Auto merge of #51806 - oli-obk:lowering_cleanups1, r=cramertj

Lowering cleanups [1/N]

src/librustc/hir/intravisit.rs

@@ -607,9 +607,11 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             }
             visitor.visit_lifetime(lifetime);
         }
-        TyImplTraitExistential(item_id, def_id, ref lifetimes) => {
+        TyImplTraitExistential(_, def_id, ref lifetimes) => {
+            // we are not recursing into the `existential` item, because it is already being visited
+            // as part of the surrounding module. The `NodeId` just exists so we don't have to look
+            // it up everywhere else in the compiler
             visitor.visit_def_mention(Def::Existential(def_id));
-            visitor.visit_nested_item(item_id);
             walk_list!(visitor, visit_lifetime, lifetimes);
         }
         TyTypeof(ref expression) => {

src/librustc/hir/map/collector.rs

@@ -221,23 +221,27 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
         // Make sure that the DepNode of some node coincides with the HirId
         // owner of that node.
         if cfg!(debug_assertions) {
-            let hir_id_owner = self.definitions.node_to_hir_id(id).owner;
+            let hir_id = self.definitions.node_to_hir_id(id);
 
-            if hir_id_owner != self.current_dep_node_owner {
+            if hir_id.owner != self.current_dep_node_owner {
                 let node_str = match self.definitions.opt_def_index(id) {
                     Some(def_index) => {
                         self.definitions.def_path(def_index).to_string_no_crate()
                     }
                     None => format!("{:?}", node)
                 };
 
+                if hir_id == ::hir::DUMMY_HIR_ID {
+                    debug!("Maybe you forgot to lower the node id {:?}?", id);
+                }
+
                 bug!("inconsistent DepNode for `{}`: \
                       current_dep_node_owner={}, hir_id.owner={}",
                     node_str,
                     self.definitions
                         .def_path(self.current_dep_node_owner)
                         .to_string_no_crate(),
-                    self.definitions.def_path(hir_id_owner).to_string_no_crate())
+                    self.definitions.def_path(hir_id.owner).to_string_no_crate())
             }
         }
 

src/librustc/hir/map/def_collector.rs

@@ -77,6 +77,7 @@ impl<'a> DefCollector<'a> {
         &mut self,
         id: NodeId,
         async_node_id: NodeId,
+        return_impl_trait_id: NodeId,
         name: Name,
         span: Span,
         visit_fn: impl FnOnce(&mut DefCollector<'a>)
@@ -86,6 +87,7 @@ impl<'a> DefCollector<'a> {
         let fn_def_data = DefPathData::ValueNs(name.as_interned_str());
         let fn_def = self.create_def(id, fn_def_data, ITEM_LIKE_SPACE, span);
         return self.with_parent(fn_def, |this| {
+            this.create_def(return_impl_trait_id, DefPathData::ImplTrait, REGULAR_SPACE, span);
             let closure_def = this.create_def(async_node_id,
                                   DefPathData::ClosureExpr,
                                   REGULAR_SPACE,
@@ -120,10 +122,14 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             ItemKind::Mod(..) if i.ident == keywords::Invalid.ident() => {
                 return visit::walk_item(self, i);
             }
-            ItemKind::Fn(_, FnHeader { asyncness: IsAsync::Async(async_node_id), .. }, ..) => {
+            ItemKind::Fn(_, FnHeader { asyncness: IsAsync::Async {
+                closure_id,
+                return_impl_trait_id,
+            }, .. }, ..) => {
                 return self.visit_async_fn(
                     i.id,
-                    async_node_id,
+                    closure_id,
+                    return_impl_trait_id,
                     i.ident.name,
                     i.span,
                     |this| visit::walk_item(this, i)
@@ -227,11 +233,15 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
     fn visit_impl_item(&mut self, ii: &'a ImplItem) {
         let def_data = match ii.node {
             ImplItemKind::Method(MethodSig {
-                header: FnHeader { asyncness: IsAsync::Async(async_node_id), .. }, ..
+                header: FnHeader { asyncness: IsAsync::Async {
+                    closure_id,
+                    return_impl_trait_id,
+                }, .. }, ..
             }, ..) => {
                 return self.visit_async_fn(
                     ii.id,
-                    async_node_id,
+                    closure_id,
+                    return_impl_trait_id,
                     ii.ident.name,
                     ii.span,
                     |this| visit::walk_impl_item(this, ii)
@@ -276,8 +286,8 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
 
