Auto merge of #81355 - jonas-schievink:rollup-vpaadij, r=jonas-schievink

Rollup of 14 pull requests

Successful merges:

 - #75180 (Implement Error for &(impl Error))
 - #78578 (Permit mutable references in all const contexts)
 - #79174 (Make std::future a re-export of core::future)
 - #79884 (Replace magic numbers with existing constants)
 - #80855 (Expand assert!(expr, args..) to include $crate for hygiene on 2021.)
 - #80933 (Fix sysroot option not being honored across rustc)
 - #81259 (Replace version_check dependency with own version parsing code)
 - #81264 (Add unstable option to control doctest run directory)
 - #81279 (Small refactor in typeck)
 - #81297 (Don't provide backend_optimization_level query for extern crates)
 - #81302 (Fix rendering of stabilization version for trait implementors)
 - #81310 (Do not mark unit variants as used when in path pattern)
 - #81320 (Make bad shlex parsing a pretty error)
 - #81338 (Clean up `dominators_given_rpo`)

Failed merges:

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

Cargo.lock

@@ -3568,7 +3568,6 @@ dependencies = [
  "rustc_serialize",
  "rustc_session",
  "rustc_span",
- "version_check",
 ]
 
 [[package]]

compiler/rustc_attr/Cargo.toml

@@ -18,4 +18,3 @@ rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_session = { path = "../rustc_session" }
 rustc_ast = { path = "../rustc_ast" }
-version_check = "0.9"

compiler/rustc_attr/src/builtin.rs

@@ -10,7 +10,6 @@ use rustc_session::Session;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{symbol::sym, symbol::Symbol, Span};
 use std::num::NonZeroU32;
-use version_check::Version;
 
 pub fn is_builtin_attr(attr: &Attribute) -> bool {
     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
@@ -526,6 +525,26 @@ fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &F
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+struct Version {
+    major: u16,
+    minor: u16,
+    patch: u16,
+}
+
+fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
+    let mut components = s.split('-');
+    let d = components.next()?;
+    if !allow_appendix && components.next().is_some() {
+        return None;
+    }
+    let mut digits = d.splitn(3, '.');
+    let major = digits.next()?.parse().ok()?;
+    let minor = digits.next()?.parse().ok()?;
+    let patch = digits.next().unwrap_or("0").parse().ok()?;
+    Some(Version { major, minor, patch })
+}
+
 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 /// evaluate individual items.
 pub fn eval_condition(
@@ -555,16 +574,21 @@ pub fn eval_condition(
                     return false;
                 }
             };
-            let min_version = match Version::parse(&min_version.as_str()) {
+            let min_version = match parse_version(&min_version.as_str(), false) {
                 Some(ver) => ver,
                 None => {
-                    sess.span_diagnostic.struct_span_err(*span, "invalid version literal").emit();
+                    sess.span_diagnostic
+                        .struct_span_warn(
+                            *span,
+                            "unknown version literal format, assuming it refers to a future version",
+                        )
+                        .emit();
                     return false;
                 }
             };
             let channel = env!("CFG_RELEASE_CHANNEL");
             let nightly = channel == "nightly" || channel == "dev";
-            let rustc_version = Version::parse(env!("CFG_RELEASE")).unwrap();
+            let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 
             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-625474439 for details
             if nightly { rustc_version > min_version } else { rustc_version >= min_version }

compiler/rustc_builtin_macros/src/assert.rs

@@ -12,27 +12,43 @@ use rustc_span::{Span, DUMMY_SP};
 
 pub fn expand_assert<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
-    sp: Span,
+    span: Span,
     tts: TokenStream,
 ) -> Box<dyn MacResult + 'cx> {
-    let Assert { cond_expr, custom_message } = match parse_assert(cx, sp, tts) {
+    let Assert { cond_expr, custom_message } = match parse_assert(cx, span, tts) {
         Ok(assert) => assert,
         Err(mut err) => {
             err.emit();
-            return DummyResult::any(sp);
+            return DummyResult::any(span);
         }
     };
 
