Rollup of 8 pull requests

Cargo.lock

@@ -2608,6 +2608,7 @@ dependencies = [
  "rustc-std-workspace-alloc",
  "rustc-std-workspace-core",
  "ruzstd",
+ "wasmparser",
 ]
 
 [[package]]
@@ -6036,6 +6037,16 @@ version = "0.2.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ca6ad05a4870b2bf5fe995117d3728437bd27d7cd5f06f13c17443ef369775a1"
 
+[[package]]
+name = "wasmparser"
+version = "0.118.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95ee9723b928e735d53000dec9eae7b07a60e490c85ab54abb66659fc61bfcd9"
+dependencies = [
+ "indexmap",
+ "semver",
+]
+
 [[package]]
 name = "web-sys"
 version = "0.3.61"

compiler/rustc_ast/src/lib.rs

@@ -15,7 +15,7 @@
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(negative_impls)]
 #![feature(stmt_expr_attributes)]
 

compiler/rustc_ast_lowering/messages.ftl

@@ -8,6 +8,10 @@ ast_lowering_arbitrary_expression_in_pattern =
 
 ast_lowering_argument = argument
 
+ast_lowering_assoc_ty_binding_in_dyn =
+    associated type bounds are not allowed in `dyn` types
+    .suggestion = use `impl Trait` to introduce a type instead
+
 ast_lowering_assoc_ty_parentheses =
     parenthesized generic arguments cannot be used in associated type constraints
 
@@ -100,9 +104,6 @@ ast_lowering_match_arm_with_no_body =
     `match` arm with no body
     .suggestion = add a body after the pattern
 
-ast_lowering_misplaced_assoc_ty_binding =
-    associated type bounds are only allowed in where clauses and function signatures, not in {$position}
-
 ast_lowering_misplaced_double_dot =
     `..` patterns are not allowed here
     .note = only allowed in tuple, tuple struct, and slice patterns

compiler/rustc_ast_lowering/src/errors.rs

@@ -94,11 +94,12 @@ pub struct MisplacedImplTrait<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(ast_lowering_misplaced_assoc_ty_binding)]
-pub struct MisplacedAssocTyBinding<'a> {
+#[diag(ast_lowering_assoc_ty_binding_in_dyn)]
+pub struct MisplacedAssocTyBinding {
     #[primary_span]
     pub span: Span,
-    pub position: DiagnosticArgFromDisplay<'a>,
+    #[suggestion(code = " = impl", applicability = "maybe-incorrect", style = "verbose")]
+    pub suggestion: Option<Span>,
 }
 
 #[derive(Diagnostic, Clone, Copy)]

compiler/rustc_ast_lowering/src/lib.rs

@@ -197,7 +197,6 @@ trait ResolverAstLoweringExt {
     fn get_label_res(&self, id: NodeId) -> Option<NodeId>;
     fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>;
     fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>;
-    fn remap_extra_lifetime_params(&mut self, from: NodeId, to: NodeId);
 }
 
 impl ResolverAstLoweringExt for ResolverAstLowering {
@@ -256,11 +255,6 @@ impl ResolverAstLoweringExt for ResolverAstLowering {
     fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)> {
         self.extra_lifetime_params_map.remove(&id).unwrap_or_default()
     }
-
-    fn remap_extra_lifetime_params(&mut self, from: NodeId, to: NodeId) {
-        let lifetimes = self.extra_lifetime_params_map.remove(&from).unwrap_or_default();
-        self.extra_lifetime_params_map.insert(to, lifetimes);
-    }
 }
 
