Auto merge of #111848 - Dylan-DPC:rollup-7jqydzg, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #111501 (MIR drive-by cleanups)
 - #111609 (Mark internal functions and traits unsafe to reflect preconditions)
 - #111612 (Give better error when collecting into `&[T]`)
 - #111756 (Rename `{drop,forget}_{copy,ref}` lints to more consistent naming)
 - #111843 (move lcnr to only review types stuff)
 - #111844 (Migrate GUI colors test to original CSS color format)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_lint/messages.ftl

@@ -521,18 +521,18 @@ lint_opaque_hidden_inferred_bound = opaque type `{$ty}` does not satisfy its ass
 
 lint_opaque_hidden_inferred_bound_sugg = add this bound
 
-lint_drop_ref = calls to `std::mem::drop` with a reference instead of an owned value does nothing
+lint_dropping_references = calls to `std::mem::drop` with a reference instead of an owned value does nothing
     .label = argument has type `{$arg_ty}`
     .note = use `let _ = ...` to ignore the expression or result
 
-lint_drop_copy = calls to `std::mem::drop` with a value that implements `Copy` does nothing
+lint_dropping_copy_types = calls to `std::mem::drop` with a value that implements `Copy` does nothing
     .label = argument has type `{$arg_ty}`
     .note = use `let _ = ...` to ignore the expression or result
 
-lint_forget_ref = calls to `std::mem::forget` with a reference instead of an owned value does nothing
+lint_forgetting_references = calls to `std::mem::forget` with a reference instead of an owned value does nothing
     .label = argument has type `{$arg_ty}`
     .note = use `let _ = ...` to ignore the expression or result
 
-lint_forget_copy = calls to `std::mem::forget` with a value that implements `Copy` does nothing
+lint_forgetting_copy_types = calls to `std::mem::forget` with a value that implements `Copy` does nothing
     .label = argument has type `{$arg_ty}`
     .note = use `let _ = ...` to ignore the expression or result

compiler/rustc_lint/src/drop_forget_useless.rs

@@ -7,7 +7,7 @@ use crate::{
 };
 
 declare_lint! {
-    /// The `drop_ref` lint checks for calls to `std::mem::drop` with a reference
+    /// The `dropping_references` lint checks for calls to `std::mem::drop` with a reference
     /// instead of an owned value.
     ///
     /// ### Example
@@ -29,13 +29,13 @@ declare_lint! {
     /// reference itself, which is a no-op. It will not call the `drop` method (from
     /// the `Drop` trait implementation) on the underlying referenced value, which
     /// is likely what was intended.
-    pub DROP_REF,
+    pub DROPPING_REFERENCES,
     Warn,
     "calls to `std::mem::drop` with a reference instead of an owned value"
 }
 
 declare_lint! {
-    /// The `forget_ref` lint checks for calls to `std::mem::forget` with a reference
+    /// The `forgetting_references` lint checks for calls to `std::mem::forget` with a reference
     /// instead of an owned value.
     ///
     /// ### Example
@@ -52,13 +52,13 @@ declare_lint! {
     /// Calling `forget` on a reference will only forget the
     /// reference itself, which is a no-op. It will not forget the underlying
     /// referenced value, which is likely what was intended.
-    pub FORGET_REF,
+    pub FORGETTING_REFERENCES,
     Warn,
     "calls to `std::mem::forget` with a reference instead of an owned value"
 }
 
 declare_lint! {
-    /// The `drop_copy` lint checks for calls to `std::mem::drop` with a value
+    /// The `dropping_copy_types` lint checks for calls to `std::mem::drop` with a value
     /// that derives the Copy trait.
     ///
     /// ### Example
@@ -76,13 +76,13 @@ declare_lint! {
     /// Calling `std::mem::drop` [does nothing for types that
     /// implement Copy](https://doc.rust-lang.org/std/mem/fn.drop.html), since the
     /// value will be copied and moved into the function on invocation.
-    pub DROP_COPY,
+    pub DROPPING_COPY_TYPES,
     Warn,
     "calls to `std::mem::drop` with a value that implements Copy"
 }
 
 declare_lint! {
-    /// The `forget_copy` lint checks for calls to `std::mem::forget` with a value
+    /// The `forgetting_copy_types` lint checks for calls to `std::mem::forget` with a value
     /// that derives the Copy trait.
     ///
     /// ### Example
@@ -104,12 +104,12 @@ declare_lint! {
     /// An alternative, but also valid, explanation is that Copy types do not
     /// implement the Drop trait, which means they have no destructors. Without a
     /// destructor, there is nothing for `std::mem::forget` to ignore.
-    pub FORGET_COPY,
+    pub FORGETTING_COPY_TYPES,
     Warn,
     "calls to `std::mem::forget` with a value that implements Copy"
 }
 
