Rollup of 9 pull requests

compiler/rustc_ast/src/ast.rs

@@ -2117,10 +2117,9 @@ pub struct MacroDef {
 
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic, Walkable)]
 pub struct EiiExternTarget {
-    /// path to the extern item we're targetting
+    /// path to the extern item we're targeting
     pub extern_item_path: Path,
     pub impl_unsafe: bool,
-    pub span: Span,
 }
 
 #[derive(Clone, Encodable, Decodable, Debug, Copy, Hash, Eq, PartialEq)]
@@ -3813,6 +3812,19 @@ pub struct Fn {
 pub struct EiiImpl {
     pub node_id: NodeId,
     pub eii_macro_path: Path,
+    /// This field is an implementation detail that prevents a lot of bugs.
+    /// See <https://github.com/rust-lang/rust/issues/149981> for an example.
+    ///
+    /// The problem is, that if we generate a declaration *together* with its default,
+    /// we generate both a declaration and an implementation. The generated implementation
+    /// uses the same mechanism to register itself as a user-defined implementation would,
+    /// despite being invisible to users. What does happen is a name resolution step.
+    /// The invisible default implementation has to find the declaration.
+    /// Both are generated at the same time, so we can skip that name resolution step.
+    ///
+    /// This field is that shortcut: we prefill the extern target to skip a name resolution step,
+    /// making sure it never fails. It'd be awful UX if we fail name resolution in code invisible to the user.
+    pub known_eii_macro_resolution: Option<EiiExternTarget>,
     pub impl_safety: Safety,
     pub span: Span,
     pub inner_span: Span,

compiler/rustc_ast_lowering/src/item.rs

@@ -2,7 +2,7 @@ use rustc_abi::ExternAbi;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
 use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
-use rustc_hir::attrs::{AttributeKind, EiiDecl};
+use rustc_hir::attrs::{AttributeKind, EiiDecl, EiiImplResolution};
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
 use rustc_hir::{
@@ -134,6 +134,56 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
+    fn lower_eii_extern_target(
+        &mut self,
+        id: NodeId,
+        eii_name: Ident,
+        EiiExternTarget { extern_item_path, impl_unsafe }: &EiiExternTarget,
+    ) -> Option<EiiDecl> {
+        self.lower_path_simple_eii(id, extern_item_path).map(|did| EiiDecl {
+            eii_extern_target: did,
+            impl_unsafe: *impl_unsafe,
+            name: eii_name,
+        })
+    }
+
+    fn lower_eii_impl(
+        &mut self,
+        EiiImpl {
+            node_id,
+            eii_macro_path,
+            impl_safety,
+            span,
+            inner_span,
+            is_default,
+            known_eii_macro_resolution,
+        }: &EiiImpl,
+    ) -> hir::attrs::EiiImpl {
+        let resolution = if let Some(target) = known_eii_macro_resolution
+            && let Some(decl) = self.lower_eii_extern_target(
+                *node_id,
+                // the expect is ok here since we always generate this path in the eii macro.
+                eii_macro_path.segments.last().expect("at least one segment").ident,
+                target,
+            ) {
+            EiiImplResolution::Known(decl)
+        } else if let Some(macro_did) = self.lower_path_simple_eii(*node_id, eii_macro_path) {
+            EiiImplResolution::Macro(macro_did)
+        } else {
+            EiiImplResolution::Error(
+                self.dcx().span_delayed_bug(*span, "eii never resolved without errors given"),
+            )
+        };
+
+        hir::attrs::EiiImpl {
+            span: self.lower_span(*span),
+            inner_span: self.lower_span(*inner_span),
+            impl_marked_unsafe: self.lower_safety(*impl_safety, hir::Safety::Safe).is_unsafe(),
+            is_default: *is_default,
+            resolution,
+        }
+    }
+
     fn generate_extra_attrs_for_item_kind(
         &mut self,
         id: NodeId,
@@ -143,49 +193,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
             ItemKind::Fn(box Fn { eii_impls, .. }) if eii_impls.is_empty() => Vec::new(),
             ItemKind::Fn(box Fn { eii_impls, .. }) => {
                 vec![hir::Attribute::Parsed(AttributeKind::EiiImpls(
-                    eii_impls
-                        .iter()
-                        .flat_map(
-                            |EiiImpl {
-                                 node_id,
-                                 eii_macro_path,
-                                 impl_safety,
-                                 span,
-                                 inner_span,
-                                 is_default,
-                             }| {
-                                self.lower_path_simple_eii(*node_id, eii_macro_path).map(|did| {
-                                    hir::attrs::EiiImpl {
-                                        eii_macro: did,
-                                        span: self.lower_span(*span),
-                                        inner_span: self.lower_span(*inner_span),
-                                        impl_marked_unsafe: self
-                                            .lower_safety(*impl_safety, hir::Safety::Safe)
-                                            .is_unsafe(),
-                                        is_default: *is_default,
-                                    }
-                                })
-                            },
-                        )
-                        .collect(),
+                    eii_impls.iter().map(|i| self.lower_eii_impl(i)).collect(),
                 ))]
             }
-            ItemKind::MacroDef(
-                _,
-                MacroDef {
-                    eii_extern_target: Some(EiiExternTarget { extern_item_path, impl_unsafe, span }),
-                    ..
-                },
-            ) => self
-                .lower_path_simple_eii(id, extern_item_path)
-                .map(|did| {
-                    vec![hir::Attribute::Parsed(AttributeKind::EiiExternTarget(EiiDecl {
-                        eii_extern_target: did,
-                        impl_unsafe: *impl_unsafe,
-                        span: self.lower_span(*span),
-                    }))]
-                })
+            ItemKind::MacroDef(name, MacroDef { eii_extern_target: Some(target), .. }) => self
+                .lower_eii_extern_target(id, *name, target)
+                .map(|decl| vec![hir::Attribute::Parsed(AttributeKind::EiiExternTarget(decl))])
                 .unwrap_or_default(),
+
             ItemKind::ExternCrate(..)
             | ItemKind::Use(..)
             | ItemKind::Static(..)

