Lower anonymous structs or unions to HIR

Author: frank-king

compiler/rustc_ast/src/ast.rs

@@ -2108,9 +2108,9 @@ pub enum TyKind {
     /// A tuple (`(A, B, C, D,...)`).
     Tup(ThinVec<P<Ty>>),
     /// An anonymous struct type i.e. `struct { foo: Type }`
-    AnonStruct(ThinVec<FieldDef>),
+    AnonStruct(NodeId, ThinVec<FieldDef>),
     /// An anonymous union type i.e. `union { bar: Type }`
-    AnonUnion(ThinVec<FieldDef>),
+    AnonUnion(NodeId, ThinVec<FieldDef>),
     /// A path (`module::module::...::Type`), optionally
     /// "qualified", e.g., `<Vec<T> as SomeTrait>::SomeType`.
     ///

compiler/rustc_ast/src/mut_visit.rs

@@ -514,7 +514,8 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
             visit_vec(bounds, |bound| vis.visit_param_bound(bound));
         }
         TyKind::MacCall(mac) => vis.visit_mac_call(mac),
-        TyKind::AnonStruct(fields) | TyKind::AnonUnion(fields) => {
+        TyKind::AnonStruct(id, fields) | TyKind::AnonUnion(id, fields) => {
+            vis.visit_id(id);
             fields.flat_map_in_place(|field| vis.flat_map_field_def(field));
         }
     }

compiler/rustc_ast/src/visit.rs

@@ -441,7 +441,7 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
         TyKind::MacCall(mac) => visitor.visit_mac_call(mac),
         TyKind::Never | TyKind::CVarArgs => {}
-        TyKind::AnonStruct(ref fields, ..) | TyKind::AnonUnion(ref fields, ..) => {
+        TyKind::AnonStruct(_, ref fields) | TyKind::AnonUnion(_, ref fields) => {
             walk_list!(visitor, visit_field_def, fields)
         }
     }

compiler/rustc_ast_lowering/src/item.rs

@@ -680,7 +680,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> {
+    pub(super) fn lower_field_def(
+        &mut self,
+        (index, f): (usize, &FieldDef),
+    ) -> hir::FieldDef<'hir> {
         let ty = if let TyKind::Path(qself, path) = &f.ty.kind {
             let t = self.lower_path_ty(
                 &f.ty,

compiler/rustc_ast_lowering/src/lib.rs

@@ -1326,18 +1326,50 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             TyKind::Err => {
                 hir::TyKind::Err(self.tcx.sess.span_delayed_bug(t.span, "TyKind::Err lowered"))
             }
-            // FIXME(unnamed_fields): IMPLEMENTATION IN PROGRESS
-            #[allow(rustc::untranslatable_diagnostic)]
-            #[allow(rustc::diagnostic_outside_of_impl)]
-            TyKind::AnonStruct(ref _fields) => hir::TyKind::Err(
-                self.tcx.sess.span_err(t.span, "anonymous structs are unimplemented"),
-            ),
-            // FIXME(unnamed_fields): IMPLEMENTATION IN PROGRESS
-            #[allow(rustc::untranslatable_diagnostic)]
-            #[allow(rustc::diagnostic_outside_of_impl)]
-            TyKind::AnonUnion(ref _fields) => hir::TyKind::Err(
-                self.tcx.sess.span_err(t.span, "anonymous unions are unimplemented"),
-            ),
+            // Lower the anonymous structs or unions in a nested lowering context.
+            //
+            // ```
+            // struct Foo {
+            //     _: union {
+            // //     ^__________________  <-- within the nested lowering context,
+            //         /* fields */ //   |     we lower all fields defined into an
+            //     } //                  |     owner node of struct or union item
+            // //  ^_____________________|
+            // }
+            //
+            TyKind::AnonStruct(def_node_id, fields) | TyKind::AnonUnion(def_node_id, fields) => {
+                let (def_kind, item_kind): (DefKind, fn(_, _) -> _) = match t.kind {
+                    TyKind::AnonStruct(..) => (DefKind::Struct, hir::ItemKind::Struct),
+                    TyKind::AnonUnion(..) => (DefKind::Union, hir::ItemKind::Union),
+                    _ => unreachable!(),
+                };
+                let def_id = self.create_def(
+                    self.current_hir_id_owner.def_id,
+                    *def_node_id,
+                    kw::Empty,
+                    def_kind,
+                    t.span,
+                );
+                debug!(?def_id);
+                let owner_id = hir::OwnerId { def_id };
+                self.with_hir_id_owner(*def_node_id, |this| {
+                    let fields = this.arena.alloc_from_iter(
+                        fields.iter().enumerate().map(|f| this.lower_field_def(f)),
+                    );
+                    let span = t.span;
+                    let variant_data = hir::VariantData::Struct(fields, false);
+                    // FIXME: capture the generics from the outer adt.
+                    let generics = hir::Generics::empty();
+                    hir::OwnerNode::Item(this.arena.alloc(hir::Item {
+                        ident: Ident::new(kw::Empty, span),
+                        owner_id,
+                        kind: item_kind(variant_data, generics),
+                        span: this.lower_span(span),
+                        vis_span: this.lower_span(span.shrink_to_lo()),
+                    }))
+                });
+                hir::TyKind::AnonAdt(hir::ItemId { owner_id })
+            }
             TyKind::Slice(ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
             TyKind::Ptr(mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
             TyKind::Ref(region, mt) => {