 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
@@ -1084,88 +1078,38 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 hir::TypeBindingKind::Equality { term }
             }
             AssocConstraintKind::Bound { bounds } => {
-                enum DesugarKind {
-                    ImplTrait,
-                    Error(ImplTraitPosition),
-                    Bound,
-                }
-
-                // Piggy-back on the `impl Trait` context to figure out the correct behavior.
-                let desugar_kind = match itctx {
-                    // in an argument, RPIT, or TAIT, if we are within a dyn type:
-                    //
-                    //     fn foo(x: dyn Iterator<Item: Debug>)
-                    //
-                    // then desugar to:
-                    //
-                    //     fn foo(x: dyn Iterator<Item = impl Debug>)
-                    //
-                    // This is because dyn traits must have all of their associated types specified.
-                    ImplTraitContext::ReturnPositionOpaqueTy { .. }
-                    | ImplTraitContext::TypeAliasesOpaqueTy { .. }
-                    | ImplTraitContext::Universal
-                        if self.is_in_dyn_type =>
-                    {
-                        DesugarKind::ImplTrait
-                    }
-
-                    ImplTraitContext::Disallowed(position) if self.is_in_dyn_type => {
-                        DesugarKind::Error(position)
-                    }
-
-                    // We are in the parameter position, but not within a dyn type:
-                    //
-                    //     fn foo(x: impl Iterator<Item: Debug>)
-                    //
-                    // so we leave it as is and this gets expanded in astconv to a bound like
-                    // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
-                    // `impl Iterator`.
-                    _ => DesugarKind::Bound,
-                };
-
-                match desugar_kind {
-                    DesugarKind::ImplTrait => {
-                        // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
-                        // constructing the HIR for `impl bounds...` and then lowering that.
-
-                        let impl_trait_node_id = self.next_node_id();
-                        // Shift `impl Trait` lifetime captures from the associated type bound's
-                        // node id to the opaque node id, so that the opaque can actually use
-                        // these lifetime bounds.
-                        self.resolver
-                            .remap_extra_lifetime_params(constraint.id, impl_trait_node_id);
-
-                        self.with_dyn_type_scope(false, |this| {
-                            let node_id = this.next_node_id();
-                            let ty = this.lower_ty(
-                                &Ty {
-                                    id: node_id,
-                                    kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
-                                    span: this.lower_span(constraint.span),
-                                    tokens: None,
-                                },
-                                itctx,
-                            );
+                // Disallow ATB in dyn types
+                if self.is_in_dyn_type {
+                    let suggestion = match itctx {
+                        ImplTraitContext::ReturnPositionOpaqueTy { .. }
+                        | ImplTraitContext::TypeAliasesOpaqueTy { .. }
+                        | ImplTraitContext::Universal => {
+                            let bound_end_span = constraint
+                                .gen_args
+                                .as_ref()
+                                .map_or(constraint.ident.span, |args| args.span());
+                            if bound_end_span.eq_ctxt(constraint.span) {
+                                Some(self.tcx.sess.source_map().next_point(bound_end_span))
+                            } else {
+                                None
+                            }
+                        }
+                        _ => None,
+                    };
 
-                            hir::TypeBindingKind::Equality { term: ty.into() }
-                        })
-                    }
-                    DesugarKind::Bound => {
-                        // Desugar `AssocTy: Bounds` into a type binding where the
-                        // later desugars into a trait predicate.
-                        let bounds = self.lower_param_bounds(bounds, itctx);
+                    let guar = self.dcx().emit_err(errors::MisplacedAssocTyBinding {
+                        span: constraint.span,
+                        suggestion,
+                    });
+                    let err_ty =
+                        &*self.arena.alloc(self.ty(constraint.span, hir::TyKind::Err(guar)));
+                    hir::TypeBindingKind::Equality { term: err_ty.into() }
+                } else {
+                    // Desugar `AssocTy: Bounds` into a type binding where the
+                    // later desugars into a trait predicate.
+                    let bounds = self.lower_param_bounds(bounds, itctx);
 