compiler/rustc_builtin_macros/src/eii.rs

@@ -103,19 +103,19 @@ fn eii_(
 
     // span of the declaring item without attributes
     let item_span = func.sig.span;
-    // span of the eii attribute and the item below it, i.e. the full declaration
-    let decl_span = eii_attr_span.to(item_span);
     let foreign_item_name = func.ident;
 
     let mut return_items = Vec::new();
 
     if func.body.is_some() {
         return_items.push(Box::new(generate_default_impl(
+            ecx,
             &func,
             impl_unsafe,
             macro_name,
             eii_attr_span,
             item_span,
+            foreign_item_name,
         )))
     }
 
@@ -133,7 +133,6 @@ fn eii_(
         macro_name,
         foreign_item_name,
         impl_unsafe,
-        decl_span,
     )));
 
     return_items.into_iter().map(wrap_item).collect()
@@ -187,11 +186,13 @@ fn filter_attrs_for_multiple_eii_attr(
 }
 
 fn generate_default_impl(
+    ecx: &mut ExtCtxt<'_>,
     func: &ast::Fn,
     impl_unsafe: bool,
     macro_name: Ident,
     eii_attr_span: Span,
     item_span: Span,
+    foreign_item_name: Ident,
 ) -> ast::Item {
     // FIXME: re-add some original attrs
     let attrs = ThinVec::new();
@@ -208,6 +209,21 @@ fn generate_default_impl(
         },
         span: eii_attr_span,
         is_default: true,
+        known_eii_macro_resolution: Some(ast::EiiExternTarget {
+            extern_item_path: ast::Path {
+                span: foreign_item_name.span,
+                segments: thin_vec![
+                    ast::PathSegment {
+                        ident: Ident::from_str_and_span("super", foreign_item_name.span,),
+                        id: DUMMY_NODE_ID,
+                        args: None
+                    },
+                    ast::PathSegment { ident: foreign_item_name, id: DUMMY_NODE_ID, args: None },
+                ],
+                tokens: None,
+            },
+            impl_unsafe,
+        }),
     });
 
     ast::Item {
@@ -236,18 +252,66 @@ fn generate_default_impl(
                         stmts: thin_vec![ast::Stmt {
                             id: DUMMY_NODE_ID,
                             kind: ast::StmtKind::Item(Box::new(ast::Item {
-                                attrs,
+                                attrs: ThinVec::new(),
                                 id: DUMMY_NODE_ID,
                                 span: item_span,
                                 vis: ast::Visibility {
-                                    span: eii_attr_span,
+                                    span: item_span,
                                     kind: ast::VisibilityKind::Inherited,
                                     tokens: None
                                 },
-                                kind: ItemKind::Fn(Box::new(default_func)),
+                                kind: ItemKind::Mod(
+                                    ast::Safety::Default,
+                                    Ident::from_str_and_span("dflt", item_span),
+                                    ast::ModKind::Loaded(
+                                        thin_vec![
+                                            Box::new(ast::Item {
+                                                attrs: thin_vec![ecx.attr_nested_word(
+                                                    sym::allow,
+                                                    sym::unused_imports,
+                                                    item_span
+                                                ),],
+                                                id: DUMMY_NODE_ID,
+                                                span: item_span,
+                                                vis: ast::Visibility {
+                                                    span: eii_attr_span,
+                                                    kind: ast::VisibilityKind::Inherited,
+                                                    tokens: None
+                                                },
+                                                kind: ItemKind::Use(ast::UseTree {
+                                                    prefix: ast::Path::from_ident(
+                                                        Ident::from_str_and_span(
+                                                            "super", item_span,
+                                                        )
+                                                    ),
+                                                    kind: ast::UseTreeKind::Glob,
+                                                    span: item_span,
+                                                }),
+                                                tokens: None,
+                                            }),
+                                            Box::new(ast::Item {
+                                                attrs,
+                                                id: DUMMY_NODE_ID,
+                                                span: item_span,
+                                                vis: ast::Visibility {
+                                                    span: eii_attr_span,
+                                                    kind: ast::VisibilityKind::Inherited,
+                                                    tokens: None
+                                                },
+                                                kind: ItemKind::Fn(Box::new(default_func)),
+                                                tokens: None,
+                                            }),
+                                        ],
+                                        ast::Inline::Yes,
+                                        ast::ModSpans {
+                                            inner_span: item_span,
+                                            inject_use_span: item_span,
+                                        }
+                                    )
+                                ),
                                 tokens: None,
                             })),
-                            span: eii_attr_span
+                            span: eii_attr_span,
                         }],
                         id: DUMMY_NODE_ID,
                         rules: ast::BlockCheckMode::Default,
@@ -352,7 +416,6 @@ fn generate_attribute_macro_to_implement(
     macro_name: Ident,
     foreign_item_name: Ident,
     impl_unsafe: bool,
-    decl_span: Span,
 ) -> ast::Item {
     let mut macro_attrs = ThinVec::new();
 
