Rollup of 26 pull requests

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
           - name: mingw-check
             os: ubuntu-latest-xl
             env: {}
-          - name: x86_64-gnu-llvm-8
+          - name: x86_64-gnu-llvm-9
             os: ubuntu-latest-xl
             env: {}
           - name: x86_64-gnu-tools
@@ -265,7 +265,7 @@ jobs:
           - name: x86_64-gnu-distcheck
             os: ubuntu-latest-xl
             env: {}
-          - name: x86_64-gnu-llvm-8
+          - name: x86_64-gnu-llvm-9
             env:
               RUST_BACKTRACE: 1
             os: ubuntu-latest-xl

Cargo.lock

@@ -721,6 +721,13 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a21fa21941700a3cd8fcb4091f361a6a712fac632f85d9f487cc892045d55c6"
 
+[[package]]
+name = "coverage_test_macros"
+version = "0.0.0"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "cpuid-bool"
 version = "0.1.2"
@@ -3922,6 +3929,7 @@ dependencies = [
 name = "rustc_mir"
 version = "0.0.0"
 dependencies = [
+ "coverage_test_macros",
  "either",
  "itertools 0.9.0",
  "polonius-engine",

compiler/rustc_ast/src/ast.rs

@@ -1192,6 +1192,7 @@ impl Expr {
             ExprKind::Field(..) => ExprPrecedence::Field,
             ExprKind::Index(..) => ExprPrecedence::Index,
             ExprKind::Range(..) => ExprPrecedence::Range,
+            ExprKind::Underscore => ExprPrecedence::Path,
             ExprKind::Path(..) => ExprPrecedence::Path,
             ExprKind::AddrOf(..) => ExprPrecedence::AddrOf,
             ExprKind::Break(..) => ExprPrecedence::Break,
@@ -1324,6 +1325,8 @@ pub enum ExprKind {
     Index(P<Expr>, P<Expr>),
     /// A range (e.g., `1..2`, `1..`, `..2`, `1..=2`, `..=2`; and `..` in destructuring assingment).
     Range(Option<P<Expr>>, Option<P<Expr>>, RangeLimits),
+    /// An underscore, used in destructuring assignment to ignore a value.
+    Underscore,
 
     /// Variable reference, possibly containing `::` and/or type
     /// parameters (e.g., `foo::bar::<baz>`).

compiler/rustc_ast/src/mut_visit.rs

@@ -1232,6 +1232,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
             visit_opt(e1, |e1| vis.visit_expr(e1));
             visit_opt(e2, |e2| vis.visit_expr(e2));
         }
+        ExprKind::Underscore => {}
         ExprKind::Path(qself, path) => {
             vis.visit_qself(qself);
             vis.visit_path(path);

compiler/rustc_ast/src/visit.rs

@@ -806,6 +806,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             walk_list!(visitor, visit_expr, start);
             walk_list!(visitor, visit_expr, end);
         }
+        ExprKind::Underscore => {}
         ExprKind::Path(ref maybe_qself, ref path) => {
             if let Some(ref qself) = *maybe_qself {
                 visitor.visit_ty(&qself.ty);

