Rollup of 5 pull requests

compiler/rustc_expand/src/expand.rs

@@ -12,7 +12,7 @@ use rustc_ast::ptr::P;
 use rustc_ast::token;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::visit::{self, AssocCtxt, Visitor};
-use rustc_ast::{AstLike, Block, Inline, ItemKind, Local, MacArgs};
+use rustc_ast::{AstLike, Block, Inline, ItemKind, Local, MacArgs, MacCall};
 use rustc_ast::{MacCallStmt, MacStmtStyle, MetaItemKind, ModKind, NestedMetaItem};
 use rustc_ast::{NodeId, PatKind, Path, StmtKind, Unsafe};
 use rustc_ast_pretty::pprust;
@@ -26,7 +26,7 @@ use rustc_parse::parser::{
     AttemptLocalParseRecovery, ForceCollect, Parser, RecoverColon, RecoverComma,
 };
 use rustc_parse::validate_attr;
-use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
+use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
 use rustc_session::lint::BuiltinLintDiagnostics;
 use rustc_session::parse::{feature_err, ParseSess};
 use rustc_session::Limit;
@@ -1070,7 +1070,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
 
     // Detect use of feature-gated or invalid attributes on macro invocations
     // since they will not be detected after macro expansion.
-    fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
+    fn check_attributes(&mut self, attrs: &[ast::Attribute], call: &MacCall) {
         let features = self.cx.ecfg.features.unwrap();
         let mut attrs = attrs.iter().peekable();
         let mut span: Option<Span> = None;
@@ -1085,14 +1085,31 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                 continue;
             }
 
-            if attr.doc_str().is_some() {
+            if attr.is_doc_comment() {
                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
                     &UNUSED_DOC_COMMENTS,
                     current_span,
-                    ast::CRATE_NODE_ID,
+                    self.cx.current_expansion.lint_node_id,
                     "unused doc comment",
                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
                 );
+            } else if rustc_attr::is_builtin_attr(attr) {
+                let attr_name = attr.ident().unwrap().name;
+                // `#[cfg]` and `#[cfg_attr]` are special - they are
+                // eagerly evaluated.
+                if attr_name != sym::cfg && attr_name != sym::cfg_attr {
+                    self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
+                        &UNUSED_ATTRIBUTES,
+                        attr.span,
+                        self.cx.current_expansion.lint_node_id,
+                        &format!("unused attribute `{}`", attr_name),
+                        BuiltinLintDiagnostics::UnusedBuiltinAttribute {
+                            attr_name,
+                            macro_name: pprust::path_to_string(&call.path),
+                            invoc_span: call.path.span,
+                        },
+                    );
+                }
             }
         }
     }
@@ -1152,7 +1169,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
             }
 
             if let ast::ExprKind::MacCall(mac) = expr.kind {
-                self.check_attributes(&expr.attrs);
+                self.check_attributes(&expr.attrs, &mac);
                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
             } else {
                 assign_id!(self, &mut expr.id, || {
@@ -1253,7 +1270,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
             }
 
             if let ast::ExprKind::MacCall(mac) = expr.kind {
-                self.check_attributes(&expr.attrs);
+                self.check_attributes(&expr.attrs, &mac);
                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
                     .make_opt_expr()
                     .map(|expr| expr.into_inner())
@@ -1296,7 +1313,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
 
         if let StmtKind::MacCall(mac) = stmt.kind {
             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
-            self.check_attributes(&attrs);
+            self.check_attributes(&attrs, &mac);
             let mut placeholder =
                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
 
