Rollup of 8 pull requests

compiler/rustc_arena/src/lib.rs

@@ -542,11 +542,12 @@ impl DroplessArena {
 
     #[inline]
     pub fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] {
+        assert!(!mem::needs_drop::<T>());
+        assert!(size_of::<T>() != 0);
+
         // Warning: this function is reentrant: `iter` could hold a reference to `&self` and
         // allocate additional elements while we're iterating.
         let iter = iter.into_iter();
-        assert!(size_of::<T>() != 0);
-        assert!(!mem::needs_drop::<T>());
 
         let size_hint = iter.size_hint();
 
@@ -577,6 +578,7 @@ impl DroplessArena {
     ) -> Result<&mut [T], E> {
         // Despite the similarity with `alloc_from_iter`, we cannot reuse their fast case, as we
         // cannot know the minimum length of the iterator in this case.
+        assert!(!mem::needs_drop::<T>());
         assert!(size_of::<T>() != 0);
 
         // Takes care of reentrancy.

compiler/rustc_ast_lowering/src/delegation.rs

@@ -53,7 +53,7 @@ use rustc_middle::span_bug;
 use rustc_middle::ty::{Asyncness, PerOwnerResolverData};
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::symbol::kw;
-use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
+use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, sym};
 
 use crate::delegation::generics::{
     GenericsGenerationResult, GenericsGenerationResults, GenericsPosition,
@@ -664,11 +664,34 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let callee_path = self.arena.alloc(self.mk_expr(hir::ExprKind::Path(new_path), span));
         let args = self.arena.alloc_from_iter(args);
-        let call = self.arena.alloc(self.mk_expr(hir::ExprKind::Call(callee_path, args), span));
+        let call = self.mk_expr(hir::ExprKind::Call(callee_path, args), span);
+
+        let expr = if let Some((parent, of_trait)) = self.should_wrap_return_value(delegation) {
+            let res = Res::SelfTyAlias { alias_to: parent.to_def_id(), is_trait_impl: of_trait };
+            let ident = Ident::new(kw::SelfUpper, span);
+            let path = self.create_resolved_path(res, ident, span);
+
+            // FIXME(fn_delegation): add default `..` for all other fields.
+            let initializer = hir::ExprKind::Struct(
+                self.arena.alloc(path),
+                self.arena.alloc_slice(&[hir::ExprField {
+                    hir_id: self.next_id(),
+                    is_shorthand: false,
+                    ident: Ident::new(sym::integer(0), span),
+                    expr: self.arena.alloc(call),
+                    span,
+                }]),
+                hir::StructTailExpr::None,
+            );
+
+            self.arena.alloc(self.mk_expr(initializer, span))
+        } else {
+            self.arena.alloc(call)
+        };
 
         let block = self.arena.alloc(hir::Block {
             stmts,
-            expr: Some(call),
+            expr: Some(expr),
             hir_id: self.next_id(),
             rules: hir::BlockCheckMode::DefaultBlock,
             span,
@@ -678,6 +701,45 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (self.mk_expr(hir::ExprKind::Block(block, None), span), call.hir_id)
     }
 
+    fn should_wrap_return_value(&self, delegation: &Delegation) -> Option<(LocalDefId, bool)> {
+        // Heuristic: don't do wrapping if there is no target expression.
+        if delegation.body.is_none() {
+            return None;
+        }
+
+        let tcx = self.tcx;
+        let parent = tcx.local_parent(self.owner.def_id);
+        let parent_kind = tcx.def_kind(parent);
+
+        // Apply wrapping for delegations inside
+        // 1) Trait impls, as the return type of both signature function
+        //    and generated delegation has `Self` generic param returned
+        //    (checked below).
+        //    FIXME(fn_delegation): think of enabling wrapping in more scenarios:
+        //      trait-(impl)-to-free
+        //      trait-(impl)-to-inherent
+        //      inherent-to-free
+        // 2) Inherent methods when delegating to trait, as we change the type of
+        //    `Self` to type of struct or enum we delegate from.
+        if !matches!(tcx.def_kind(parent), DefKind::Impl { .. }) {
+            return None;
+        }
+
+        let is_trait_impl = parent_kind == DefKind::Impl { of_trait: true };
+
+        // Check that delegation path resolves to a trait AssocFn, not to a free method.
+        Some((parent, is_trait_impl)).filter(|_| {
+            self.get_resolution_id(delegation.id).is_some_and(|id| {
+                tcx.def_kind(id) == DefKind::AssocFn
+                    // Check that the return type of the callee is `Self` param.
+                    // After previous check we are sure that `sig_id` and `delegation.id`
+                    // point to the same function.
+                    && tcx.def_kind(tcx.parent(id)) == DefKind::Trait
+                    && tcx.fn_sig(id).skip_binder().output().skip_binder().is_param(0)
+            })
+        })
+    }
+
     fn process_segment(
         &mut self,
         span: Span,

compiler/rustc_ast_lowering/src/delegation/generics.rs

@@ -588,19 +588,28 @@ impl<'hir> LoweringContext<'_, 'hir> {
             p.def_id.to_def_id(),
         );
 
+        self.create_resolved_path(res, p.name.ident(), p.span)
+    }
+
+    pub(super) fn create_resolved_path(
+        &mut self,
+        res: Res,
+        ident: Ident,
+        span: Span,
+    ) -> hir::QPath<'hir> {
         hir::QPath::Resolved(
             None,
             self.arena.alloc(hir::Path {
                 segments: self.arena.alloc_slice(&[hir::PathSegment {
                     args: None,
                     hir_id: self.next_id(),
-                    ident: p.name.ident(),
+                    ident,
                     infer_args: false,
                     res,
                     delegation_child_segment: false,
                 }]),
                 res,
-                span: p.span,
+                span,
             }),
         )
     }