                 // Async closures desugar to closures inside of closures, so
                 // we must create two defs.
-                if let IsAsync::Async(async_id) = asyncness {
-                    let async_def = self.create_def(async_id,
+                if let IsAsync::Async { closure_id, .. } = asyncness {
+                    let async_def = self.create_def(closure_id,
                                                     DefPathData::ClosureExpr,
                                                     REGULAR_SPACE,
                                                     expr.span);
@@ -301,6 +311,9 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
     fn visit_ty(&mut self, ty: &'a Ty) {
         match ty.node {
             TyKind::Mac(..) => return self.visit_macro_invoc(ty.id),
+            TyKind::ImplTrait(node_id, _) => {
+                self.create_def(node_id, DefPathData::ImplTrait, REGULAR_SPACE, ty.span);
+            }
             _ => {}
         }
         visit::walk_ty(self, ty);

src/librustc/hir/map/definitions.rs

@@ -374,10 +374,8 @@ pub enum DefPathData {
     StructCtor,
     /// A constant expression (see {ast,hir}::AnonConst).
     AnonConst,
-    /// An `impl Trait` type node in argument position.
-    UniversalImplTrait,
-    /// An `impl Trait` type node in return position.
-    ExistentialImplTrait,
+    /// An `impl Trait` type node
+    ImplTrait,
 
     /// GlobalMetaData identifies a piece of crate metadata that is global to
     /// a whole crate (as opposed to just one item). GlobalMetaData components
@@ -641,8 +639,7 @@ impl DefPathData {
             ClosureExpr |
             StructCtor |
             AnonConst |
-            ExistentialImplTrait |
-            UniversalImplTrait => None
+            ImplTrait => None
         }
     }
 
@@ -672,8 +669,7 @@ impl DefPathData {
             ClosureExpr => "{{closure}}",
             StructCtor => "{{constructor}}",
             AnonConst => "{{constant}}",
-            ExistentialImplTrait => "{{exist-impl-Trait}}",
-            UniversalImplTrait => "{{univ-impl-Trait}}",
+            ImplTrait => "{{impl-Trait}}",
         };
 
         Symbol::intern(s).as_interned_str()

src/librustc/ty/item_path.rs

@@ -221,8 +221,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             data @ DefPathData::AnonConst |
             data @ DefPathData::MacroDef(..) |
             data @ DefPathData::ClosureExpr |
-            data @ DefPathData::ExistentialImplTrait |
-            data @ DefPathData::UniversalImplTrait |
+            data @ DefPathData::ImplTrait |
             data @ DefPathData::GlobalMetaData(..) => {
                 let parent_def_id = self.parent_def_id(def_id).unwrap();
                 self.push_item_path(buffer, parent_def_id);

src/librustc/util/ppaux.rs

@@ -291,8 +291,7 @@ impl PrintContext {
                     DefPathData::Field(_) |
                     DefPathData::StructCtor |
                     DefPathData::AnonConst |
-                    DefPathData::ExistentialImplTrait |
-                    DefPathData::UniversalImplTrait |
+                    DefPathData::ImplTrait |
                     DefPathData::GlobalMetaData(_) => {
                         // if we're making a symbol for something, there ought
                         // to be a value or type-def or something in there

src/librustc_driver/pretty.rs

@@ -669,7 +669,7 @@ impl<'a> ReplaceBodyWithLoop<'a> {
         if let ast::FunctionRetTy::Ty(ref ty) = ret_ty.output {
             fn involves_impl_trait(ty: &ast::Ty) -> bool {
                 match ty.node {
-                    ast::TyKind::ImplTrait(_) => true,
+                    ast::TyKind::ImplTrait(..) => true,
                     ast::TyKind::Slice(ref subty) |
                     ast::TyKind::Array(ref subty, _) |
                     ast::TyKind::Ptr(ast::MutTy { ty: ref subty, .. }) |