     // `core::panic` and `std::panic` are different macros, so we use call-site
     // context to pick up whichever is currently in scope.
-    let sp = cx.with_call_site_ctxt(sp);
+    let sp = cx.with_call_site_ctxt(span);
 
     let panic_call = if let Some(tokens) = custom_message {
+        let path = if span.rust_2021() {
+            // On edition 2021, we always call `$crate::panic!()`.
+            Path {
+                span: sp,
+                segments: cx
+                    .std_path(&[sym::panic])
+                    .into_iter()
+                    .map(|ident| PathSegment::from_ident(ident))
+                    .collect(),
+                tokens: None,
+            }
+        } else {
+            // Before edition 2021, we call `panic!()` unqualified,
+            // such that it calls either `std::panic!()` or `core::panic!()`.
+            Path::from_ident(Ident::new(sym::panic, sp))
+        };
         // Pass the custom message to panic!().
         cx.expr(
             sp,
             ExprKind::MacCall(MacCall {
-                path: Path::from_ident(Ident::new(sym::panic, sp)),
+                path,
                 args: P(MacArgs::Delimited(
                     DelimSpan::from_single(sp),
                     MacDelimiter::Parenthesis,

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -885,9 +885,22 @@ fn link_sanitizers(sess: &Session, crate_type: CrateType, linker: &mut dyn Linke
 }
 
 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
-    let default_sysroot = filesearch::get_or_default_sysroot();
-    let default_tlib =
-        filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.triple());
+    fn find_sanitizer_runtime(sess: &Session, filename: &String) -> PathBuf {
+        let session_tlib =
+            filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
+        let path = session_tlib.join(&filename);
+        if path.exists() {
+            return session_tlib;
+        } else {
+            let default_sysroot = filesearch::get_or_default_sysroot();
+            let default_tlib = filesearch::make_target_lib_path(
+                &default_sysroot,
+                sess.opts.target_triple.triple(),
+            );
+            return default_tlib;
+        }
+    }
+
     let channel = option_env!("CFG_RELEASE_CHANNEL")
         .map(|channel| format!("-{}", channel))
         .unwrap_or_default();
@@ -898,18 +911,19 @@ fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
             // LLVM will link to `@rpath/*.dylib`, so we need to specify an
             // rpath to the library as well (the rpath should be absolute, see
             // PR #41352 for details).
-            let libname = format!("rustc{}_rt.{}", channel, name);
-            let rpath = default_tlib.to_str().expect("non-utf8 component in path");
+            let filename = format!("rustc{}_rt.{}", channel, name);
+            let path = find_sanitizer_runtime(&sess, &filename);
+            let rpath = path.to_str().expect("non-utf8 component in path");
             linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
-            linker.link_dylib(Symbol::intern(&libname));
+            linker.link_dylib(Symbol::intern(&filename));
         }
         "aarch64-fuchsia"
         | "aarch64-unknown-linux-gnu"
         | "x86_64-fuchsia"
         | "x86_64-unknown-freebsd"
         | "x86_64-unknown-linux-gnu" => {
             let filename = format!("librustc{}_rt.{}.a", channel, name);
-            let path = default_tlib.join(&filename);
+            let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
             linker.link_whole_rlib(&path);
         }
         _ => {}

compiler/rustc_codegen_ssa/src/base.rs

@@ -783,7 +783,7 @@ impl CrateInfo {
     }
 }
 
-pub fn provide_both(providers: &mut Providers) {
+pub fn provide(providers: &mut Providers) {
     providers.backend_optimization_level = |tcx, cratenum| {
         let for_speed = match tcx.sess.opts.optimize {
             // If globally no optimisation is done, #[optimize] has no effect.

compiler/rustc_codegen_ssa/src/lib.rs

@@ -160,13 +160,12 @@ pub struct CodegenResults {
 
 pub fn provide(providers: &mut Providers) {
     crate::back::symbol_export::provide(providers);
-    crate::base::provide_both(providers);
+    crate::base::provide(providers);
     crate::target_features::provide(providers);
 }
 
 pub fn provide_extern(providers: &mut Providers) {
     crate::back::symbol_export::provide_extern(providers);
-    crate::base::provide_both(providers);
 }
 