@@ -394,7 +457,6 @@ fn generate_attribute_macro_to_implement(
                 eii_extern_target: Some(ast::EiiExternTarget {
                     extern_item_path: ast::Path::from_ident(foreign_item_name),
                     impl_unsafe,
-                    span: decl_span,
                 }),
             },
         ),
@@ -451,7 +513,7 @@ pub(crate) fn eii_extern_target(
         false
     };
 
-    d.eii_extern_target = Some(EiiExternTarget { extern_item_path, impl_unsafe, span });
+    d.eii_extern_target = Some(EiiExternTarget { extern_item_path, impl_unsafe });
 
     // Return the original item and the new methods.
     vec![item]
@@ -508,6 +570,7 @@ pub(crate) fn eii_shared_macro(
         impl_safety: meta_item.unsafety,
         span,
         is_default,
+        known_eii_macro_resolution: None,
     });
 
     vec![item]

compiler/rustc_codegen_llvm/src/mono_item.rs

@@ -111,7 +111,7 @@ impl CodegenCx<'_, '_> {
         }
     }
 
-    /// Whether a definition or declaration can be assumed to be local to a group of
+    /// A definition or declaration can be assumed to be local to a group of
     /// libraries that form a single DSO or executable.
     /// Marks the local as DSO if so.
     pub(crate) fn assume_dso_local(&self, llval: &llvm::Value, is_declaration: bool) -> bool {
@@ -153,7 +153,7 @@ impl CodegenCx<'_, '_> {
             return false;
         }
 
-        // With pie relocation model calls of functions defined in the translation
+        // With pie relocation model, calls of functions defined in the translation
         // unit can use copy relocations.
         if self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration {
             return true;

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -3,7 +3,9 @@ use std::str::FromStr;
 use rustc_abi::{Align, ExternAbi};
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, attr};
-use rustc_hir::attrs::{AttributeKind, InlineAttr, Linkage, RtsanSetting, UsedBy};
+use rustc_hir::attrs::{
+    AttributeKind, EiiImplResolution, InlineAttr, Linkage, RtsanSetting, UsedBy,
+};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::{self as hir, Attribute, LangItem, find_attr, lang_items};
@@ -285,11 +287,23 @@ fn process_builtin_attrs(
                 }
                 AttributeKind::EiiImpls(impls) => {
                     for i in impls {
-                        let extern_item = find_attr!(
-                            tcx.get_all_attrs(i.eii_macro),
-                            AttributeKind::EiiExternTarget(target) => target.eii_extern_target
-                        )
-                        .expect("eii should have declaration macro with extern target attribute");
+                        let extern_item = match i.resolution {
+                            EiiImplResolution::Macro(def_id) => {
+                                let Some(extern_item) = find_attr!(
+                                    tcx.get_all_attrs(def_id),
+                                    AttributeKind::EiiExternTarget(target) => target.eii_extern_target
+                                ) else {
+                                    tcx.dcx().span_delayed_bug(
+                                        i.span,
+                                        "resolved to something that's not an EII",
+                                    );
+                                    continue;
+                                };
+                                extern_item
+                            }
+                            EiiImplResolution::Known(decl) => decl.eii_extern_target,
+                            EiiImplResolution::Error(_eg) => continue,
+                        };
 
                         // this is to prevent a bug where a single crate defines both the default and explicit implementation
                         // for an EII. In that case, both of them may be part of the same final object file. I'm not 100% sure
@@ -302,7 +316,7 @@ fn process_builtin_attrs(
                             // iterate over all implementations *in the current crate*
                             // (this is ok since we generate codegen fn attrs in the local crate)
                             // if any of them is *not default* then don't emit the alias.
-                            && tcx.externally_implementable_items(LOCAL_CRATE).get(&i.eii_macro).expect("at least one").1.iter().any(|(_, imp)| !imp.is_default)
+                            && tcx.externally_implementable_items(LOCAL_CRATE).get(&extern_item).expect("at least one").1.iter().any(|(_, imp)| !imp.is_default)
                         {
                             continue;
                         }