compiler/rustc_ast_lowering/src/expr.rs

@@ -164,6 +164,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ExprKind::Range(ref e1, ref e2, lims) => {
                     self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), lims)
                 }
+                ExprKind::Underscore => {
+                    self.sess
+                        .struct_span_err(
+                            e.span,
+                            "in expressions, `_` can only be used on the left-hand side of an assignment",
+                        )
+                        .span_label(e.span, "`_` not allowed here")
+                        .emit();
+                    hir::ExprKind::Err
+                }
                 ExprKind::Path(ref qself, ref path) => {
                     let qpath = self.lower_qpath(
                         e.id,
@@ -863,7 +873,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // Return early in case of an ordinary assignment.
         fn is_ordinary(lower_ctx: &mut LoweringContext<'_, '_>, lhs: &Expr) -> bool {
             match &lhs.kind {
-                ExprKind::Array(..) | ExprKind::Struct(..) | ExprKind::Tup(..) => false,
+                ExprKind::Array(..)
+                | ExprKind::Struct(..)
+                | ExprKind::Tup(..)
+                | ExprKind::Underscore => false,
                 // Check for tuple struct constructor.
                 ExprKind::Call(callee, ..) => lower_ctx.extract_tuple_struct_path(callee).is_none(),
                 ExprKind::Paren(e) => {
@@ -943,6 +956,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         assignments: &mut Vec<hir::Stmt<'hir>>,
     ) -> &'hir hir::Pat<'hir> {
         match &lhs.kind {
+            // Underscore pattern.
+            ExprKind::Underscore => {
+                return self.pat_without_dbm(lhs.span, hir::PatKind::Wild);
+            }
             // Slice patterns.
             ExprKind::Array(elements) => {
                 let (pats, rest) =

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -630,7 +630,11 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(const_trait_impl, "const trait impls are experimental");
     gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
     gate_all!(inline_const, "inline-const is experimental");
-    gate_all!(destructuring_assignment, "destructuring assignments are unstable");
+    if sess.parse_sess.span_diagnostic.err_count() == 0 {
+        // Errors for `destructuring_assignment` can get quite noisy, especially where `_` is
+        // involved, so we only emit errors where there are no other parsing errors.
+        gate_all!(destructuring_assignment, "destructuring assignments are unstable");
+    }
 
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -109,7 +109,6 @@ pub fn print_crate<'a>(
     ann: &'a dyn PpAnn,
     is_expanded: bool,
     edition: Edition,
-    has_injected_crate: bool,
 ) -> String {
     let mut s = State {
         s: pp::mk_printer(),
@@ -119,7 +118,7 @@ pub fn print_crate<'a>(
         insert_extra_parens: true,
     };
 
-    if is_expanded && has_injected_crate {
+    if is_expanded && !krate.attrs.iter().any(|attr| attr.has_name(sym::no_core)) {
         // We need to print `#![no_std]` (and its feature gate) so that
         // compiling pretty-printed source won't inject libstd again.
         // However, we don't want these attributes in the AST because
@@ -2068,6 +2067,7 @@ impl<'a> State<'a> {
                     self.print_expr_maybe_paren(e, fake_prec);
                 }
             }
+            ast::ExprKind::Underscore => self.s.word("_"),
             ast::ExprKind::Path(None, ref path) => self.print_path(path, true, 0),
             ast::ExprKind::Path(Some(ref qself), ref path) => self.print_qpath(path, qself, true),
             ast::ExprKind::Break(opt_label, ref opt_expr) => {
@@ -2327,11 +2327,12 @@ impl<'a> State<'a> {
             self.print_path(path, false, depth);
         }
         self.s.word(">");
-        self.s.word("::");
-        let item_segment = path.segments.last().unwrap();
-        self.print_ident(item_segment.ident);
-        if let Some(ref args) = item_segment.args {
-            self.print_generic_args(args, colons_before_params)
+        for item_segment in &path.segments[qself.position..] {
+            self.s.word("::");
+            self.print_ident(item_segment.ident);
+            if let Some(ref args) = item_segment.args {
+                self.print_generic_args(args, colons_before_params)
+            }
         }
     }
 

compiler/rustc_builtin_macros/src/standard_library_imports.rs

@@ -13,12 +13,12 @@ pub fn inject(
     resolver: &mut dyn ResolverExpand,
     sess: &Session,
     alt_std_name: Option<Symbol>,
-) -> (ast::Crate, Option<Symbol>) {
+) -> ast::Crate {
     let rust_2018 = sess.parse_sess.edition >= Edition::Edition2018;
 
