./struct.Foo.html
 assert: ("div.type-decl")
diff --git a/src/test/rustdoc-gui/check_info_sign_position.goml b/src/test/rustdoc-gui/check_info_sign_position.goml
index 9aa72a3ad53e7..d64ee0261370c 100644
--- a/src/test/rustdoc-gui/check_info_sign_position.goml
+++ b/src/test/rustdoc-gui/check_info_sign_position.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 goto: ./fn.check_list_code_block.html
 // If the codeblock is the first element of the docblock, the information tooltip must have
 // have some top margin to avoid going over the toggle (the "[+]").
diff --git a/src/test/rustdoc-gui/code-sidebar-toggle.goml b/src/test/rustdoc-gui/code-sidebar-toggle.goml
index 69fc860244b7b..7e7003d4340a3 100644
--- a/src/test/rustdoc-gui/code-sidebar-toggle.goml
+++ b/src/test/rustdoc-gui/code-sidebar-toggle.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 click: ".srclink"
 click: "#sidebar-toggle"
 wait-for: 500
diff --git a/src/test/rustdoc-gui/hash-item-expansion.goml b/src/test/rustdoc-gui/hash-item-expansion.goml
index d736d15d184a3..1248d11200e6c 100644
--- a/src/test/rustdoc-gui/hash-item-expansion.goml
+++ b/src/test/rustdoc-gui/hash-item-expansion.goml
@@ -1,5 +1,5 @@
 // This test ensures that the element corresponding to the hash is displayed.
-goto: file://|DOC_PATH|/struct.Foo.html#method.borrow
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html#method.borrow
 // In the blanket implementations list, "Borrow" is the second one, hence the ":nth(2)".
 assert: ("#blanket-implementations-list > details:nth-child(2)", "open", "")
 // Please note the "\" below is needed because otherwise ".borrow" would be interpreted as
diff --git a/src/test/rustdoc-gui/impl-default-expansion.goml b/src/test/rustdoc-gui/impl-default-expansion.goml
index 686d98f9736e4..3f1e7ec4a789c 100644
--- a/src/test/rustdoc-gui/impl-default-expansion.goml
+++ b/src/test/rustdoc-gui/impl-default-expansion.goml
@@ -1,3 +1,3 @@
 // This test ensures that the impl blocks are open by default.
-goto: file://|DOC_PATH|/struct.Foo.html
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html
 assert: ("#main > details.implementors-toggle", "open", "")
diff --git a/src/test/rustdoc-gui/list_code_block.goml b/src/test/rustdoc-gui/list_code_block.goml
index 6f2465a5587f2..7d3490e9d9410 100644
--- a/src/test/rustdoc-gui/list_code_block.goml
+++ b/src/test/rustdoc-gui/list_code_block.goml
@@ -1,3 +1,3 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 goto: ./fn.check_list_code_block.html
 assert: ("pre.rust.fn")
diff --git a/src/test/rustdoc-gui/search-input-mobile.goml b/src/test/rustdoc-gui/search-input-mobile.goml
index 3eec3459a6393..5c95db70aecdd 100644
--- a/src/test/rustdoc-gui/search-input-mobile.goml
+++ b/src/test/rustdoc-gui/search-input-mobile.goml
@@ -1,6 +1,6 @@
 // Test to ensure that you can click on the search input, whatever the width.
 // The PR which fixed it is: https://github.com/rust-lang/rust/pull/81592
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 size: (463, 700)
 // We first check that the search input isn't already focused.
 assert-false: ("input.search-input:focus")
diff --git a/src/test/rustdoc-gui/search-tab-selection-if-current-is-empty.goml b/src/test/rustdoc-gui/search-tab-selection-if-current-is-empty.goml
index a4df102d245be..c828c72e910d5 100644
--- a/src/test/rustdoc-gui/search-tab-selection-if-current-is-empty.goml
+++ b/src/test/rustdoc-gui/search-tab-selection-if-current-is-empty.goml
@@ -1,11 +1,11 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "Foo")
 // Waiting for the search results to appear...
 wait-for: "#titles"
 assert: ("#titles > button:nth-of-type(1)", "class", "selected")
 
 // To go back to the original "state"
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "-> String")
 // Waiting for the search results to appear...
 wait-for: "#titles"
@@ -13,7 +13,7 @@ wait-for: "#titles"
 assert: ("#titles > button:nth-of-type(3)", "class", "selected")
 
