ast: Unmerge structures for associated items and foreign items

src/librustc_ast/ast.rs

@@ -38,6 +38,7 @@ use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
+use std::convert::TryFrom;
 use std::fmt;
 use std::iter;
 
@@ -2441,10 +2442,10 @@ impl Item {
     }
 }
 
-impl<K: IntoItemKind> Item<K> {
+impl<K: Into<ItemKind>> Item<K> {
     pub fn into_item(self) -> Item {
         let Item { attrs, id, span, vis, ident, kind, tokens } = self;
-        Item { attrs, id, span, vis, ident, kind: kind.into_item_kind(), tokens }
+        Item { attrs, id, span, vis, ident, kind: kind.into(), tokens }
     }
 }
 
@@ -2624,20 +2625,11 @@ impl ItemKind {
     }
 }
 
-pub trait IntoItemKind {
-    fn into_item_kind(self) -> ItemKind;
-}
-
-// FIXME(Centril): These definitions should be unmerged;
-// see https://github.com/rust-lang/rust/pull/69194#discussion_r379899975
-pub type ForeignItem = Item<AssocItemKind>;
-pub type ForeignItemKind = AssocItemKind;
-
 /// Represents associated items.
 /// These include items in `impl` and `trait` definitions.
 pub type AssocItem = Item<AssocItemKind>;
 
-/// Represents non-free item kinds.
+/// Represents associated item kinds.
 ///
 /// The term "provided" in the variants below refers to the item having a default
 /// definition / body. Meanwhile, a "required" item lacks a definition / body.
@@ -2646,36 +2638,87 @@ pub type AssocItem = Item<AssocItemKind>;
 /// means "provided" and conversely `None` means "required".
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub enum AssocItemKind {
-    /// A constant, `const $ident: $ty $def?;` where `def ::= "=" $expr? ;`.
+    /// An associated constant, `const $ident: $ty $def?;` where `def ::= "=" $expr? ;`.
     /// If `def` is parsed, then the constant is provided, and otherwise required.
     Const(Defaultness, P<Ty>, Option<P<Expr>>),
-    /// A static item (`static FOO: u8`).
-    Static(P<Ty>, Mutability, Option<P<Expr>>),
-    /// A function.
+    /// An associated function.
     Fn(Defaultness, FnSig, Generics, Option<P<Block>>),
-    /// A type.
+    /// An associated type.
     TyAlias(Defaultness, Generics, GenericBounds, Option<P<Ty>>),
-    /// A macro expanding to items.
+    /// A macro expanding to associated items.
     Macro(Mac),
 }
 
 impl AssocItemKind {
     pub fn defaultness(&self) -> Defaultness {
         match *self {
             Self::Const(def, ..) | Self::Fn(def, ..) | Self::TyAlias(def, ..) => def,
-            Self::Macro(..) | Self::Static(..) => Defaultness::Final,
+            Self::Macro(..) => Defaultness::Final,
         }
     }
 }
 
