Rollup of 9 pull requests

compiler/rustc_ast_lowering/src/item.rs

@@ -2,7 +2,7 @@ use rustc_abi::ExternAbi;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_errors::ErrorGuaranteed;
+use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
 use rustc_hir::{self as hir, HirId, LifetimeSource, PredicateOrigin};
@@ -1644,9 +1644,29 @@ impl<'hir> LoweringContext<'_, 'hir> {
             self.error_on_invalid_abi(abi_str);
             ExternAbi::Rust
         });
-        let sess = self.tcx.sess;
-        let features = self.tcx.features();
-        gate_unstable_abi(sess, features, span, extern_abi);
+        let tcx = self.tcx;
+
+        // we can't do codegen for unsupported ABIs, so error now so we won't get farther
+        if !tcx.sess.target.is_abi_supported(extern_abi) {
+            let mut err = struct_span_code_err!(
+                tcx.dcx(),
+                span,
+                E0570,
+                "{extern_abi} is not a supported ABI for the current target",
+            );
+
+            if let ExternAbi::Stdcall { unwind } = extern_abi {
+                let c_abi = ExternAbi::C { unwind };
+                let system_abi = ExternAbi::System { unwind };
+                err.help(format!("if you need `extern {extern_abi}` on win32 and `extern {c_abi}` everywhere else, \
+                    use `extern {system_abi}`"
+                ));
+            }
+            err.emit();
+        }
+        // Show required feature gate even if we already errored, as the user is likely to build the code
+        // for the actually intended target next and then they will need the feature gate.
+        gate_unstable_abi(tcx.sess, tcx.features(), span, extern_abi);
         extern_abi
     }
 

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -146,12 +146,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             }
         }
 
-        // Apply the minimum function alignment here, so that individual backends don't have to.
-        codegen_fn_attrs.alignment = Ord::max(
-            codegen_fn_attrs.alignment,
-            tcx.sess.opts.unstable_opts.min_function_alignment,
-        );
-
         let Some(Ident { name, .. }) = attr.ident() else {
             continue;
         };
@@ -454,6 +448,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
 
     mixed_export_name_no_mangle_lint_state.lint_if_mixed(tcx);
 
+    // Apply the minimum function alignment here, so that individual backends don't have to.
+    codegen_fn_attrs.alignment =
+        Ord::max(codegen_fn_attrs.alignment, tcx.sess.opts.unstable_opts.min_function_alignment);
+
     let inline_span;
     (codegen_fn_attrs.inline, inline_span) = if let Some((inline_attr, span)) =
         find_attr!(attrs, AttributeKind::Inline(i, span) => (*i, *span))

compiler/rustc_errors/src/json.rs

@@ -129,6 +129,7 @@ impl Emitter for JsonEmitter {
         };
         let name = match record.section {
             TimingSection::Linking => "link",
+            TimingSection::Codegen => "codegen",
         };
         let data = SectionTimestamp { name, event, timestamp: record.timestamp };
         let result = self.emit(EmitTyped::SectionTiming(data));

compiler/rustc_errors/src/timings.rs

@@ -1,10 +1,15 @@
 use std::time::Instant;
 
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::sync::Lock;
+
 use crate::DiagCtxtHandle;
 
 /// A high-level section of the compilation process.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum TimingSection {
+    /// Time spent doing codegen.
+    Codegen,
     /// Time spent linking.
     Linking,
 }
@@ -36,23 +41,59 @@ pub struct TimingSectionHandler {
     /// Time when the compilation session started.
     /// If `None`, timing is disabled.
     origin: Option<Instant>,
+    /// Sanity check to ensure that we open and close sections correctly.
+    opened_sections: Lock<FxHashSet<TimingSection>>,
 }
 
 impl TimingSectionHandler {
     pub fn new(enabled: bool) -> Self {
         let origin = if enabled { Some(Instant::now()) } else { None };
-        Self { origin }
+        Self { origin, opened_sections: Lock::new(FxHashSet::default()) }
     }
 
     /// Returns a RAII guard that will immediately emit a start the provided section, and then emit
     /// its end when it is dropped.
-    pub fn start_section<'a>(
+    pub fn section_guard<'a>(
         &self,
         diag_ctxt: DiagCtxtHandle<'a>,
         section: TimingSection,
     ) -> TimingSectionGuard<'a> {
+        if self.is_enabled() && self.opened_sections.borrow().contains(&section) {
+            diag_ctxt
+                .bug(format!("Section `{section:?}` was started again before it was finished"));
+        }
+
         TimingSectionGuard::create(diag_ctxt, section, self.origin)
     }
+
+    /// Start the provided section.
+    pub fn start_section(&self, diag_ctxt: DiagCtxtHandle<'_>, section: TimingSection) {
+        if let Some(origin) = self.origin {
+            let mut opened = self.opened_sections.borrow_mut();
+            if !opened.insert(section) {
+                diag_ctxt
+                    .bug(format!("Section `{section:?}` was started again before it was finished"));
+            }
+
+            diag_ctxt.emit_timing_section_start(TimingRecord::from_origin(origin, section));
+        }
+    }
+
+    /// End the provided section.
+    pub fn end_section(&self, diag_ctxt: DiagCtxtHandle<'_>, section: TimingSection) {
+        if let Some(origin) = self.origin {
+            let mut opened = self.opened_sections.borrow_mut();
+            if !opened.remove(&section) {
+                diag_ctxt.bug(format!("Section `{section:?}` was ended before being started"));
+            }
+
+            diag_ctxt.emit_timing_section_end(TimingRecord::from_origin(origin, section));
+        }
+    }
+
+    fn is_enabled(&self) -> bool {
+        self.origin.is_some()
+    }
 }
 