 // To go back to the original "state"
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 write: (".search-input", "-> Something")
 // Waiting for the search results to appear...
 wait-for: "#titles"
diff --git a/src/test/rustdoc-gui/shortcuts.goml b/src/test/rustdoc-gui/shortcuts.goml
index c35b48f57f4d2..884c38d85fbdb 100644
--- a/src/test/rustdoc-gui/shortcuts.goml
+++ b/src/test/rustdoc-gui/shortcuts.goml
@@ -1,5 +1,5 @@
 // Check that the various shortcuts are working.
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 // We first check that the search input isn't already focused.
 assert-false: "input.search-input:focus"
 press-key: "s"
diff --git a/src/test/rustdoc-gui/source-code-page.goml b/src/test/rustdoc-gui/source-code-page.goml
index f11c41e8bd552..ff33a541a1801 100644
--- a/src/test/rustdoc-gui/source-code-page.goml
+++ b/src/test/rustdoc-gui/source-code-page.goml
@@ -1,11 +1,11 @@
-goto: file://|DOC_PATH|/../src/test_docs/lib.rs.html
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
 // Check that we can click on the line number.
 click: (40, 224) // This is the position of the span for line 4.
 // Unfortunately, "#4" isn't a valid query selector, so we have to go around that limitation
 // by instead getting the nth span.
 assert: (".line-numbers > span:nth-child(4)", "class", "line-highlighted")
 // We now check that the good spans are highlighted
-goto: file://|DOC_PATH|/../src/test_docs/lib.rs.html#4-6
+goto: file://|DOC_PATH|/src/test_docs/lib.rs.html#4-6
 assert-false: (".line-numbers > span:nth-child(3)", "class", "line-highlighted")
 assert: (".line-numbers > span:nth-child(4)", "class", "line-highlighted")
 assert: (".line-numbers > span:nth-child(5)", "class", "line-highlighted")
diff --git a/src/test/rustdoc-gui/lib.rs b/src/test/rustdoc-gui/src/lib.rs
similarity index 100%
rename from src/test/rustdoc-gui/lib.rs
rename to src/test/rustdoc-gui/src/lib.rs
diff --git a/src/test/rustdoc-gui/theme-change.goml b/src/test/rustdoc-gui/theme-change.goml
index 5bd65f61f4905..bc9063edd1e7a 100644
--- a/src/test/rustdoc-gui/theme-change.goml
+++ b/src/test/rustdoc-gui/theme-change.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 click: "#theme-picker"
 click: "#theme-choices > button:first-child"
 wait-for: 500
diff --git a/src/test/rustdoc-gui/toggle-docs.goml b/src/test/rustdoc-gui/toggle-docs.goml
index 1ded33f659d3c..93bdf41a6a09e 100644
--- a/src/test/rustdoc-gui/toggle-docs.goml
+++ b/src/test/rustdoc-gui/toggle-docs.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/index.html
+goto: file://|DOC_PATH|/test_docs/index.html
 click: "#toggle-all-docs"
 wait-for: 5000
 assert: ("#main > div.docblock.hidden-by-usual-hider")
diff --git a/src/test/rustdoc-gui/trait-sidebar-item-order.goml b/src/test/rustdoc-gui/trait-sidebar-item-order.goml
index 914486e1c281d..2e9f85336ecd8 100644
--- a/src/test/rustdoc-gui/trait-sidebar-item-order.goml
+++ b/src/test/rustdoc-gui/trait-sidebar-item-order.goml
@@ -1,4 +1,4 @@
-goto: file://|DOC_PATH|/trait.AnotherOne.html
+goto: file://|DOC_PATH|/test_docs/trait.AnotherOne.html
 assert: (".sidebar-links a:nth-of-type(1)", "another")
 assert: (".sidebar-links a:nth-of-type(2)", "func1")
 assert: (".sidebar-links a:nth-of-type(3)", "func2")

From 1b0976c42f0dc83f3d963e014d685e579a7a9b33 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Tue, 11 May 2021 20:56:07 +0200
Subject: [PATCH 23/26] Update toggle-docs GUI test to last version

