Store a resolved def on hir::PathSegment

src/librustc/hir/lowering.rs

@@ -143,8 +143,13 @@ pub struct LoweringContext<'a> {
 }
 
 pub trait Resolver {
-    /// Resolve a hir path generated by the lowerer when expanding `for`, `if let`, etc.
-    fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool);
+    /// Resolve a path generated by the lowerer when expanding `for`, `if let`, etc.
+    fn resolve_hir_path(
+        &mut self,
+        path: &ast::Path,
+        args: Option<P<hir::GenericArgs>>,
+        is_value: bool,
+    ) -> hir::Path;
 
     /// Obtain the resolution for a node id
     fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution>;
@@ -163,7 +168,7 @@ pub trait Resolver {
         span: Span,
         crate_root: Option<&str>,
         components: &[&str],
-        params: Option<P<hir::GenericArgs>>,
+        args: Option<P<hir::GenericArgs>>,
         is_value: bool,
     ) -> hir::Path;
 }
@@ -1380,6 +1385,7 @@ impl<'a> LoweringContext<'a> {
             // does not actually exist in the AST.
             lctx.items.insert(exist_ty_id.node_id, exist_ty_item);
 
+            let def = Def::Existential(DefId::local(exist_ty_def_index));
             // `impl Trait` now just becomes `Foo<'a, 'b, ..>`
             hir::TyKind::Def(hir::ItemId { id: exist_ty_id.node_id }, lifetimes)
         })
@@ -1852,8 +1858,10 @@ impl<'a> LoweringContext<'a> {
             }
         }
 
+        let def = self.expect_full_def(segment.id);
         hir::PathSegment::new(
             segment.ident,
+            Some(def),
             generic_args,
             infer_types,
         )

src/librustc/hir/mod.rs

@@ -347,6 +347,7 @@ impl fmt::Display for Path {
 pub struct PathSegment {
     /// The identifier portion of this path segment.
     pub ident: Ident,
+    pub def: Option<Def>,
 
     /// Type/lifetime parameters attached to this path. They come in
     /// two flavors: `Path<A,B,C>` and `Path(A,B) -> C`. Note that
@@ -367,14 +368,16 @@ impl PathSegment {
     pub fn from_ident(ident: Ident) -> PathSegment {
         PathSegment {
             ident,
+            def: None,
             infer_types: true,
             args: None,
         }
     }
 
-    pub fn new(ident: Ident, args: GenericArgs, infer_types: bool) -> Self {
+    pub fn new(ident: Ident, def: Option<Def>, args: GenericArgs, infer_types: bool) -> Self {
         PathSegment {
             ident,
+            def,
             infer_types,
             args: if args.is_empty() {
                 None

src/librustc/ich/impls_hir.rs

@@ -174,6 +174,7 @@ impl_stable_hash_for!(struct hir::Path {
 
 impl_stable_hash_for!(struct hir::PathSegment {
     ident -> (ident.name),
+    def,
     infer_types,
     args
 });

src/librustc_resolve/build_reduced_graph.rs

@@ -141,7 +141,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
         let prefix_iter = || parent_prefix.iter().cloned()
             .chain(use_tree.prefix.segments.iter().map(|seg| seg.ident));
         let prefix_start = prefix_iter().next();
-        let starts_with_non_keyword = prefix_start.map_or(false, |ident| {
+        let starts_with_non_keyword = prefix_start.map_or(false, |(ident, _)| {
             !ident.is_path_segment_keyword()
         });
 
@@ -202,13 +202,13 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
             let source = prefix_start.unwrap();
 