-declare_lint_pass!(DropForgetUseless => [DROP_REF, FORGET_REF, DROP_COPY, FORGET_COPY]);
+declare_lint_pass!(DropForgetUseless => [DROPPING_REFERENCES, FORGETTING_REFERENCES, DROPPING_COPY_TYPES, FORGETTING_COPY_TYPES]);
 
 impl<'tcx> LateLintPass<'tcx> for DropForgetUseless {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
@@ -123,16 +123,16 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetUseless {
             let drop_is_single_call_in_arm = is_single_call_in_arm(cx, arg, expr);
             match fn_name {
                 sym::mem_drop if arg_ty.is_ref() && !drop_is_single_call_in_arm => {
-                    cx.emit_spanned_lint(DROP_REF, expr.span, DropRefDiag { arg_ty, label: arg.span });
+                    cx.emit_spanned_lint(DROPPING_REFERENCES, expr.span, DropRefDiag { arg_ty, label: arg.span });
                 },
                 sym::mem_forget if arg_ty.is_ref() => {
-                    cx.emit_spanned_lint(FORGET_REF, expr.span, ForgetRefDiag { arg_ty, label: arg.span });
+                    cx.emit_spanned_lint(FORGETTING_REFERENCES, expr.span, ForgetRefDiag { arg_ty, label: arg.span });
                 },
                 sym::mem_drop if is_copy && !drop_is_single_call_in_arm => {
-                    cx.emit_spanned_lint(DROP_COPY, expr.span, DropCopyDiag { arg_ty, label: arg.span });
+                    cx.emit_spanned_lint(DROPPING_COPY_TYPES, expr.span, DropCopyDiag { arg_ty, label: arg.span });
                 }
                 sym::mem_forget if is_copy => {
-                    cx.emit_spanned_lint(FORGET_COPY, expr.span, ForgetCopyDiag { arg_ty, label: arg.span });
+                    cx.emit_spanned_lint(FORGETTING_COPY_TYPES, expr.span, ForgetCopyDiag { arg_ty, label: arg.span });
                 }
                 _ => return,
             };

compiler/rustc_lint/src/lints.rs

@@ -662,9 +662,9 @@ pub struct ForLoopsOverFalliblesSuggestion<'a> {
     pub end_span: Span,
 }
 
-// drop_ref.rs
+// drop_forget_useless.rs
 #[derive(LintDiagnostic)]
-#[diag(lint_drop_ref)]
+#[diag(lint_dropping_references)]
 #[note]
 pub struct DropRefDiag<'a> {
     pub arg_ty: Ty<'a>,
@@ -673,7 +673,7 @@ pub struct DropRefDiag<'a> {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_drop_copy)]
+#[diag(lint_dropping_copy_types)]
 #[note]
 pub struct DropCopyDiag<'a> {
     pub arg_ty: Ty<'a>,
@@ -682,7 +682,7 @@ pub struct DropCopyDiag<'a> {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_forget_ref)]
+#[diag(lint_forgetting_references)]
 #[note]
 pub struct ForgetRefDiag<'a> {
     pub arg_ty: Ty<'a>,
@@ -691,7 +691,7 @@ pub struct ForgetRefDiag<'a> {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_forget_copy)]
+#[diag(lint_forgetting_copy_types)]
 #[note]
 pub struct ForgetCopyDiag<'a> {
     pub arg_ty: Ty<'a>,