 /// RAII wrapper for starting and ending section timings.

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1,7 +1,7 @@
 use std::cell::LazyCell;
 use std::ops::ControlFlow;
 
-use rustc_abi::FieldIdx;
+use rustc_abi::{ExternAbi, FieldIdx};
 use rustc_attr_data_structures::ReprAttr::ReprPacked;
 use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
@@ -13,7 +13,6 @@ use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, ObligationCauseCode};
 use rustc_lint_defs::builtin::{
     REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS, UNSUPPORTED_CALLING_CONVENTIONS,
-    UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
@@ -53,49 +52,22 @@ fn add_abi_diag_help<T: EmissionGuarantee>(abi: ExternAbi, diag: &mut Diag<'_, T
 }
 
 pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: ExternAbi) {
-    // FIXME: this should be checked earlier, e.g. in `rustc_ast_lowering`, to fix
-    // things like #86232.
+    // FIXME: This should be checked earlier, e.g. in `rustc_ast_lowering`, as this
+    // currently only guards function imports, function definitions, and function pointer types.
+    // Functions in trait declarations can still use "deprecated" ABIs without any warning.
 
     match AbiMap::from_target(&tcx.sess.target).canonize_abi(abi, false) {
         AbiMapping::Direct(..) => (),
+        // already erred in rustc_ast_lowering
         AbiMapping::Invalid => {
-            let mut err = struct_span_code_err!(
-                tcx.dcx(),
-                span,
-                E0570,
-                "`{abi}` is not a supported ABI for the current target",
-            );
-            add_abi_diag_help(abi, &mut err);
-            err.emit();
+            tcx.dcx().span_delayed_bug(span, format!("{abi} should be rejected in ast_lowering"));
         }
         AbiMapping::Deprecated(..) => {
             tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
-                lint.primary_message("use of calling convention not supported on this target");
-                add_abi_diag_help(abi, lint);
-            });
-        }
-    }
-}
-
-pub fn check_abi_fn_ptr(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: ExternAbi) {
-    // This is always an FCW, even for `AbiMapping::Invalid`, since we started linting later than
-    // in `check_abi` above.
-    match AbiMap::from_target(&tcx.sess.target).canonize_abi(abi, false) {
-        AbiMapping::Direct(..) => (),
-        // This is not a redundant match arm: these ABIs started linting after introducing
-        // UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS already existed and we want to
-        // avoid expanding the scope of that lint so it can move to a hard error sooner.
-        AbiMapping::Deprecated(..) => {
-            tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
-                lint.primary_message("use of calling convention not supported on this target");
-                add_abi_diag_help(abi, lint);
-            });
-        }
-        AbiMapping::Invalid => {
-            tcx.node_span_lint(UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS, hir_id, span, |lint| {
                 lint.primary_message(format!(
-                    "the calling convention {abi} is not supported on this target"
+                    "{abi} is not a supported ABI for the current target"
                 ));
+                add_abi_diag_help(abi, lint);
             });
         }
     }
@@ -868,6 +840,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             let hir::ItemKind::ForeignMod { abi, items } = it.kind else {
                 return;
             };
+
             check_abi(tcx, it.hir_id(), it.span, abi);
 
             for item in items {

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -72,8 +72,8 @@ pub mod wfcheck;
 
 use std::num::NonZero;
 
-pub use check::{check_abi, check_abi_fn_ptr, check_custom_abi};
-use rustc_abi::{ExternAbi, VariantIdx};
+pub use check::{check_abi, check_custom_abi};
+use rustc_abi::VariantIdx;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::{Diag, ErrorGuaranteed, pluralize, struct_span_code_err};
 use rustc_hir::LangItem;

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -51,7 +51,7 @@ use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, FulfillmentError};
 use tracing::{debug, instrument};
 