-                        hir::TypeBindingKind::Constraint { bounds }
-                    }
-                    DesugarKind::Error(position) => {
-                        let guar = self.dcx().emit_err(errors::MisplacedAssocTyBinding {
-                            span: constraint.span,
-                            position: DiagnosticArgFromDisplay(&position),
-                        });
-                        let err_ty =
-                            &*self.arena.alloc(self.ty(constraint.span, hir::TyKind::Err(guar)));
-                        hir::TypeBindingKind::Equality { term: err_ty.into() }
-                    }
+                    hir::TypeBindingKind::Constraint { bounds }
                 }
             }
         };

compiler/rustc_codegen_llvm/src/lib.rs

@@ -13,7 +13,6 @@
 #![feature(hash_raw_entry)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
 #![feature(impl_trait_in_assoc_type)]
 
 #[macro_use]

compiler/rustc_codegen_ssa/Cargo.toml

@@ -48,7 +48,7 @@ libc = "0.2.50"
 [dependencies.object]
 version = "0.32.1"
 default-features = false
-features = ["read_core", "elf", "macho", "pe", "xcoff", "unaligned", "archive", "write"]
+features = ["read_core", "elf", "macho", "pe", "xcoff", "unaligned", "archive", "write", "wasm"]
 
 [target.'cfg(windows)'.dependencies.windows]
 version = "0.48.0"

compiler/rustc_codegen_ssa/messages.ftl

@@ -190,6 +190,8 @@ codegen_ssa_no_module_named =
 
 codegen_ssa_no_natvis_directory = error enumerating natvis directory: {$error}
 
+codegen_ssa_no_saved_object_file = cached cgu {$cgu_name} should have an object file, but doesn't
+
 codegen_ssa_processing_dymutil_failed = processing debug info with `dsymutil` failed: {$status}
     .note = {$output}
 

compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -15,6 +15,7 @@ use rustc_data_structures::owned_slice::{try_slice_owned, OwnedSlice};
 use rustc_metadata::creader::MetadataLoader;
 use rustc_metadata::fs::METADATA_FILENAME;
 use rustc_metadata::EncodedMetadata;
+use rustc_serialize::leb128;
 use rustc_session::Session;
 use rustc_span::sym;
 use rustc_target::abi::Endian;
@@ -420,10 +421,9 @@ pub enum MetadataPosition {
 ///   it's not in an allowlist of otherwise well known dwarf section names to
 ///   go into the final artifact.
 ///
-/// * WebAssembly - we actually don't have any container format for this
-///   target. WebAssembly doesn't support the `dylib` crate type anyway so
-///   there's no need for us to support this at this time. Consequently the
-///   metadata bytes are simply stored as-is into an rlib.
+/// * WebAssembly - this uses wasm files themselves as the object file format
+///   so an empty file with no linking metadata but a single custom section is
+///   created holding our metadata.
 ///
 /// * COFF - Windows-like targets create an object with a section that has
 ///   the `IMAGE_SCN_LNK_REMOVE` flag set which ensures that if the linker
@@ -438,22 +438,13 @@ pub fn create_wrapper_file(
     data: &[u8],
 ) -> (Vec<u8>, MetadataPosition) {
     let Some(mut file) = create_object_file(sess) else {
-        // This is used to handle all "other" targets. This includes targets
-        // in two categories:
-        //
-        // * Some targets don't have support in the `object` crate just yet
-        //   to write an object file. These targets are likely to get filled
-        //   out over time.
-        //
-        // * Targets like WebAssembly don't support dylibs, so the purpose
-        //   of putting metadata in object files, to support linking rlibs
-        //   into dylibs, is moot.
-        //
-        // In both of these cases it means that linking into dylibs will
-        // not be supported by rustc. This doesn't matter for targets like
-        // WebAssembly and for targets not supported by the `object` crate
-        // yet it means that work will need to be done in the `object` crate
-        // to add a case above.
+        if sess.target.is_like_wasm {
+            return (create_metadata_file_for_wasm(data, &section_name), MetadataPosition::First);
+        }
+
+        // Targets using this branch don't have support implemented here yet or
+        // they're not yet implemented in the `object` crate and will likely
+        // fill out this module over time.
         return (data.to_vec(), MetadataPosition::Last);
     };
     let section = if file.format() == BinaryFormat::Xcoff {
@@ -532,6 +523,9 @@ pub fn create_compressed_metadata_file(
     packed_metadata.extend(metadata.raw_data());
 