     // the first name in this list is the crate name of the crate with the prelude
     let names: &[Symbol] = if sess.contains_name(&krate.attrs, sym::no_core) {
-        return (krate, None);
+        return krate;
     } else if sess.contains_name(&krate.attrs, sym::no_std) {
         if sess.contains_name(&krate.attrs, sym::compiler_builtins) {
             &[sym::core]
@@ -81,5 +81,5 @@ pub fn inject(
 
     krate.module.items.insert(0, use_item);
 
-    (krate, Some(name))
+    krate
 }

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -144,25 +144,6 @@ fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
     );
 }
 
-fn translate_obsolete_target_features(feature: &str) -> &str {
-    const LLVM9_FEATURE_CHANGES: &[(&str, &str)] =
-        &[("+fp-only-sp", "-fp64"), ("-fp-only-sp", "+fp64"), ("+d16", "-d32"), ("-d16", "+d32")];
-    if llvm_util::get_major_version() >= 9 {
-        for &(old, new) in LLVM9_FEATURE_CHANGES {
-            if feature == old {
-                return new;
-            }
-        }
-    } else {
-        for &(old, new) in LLVM9_FEATURE_CHANGES {
-            if feature == new {
-                return old;
-            }
-        }
-    }
-    feature
-}
-
 pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {
     const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"];
 
@@ -172,12 +153,7 @@ pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {
         .target_feature
         .split(',')
         .filter(|f| !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s)));
-    sess.target
-        .features
-        .split(',')
-        .chain(cmdline)
-        .filter(|l| !l.is_empty())
-        .map(translate_obsolete_target_features)
+    sess.target.features.split(',').chain(cmdline).filter(|l| !l.is_empty())
 }
 
 pub fn apply_target_cpu_attr(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -377,11 +377,6 @@ fn get_pgo_use_path(config: &ModuleConfig) -> Option<CString> {
 }
 
 pub(crate) fn should_use_new_llvm_pass_manager(config: &ModuleConfig) -> bool {
-    // We only support the new pass manager starting with LLVM 9.
-    if llvm_util::get_major_version() < 9 {
-        return false;
-    }
-
     // The new pass manager is disabled by default.
     config.new_llvm_pass_manager
 }

compiler/rustc_codegen_llvm/src/context.rs

@@ -100,11 +100,6 @@ fn to_llvm_tls_model(tls_model: TlsModel) -> llvm::ThreadLocalMode {
     }
 }
 
-fn strip_function_ptr_alignment(data_layout: String) -> String {
-    // FIXME: Make this more general.
-    data_layout.replace("-Fi8-", "-")
-}
-
 fn strip_x86_address_spaces(data_layout: String) -> String {
     data_layout.replace("-p270:32:32-p271:32:32-p272:64:64-", "-")
 }
@@ -119,9 +114,6 @@ pub unsafe fn create_module(
     let llmod = llvm::LLVMModuleCreateWithNameInContext(mod_name.as_ptr(), llcx);
 
     let mut target_data_layout = sess.target.data_layout.clone();
-    if llvm_util::get_major_version() < 9 {
-        target_data_layout = strip_function_ptr_alignment(target_data_layout);
-    }
     if llvm_util::get_major_version() < 10
         && (sess.target.arch == "x86" || sess.target.arch == "x86_64")
     {

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -104,7 +104,7 @@ unsafe fn configure_llvm(sess: &Session) {
         }
     }
 
-    if sess.opts.debugging_opts.llvm_time_trace && get_major_version() >= 9 {
+    if sess.opts.debugging_opts.llvm_time_trace {
         // time-trace is not thread safe and running it in parallel will cause seg faults.
         if !sess.opts.debugging_opts.no_parallel_llvm {
             bug!("`-Z llvm-time-trace` requires `-Z no-parallel-llvm")
@@ -122,10 +122,8 @@ unsafe fn configure_llvm(sess: &Session) {
 
 pub fn time_trace_profiler_finish(file_name: &str) {
     unsafe {
-        if get_major_version() >= 9 {
-            let file_name = CString::new(file_name).unwrap();
-            llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
-        }
+        let file_name = CString::new(file_name).unwrap();
+        llvm::LLVMTimeTraceProfilerFinish(file_name.as_ptr());
     }
 }
 