---
 src/test/rustdoc-gui/toggle-docs.goml | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/test/rustdoc-gui/toggle-docs.goml b/src/test/rustdoc-gui/toggle-docs.goml
index 93bdf41a6a09e..062bc7d51e542 100644
--- a/src/test/rustdoc-gui/toggle-docs.goml
+++ b/src/test/rustdoc-gui/toggle-docs.goml
@@ -1,7 +1,10 @@
 goto: file://|DOC_PATH|/test_docs/index.html
+assert: ("#main > details.top-doc", "open", "")
 click: "#toggle-all-docs"
-wait-for: 5000
-assert: ("#main > div.docblock.hidden-by-usual-hider")
+wait-for: 1000
+// This is now collapsed so there shouldn't be the "open" attribute on details.
+assert-false: ("#main > details.top-doc", "open", "")
 click: "#toggle-all-docs"
-wait-for: 5000
-assert: ("#main > div.docblock.hidden-by-usual-hider", 0)
+wait-for: 1000
+// Not collapsed anymore so the "open" attribute should be back.
+assert: ("#main > details.top-doc", "open", "")

From 6b9499085be274226bfc3eb2434bea4e0e90096d Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Tue, 11 May 2021 21:14:40 +0200
Subject: [PATCH 24/26] Make rustdoc-gui test suite able to run with different
 sub directories

---
 src/bootstrap/test.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index de5eb7a2800e5..0e9c561c68994 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -832,7 +832,7 @@ impl Step for RustdocGUI {
             let _ = fs::remove_dir_all(&out_dir);
 
             // We generate docs for the libraries present in the rustdoc-gui's src folder.
-            let libs_dir = Path::new("src/test/rustdoc-gui/src");
+            let libs_dir = builder.build.src.join("src/test/rustdoc-gui/src");
             for entry in libs_dir.read_dir().expect("read_dir call failed") {
                 let entry = entry.expect("invalid entry");
                 let path = entry.path();
@@ -846,11 +846,11 @@ impl Step for RustdocGUI {
             // We now run GUI tests.
             let mut command = Command::new(&nodejs);
             command
-                .arg("src/tools/rustdoc-gui/tester.js")
+                .arg(builder.build.src.join("src/tools/rustdoc-gui/tester.js"))
                 .arg("--doc-folder")
                 .arg(out_dir)
                 .arg("--tests-folder")
-                .arg("src/test/rustdoc-gui");
+                .arg(builder.build.src.join("src/test/rustdoc-gui"));
             builder.run(&mut command);
         } else {
             builder.info("No nodejs found, skipping \"src/test/rustdoc-gui\" tests");

From bea112ba07ec3da0de8de041bc3d510fe445b157 Mon Sep 17 00:00:00 2001
From: Rich Kadel <richkadel@google.com>
Date: Tue, 11 May 2021 12:47:08 -0700
Subject: [PATCH 25/26] Revert "Auto merge of #84797 -
 richkadel:cover-unreachable-statements, r=tmandry"

This reverts commit e5f83d24aee866a14753a7cedbb4e301dfe5bef5, reversing
changes made to ac888e8675182c703c2cd097957878faf88dad94.
---
 .../rustc_mir/src/transform/const_goto.rs     |  2 +-
 .../src/transform/deduplicate_blocks.rs       |  2 +-
 .../src/transform/early_otherwise_branch.rs   |  2 +-
 compiler/rustc_mir/src/transform/generator.rs |  4 +-
 compiler/rustc_mir/src/transform/inline.rs    |  2 +-
 .../rustc_mir/src/transform/match_branches.rs |  2 +-
 .../transform/multiple_return_terminators.rs  |  2 +-
 .../src/transform/remove_unneeded_drops.rs    |  2 +-
 compiler/rustc_mir/src/transform/simplify.rs  | 42 +++----------------
 .../rustc_mir/src/transform/simplify_try.rs   |  2 +-
 .../src/transform/unreachable_prop.rs         |  2 +-
 .../expected_show_coverage.async2.txt         |  1 -
 .../expected_show_coverage.conditions.txt     |  8 +---
 .../expected_show_coverage.doctest.txt        |  4 +-
 .../expected_show_coverage.drop_trait.txt     | 10 ++---
 .../expected_show_coverage.generics.txt       | 18 ++++----
 .../expected_show_coverage.loops_branches.txt | 38 ++++++++---------
 .../expected_show_coverage.tight_inf_loop.txt |  2 +-
 .../run-make-fulldeps/coverage/conditions.rs  |  4 +-
 .../run-make-fulldeps/coverage/generics.rs    | 10 ++---
 .../coverage/loops_branches.rs                |  8 ++--
 21 files changed, 65 insertions(+), 102 deletions(-)