-impl IntoItemKind for AssocItemKind {
-    fn into_item_kind(self) -> ItemKind {
-        match self {
+impl From<AssocItemKind> for ItemKind {
+    fn from(assoc_item_kind: AssocItemKind) -> ItemKind {
+        match assoc_item_kind {
             AssocItemKind::Const(a, b, c) => ItemKind::Const(a, b, c),
-            AssocItemKind::Static(a, b, c) => ItemKind::Static(a, b, c),
             AssocItemKind::Fn(a, b, c, d) => ItemKind::Fn(a, b, c, d),
             AssocItemKind::TyAlias(a, b, c, d) => ItemKind::TyAlias(a, b, c, d),
             AssocItemKind::Macro(a) => ItemKind::Mac(a),
         }
     }
 }
+
+impl TryFrom<ItemKind> for AssocItemKind {
+    type Error = ItemKind;
+
+    fn try_from(item_kind: ItemKind) -> Result<AssocItemKind, ItemKind> {
+        Ok(match item_kind {
+            ItemKind::Const(a, b, c) => AssocItemKind::Const(a, b, c),
+            ItemKind::Fn(a, b, c, d) => AssocItemKind::Fn(a, b, c, d),
+            ItemKind::TyAlias(a, b, c, d) => AssocItemKind::TyAlias(a, b, c, d),
+            ItemKind::Mac(a) => AssocItemKind::Macro(a),
+            _ => return Err(item_kind),
+        })
+    }
+}
+
+/// An item in `extern` block.
+#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
+pub enum ForeignItemKind {
+    /// A foreign static item (`static FOO: u8`).
+    Static(P<Ty>, Mutability, Option<P<Expr>>),
+    /// A foreign function.
+    Fn(Defaultness, FnSig, Generics, Option<P<Block>>),
+    /// A foreign type.
+    TyAlias(Defaultness, Generics, GenericBounds, Option<P<Ty>>),
+    /// A macro expanding to foreign items.
+    Macro(Mac),
+}
+
+impl From<ForeignItemKind> for ItemKind {
+    fn from(foreign_item_kind: ForeignItemKind) -> ItemKind {
+        match foreign_item_kind {
+            ForeignItemKind::Static(a, b, c) => ItemKind::Static(a, b, c),
+            ForeignItemKind::Fn(a, b, c, d) => ItemKind::Fn(a, b, c, d),
+            ForeignItemKind::TyAlias(a, b, c, d) => ItemKind::TyAlias(a, b, c, d),
+            ForeignItemKind::Macro(a) => ItemKind::Mac(a),
+        }
+    }
+}
+
+impl TryFrom<ItemKind> for ForeignItemKind {
+    type Error = ItemKind;
+
+    fn try_from(item_kind: ItemKind) -> Result<ForeignItemKind, ItemKind> {
+        Ok(match item_kind {
+            ItemKind::Static(a, b, c) => ForeignItemKind::Static(a, b, c),
+            ItemKind::Fn(a, b, c, d) => ForeignItemKind::Fn(a, b, c, d),
+            ItemKind::TyAlias(a, b, c, d) => ForeignItemKind::TyAlias(a, b, c, d),
+            ItemKind::Mac(a) => ForeignItemKind::Macro(a),
+            _ => return Err(item_kind),
+        })
+    }
+}
+
+pub type ForeignItem = Item<ForeignItemKind>;

src/librustc_ast/attr/mod.rs

@@ -722,6 +722,6 @@ macro_rules! derive_has_attrs {
 }
 
 derive_has_attrs! {
-    Item, Expr, Local, ast::ForeignItem, ast::StructField, ast::Arm,
+    Item, Expr, Local, ast::AssocItem, ast::ForeignItem, ast::StructField, ast::Arm,
     ast::Field, ast::FieldPat, ast::Variant, ast::Param, GenericParam
 }

src/librustc_ast/mut_visit.rs

@@ -936,25 +936,12 @@ pub fn noop_flat_map_assoc_item<T: MutVisitor>(
     visitor: &mut T,
 ) -> SmallVec<[P<AssocItem>; 1]> {
     let Item { id, ident, vis, attrs, kind, span, tokens: _ } = item.deref_mut();
-    walk_nested_item(visitor, id, span, ident, vis, attrs, kind);
-    smallvec![item]
-}
-
-pub fn walk_nested_item(
-    visitor: &mut impl MutVisitor,
-    id: &mut NodeId,
-    span: &mut Span,
-    ident: &mut Ident,
-    vis: &mut Visibility,
-    attrs: &mut Vec<Attribute>,
-    kind: &mut AssocItemKind,
-) {
     visitor.visit_id(id);
     visitor.visit_ident(ident);
     visitor.visit_vis(vis);
     visit_attrs(attrs, visitor);
     match kind {
-        AssocItemKind::Const(_, ty, expr) | AssocItemKind::Static(ty, _, expr) => {
+        AssocItemKind::Const(_, ty, expr) => {
             visitor.visit_ty(ty);
             visit_opt(expr, |expr| visitor.visit_expr(expr));
         }
@@ -971,6 +958,7 @@ pub fn walk_nested_item(
         AssocItemKind::Macro(mac) => visitor.visit_mac(mac),
     }
     visitor.visit_span(span);
+    smallvec![item]
 }
 