compiler/rustc_data_structures/src/lib.rs

@@ -102,6 +102,7 @@ pub mod work_queue;
 pub use atomic_ref::AtomicRef;
 pub mod frozen;
 pub mod sso;
+pub mod steal;
 pub mod tagged_ptr;
 pub mod temp_dir;
 pub mod unhash;

compiler/rustc_middle/src/ty/steal.rs → compiler/rustc_data_structures/src/steal.rs

@@ -1,4 +1,5 @@
-use rustc_data_structures::sync::{MappedReadGuard, ReadGuard, RwLock};
+use crate::stable_hasher::{HashStable, StableHasher};
+use crate::sync::{MappedReadGuard, ReadGuard, RwLock};
 
 /// The `Steal` struct is intended to used as the value for a query.
 /// Specifically, we sometimes have queries (*cough* MIR *cough*)
@@ -31,7 +32,7 @@ impl<T> Steal<T> {
 
     pub fn borrow(&self) -> MappedReadGuard<'_, T> {
         ReadGuard::map(self.value.borrow(), |opt| match *opt {
-            None => bug!("attempted to read from stolen value"),
+            None => panic!("attempted to read from stolen value"),
             Some(ref v) => v,
         })
     }
@@ -42,3 +43,9 @@ impl<T> Steal<T> {
         value.expect("attempt to read from stolen value")
     }
 }
+
+impl<CTX, T: HashStable<CTX>> HashStable<CTX> for Steal<T> {
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        self.borrow().hash_stable(hcx, hasher);
+    }
+}

compiler/rustc_driver/src/pretty.rs

@@ -407,7 +407,6 @@ pub fn print_after_parsing(
                 annotation.pp_ann(),
                 false,
                 parse.edition,
-                parse.injected_crate_name.get().is_some(),
             )
         })
     } else {
@@ -449,7 +448,6 @@ pub fn print_after_hir_lowering<'tcx>(
                     annotation.pp_ann(),
                     true,
                     parse.edition,
-                    parse.injected_crate_name.get().is_some(),
                 )
             })
         }

compiler/rustc_expand/src/expand.rs

@@ -22,7 +22,7 @@ use rustc_errors::{struct_span_err, Applicability, PResult};
 use rustc_feature::Features;
 use rustc_parse::parser::{AttemptLocalParseRecovery, Parser};
 use rustc_parse::validate_attr;
-use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
+use rustc_session::lint::builtin::{SOFT_UNSTABLE, UNUSED_DOC_COMMENTS};
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::parse::{feature_err, ParseSess};
 use rustc_session::Limit;
@@ -1064,17 +1064,24 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
             })
             .map(|i| attrs.remove(i));
         if let Some(attr) = &attr {
-            if !self.cx.ecfg.custom_inner_attributes()
-                && attr.style == ast::AttrStyle::Inner
-                && !attr.has_name(sym::test)
-            {
-                feature_err(
-                    &self.cx.sess.parse_sess,
-                    sym::custom_inner_attributes,
-                    attr.span,
-                    "non-builtin inner attributes are unstable",
-                )
-                .emit();
+            if attr.style == ast::AttrStyle::Inner && !self.cx.ecfg.custom_inner_attributes() {
+                let msg = "non-builtin inner attributes are unstable";
+                if attr.has_name(sym::test) {
+                    self.cx.sess.parse_sess.buffer_lint(
+                        SOFT_UNSTABLE,
+                        attr.span,
+                        ast::CRATE_NODE_ID,
+                        msg,
+                    );
+                } else {
+                    feature_err(
+                        &self.cx.sess.parse_sess,
+                        sym::custom_inner_attributes,
+                        attr.span,
+                        msg,
+                    )
+                    .emit();
+                }
             }
         }
         attr