diff --git a/compiler/rustc_mir/src/transform/const_goto.rs b/compiler/rustc_mir/src/transform/const_goto.rs
index ba10b54c5ae2e..b5c8b4bebc360 100644
--- a/compiler/rustc_mir/src/transform/const_goto.rs
+++ b/compiler/rustc_mir/src/transform/const_goto.rs
@@ -47,7 +47,7 @@ impl<'tcx> MirPass<'tcx> for ConstGoto {
         // if we applied optimizations, we potentially have some cfg to cleanup to
         // make it easier for further passes
         if should_simplify {
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
             simplify_locals(body, tcx);
         }
     }
diff --git a/compiler/rustc_mir/src/transform/deduplicate_blocks.rs b/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
index 912505c65983e..c41e71e09a4ef 100644
--- a/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
+++ b/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
@@ -26,7 +26,7 @@ impl<'tcx> MirPass<'tcx> for DeduplicateBlocks {
         if has_opts_to_apply {
             let mut opt_applier = OptApplier { tcx, duplicates };
             opt_applier.visit_body(body);
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/early_otherwise_branch.rs b/compiler/rustc_mir/src/transform/early_otherwise_branch.rs
index ac39206623308..f7ea9faec4728 100644
--- a/compiler/rustc_mir/src/transform/early_otherwise_branch.rs
+++ b/compiler/rustc_mir/src/transform/early_otherwise_branch.rs
@@ -164,7 +164,7 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
         // Since this optimization adds new basic blocks and invalidates others,
         // clean up the cfg to make it nicer for other passes
         if should_cleanup {
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/generator.rs b/compiler/rustc_mir/src/transform/generator.rs
index 3560b4b1e8645..003003a8abbea 100644
--- a/compiler/rustc_mir/src/transform/generator.rs
+++ b/compiler/rustc_mir/src/transform/generator.rs
@@ -964,7 +964,7 @@ fn create_generator_drop_shim<'tcx>(
 
     // Make sure we remove dead blocks to remove
     // unrelated code from the resume part of the function
-    simplify::remove_dead_blocks(tcx, &mut body);
+    simplify::remove_dead_blocks(&mut body);
 
     dump_mir(tcx, None, "generator_drop", &0, &body, |_, _| Ok(()));
 
@@ -1137,7 +1137,7 @@ fn create_generator_resume_function<'tcx>(
 
     // Make sure we remove dead blocks to remove
     // unrelated code from the drop part of the function
-    simplify::remove_dead_blocks(tcx, body);
+    simplify::remove_dead_blocks(body);
 
     dump_mir(tcx, None, "generator_resume", &0, body, |_, _| Ok(()));
 }
diff --git a/compiler/rustc_mir/src/transform/inline.rs b/compiler/rustc_mir/src/transform/inline.rs
index f1c95a84ade85..b6f80763bc8c4 100644
--- a/compiler/rustc_mir/src/transform/inline.rs
+++ b/compiler/rustc_mir/src/transform/inline.rs
@@ -57,7 +57,7 @@ impl<'tcx> MirPass<'tcx> for Inline {
         if inline(tcx, body) {
             debug!("running simplify cfg on {:?}", body.source);
             CfgSimplifier::new(body).simplify();
-            remove_dead_blocks(tcx, body);
+            remove_dead_blocks(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/match_branches.rs b/compiler/rustc_mir/src/transform/match_branches.rs
index 21b208a08c2dc..f7a9835353e5c 100644
--- a/compiler/rustc_mir/src/transform/match_branches.rs
+++ b/compiler/rustc_mir/src/transform/match_branches.rs
@@ -167,7 +167,7 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
         }
 
         if should_cleanup {
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/multiple_return_terminators.rs b/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
index cd2db18055286..4aaa0baa9f46a 100644
--- a/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
+++ b/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
@@ -38,6 +38,6 @@ impl<'tcx> MirPass<'tcx> for MultipleReturnTerminators {
             }
         }
 