 pub fn noop_visit_fn_header<T: MutVisitor>(header: &mut FnHeader, vis: &mut T) {
@@ -1036,7 +1024,28 @@ pub fn noop_flat_map_foreign_item<T: MutVisitor>(
     visitor: &mut T,
 ) -> SmallVec<[P<ForeignItem>; 1]> {
     let Item { ident, attrs, id, kind, vis, span, tokens: _ } = item.deref_mut();
-    walk_nested_item(visitor, id, span, ident, vis, attrs, kind);
+    visitor.visit_id(id);
+    visitor.visit_ident(ident);
+    visitor.visit_vis(vis);
+    visit_attrs(attrs, visitor);
+    match kind {
+        ForeignItemKind::Static(ty, _, expr) => {
+            visitor.visit_ty(ty);
+            visit_opt(expr, |expr| visitor.visit_expr(expr));
+        }
+        ForeignItemKind::Fn(_, sig, generics, body) => {
+            visitor.visit_generics(generics);
+            visit_fn_sig(sig, visitor);
+            visit_opt(body, |body| visitor.visit_block(body));
+        }
+        ForeignItemKind::TyAlias(_, generics, bounds, ty) => {
+            visitor.visit_generics(generics);
+            visit_bounds(bounds, visitor);
+            visit_opt(ty, |ty| visitor.visit_ty(ty));
+        }
+        ForeignItemKind::Macro(mac) => visitor.visit_mac(mac),
+    }
+    visitor.visit_span(span);
     smallvec![item]
 }
 

src/librustc_ast/visit.rs

@@ -526,8 +526,29 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
 }
 
 pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a ForeignItem) {
-    let Item { id, span, ident, vis, attrs, kind, tokens: _ } = item;
-    walk_nested_item(visitor, *id, *span, *ident, vis, attrs, kind, FnCtxt::Foreign);
+    let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
+    visitor.visit_vis(vis);
+    visitor.visit_ident(ident);
+    walk_list!(visitor, visit_attribute, attrs);
+    match kind {
+        ForeignItemKind::Static(ty, _, expr) => {
+            visitor.visit_ty(ty);
+            walk_list!(visitor, visit_expr, expr);
+        }
+        ForeignItemKind::Fn(_, sig, generics, body) => {
+            visitor.visit_generics(generics);
+            let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, body.as_deref());
+            visitor.visit_fn(kind, span, id);
+        }
+        ForeignItemKind::TyAlias(_, generics, bounds, ty) => {
+            visitor.visit_generics(generics);
+            walk_list!(visitor, visit_param_bound, bounds);
+            walk_list!(visitor, visit_ty, ty);
+        }
+        ForeignItemKind::Macro(mac) => {
+            visitor.visit_mac(mac);
+        }
+    }
 }
 
 pub fn walk_global_asm<'a, V: Visitor<'a>>(_: &mut V, _: &'a GlobalAsm) {
@@ -610,31 +631,18 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>, _span: Spa
 }
 
 pub fn walk_assoc_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a AssocItem, ctxt: AssocCtxt) {
-    let Item { id, span, ident, vis, attrs, kind, tokens: _ } = item;
-    walk_nested_item(visitor, *id, *span, *ident, vis, attrs, kind, FnCtxt::Assoc(ctxt));
-}
-
-fn walk_nested_item<'a, V: Visitor<'a>>(
-    visitor: &mut V,
-    id: NodeId,
-    span: Span,
-    ident: Ident,
-    vis: &'a Visibility,
-    attrs: &'a [Attribute],
-    kind: &'a AssocItemKind,
-    ctxt: FnCtxt,
-) {
+    let Item { id, span, ident, ref vis, ref attrs, ref kind, tokens: _ } = *item;
     visitor.visit_vis(vis);
     visitor.visit_ident(ident);
     walk_list!(visitor, visit_attribute, attrs);
     match kind {
-        AssocItemKind::Const(_, ty, expr) | AssocItemKind::Static(ty, _, expr) => {
+        AssocItemKind::Const(_, ty, expr) => {
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_expr, expr);
         }
         AssocItemKind::Fn(_, sig, generics, body) => {
             visitor.visit_generics(generics);
-            let kind = FnKind::Fn(ctxt, ident, sig, vis, body.as_deref());
+            let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, body.as_deref());
             visitor.visit_fn(kind, span, id);
         }
         AssocItemKind::TyAlias(_, generics, bounds, ty) => {