 /// Checks if the given filename ends with the `.rcgu.o` extension that `rustc`

compiler/rustc_data_structures/src/graph/dominators/mod.rs

@@ -8,7 +8,6 @@
 use super::iterate::reverse_post_order;
 use super::ControlFlowGraph;
 use rustc_index::vec::{Idx, IndexVec};
-use std::borrow::BorrowMut;
 use std::cmp::Ordering;
 
 #[cfg(test)]
@@ -20,22 +19,17 @@ pub fn dominators<G: ControlFlowGraph>(graph: G) -> Dominators<G::Node> {
     dominators_given_rpo(graph, &rpo)
 }
 
-fn dominators_given_rpo<G: ControlFlowGraph + BorrowMut<G>>(
-    mut graph: G,
-    rpo: &[G::Node],
-) -> Dominators<G::Node> {
-    let start_node = graph.borrow().start_node();
+fn dominators_given_rpo<G: ControlFlowGraph>(graph: G, rpo: &[G::Node]) -> Dominators<G::Node> {
+    let start_node = graph.start_node();
     assert_eq!(rpo[0], start_node);
 
     // compute the post order index (rank) for each node
-    let mut post_order_rank: IndexVec<G::Node, usize> =
-        (0..graph.borrow().num_nodes()).map(|_| 0).collect();
+    let mut post_order_rank = IndexVec::from_elem_n(0, graph.num_nodes());
     for (index, node) in rpo.iter().rev().cloned().enumerate() {
         post_order_rank[node] = index;
     }
 
-    let mut immediate_dominators: IndexVec<G::Node, Option<G::Node>> =
-        (0..graph.borrow().num_nodes()).map(|_| None).collect();
+    let mut immediate_dominators = IndexVec::from_elem_n(None, graph.num_nodes());
     immediate_dominators[start_node] = Some(start_node);
 
     let mut changed = true;
@@ -44,7 +38,7 @@ fn dominators_given_rpo<G: ControlFlowGraph + BorrowMut<G>>(
 
         for &node in &rpo[1..] {
             let mut new_idom = None;
-            for pred in graph.borrow_mut().predecessors(node) {
+            for pred in graph.predecessors(node) {
                 if immediate_dominators[pred].is_some() {
                     // (*) dominators for `pred` have been calculated
                     new_idom = Some(if let Some(new_idom) = new_idom {

compiler/rustc_mir/src/transform/check_consts/ops.rs

@@ -268,16 +268,20 @@ impl NonConstOp for CellBorrow {
 }
 
 #[derive(Debug)]
+/// This op is for `&mut` borrows in the trailing expression of a constant
+/// which uses the "enclosing scopes rule" to leak its locals into anonymous
+/// static or const items.
 pub struct MutBorrow(pub hir::BorrowKind);
 
 impl NonConstOp for MutBorrow {
-    fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status {
-        // Forbid everywhere except in const fn with a feature gate
-        if ccx.const_kind() == hir::ConstContext::ConstFn {
-            Status::Unstable(sym::const_mut_refs)
-        } else {
-            Status::Forbidden
-        }
+    fn status_in_item(&self, _ccx: &ConstCx<'_, '_>) -> Status {
+        Status::Forbidden
+    }
+
+    fn importance(&self) -> DiagnosticImportance {
+        // If there were primary errors (like non-const function calls), do not emit further
+        // errors about mutable references.
+        DiagnosticImportance::Secondary
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
@@ -286,25 +290,15 @@ impl NonConstOp for MutBorrow {
             hir::BorrowKind::Ref => "",
         };
 