     let Some(mut file) = create_object_file(sess) else {
+        if sess.target.is_like_wasm {
+            return create_metadata_file_for_wasm(&packed_metadata, b".rustc");
+        }
         return packed_metadata.to_vec();
     };
     if file.format() == BinaryFormat::Xcoff {
@@ -624,3 +618,57 @@ pub fn create_compressed_metadata_file_for_xcoff(
     file.append_section_data(section, data, 1);
     file.write().unwrap()
 }
+
+/// Creates a simple WebAssembly object file, which is itself a wasm module,
+/// that contains a custom section of the name `section_name` with contents
+/// `data`.
+///
+/// NB: the `object` crate does not yet have support for writing the the wasm
+/// object file format. The format is simple enough that for now an extra crate
+/// from crates.io (such as `wasm-encoder`). The file format is:
+///
+/// * 4-byte header "\0asm"
+/// * 4-byte version number - 1u32 in little-endian format
+/// * concatenated sections, which for this object is always "custom sections"
+///
+/// Custom sections are then defined by:
+/// * 1-byte section identifier - 0 for a custom section
+/// * leb-encoded section length (size of the contents beneath this bullet)
+///   * leb-encoded custom section name length
+///   * custom section name
+///   * section contents
+///
+/// One custom section, `linking`, is added here in accordance with
+/// <https://github.com/WebAssembly/tool-conventions/blob/main/Linking.md>
+/// which is required to inform LLD that this is an object file but it should
+/// otherwise basically ignore it if it otherwise looks at it. The linking
+/// section currently is defined by a single version byte (2) and then further
+/// sections, but we have no more sections, so it's just the byte "2".
+///
+/// The next custom section is the one we're interested in.
+pub fn create_metadata_file_for_wasm(data: &[u8], section_name: &[u8]) -> Vec<u8> {
+    let mut bytes = b"\0asm\x01\0\0\0".to_vec();
+
+    let mut append_custom_section = |section_name: &[u8], data: &[u8]| {
+        let mut section_name_len = [0; leb128::max_leb128_len::<usize>()];
+        let off = leb128::write_usize_leb128(&mut section_name_len, section_name.len());
+        let section_name_len = &section_name_len[..off];
+
+        let mut section_len = [0; leb128::max_leb128_len::<usize>()];
+        let off = leb128::write_usize_leb128(
+            &mut section_len,
+            data.len() + section_name_len.len() + section_name.len(),
+        );
+        let section_len = &section_len[..off];
+
+        bytes.push(0u8);
+        bytes.extend_from_slice(section_len);
+        bytes.extend_from_slice(section_name_len);
+        bytes.extend_from_slice(section_name);
+        bytes.extend_from_slice(data);
+    };
+
+    append_custom_section(b"linking", &[2]);
+    append_custom_section(section_name, data);
+    bytes
+}

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -913,7 +913,9 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
     let object = load_from_incr_comp_dir(
         cgcx.output_filenames.temp_path(OutputType::Object, Some(&module.name)),
-        module.source.saved_files.get("o").expect("no saved object file in work product"),
+        module.source.saved_files.get("o").unwrap_or_else(|| {
+            cgcx.create_dcx().emit_fatal(errors::NoSavedObjectFile { cgu_name: &module.name })
+        }),
     );
     let dwarf_object =
         module.source.saved_files.get("dwo").as_ref().and_then(|saved_dwarf_object_file| {

compiler/rustc_codegen_ssa/src/errors.rs

@@ -121,6 +121,12 @@ pub struct NoNatvisDirectory {
     pub error: Error,
 }
 
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_no_saved_object_file)]
+pub struct NoSavedObjectFile<'a> {
+    pub cgu_name: &'a str,
+}
+
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_copy_path_buf)]
 pub struct CopyPathBuf {