-        simplify::remove_dead_blocks(tcx, body)
+        simplify::remove_dead_blocks(body)
     }
 }
diff --git a/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs b/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
index 02e45021a0aaf..5144d48750de7 100644
--- a/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
+++ b/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
@@ -36,7 +36,7 @@ impl<'tcx> MirPass<'tcx> for RemoveUnneededDrops {
         // if we applied optimizations, we potentially have some cfg to cleanup to
         // make it easier for further passes
         if should_simplify {
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/simplify.rs b/compiler/rustc_mir/src/transform/simplify.rs
index 63373b0cffbb0..65e2d096b2094 100644
--- a/compiler/rustc_mir/src/transform/simplify.rs
+++ b/compiler/rustc_mir/src/transform/simplify.rs
@@ -29,7 +29,6 @@
 
 use crate::transform::MirPass;
 use rustc_index::vec::{Idx, IndexVec};
-use rustc_middle::mir::coverage::*;
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
@@ -47,9 +46,9 @@ impl SimplifyCfg {
     }
 }
 
-pub fn simplify_cfg(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
+pub fn simplify_cfg(body: &mut Body<'_>) {
     CfgSimplifier::new(body).simplify();
-    remove_dead_blocks(tcx, body);
+    remove_dead_blocks(body);
 
     // FIXME: Should probably be moved into some kind of pass manager
     body.basic_blocks_mut().raw.shrink_to_fit();
@@ -60,9 +59,9 @@ impl<'tcx> MirPass<'tcx> for SimplifyCfg {
         Cow::Borrowed(&self.label)
     }
 
-    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+    fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         debug!("SimplifyCfg({:?}) - simplifying {:?}", self.label, body.source);
-        simplify_cfg(tcx, body);
+        simplify_cfg(body);
     }
 }
 
@@ -287,7 +286,7 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
     }
 }
 
-pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
+pub fn remove_dead_blocks(body: &mut Body<'_>) {
     let reachable = traversal::reachable_as_bitset(body);
     let num_blocks = body.basic_blocks().len();
     if num_blocks == reachable.count() {
@@ -307,11 +306,6 @@ pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
         }
         used_blocks += 1;
     }
-
-    if tcx.sess.instrument_coverage() {
-        save_unreachable_coverage(basic_blocks, used_blocks);
-    }
-
     basic_blocks.raw.truncate(used_blocks);
 
     for block in basic_blocks {
@@ -321,32 +315,6 @@ pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
     }
 }
 
-fn save_unreachable_coverage(
-    basic_blocks: &mut IndexVec<BasicBlock, BasicBlockData<'_>>,
-    first_dead_block: usize,
-) {
-    // retain coverage info for dead blocks, so coverage reports will still
-    // report `0` executions for the uncovered code regions.
-    let mut dropped_coverage = Vec::new();
-    for dead_block in first_dead_block..basic_blocks.len() {
-        for statement in basic_blocks[BasicBlock::new(dead_block)].statements.iter() {
-            if let StatementKind::Coverage(coverage) = &statement.kind {
-                if let Some(code_region) = &coverage.code_region {
-                    dropped_coverage.push((statement.source_info, code_region.clone()));
-                }
-            }
-        }
-    }
-    for (source_info, code_region) in dropped_coverage {
-        basic_blocks[START_BLOCK].statements.push(Statement {
-            source_info,
-            kind: StatementKind::Coverage(box Coverage {
-                kind: CoverageKind::Unreachable,
-                code_region: Some(code_region),
-            }),
-        })
-    }
-}
 pub struct SimplifyLocals;
 
 impl<'tcx> MirPass<'tcx> for SimplifyLocals {
diff --git a/compiler/rustc_mir/src/transform/simplify_try.rs b/compiler/rustc_mir/src/transform/simplify_try.rs
index c9c4492062720..b42543c04eb3d 100644
--- a/compiler/rustc_mir/src/transform/simplify_try.rs
+++ b/compiler/rustc_mir/src/transform/simplify_try.rs
@@ -558,7 +558,7 @@ impl<'tcx> MirPass<'tcx> for SimplifyBranchSame {
 