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -198,7 +198,7 @@ impl<'a> AstValidator<'a> {
                     }
                 }
             }
-            TyKind::AnonStruct(ref fields, ..) | TyKind::AnonUnion(ref fields, ..) => {
+            TyKind::AnonStruct(_, ref fields) | TyKind::AnonUnion(_, ref fields) => {
                 walk_list!(self, visit_field_def, fields)
             }
             _ => visit::walk_ty(self, t),

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -987,11 +987,11 @@ impl<'a> State<'a> {
                 }
                 self.pclose();
             }
-            ast::TyKind::AnonStruct(fields) => {
+            ast::TyKind::AnonStruct(_, fields) => {
                 self.head("struct");
                 self.print_record_struct_body(fields, ty.span);
             }
-            ast::TyKind::AnonUnion(fields) => {
+            ast::TyKind::AnonUnion(_, fields) => {
                 self.head("union");
                 self.print_record_struct_body(fields, ty.span);
             }

compiler/rustc_hir/src/def.rs

@@ -8,6 +8,7 @@ use rustc_data_structures::stable_hasher::ToStableHashKey;
 use rustc_macros::HashStable_Generic;
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::hygiene::MacroKind;
+use rustc_span::symbol::kw;
 use rustc_span::Symbol;
 
 use std::array::IntoIter;
@@ -225,6 +226,7 @@ impl DefKind {
 
     pub fn def_path_data(self, name: Symbol) -> DefPathData {
         match self {
+            DefKind::Struct | DefKind::Union if name == kw::Empty => DefPathData::AnonAdt,
             DefKind::Mod
             | DefKind::Struct
             | DefKind::Union

compiler/rustc_hir/src/definitions.rs

@@ -282,6 +282,8 @@ pub enum DefPathData {
     /// An existential `impl Trait` type node.
     /// Argument position `impl Trait` have a `TypeNs` with their pretty-printed name.
     OpaqueTy,
+    /// An anonymous struct or union type i.e. `struct { foo: Type }` or `union { bar: Type }`
+    AnonAdt,
 }
 
 impl Definitions {
@@ -404,8 +406,9 @@ impl DefPathData {
         match *self {
             TypeNs(name) if name == kw::Empty => None,
             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
+
             Impl | ForeignMod | CrateRoot | Use | GlobalAsm | Closure | Ctor | AnonConst
-            | OpaqueTy => None,
+            | OpaqueTy | AnonAdt => None,
         }
     }
 
@@ -426,6 +429,7 @@ impl DefPathData {
             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
             OpaqueTy => DefPathDataName::Anon { namespace: sym::opaque },
+            AnonAdt => DefPathDataName::Anon { namespace: sym::anon_adt },
         }
     }
 }

compiler/rustc_hir/src/hir.rs

@@ -2543,6 +2543,8 @@ pub enum TyKind<'hir> {
     Never,
     /// A tuple (`(A, B, C, D, ...)`).
     Tup(&'hir [Ty<'hir>]),
+    /// An anonymous struct or union type i.e. `struct { foo: Type }` or `union { foo: Type }`
+    AnonAdt(ItemId),
     /// A path to a type definition (`module::module::...::Type`), or an
     /// associated type (e.g., `<Vec<T> as Trait>::Type` or `<T>::Target`).
     ///