@@ -1344,9 +1361,9 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         let span = item.span;
 
         match item.kind {
-            ast::ItemKind::MacCall(..) => {
+            ast::ItemKind::MacCall(ref mac) => {
+                self.check_attributes(&attrs, &mac);
                 item.attrs = attrs;
-                self.check_attributes(&item.attrs);
                 item.and_then(|item| match item.kind {
                     ItemKind::MacCall(mac) => {
                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
@@ -1455,8 +1472,8 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         }
 
         match item.kind {
-            ast::AssocItemKind::MacCall(..) => {
-                self.check_attributes(&item.attrs);
+            ast::AssocItemKind::MacCall(ref mac) => {
+                self.check_attributes(&item.attrs, &mac);
                 item.and_then(|item| match item.kind {
                     ast::AssocItemKind::MacCall(mac) => self
                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
@@ -1480,8 +1497,8 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         }
 
         match item.kind {
-            ast::AssocItemKind::MacCall(..) => {
-                self.check_attributes(&item.attrs);
+            ast::AssocItemKind::MacCall(ref mac) => {
+                self.check_attributes(&item.attrs, &mac);
                 item.and_then(|item| match item.kind {
                     ast::AssocItemKind::MacCall(mac) => self
                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
@@ -1526,8 +1543,8 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         }
 
         match foreign_item.kind {
-            ast::ForeignItemKind::MacCall(..) => {
-                self.check_attributes(&foreign_item.attrs);
+            ast::ForeignItemKind::MacCall(ref mac) => {
+                self.check_attributes(&foreign_item.attrs, &mac);
                 foreign_item.and_then(|item| match item.kind {
                     ast::ForeignItemKind::MacCall(mac) => self
                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)

compiler/rustc_lint/src/context.rs

@@ -734,6 +734,16 @@ pub trait LintContext: Sized {
                         Applicability::MachineApplicable,
                     );
                 }
+                BuiltinLintDiagnostics::UnusedBuiltinAttribute {
+                    attr_name,
+                    macro_name,
+                    invoc_span
+                } => {
+                    db.span_note(
+                        invoc_span,
+                        &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
+                    );
+                }
             }
             // Rewrap `db`, and pass control to the user.
             decorate(LintDiagnosticBuilder::new(db));

compiler/rustc_lint/src/lib.rs

@@ -32,6 +32,7 @@
 #![feature(box_syntax)]
 #![feature(box_patterns)]
 #![feature(crate_visibility_modifier)]
+#![feature(format_args_capture)]
 #![feature(iter_order_by)]
 #![feature(iter_zip)]
 #![feature(never_type)]

compiler/rustc_lint_defs/src/lib.rs

@@ -296,6 +296,7 @@ pub enum BuiltinLintDiagnostics {
     DeprecatedMacro(Option<Symbol>, Span),
     MissingAbi(Span, Abi),
     UnusedDocComment(Span),
+    UnusedBuiltinAttribute { attr_name: Symbol, macro_name: String, invoc_span: Span },
     PatternsInFnsWithoutBody(Span, Ident),
     LegacyDeriveHelpers(Span),
     ExternDepSpec(String, ExternDepSpec),

compiler/rustc_metadata/src/locator.rs

@@ -1080,7 +1080,10 @@ impl CrateError {
                                 locator.triple
                             ));
                         }
-                        if missing_core && std::env::var("RUSTUP_HOME").is_ok() {
+                        // NOTE: this suggests using rustup, even though the user may not have it installed.
+                        // That's because they could choose to install it; or this may give them a hint which
+                        // target they need to install from their distro.
+                        if missing_core {
                             err.help(&format!(
                                 "consider downloading the target with `rustup target add {}`",
                                 locator.triple
@@ -1097,7 +1100,7 @@ impl CrateError {
                                 current_crate
                             ));
                         }
-                        if sess.is_nightly_build() && std::env::var("CARGO").is_ok() {
+                        if sess.is_nightly_build() {
                             err.help("consider building the standard library from source with `cargo build -Zbuild-std`");
                         }
                     } else if Some(crate_name)