         if did_remove_blocks {
             // We have dead blocks now, so remove those.
-            simplify::remove_dead_blocks(tcx, body);
+            simplify::remove_dead_blocks(body);
         }
     }
 }
diff --git a/compiler/rustc_mir/src/transform/unreachable_prop.rs b/compiler/rustc_mir/src/transform/unreachable_prop.rs
index e7fb6b4f6b4ad..658c6b6e9db20 100644
--- a/compiler/rustc_mir/src/transform/unreachable_prop.rs
+++ b/compiler/rustc_mir/src/transform/unreachable_prop.rs
@@ -60,7 +60,7 @@ impl MirPass<'_> for UnreachablePropagation {
         }
 
         if replaced {
-            simplify::remove_dead_blocks(tcx, body);
+            simplify::remove_dead_blocks(body);
         }
     }
 }
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.async2.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.async2.txt
index dc06a485a8fc1..322f5681b3fd9 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.async2.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.async2.txt
@@ -12,7 +12,6 @@
    12|      1|    if b {
    13|      1|        println!("non_async_func println in block");
    14|      1|    }
-                   ^0
    15|      1|}
    16|       |
    17|       |
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.conditions.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.conditions.txt
index 2d8a98a5d0c92..656a26597759d 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.conditions.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.conditions.txt
@@ -5,7 +5,6 @@
     5|      1|    if true {
     6|      1|        countdown = 10;
     7|      1|    }
-                   ^0
     8|       |
     9|       |    const B: u32 = 100;
    10|      1|    let x = if countdown > 7 {
@@ -25,7 +24,6 @@
    24|      1|    if true {
    25|      1|        countdown = 10;
    26|      1|    }
-                   ^0
    27|       |
    28|      1|    if countdown > 7 {
    29|      1|        countdown -= 4;
@@ -44,7 +42,6 @@
    41|      1|        if true {
    42|      1|            countdown = 10;
    43|      1|        }
-                       ^0
    44|       |
    45|      1|        if countdown > 7 {
    46|      1|            countdown -= 4;
@@ -57,14 +54,13 @@
    53|       |        } else {
    54|      0|            return;
    55|       |        }
-   56|      0|    }
-   57|       |
+   56|       |    } // Note: closing brace shows uncovered (vs. `0` for implicit else) because condition literal
+   57|       |      // `true` was const-evaluated. The compiler knows the `if` block will be executed.
    58|       |
    59|      1|    let mut countdown = 0;
    60|      1|    if true {
    61|      1|        countdown = 1;
    62|      1|    }
-                   ^0
    63|       |
    64|      1|    let z = if countdown > 7 {
                       ^0
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.doctest.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.doctest.txt
index 7ae0e978808e7..1b6bb9ff8891d 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.doctest.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.doctest.txt
@@ -9,7 +9,7 @@
     8|      1|//!     assert_eq!(1, 1);
     9|       |//! } else {
    10|       |//!     // this is not!
-   11|      0|//!     assert_eq!(1, 2);
+   11|       |//!     assert_eq!(1, 2);
    12|       |//! }
    13|      1|//! ```
    14|       |//!
@@ -84,7 +84,7 @@
    74|      1|    if true {
    75|      1|        assert_eq!(1, 1);
    76|       |    } else {
-   77|      0|        assert_eq!(1, 2);
+   77|       |        assert_eq!(1, 2);
    78|       |    }
    79|      1|}
    80|       |
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.drop_trait.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.drop_trait.txt
index fe6a9e93cbf71..fab5be41901c9 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.drop_trait.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.drop_trait.txt
@@ -19,11 +19,11 @@
    19|      1|    if true {
    20|      1|        println!("Exiting with error...");
    21|      1|        return Err(1);
-   22|      0|    }
-   23|      0|
-   24|      0|    let _ = Firework { strength: 1000 };
-   25|      0|
-   26|      0|    Ok(())
+   22|       |    }
+   23|       |
+   24|       |    let _ = Firework { strength: 1000 };
+   25|       |
+   26|       |    Ok(())
    27|      1|}
    28|       |
    29|       |// Expected program output:
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.generics.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.generics.txt
index 8e8bc0fd18943..7b38ffb87cba8 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.generics.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.generics.txt
@@ -52,15 +52,15 @@
    30|      1|    if true {
    31|      1|        println!("Exiting with error...");
    32|      1|        return Err(1);
-   33|      0|    }
-   34|      0|
-   35|      0|
-   36|      0|
-   37|      0|
-   38|      0|
-   39|      0|    let _ = Firework { strength: 1000 };
-   40|      0|
-   41|      0|    Ok(())
+   33|       |    } // The remaining lines below have no coverage because `if true` (with the constant literal
+   34|       |      // `true`) is guaranteed to execute the `then` block, which is also guaranteed to `return`.
+   35|       |      // Thankfully, in the normal case, conditions are not guaranteed ahead of time, and as shown
+   36|       |      // in other tests, the lines below would have coverage (which would show they had `0`
+   37|       |      // executions, assuming the condition still evaluated to `true`).
+   38|       |
+   39|       |    let _ = Firework { strength: 1000 };
+   40|       |
+   41|       |    Ok(())
    42|      1|}
    43|       |
    44|       |// Expected program output:
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.loops_branches.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.loops_branches.txt
index 5d572db7cc60d..81d5c7d90346d 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.loops_branches.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.loops_branches.txt
@@ -9,23 +9,23 @@
     9|      1|    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
    10|      1|        if true {
    11|      1|            if false {
-   12|      0|                while true {
-   13|      0|                }
+   12|       |                while true {
+   13|       |                }
    14|      1|            }
-   15|      1|            write!(f, "cool")?;
-                                           ^0
-   16|      0|        } else {
-   17|      0|        }
+   15|      1|            write!(f, "error")?;
+                                            ^0
+   16|       |        } else {
+   17|       |        }
    18|       |
    19|     10|        for i in 0..10 {
    20|     10|            if true {
    21|     10|                if false {
-   22|      0|                    while true {}
+   22|       |                    while true {}
    23|     10|                }
-   24|     10|                write!(f, "cool")?;
-                                               ^0
-   25|      0|            } else {
-   26|      0|            }
+   24|     10|                write!(f, "error")?;
+                                                ^0
+   25|       |            } else {
+   26|       |            }
    27|       |        }
    28|      1|        Ok(())
    29|      1|    }
@@ -36,21 +36,21 @@
    34|       |impl std::fmt::Display for DisplayTest {
    35|      1|    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
    36|      1|        if false {
-   37|      0|        } else {
+   37|       |        } else {
    38|      1|            if false {
-   39|      0|                while true {}
+   39|       |                while true {}
    40|      1|            }
-   41|      1|            write!(f, "cool")?;
-                                           ^0
+   41|      1|            write!(f, "error")?;
+                                            ^0
    42|       |        }
    43|     10|        for i in 0..10 {
    44|     10|            if false {
-   45|      0|            } else {
+   45|       |            } else {
    46|     10|                if false {
-   47|      0|                    while true {}
+   47|       |                    while true {}
    48|     10|                }
-   49|     10|                write!(f, "cool")?;
-                                               ^0
+   49|     10|                write!(f, "error")?;
+                                                ^0
    50|       |            }
    51|       |        }
    52|      1|        Ok(())
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.tight_inf_loop.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.tight_inf_loop.txt
index 2d4c57f451a2d..5adeef7d0850b 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.tight_inf_loop.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.tight_inf_loop.txt
@@ -1,6 +1,6 @@
     1|      1|fn main() {
     2|      1|    if false {
-    3|      0|        loop {}
+    3|       |        loop {}
     4|      1|    }
     5|      1|}
 