-use crate::check::check_abi_fn_ptr;
+use crate::check::check_abi;
 use crate::errors::{AmbiguousLifetimeBound, BadReturnTypeNotation};
 use crate::hir_ty_lowering::errors::{GenericsArgsErrExtend, prohibit_assoc_item_constraint};
 use crate::hir_ty_lowering::generics::{check_generic_arg_count, lower_generic_args};
@@ -2660,7 +2660,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         if let hir::Node::Ty(hir::Ty { kind: hir::TyKind::BareFn(bare_fn_ty), span, .. }) =
             tcx.hir_node(hir_id)
         {
-            check_abi_fn_ptr(tcx, hir_id, *span, bare_fn_ty.abi);
+            check_abi(tcx, hir_id, *span, bare_fn_ty.abi);
         }
 
         // reject function types that violate cmse ABI requirements

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1723,8 +1723,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Don't emit a suggestion if we found an actual method
             // that had unsatisfied trait bounds
             if unsatisfied_predicates.is_empty()
-                // ...or if we already suggested that name because of `rustc_confusable` annotation.
+                // ...or if we already suggested that name because of `rustc_confusable` annotation
                 && Some(similar_candidate.name()) != confusable_suggested
+                // and if the we aren't in an expansion.
+                && !span.from_expansion()
             {
                 self.find_likely_intended_associated_item(
                     &mut err,

compiler/rustc_interface/src/passes.rs

@@ -11,6 +11,7 @@ use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, WorkerLocal};
 use rustc_data_structures::{parallel, thousands};
+use rustc_errors::timings::TimingSection;
 use rustc_expand::base::{ExtCtxt, LintStoreExpand};
 use rustc_feature::Features;
 use rustc_fs_util::try_canonicalize;
@@ -1176,6 +1177,8 @@ pub(crate) fn start_codegen<'tcx>(
     codegen_backend: &dyn CodegenBackend,
     tcx: TyCtxt<'tcx>,
 ) -> (Box<dyn Any>, EncodedMetadata) {
+    tcx.sess.timings.start_section(tcx.sess.dcx(), TimingSection::Codegen);
+
     // Hook for tests.
     if let Some((def_id, _)) = tcx.entry_fn(())
         && tcx.has_attr(def_id, sym::rustc_delayed_bug_from_inside_query)

compiler/rustc_interface/src/queries.rs

@@ -48,6 +48,7 @@ impl Linker {
         let (codegen_results, work_products) = sess.time("finish_ongoing_codegen", || {
             codegen_backend.join_codegen(self.ongoing_codegen, sess, &self.output_filenames)
         });
+        sess.timings.end_section(sess.dcx(), TimingSection::Codegen);
 
         sess.dcx().abort_if_errors();
 
@@ -89,7 +90,7 @@ impl Linker {
         }
 
         let _timer = sess.prof.verbose_generic_activity("link_crate");
-        let _timing = sess.timings.start_section(sess.dcx(), TimingSection::Linking);
+        let _timing = sess.timings.section_guard(sess.dcx(), TimingSection::Linking);
         codegen_backend.link(sess, codegen_results, self.metadata, &self.output_filenames)
     }
 }

compiler/rustc_lint/src/lib.rs

@@ -608,6 +608,7 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see issue #127323 \
          <https://github.com/rust-lang/rust/issues/127323> for more information",
     );
+    store.register_removed("unsupported_fn_ptr_calling_conventions", "converted into hard error");
     store.register_removed(
         "undefined_naked_function_abi",
         "converted into hard error, see PR #139001 \

compiler/rustc_lint_defs/src/builtin.rs

@@ -122,7 +122,6 @@ declare_lint_pass! {
         UNSAFE_OP_IN_UNSAFE_FN,
         UNSTABLE_NAME_COLLISIONS,
         UNSTABLE_SYNTAX_PRE_EXPANSION,
-        UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS,
         UNUSED_ASSIGNMENTS,
         UNUSED_ASSOCIATED_TYPE_BOUNDS,
         UNUSED_ATTRIBUTES,

library/core/src/iter/adapters/fuse.rs

@@ -198,8 +198,30 @@ impl<I: Default> Default for Fuse<I> {
     /// let iter: Fuse<slice::Iter<'_, u8>> = Default::default();
     /// assert_eq!(iter.len(), 0);
     /// ```
+    ///
+    /// This is equivalent to `I::default().fuse()`[^fuse_note]; e.g. if
+    /// `I::default()` is not an empty iterator, then this will not be
+    /// an empty iterator.
+    ///
+    /// ```
+    /// # use std::iter::Fuse;
+    /// #[derive(Default)]
+    /// struct Fourever;
+    ///
+    /// impl Iterator for Fourever {
+    ///     type Item = u32;
+    ///     fn next(&mut self) -> Option<u32> {
+    ///         Some(4)
+    ///     }
+    /// }
+    ///
+    /// let mut iter: Fuse<Fourever> = Default::default();
+    /// assert_eq!(iter.next(), Some(4));
+    /// ```
+    ///
+    /// [^fuse_note]: if `I` does not override `Iterator::fuse`'s default implementation
     fn default() -> Self {
-        Fuse { iter: Default::default() }
+        Fuse { iter: Some(I::default()) }
     }
 }