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -5,7 +5,7 @@ use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_middle::mir::BorrowKind;
 use rustc_middle::thir::*;
-use rustc_middle::ty::{self, ParamEnv, TyCtxt};
+use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt};
 use rustc_session::lint::builtin::{UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
 use rustc_session::lint::Level;
 use rustc_span::def_id::{DefId, LocalDefId};
@@ -27,7 +27,9 @@ struct UnsafetyVisitor<'a, 'tcx> {
     /// The `#[target_feature]` attributes of the body. Used for checking
     /// calls to functions with `#[target_feature]` (RFC 2396).
     body_target_features: &'tcx Vec<Symbol>,
-    in_possible_lhs_union_assign: bool,
+    /// When inside the LHS of an assignment to a field, this is the type
+    /// of the LHS and the span of the assignment expression.
+    assignment_info: Option<(Ty<'tcx>, Span)>,
     in_union_destructure: bool,
     param_env: ParamEnv<'tcx>,
     inside_adt: bool,
@@ -287,7 +289,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
     }
 
     fn visit_expr(&mut self, expr: &Expr<'tcx>) {
-        // could we be in a the LHS of an assignment of a union?
+        // could we be in the LHS of an assignment to a field?
         match expr.kind {
             ExprKind::Field { .. }
             | ExprKind::VarRef { .. }
@@ -329,7 +331,12 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             | ExprKind::InlineAsm { .. }
             | ExprKind::LlvmInlineAsm { .. }
             | ExprKind::LogicalOp { .. }
-            | ExprKind::Use { .. } => self.in_possible_lhs_union_assign = false,
+            | ExprKind::Use { .. } => {
+                // We don't need to save the old value and restore it
+                // because all the place expressions can't have more
+                // than one child.
+                self.assignment_info = None;
+            }
         };
         match expr.kind {
             ExprKind::Scope { value, lint_level: LintLevel::Explicit(hir_id), region_scope: _ } => {
@@ -409,32 +416,42 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 self.safety_context = closure_visitor.safety_context;
             }
             ExprKind::Field { lhs, .. } => {
-                // assigning to union field is okay for AccessToUnionField
-                if let ty::Adt(adt_def, _) = &self.thir[lhs].ty.kind() {
+                let lhs = &self.thir[lhs];
+                if let ty::Adt(adt_def, _) = lhs.ty.kind() {
                     if adt_def.is_union() {
-                        if self.in_possible_lhs_union_assign {
-                            // FIXME: trigger AssignToDroppingUnionField unsafety if needed
+                        if let Some((assigned_ty, assignment_span)) = self.assignment_info {
+                            // To avoid semver hazard, we only consider `Copy` and `ManuallyDrop` non-dropping.
+                            if !(assigned_ty
+                                .ty_adt_def()
+                                .map_or(false, |adt| adt.is_manually_drop())
+                                || assigned_ty
+                                    .is_copy_modulo_regions(self.tcx.at(expr.span), self.param_env))
+                            {
+                                self.requires_unsafe(assignment_span, AssignToDroppingUnionField);
+                            } else {
+                                // write to non-drop union field, safe
+                            }
                         } else {
                             self.requires_unsafe(expr.span, AccessToUnionField);
                         }
                     }
                 }
             }
             ExprKind::Assign { lhs, rhs } | ExprKind::AssignOp { lhs, rhs, .. } => {
+                let lhs = &self.thir[lhs];
                 // First, check whether we are mutating a layout constrained field
                 let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
-                visit::walk_expr(&mut visitor, &self.thir[lhs]);
+                visit::walk_expr(&mut visitor, lhs);
                 if visitor.found {
                     self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField);
                 }
 
                 // Second, check for accesses to union fields
                 // don't have any special handling for AssignOp since it causes a read *and* write to lhs
                 if matches!(expr.kind, ExprKind::Assign { .. }) {
-                    // assigning to a union is safe, check here so it doesn't get treated as a read later
-                    self.in_possible_lhs_union_assign = true;
-                    visit::walk_expr(self, &self.thir()[lhs]);
-                    self.in_possible_lhs_union_assign = false;
+                    self.assignment_info = Some((lhs.ty, expr.span));
+                    visit::walk_expr(self, lhs);
+                    self.assignment_info = None;
                     visit::walk_expr(self, &self.thir()[rhs]);
                     return; // we have already visited everything by now
                 }
@@ -506,12 +523,9 @@ enum UnsafeOpKind {
     UseOfMutableStatic,
     UseOfExternStatic,
     DerefOfRawPointer,
-    #[allow(dead_code)] // FIXME
     AssignToDroppingUnionField,
     AccessToUnionField,
-    #[allow(dead_code)] // FIXME
     MutationOfLayoutConstrainedField,
-    #[allow(dead_code)] // FIXME
     BorrowOfLayoutConstrainedField,
     CallToFunctionWith,
 }
@@ -619,7 +633,7 @@ pub fn check_unsafety<'tcx>(tcx: TyCtxt<'tcx>, def: ty::WithOptConstParam<LocalD
         hir_context: hir_id,
         body_unsafety,
         body_target_features,
-        in_possible_lhs_union_assign: false,
+        assignment_info: None,
         in_union_destructure: false,
         param_env: tcx.param_env(def.did),
         inside_adt: false,