diff --git a/src/test/run-make-fulldeps/coverage/conditions.rs b/src/test/run-make-fulldeps/coverage/conditions.rs
index 057599d1b471a..8a2a0b53e5862 100644
--- a/src/test/run-make-fulldeps/coverage/conditions.rs
+++ b/src/test/run-make-fulldeps/coverage/conditions.rs
@@ -53,8 +53,8 @@ fn main() {
         } else {
             return;
         }
-    }
-
+    } // Note: closing brace shows uncovered (vs. `0` for implicit else) because condition literal
+      // `true` was const-evaluated. The compiler knows the `if` block will be executed.
 
     let mut countdown = 0;
     if true {
diff --git a/src/test/run-make-fulldeps/coverage/generics.rs b/src/test/run-make-fulldeps/coverage/generics.rs
index 18b38868496d4..cbeda35d3b8cf 100644
--- a/src/test/run-make-fulldeps/coverage/generics.rs
+++ b/src/test/run-make-fulldeps/coverage/generics.rs
@@ -30,11 +30,11 @@ fn main() -> Result<(),u8> {
     if true {
         println!("Exiting with error...");
         return Err(1);
-    }
-
-
-
-
+    } // The remaining lines below have no coverage because `if true` (with the constant literal
+      // `true`) is guaranteed to execute the `then` block, which is also guaranteed to `return`.
+      // Thankfully, in the normal case, conditions are not guaranteed ahead of time, and as shown
+      // in other tests, the lines below would have coverage (which would show they had `0`
+      // executions, assuming the condition still evaluated to `true`).
 