src/librustc_passes/ast_validation.rs

@@ -208,7 +208,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 }
                 self.no_questions_in_bounds(bounds, "trait object types", false);
             }
-            TyKind::ImplTrait(ref bounds) => {
+            TyKind::ImplTrait(_, ref bounds) => {
                 if !bounds.iter()
                           .any(|b| if let GenericBound::Trait(..) = *b { true } else { false }) {
                     self.err_handler().span_err(ty.span, "at least one trait must be specified");
@@ -505,7 +505,7 @@ impl<'a> NestedImplTraitVisitor<'a> {
 
 impl<'a> Visitor<'a> for NestedImplTraitVisitor<'a> {
     fn visit_ty(&mut self, t: &'a Ty) {
-        if let TyKind::ImplTrait(_) = t.node {
+        if let TyKind::ImplTrait(..) = t.node {
             if let Some(outer_impl_trait) = self.outer_impl_trait {
                 struct_span_err!(self.session, t.span, E0666,
                                  "nested `impl Trait` is not allowed")
@@ -570,7 +570,7 @@ impl<'a> ImplTraitProjectionVisitor<'a> {
 impl<'a> Visitor<'a> for ImplTraitProjectionVisitor<'a> {
     fn visit_ty(&mut self, t: &'a Ty) {
         match t.node {
-            TyKind::ImplTrait(_) => {
+            TyKind::ImplTrait(..) => {
                 if self.is_banned {
                     struct_span_err!(self.session, t.span, E0667,
                                  "`impl Trait` is not allowed in path parameters")

src/librustc_resolve/lib.rs

@@ -777,8 +777,8 @@ impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
         visit::walk_fn_ret_ty(self, &declaration.output);
 
         // Resolve the function body, potentially inside the body of an async closure
-        if let IsAsync::Async(async_closure_id) = asyncness {
-            let rib_kind = ClosureRibKind(async_closure_id);
+        if let IsAsync::Async { closure_id, .. } = asyncness {
+            let rib_kind = ClosureRibKind(closure_id);
             self.ribs[ValueNS].push(Rib::new(rib_kind));
             self.label_ribs.push(Rib::new(rib_kind));
         }
@@ -3933,8 +3933,9 @@ impl<'a> Resolver<'a> {
             // resolve the arguments within the proper scopes so that usages of them inside the
             // closure are detected as upvars rather than normal closure arg usages.
             ExprKind::Closure(
-                _, IsAsync::Async(inner_closure_id), _, ref fn_decl, ref body, _span) =>
-            {
+                _, IsAsync::Async { closure_id: inner_closure_id, .. }, _,
+                ref fn_decl, ref body, _span,
+            ) => {
                 let rib_kind = ClosureRibKind(expr.id);
                 self.ribs[ValueNS].push(Rib::new(rib_kind));
                 self.label_ribs.push(Rib::new(rib_kind));

src/librustc_save_analysis/sig.rs

@@ -306,7 +306,7 @@ impl Sig for ast::Ty {
                 let nested = pprust::bounds_to_string(bounds);
                 Ok(text_sig(nested))
             }
-            ast::TyKind::ImplTrait(ref bounds) => {
+            ast::TyKind::ImplTrait(_, ref bounds) => {
                 // FIXME recurse into bounds
                 let nested = pprust::bounds_to_string(bounds);
                 Ok(text_sig(format!("impl {}", nested)))

src/libsyntax/ast.rs

@@ -1547,7 +1547,11 @@ pub enum TyKind {
     TraitObject(GenericBounds, TraitObjectSyntax),
     /// An `impl Bound1 + Bound2 + Bound3` type
     /// where `Bound` is a trait or a lifetime.
-    ImplTrait(GenericBounds),
+    ///
+    /// The `NodeId` exists to prevent lowering from having to
+    /// generate `NodeId`s on the fly, which would complicate
+    /// the generation of `existential type` items significantly
+    ImplTrait(NodeId, GenericBounds),
     /// No-op; kept solely so that we can pretty-print faithfully
     Paren(P<Ty>),
     /// Unused for now
@@ -1718,18 +1722,28 @@ pub enum Unsafety {
 