compiler/rustc_middle/src/mir/syntax.rs

@@ -749,6 +749,29 @@ pub enum TerminatorKind<'tcx> {
     },
 }
 
+impl TerminatorKind<'_> {
+    /// Returns a simple string representation of a `TerminatorKind` variant, independent of any
+    /// values it might hold (e.g. `TerminatorKind::Call` always returns `"Call"`).
+    pub const fn name(&self) -> &'static str {
+        match self {
+            TerminatorKind::Goto { .. } => "Goto",
+            TerminatorKind::SwitchInt { .. } => "SwitchInt",
+            TerminatorKind::Resume => "Resume",
+            TerminatorKind::Terminate => "Terminate",
+            TerminatorKind::Return => "Return",
+            TerminatorKind::Unreachable => "Unreachable",
+            TerminatorKind::Drop { .. } => "Drop",
+            TerminatorKind::Call { .. } => "Call",
+            TerminatorKind::Assert { .. } => "Assert",
+            TerminatorKind::Yield { .. } => "Yield",
+            TerminatorKind::GeneratorDrop => "GeneratorDrop",
+            TerminatorKind::FalseEdge { .. } => "FalseEdge",
+            TerminatorKind::FalseUnwind { .. } => "FalseUnwind",
+            TerminatorKind::InlineAsm { .. } => "InlineAsm",
+        }
+    }
+}
+
 /// Action to be taken when a stack unwind happens.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]

compiler/rustc_mir_build/src/build/scope.rs

@@ -644,24 +644,27 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         };
 
-        if let Some(destination) = destination {
-            if let Some(value) = value {
+        match (destination, value) {
+            (Some(destination), Some(value)) => {
                 debug!("stmt_expr Break val block_context.push(SubExpr)");
                 self.block_context.push(BlockFrame::SubExpr);
                 unpack!(block = self.expr_into_dest(destination, block, value));
                 self.block_context.pop();
-            } else {
+            }
+            (Some(destination), None) => {
                 self.cfg.push_assign_unit(block, source_info, destination, self.tcx)
             }
-        } else {
-            assert!(value.is_none(), "`return` and `break` should have a destination");
-            if self.tcx.sess.instrument_coverage() {
+            (None, Some(_)) => {
+                panic!("`return`, `become` and `break` with value and must have a destination")
+            }
+            (None, None) if self.tcx.sess.instrument_coverage() => {
                 // Unlike `break` and `return`, which push an `Assign` statement to MIR, from which
                 // a Coverage code region can be generated, `continue` needs no `Assign`; but
                 // without one, the `InstrumentCoverage` MIR pass cannot generate a code region for
                 // `continue`. Coverage will be missing unless we add a dummy `Assign` to MIR.
                 self.add_dummy_assignment(span, block, source_info);
             }
+            (None, None) => {}
         }
 
         let region_scope = self.scopes.breakable_scopes[break_index].region_scope;
@@ -671,12 +674,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         } else {
             self.scopes.breakable_scopes[break_index].continue_drops.as_mut().unwrap()
         };
-        let mut drop_idx = ROOT_NODE;
-        for scope in &self.scopes.scopes[scope_index + 1..] {
-            for drop in &scope.drops {
-                drop_idx = drops.add_drop(*drop, drop_idx);
-            }
-        }
+
+        let drop_idx = self.scopes.scopes[scope_index + 1..]
+            .iter()
+            .flat_map(|scope| &scope.drops)
+            .fold(ROOT_NODE, |drop_idx, &drop| drops.add_drop(drop, drop_idx));
+
         drops.add_entry(block, drop_idx);
 
         // `build_drop_trees` doesn't have access to our source_info, so we

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -130,6 +130,7 @@ impl<'tcx> Cx<'tcx> {
                 ExprKind::Pointer { cast: PointerCast::Unsize, source: self.thir.exprs.push(expr) }
             }
             Adjust::Pointer(cast) => ExprKind::Pointer { cast, source: self.thir.exprs.push(expr) },
+            Adjust::NeverToAny if adjustment.target.is_never() => return expr,
             Adjust::NeverToAny => ExprKind::NeverToAny { source: self.thir.exprs.push(expr) },
             Adjust::Deref(None) => {
                 adjust_span(&mut expr);

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -118,7 +118,7 @@ use rustc_middle::mir::spanview::{self, SpanViewable};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::mir::coverage::*;
-use rustc_middle::mir::{self, BasicBlock, TerminatorKind};
+use rustc_middle::mir::{self, BasicBlock};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::Span;
 