-        let mut err = if ccx.const_kind() == hir::ConstContext::ConstFn {
-            feature_err(
-                &ccx.tcx.sess.parse_sess,
-                sym::const_mut_refs,
-                span,
-                &format!("{}mutable references are not allowed in {}s", raw, ccx.const_kind()),
-            )
-        } else {
-            let mut err = struct_span_err!(
-                ccx.tcx.sess,
-                span,
-                E0764,
-                "{}mutable references are not allowed in {}s",
-                raw,
-                ccx.const_kind(),
-            );
-            err.span_label(span, format!("`&{}mut` is only allowed in `const fn`", raw));
-            err
-        };
+        let mut err = struct_span_err!(
+            ccx.tcx.sess,
+            span,
+            E0764,
+            "{}mutable references are not allowed in the final value of {}s",
+            raw,
+            ccx.const_kind(),
+        );
+
         if ccx.tcx.sess.teach(&err.get_code().unwrap()) {
             err.note(
                 "References in statics and constants may only refer \
@@ -321,6 +315,29 @@ impl NonConstOp for MutBorrow {
     }
 }
 
+#[derive(Debug)]
+pub struct TransientMutBorrow(pub hir::BorrowKind);
+
+impl NonConstOp for TransientMutBorrow {
+    fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status {
+        Status::Unstable(sym::const_mut_refs)
+    }
+
+    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
+        let raw = match self.0 {
+            hir::BorrowKind::Raw => "raw ",
+            hir::BorrowKind::Ref => "",
+        };
+
+        feature_err(
+            &ccx.tcx.sess.parse_sess,
+            sym::const_mut_refs,
+            span,
+            &format!("{}mutable references are not allowed in {}s", raw, ccx.const_kind()),
+        )
+    }
+}
+
 #[derive(Debug)]
 pub struct MutDeref;
 impl NonConstOp for MutDeref {
@@ -329,7 +346,7 @@ impl NonConstOp for MutDeref {
     }
 
     fn importance(&self) -> DiagnosticImportance {
-        // Usually a side-effect of a `MutBorrow` somewhere.
+        // Usually a side-effect of a `TransientMutBorrow` somewhere.
         DiagnosticImportance::Secondary
     }
 

compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -466,6 +466,29 @@ impl Validator<'mir, 'tcx> {
             }
         }
     }
+
+    fn check_mut_borrow(&mut self, local: Local, kind: hir::BorrowKind) {
+        match self.const_kind() {
+            // In a const fn all borrows are transient or point to the places given via
+            // references in the arguments (so we already checked them with
+            // TransientMutBorrow/MutBorrow as appropriate).
+            // The borrow checker guarantees that no new non-transient borrows are created.
+            // NOTE: Once we have heap allocations during CTFE we need to figure out
+            // how to prevent `const fn` to create long-lived allocations that point
+            // to mutable memory.
+            hir::ConstContext::ConstFn => self.check_op(ops::TransientMutBorrow(kind)),
+            _ => {
+                // Locals with StorageDead do not live beyond the evaluation and can
+                // thus safely be borrowed without being able to be leaked to the final
+                // value of the constant.
+                if self.local_has_storage_dead(local) {
+                    self.check_op(ops::TransientMutBorrow(kind));
+                } else {
+                    self.check_op(ops::MutBorrow(kind));
+                }
+            }
+        }
+    }
 }
 
 impl Visitor<'tcx> for Validator<'mir, 'tcx> {
@@ -562,15 +585,15 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
 
                 if !is_allowed {
                     if let BorrowKind::Mut { .. } = kind {
-                        self.check_op(ops::MutBorrow(hir::BorrowKind::Ref));
+                        self.check_mut_borrow(place.local, hir::BorrowKind::Ref)
                     } else {
                         self.check_op(ops::CellBorrow);
                     }
                 }
             }
 
-            Rvalue::AddressOf(Mutability::Mut, _) => {
-                self.check_op(ops::MutBorrow(hir::BorrowKind::Raw))
+            Rvalue::AddressOf(Mutability::Mut, ref place) => {
+                self.check_mut_borrow(place.local, hir::BorrowKind::Raw)
             }
 
             Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Shallow, ref place)