library/core/src/mem/maybe_uninit.rs

@@ -461,7 +461,6 @@ impl<T> MaybeUninit<T> {
     /// With `write`, we can avoid the need to write through a raw pointer:
     ///
     /// ```rust
-    /// #![feature(maybe_uninit_extra)]
     /// use core::pin::Pin;
     /// use core::mem::MaybeUninit;
     ///

library/std/src/env.rs

@@ -294,7 +294,7 @@ impl Error for VarError {
     }
 }
 
-/// Sets the environment variable `k` to the value `v` for the currently running
+/// Sets the environment variable `key` to the value `value` for the currently running
 /// process.
 ///
 /// Note that while concurrent access to environment variables is safe in Rust,
@@ -310,9 +310,8 @@ impl Error for VarError {
 ///
 /// # Panics
 ///
-/// This function may panic if `key` is empty, contains an ASCII equals sign
-/// `'='` or the NUL character `'\0'`, or when the value contains the NUL
-/// character.
+/// This function may panic if `key` is empty, contains an ASCII equals sign `'='`
+/// or the NUL character `'\0'`, or when `value` contains the NUL character.
 ///
 /// # Examples
 ///

src/test/ui/crate-loading/missing-std.rs

@@ -1,7 +1,6 @@
 // compile-flags: --target x86_64-unknown-uefi
 // needs-llvm-components: x86
 // rustc-env:CARGO=/usr/bin/cargo
-// rustc-env:RUSTUP_HOME=/home/bors/.rustup
 #![no_core]
 extern crate core;
 //~^ ERROR can't find crate for `core`

src/test/ui/crate-loading/missing-std.stderr

@@ -1,5 +1,5 @@
 error[E0463]: can't find crate for `core`
-  --> $DIR/missing-std.rs:6:1
+  --> $DIR/missing-std.rs:5:1
    |
 LL | extern crate core;
    | ^^^^^^^^^^^^^^^^^^ can't find crate

src/test/ui/issues/issue-37131.stderr

@@ -1,6 +1,8 @@
 error[E0463]: can't find crate for `std`
    |
    = note: the `thumbv6m-none-eabi` target may not be installed
+   = help: consider downloading the target with `rustup target add thumbv6m-none-eabi`
+   = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-49851/compiler-builtins-error.stderr

@@ -1,6 +1,8 @@
 error[E0463]: can't find crate for `core`
    |
    = note: the `thumbv7em-none-eabihf` target may not be installed
+   = help: consider downloading the target with `rustup target add thumbv7em-none-eabihf`
+   = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
 error: aborting due to previous error
 

src/test/ui/lint/inert-attr-macro.rs

@@ -0,0 +1,20 @@
+// check-pass
+
+#![warn(unused)]
+
+macro_rules! foo {
+    () => {}
+}
+
+fn main() {
+    #[inline] foo!(); //~ WARN unused attribute `inline`
+
+    // This does nothing, since `#[allow(warnings)]` is itself
+    // an inert attribute on a macro call
+    #[allow(warnings)] #[inline] foo!(); //~ WARN unused attribute `allow`
+    //~^ WARN unused attribute `inline`
+
+    // This does work, since the attribute is on a parent
+    // of the macro invocation.
+    #[allow(warnings)] { #[inline] foo!(); }
+}