@@ -796,36 +796,15 @@ fn bcb_to_string_sections<'tcx>(
     }
     let non_term_blocks = bcb_data.basic_blocks[0..len - 1]
         .iter()
-        .map(|&bb| format!("{:?}: {}", bb, term_type(&mir_body[bb].terminator().kind)))
+        .map(|&bb| format!("{:?}: {}", bb, mir_body[bb].terminator().kind.name()))
         .collect::<Vec<_>>();
     if non_term_blocks.len() > 0 {
         sections.push(non_term_blocks.join("\n"));
     }
     sections.push(format!(
         "{:?}: {}",
         bcb_data.basic_blocks.last().unwrap(),
-        term_type(&bcb_data.terminator(mir_body).kind)
+        bcb_data.terminator(mir_body).kind.name(),
     ));
     sections
 }
-
-/// Returns a simple string representation of a `TerminatorKind` variant, independent of any
-/// values it might hold.
-pub(super) fn term_type(kind: &TerminatorKind<'_>) -> &'static str {
-    match kind {
-        TerminatorKind::Goto { .. } => "Goto",
-        TerminatorKind::SwitchInt { .. } => "SwitchInt",
-        TerminatorKind::Resume => "Resume",
-        TerminatorKind::Terminate => "Terminate",
-        TerminatorKind::Return => "Return",
-        TerminatorKind::Unreachable => "Unreachable",
-        TerminatorKind::Drop { .. } => "Drop",
-        TerminatorKind::Call { .. } => "Call",
-        TerminatorKind::Assert { .. } => "Assert",
-        TerminatorKind::Yield { .. } => "Yield",
-        TerminatorKind::GeneratorDrop => "GeneratorDrop",
-        TerminatorKind::FalseEdge { .. } => "FalseEdge",
-        TerminatorKind::FalseUnwind { .. } => "FalseUnwind",
-        TerminatorKind::InlineAsm { .. } => "InlineAsm",
-    }
-}

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -1,4 +1,3 @@
-use super::debug::term_type;
 use super::graph::{BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB};
 
 use itertools::Itertools;
@@ -40,7 +39,7 @@ impl CoverageStatement {
                     "{}: @{}.{}: {:?}",
                     source_range_no_file(tcx, span),
                     bb.index(),
-                    term_type(&term.kind),
+                    term.kind.name(),
                     term.kind
                 )
             }

compiler/rustc_mir_transform/src/coverage/tests.rs

@@ -25,7 +25,6 @@
 //! to: `rustc_span::create_default_session_globals_then(|| { test_here(); })`.
 
 use super::counters;
-use super::debug;
 use super::graph;
 use super::spans;
 
@@ -188,12 +187,12 @@ fn debug_basic_blocks(mir_body: &Body<'_>) -> String {
                     | TerminatorKind::Goto { target }
                     | TerminatorKind::InlineAsm { destination: Some(target), .. }
                     | TerminatorKind::Yield { resume: target, .. } => {
-                        format!("{}{:?}:{} -> {:?}", sp, bb, debug::term_type(kind), target)
+                        format!("{}{:?}:{} -> {:?}", sp, bb, kind.name(), target)
                     }
                     TerminatorKind::SwitchInt { targets, .. } => {
-                        format!("{}{:?}:{} -> {:?}", sp, bb, debug::term_type(kind), targets)
+                        format!("{}{:?}:{} -> {:?}", sp, bb, kind.name(), targets)
                     }
-                    _ => format!("{}{:?}:{}", sp, bb, debug::term_type(kind)),
+                    _ => format!("{}{:?}:{}", sp, bb, kind.name()),
                 }
             })
             .collect::<Vec<_>>()
@@ -215,7 +214,7 @@ fn print_mir_graphviz(name: &str, mir_body: &Body<'_>) {
                         "    {:?} [label=\"{:?}: {}\"];\n{}",
                         bb,
                         bb,
-                        debug::term_type(&data.terminator().kind),
+                        data.terminator().kind.name(),
                         mir_body
                             .basic_blocks
                             .successors(bb)
@@ -244,7 +243,7 @@ fn print_coverage_graphviz(
                         "    {:?} [label=\"{:?}: {}\"];\n{}",
                         bcb,
                         bcb,
-                        debug::term_type(&bcb_data.terminator(mir_body).kind),
+                        bcb_data.terminator(mir_body).kind.name(),
                         basic_coverage_blocks
                             .successors(bcb)
                             .map(|successor| { format!("    {:?} -> {:?};", bcb, successor) })

compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs

@@ -306,6 +306,14 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     }
                 }
             }
+
+            // `&[{integral}]` - `FromIterator` needs that.
+            if let ty::Ref(_, ref_ty, rustc_ast::Mutability::Not) = self_ty.kind()
+                && let ty::Slice(sty) = ref_ty.kind()
+                && sty.is_integral()
+            {
+                flags.push((sym::_Self, Some("&[{integral}]".to_owned())));
+            }
         });
 
         if let Ok(Some(command)) = OnUnimplementedDirective::of_item(self.tcx, def_id) {