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -63,7 +63,10 @@ use super::rmeta_link::RmetaLinkCache;
 use super::rpath::{self, RPathConfig};
 use super::{apple, rmeta_link, versioned_llvm_target};
 use crate::base::needs_allocator_shim_for_linking;
-use crate::{CodegenLintLevelSpecs, CompiledModule, CompiledModules, CrateInfo, NativeLib, errors};
+use crate::{
+    CodegenLintLevelSpecs, CompiledModule, CompiledModules, CrateInfo, NativeLib, SymbolExport,
+    errors,
+};
 
 pub fn ensure_removed(dcx: DiagCtxtHandle<'_>, path: &Path) {
     if let Err(e) = fs::remove_file(path) {
@@ -593,7 +596,7 @@ fn link_staticlib(
             crate_info
                 .exported_symbols
                 .get(&CrateType::StaticLib)
-                .map(|symbols| symbols.iter().map(|(s, _)| s.clone()).collect())
+                .map(|symbols| symbols.iter().map(|symbol| symbol.name.clone()).collect())
         }
     } else {
         None
@@ -2196,9 +2199,15 @@ fn add_linked_symbol_object(
     cmd: &mut dyn Linker,
     sess: &Session,
     tmpdir: &Path,
-    symbols: &[(String, SymbolExportKind)],
+    crate_type: CrateType,
+    linked_symbols: &[(String, SymbolExportKind)],
+    exported_symbols: &[SymbolExport],
 ) {
-    if symbols.is_empty() {
+    let should_export_symbols = sess.target.is_like_msvc
+        && !exported_symbols.is_empty()
+        && (crate_type != CrateType::Executable
+            || sess.opts.unstable_opts.export_executable_symbols);
+    if linked_symbols.is_empty() && !should_export_symbols {
         return;
     }
 
@@ -2235,7 +2244,7 @@ fn add_linked_symbol_object(
         None
     };
 
-    for (sym, kind) in symbols.iter() {
+    for (sym, kind) in linked_symbols.iter() {
         let symbol = file.add_symbol(object::write::Symbol {
             name: sym.clone().into(),
             value: 0,
@@ -2293,6 +2302,37 @@ fn add_linked_symbol_object(
         }
     }
 
+    if should_export_symbols {
+        // Currently the compiler doesn't use `dllexport` (an LLVM attribute) to
+        // export symbols from a dynamic library. When building a dynamic library,
+        // however, we're going to want some symbols exported, so this adds a
+        // `.drectve` section which lists all the symbols using /EXPORT arguments.
+        //
+        // The linker will read these arguments from the `.drectve` section and
+        // export all the symbols from the dynamic library. Note that this is not
+        // as simple as just exporting all the symbols in the current crate (as
+        // specified by `codegen.reachable`) but rather we also need to possibly
+        // export the symbols of upstream crates. Upstream rlibs may be linked
+        // statically to this dynamic library, in which case they may continue to
+        // transitively be used and hence need their symbols exported.
+        fn msvc_drectve_export(symbol: &SymbolExport) -> String {
+            let data = if symbol.kind == SymbolExportKind::Data { ",DATA" } else { "" };
+
+            if let Some(link_name) = symbol.link_name.as_deref() {
+                // The first name is the decorated symbol used by the import library, while
+                // EXPORTAS gives the public name written to the DLL export table.
+                format!(" /EXPORT:\"{link_name}\"{data},EXPORTAS,\"{}\"", symbol.name)
+            } else {
+                format!(" /EXPORT:\"{}\"{data}", symbol.name)
+            }
+        }
+
+        let drectve = exported_symbols.iter().map(msvc_drectve_export).collect::<String>();
+
+        let section = file.add_section(vec![], b".drectve".to_vec(), object::SectionKind::Linker);
+        file.append_section_data(section, drectve.as_bytes(), 1);
+    }
+
     let path = tmpdir.join("symbols.o");
     let result = std::fs::write(&path, file.write().unwrap());
     if let Err(error) = result {
@@ -2486,7 +2526,7 @@ fn undecorate_c_symbol<'a>(
 fn add_c_staticlib_symbols(
     sess: &Session,
     lib: &NativeLib,
-    out: &mut Vec<(String, SymbolExportKind)>,
+    out: &mut Vec<SymbolExport>,
 ) -> io::Result<()> {
     let file_path = find_native_static_library(lib.name.as_str(), lib.verbatim, sess);
 
@@ -2549,7 +2589,11 @@ fn add_c_staticlib_symbols(
             let Some(undecorated) = undecorate_c_symbol(name, sess, export_kind) else {
                 continue;
             };
-            out.push((undecorated.to_string(), export_kind));
+            out.push(SymbolExport::with_link_name(
+                undecorated.to_string(),
+                export_kind,
+                name.to_string(),
+            ));
         }
     }
 
@@ -2629,7 +2673,14 @@ fn linker_with_args(
     // Pre-link CRT objects.
     add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained_crt_objects);
 
-    add_linked_symbol_object(cmd, sess, tmpdir, &crate_info.linked_symbols[&crate_type]);
+    add_linked_symbol_object(
+        cmd,
+        sess,
+        tmpdir,
+        crate_type,
+        &crate_info.linked_symbols[&crate_type],
+        &export_symbols,
+    );
 
     // Sanitizer libraries.
     add_sanitizer_libraries(sess, flavor, crate_type, cmd);