 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum IsAsync {
-    Async(NodeId),
+    Async {
+        closure_id: NodeId,
+        return_impl_trait_id: NodeId,
+    },
     NotAsync,
 }
 
 impl IsAsync {
     pub fn is_async(self) -> bool {
-        if let IsAsync::Async(_) = self {
+        if let IsAsync::Async { .. } = self {
             true
         } else {
             false
         }
     }
+    /// In case this is an `Async` return the `NodeId` for the generated impl Trait item
+    pub fn opt_return_id(self) -> Option<NodeId> {
+        match self {
+            IsAsync::Async { return_impl_trait_id, .. } => Some(return_impl_trait_id),
+            IsAsync::NotAsync => None,
+        }
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]

src/libsyntax/feature_gate.rs

@@ -1726,7 +1726,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                                     "labels on blocks are unstable");
                 }
             }
-            ast::ExprKind::Closure(_, ast::IsAsync::Async(_), ..) => {
+            ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
                 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
             }
             ast::ExprKind::Async(..) => {

src/libsyntax/fold.rs

@@ -100,6 +100,10 @@ pub trait Folder : Sized {
         noop_fold_fn_decl(d, self)
     }
 
+    fn fold_asyncness(&mut self, a: IsAsync) -> IsAsync {
+        noop_fold_asyncness(a, self)
+    }
+
     fn fold_block(&mut self, b: P<Block>) -> P<Block> {
         noop_fold_block(b, self)
     }
@@ -396,8 +400,8 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
             TyKind::TraitObject(bounds, syntax) => {
                 TyKind::TraitObject(bounds.move_map(|b| fld.fold_param_bound(b)), syntax)
             }
-            TyKind::ImplTrait(bounds) => {
-                TyKind::ImplTrait(bounds.move_map(|b| fld.fold_param_bound(b)))
+            TyKind::ImplTrait(id, bounds) => {
+                TyKind::ImplTrait(fld.new_id(id), bounds.move_map(|b| fld.fold_param_bound(b)))
             }
             TyKind::Mac(mac) => {
                 TyKind::Mac(fld.fold_mac(mac))
@@ -669,6 +673,16 @@ pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
     }
 }
 
+pub fn noop_fold_asyncness<T: Folder>(asyncness: IsAsync, fld: &mut T) -> IsAsync {
+    match asyncness {
+        IsAsync::Async { closure_id, return_impl_trait_id } => IsAsync::Async {
+            closure_id: fld.new_id(closure_id),
+            return_impl_trait_id: fld.new_id(return_impl_trait_id),
+        },
+        IsAsync::NotAsync => IsAsync::NotAsync,
+    }
+}
+
 pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
     decl.map(|FnDecl {inputs, output, variadic}| FnDecl {
         inputs: inputs.move_map(|x| fld.fold_arg(x)),
@@ -996,10 +1010,7 @@ pub fn noop_fold_impl_item<T: Folder>(i: ImplItem, folder: &mut T)
 }
 
 pub fn noop_fold_fn_header<T: Folder>(mut header: FnHeader, folder: &mut T) -> FnHeader {
-    header.asyncness = match header.asyncness {
-        IsAsync::Async(node_id) => IsAsync::Async(folder.new_id(node_id)),
-        IsAsync::NotAsync => IsAsync::NotAsync,
-    };
+    header.asyncness = folder.fold_asyncness(header.asyncness);
     header
 }
 
@@ -1249,12 +1260,8 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mu
                           arms.move_map(|x| folder.fold_arm(x)))
             }
             ExprKind::Closure(capture_clause, asyncness, movability, decl, body, span) => {
-                let asyncness = match asyncness {
-                    IsAsync::Async(node_id) => IsAsync::Async(folder.new_id(node_id)),
-                    IsAsync::NotAsync => IsAsync::NotAsync,
-                };
                 ExprKind::Closure(capture_clause,
-                                  asyncness,
+                                  folder.fold_asyncness(asyncness),
                                   movability,
                                   folder.fold_fn_decl(decl),
                                   folder.fold_expr(body),
@@ -1265,7 +1272,11 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mu
                                 opt_label.map(|label| folder.fold_label(label)))
             }
             ExprKind::Async(capture_clause, node_id, body) => {
-                ExprKind::Async(capture_clause, folder.new_id(node_id), folder.fold_block(body))
+                ExprKind::Async(
+                    capture_clause,
+                    folder.new_id(node_id),
+                    folder.fold_block(body),
+                )
             }
             ExprKind::Assign(el, er) => {
                 ExprKind::Assign(folder.fold_expr(el), folder.fold_expr(er))