     let _ = Firework { strength: 1000 };
 
diff --git a/src/test/run-make-fulldeps/coverage/loops_branches.rs b/src/test/run-make-fulldeps/coverage/loops_branches.rs
index 7116ce47f4b9d..4d9bbad3367f6 100644
--- a/src/test/run-make-fulldeps/coverage/loops_branches.rs
+++ b/src/test/run-make-fulldeps/coverage/loops_branches.rs
@@ -12,7 +12,7 @@ impl std::fmt::Debug for DebugTest {
                 while true {
                 }
             }
-            write!(f, "cool")?;
+            write!(f, "error")?;
         } else {
         }
 
@@ -21,7 +21,7 @@ impl std::fmt::Debug for DebugTest {
                 if false {
                     while true {}
                 }
-                write!(f, "cool")?;
+                write!(f, "error")?;
             } else {
             }
         }
@@ -38,7 +38,7 @@ impl std::fmt::Display for DisplayTest {
             if false {
                 while true {}
             }
-            write!(f, "cool")?;
+            write!(f, "error")?;
         }
         for i in 0..10 {
             if false {
@@ -46,7 +46,7 @@ impl std::fmt::Display for DisplayTest {
                 if false {
                     while true {}
                 }
-                write!(f, "cool")?;
+                write!(f, "error")?;
             }
         }
         Ok(())

From 69a4ae2030c7b0ad9e228d3021dae128a443bb19 Mon Sep 17 00:00:00 2001
From: Fabian Wolff <fabi.wolff@arcor.de>
Date: Tue, 11 May 2021 21:51:58 +0200
Subject: [PATCH 26/26] Add explanatory comment to the issue-84976.rs test case

---
 src/test/ui/mismatched_types/issue-84976.rs     | 4 ++++
 src/test/ui/mismatched_types/issue-84976.stderr | 8 ++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/test/ui/mismatched_types/issue-84976.rs b/src/test/ui/mismatched_types/issue-84976.rs
index b4ea872979ada..db6fe0b45dcd3 100644
--- a/src/test/ui/mismatched_types/issue-84976.rs
+++ b/src/test/ui/mismatched_types/issue-84976.rs
@@ -1,3 +1,7 @@
+/* Checks whether primitive type names are formatted correctly in the
+ * error messages about mismatched types (#84976).
+ */
+
 fn foo(length: &u32) -> i32 {
     0
 }
diff --git a/src/test/ui/mismatched_types/issue-84976.stderr b/src/test/ui/mismatched_types/issue-84976.stderr
index b9f6954dbbb25..0c27e17294131 100644
--- a/src/test/ui/mismatched_types/issue-84976.stderr
+++ b/src/test/ui/mismatched_types/issue-84976.stderr
@@ -1,23 +1,23 @@
 error[E0308]: mismatched types
-  --> $DIR/issue-84976.rs:11:16
+  --> $DIR/issue-84976.rs:15:16
    |
 LL |     length = { foo(&length) };
    |                ^^^^^^^^^^^^ expected `u32`, found `i32`
 
 error[E0308]: mismatched types
-  --> $DIR/issue-84976.rs:13:14
+  --> $DIR/issue-84976.rs:17:14
    |
 LL |     length = foo(&length);
    |              ^^^^^^^^^^^^ expected `u32`, found `i32`
 
 error[E0308]: mismatched types
-  --> $DIR/issue-84976.rs:17:22
+  --> $DIR/issue-84976.rs:21:22
    |
 LL |     float_length = { bar(&float_length) };
    |                      ^^^^^^^^^^^^^^^^^^ expected `f32`, found `f64`
 
 error[E0308]: mismatched types
-  --> $DIR/issue-84976.rs:19:20
+  --> $DIR/issue-84976.rs:23:20
    |
 LL |     float_length = bar(&float_length);
    |                    ^^^^^^^^^^^^^^^^^^ expected `f32`, found `f64`