             // Helper closure to emit a canary with the given base path.
-            let emit = |this: &mut Self, base: Option<Ident>| {
+            let emit = |this: &mut Self, base: Option<(Ident, Option<NodeId>)>| {
                 let subclass = SingleImport {
                     target: Ident {
                         name: keywords::Underscore.name().gensymed(),
-                        span: source.span,
+                        span: source.0.span,
                     },
-                    source,
+                    source: source.0,
                     result: PerNS {
                         type_ns: Cell::new(Err(Undetermined)),
                         value_ns: Cell::new(Err(Undetermined)),
@@ -219,7 +219,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 this.add_import_directive(
                     base.into_iter().collect(),
                     subclass.clone(),
-                    source.span,
+                    source.0.span,
                     id,
                     root_use_tree.span,
                     root_id,
@@ -230,15 +230,15 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
             };
 
             // A single simple `self::x` canary.
-            emit(self, Some(Ident {
+            emit(self, Some((Ident {
                 name: keywords::SelfValue.name(),
-                span: source.span,
-            }));
+                span: source.0.span,
+            }, source.1)));
 
             // One special unprefixed canary per block scope around
             // the import, to detect items unreachable by `self::x`.
             let orig_current_module = self.current_module;
-            let mut span = source.span.modern();
+            let mut span = source.0.span.modern();
             loop {
                 match self.current_module.kind {
                     ModuleKind::Block(..) => emit(self, None),
@@ -265,10 +265,10 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
 
                 if nested {
                     // Correctly handle `self`
-                    if source.name == keywords::SelfValue.name() {
+                    if source.0.name == keywords::SelfValue.name() {
                         type_ns_only = true;
 
-                        let empty_prefix = module_path.last().map_or(true, |ident| {
+                        let empty_prefix = module_path.last().map_or(true, |(ident, _)| {
                             ident.name == keywords::CrateRoot.name()
                         });
                         if empty_prefix {
@@ -284,20 +284,20 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                         // Replace `use foo::self;` with `use foo;`
                         source = module_path.pop().unwrap();
                         if rename.is_none() {
-                            ident = source;
+                            ident = source.0;
                         }
                     }
                 } else {
                     // Disallow `self`
-                    if source.name == keywords::SelfValue.name() {
+                    if source.0.name == keywords::SelfValue.name() {
                         resolve_error(self,
                                       use_tree.span,
                                       ResolutionError::SelfImportsOnlyAllowedWithin);
                     }
 
                     // Disallow `use $crate;`
-                    if source.name == keywords::DollarCrate.name() && module_path.is_empty() {
-                        let crate_root = self.resolve_crate_root(source);
+                    if source.0.name == keywords::DollarCrate.name() && module_path.is_empty() {
+                        let crate_root = self.resolve_crate_root(source.0);
                         let crate_name = match crate_root.kind {
                             ModuleKind::Def(_, name) => name,
                             ModuleKind::Block(..) => unreachable!(),
@@ -307,11 +307,11 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                         // while the current crate doesn't have a valid `crate_name`.
                         if crate_name != keywords::Invalid.name() {
                             // `crate_name` should not be interpreted as relative.
-                            module_path.push(Ident {
+                            module_path.push((Ident {
                                 name: keywords::CrateRoot.name(),
-                                span: source.span,
-                            });
-                            source.name = crate_name;
+                                span: source.0.span,
+                            }, Some(self.session.next_node_id())));
+                            source.0.name = crate_name;
                         }
                         if rename.is_none() {
                             ident.name = crate_name;
@@ -332,7 +332,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
 
                 let subclass = SingleImport {
                     target: ident,
-                    source,
+                    source: source.0,
                     result: PerNS {
                         type_ns: Cell::new(Err(Undetermined)),
                         value_ns: Cell::new(Err(Undetermined)),
@@ -393,6 +393,17 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 }
 
                 for &(ref tree, id) in items {
+                    let prefix = ast::Path {
+                        segments: module_path.iter()
+                            .map(|ident| {
+                                let mut seg = ast::PathSegment::from_ident(ident.0);
+                                seg.id = self.session.next_node_id();
+                                seg
+                            })
+                            .collect(),
+                        span: path.span,
+                    };
+
                     self.build_reduced_graph_for_use_tree(
                         root_use_tree,
                         root_id,