src/librustc_ast_lowering/item.rs

@@ -675,11 +675,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let ty = self.lower_ty(t, ImplTraitContext::disallowed());
                     hir::ForeignItemKind::Static(ty, m)
                 }
-                ForeignItemKind::Const(_, ref t, _) => {
-                    // For recovery purposes.
-                    let ty = self.lower_ty(t, ImplTraitContext::disallowed());
-                    hir::ForeignItemKind::Static(ty, Mutability::Not)
-                }
                 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
                 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
             },
@@ -757,8 +752,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
 
         let (generics, kind) = match i.kind {
-            AssocItemKind::Static(ref ty, _, ref default) // Let's pretend this is a `const`.
-            | AssocItemKind::Const(_, ref ty, ref default) => {
+            AssocItemKind::Const(_, ref ty, ref default) => {
                 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
                 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
                 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body))
@@ -800,11 +794,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
         let (kind, has_default) = match &i.kind {
-            AssocItemKind::Static(_, _, default) // Let's pretend this is a `const` for recovery.
-            | AssocItemKind::Const(_, _, default) => {
-                (hir::AssocItemKind::Const, default.is_some())
+            AssocItemKind::Const(_, _, default) => (hir::AssocItemKind::Const, default.is_some()),
+            AssocItemKind::TyAlias(_, _, _, default) => {
+                (hir::AssocItemKind::Type, default.is_some())
             }
-            AssocItemKind::TyAlias(_, _, _, default) => (hir::AssocItemKind::Type, default.is_some()),
             AssocItemKind::Fn(_, sig, _, default) => {
                 (hir::AssocItemKind::Method { has_self: sig.decl.has_self() }, default.is_some())
             }
@@ -824,7 +817,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
 
         let (generics, kind) = match &i.kind {
-            AssocItemKind::Static(ty, _, expr) | AssocItemKind::Const(_, ty, expr) => {
+            AssocItemKind::Const(_, ty, expr) => {
                 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
                 (
                     hir::Generics::empty(),
@@ -892,8 +885,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             vis: self.lower_visibility(&i.vis, Some(i.id)),
             defaultness: self.lower_defaultness(i.kind.defaultness(), true /* [1] */),
             kind: match &i.kind {
-                AssocItemKind::Static(..) // Let's pretend this is a `const` for recovery.
-                | AssocItemKind::Const(..) => hir::AssocItemKind::Const,
+                AssocItemKind::Const(..) => hir::AssocItemKind::Const,
                 AssocItemKind::TyAlias(.., ty) => {
                     match ty.as_deref().and_then(|ty| ty.kind.opaque_top_hack()) {
                         None => hir::AssocItemKind::Type,

src/librustc_ast_passes/ast_validation.rs

@@ -976,7 +976,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             ForeignItemKind::Static(_, _, body) => {
                 self.check_foreign_kind_bodyless(fi.ident, "static", body.as_ref().map(|b| b.span));
             }
-            ForeignItemKind::Const(..) | ForeignItemKind::Macro(..) => {}
+            ForeignItemKind::Macro(..) => {}
         }
 
         visit::walk_foreign_item(self, fi)

src/librustc_ast_passes/feature_gate.rs

@@ -400,7 +400,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ForeignItemKind::TyAlias(..) => {
                 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
             }
-            ast::ForeignItemKind::Macro(..) | ast::ForeignItemKind::Const(..) => {}
+            ast::ForeignItemKind::Macro(..) => {}
         }
 
         visit::walk_foreign_item(self, i)