rustc_hir: Change representation of import paths to support multiple resolutions

2 files changed, 15 insertions, 27 deletions

diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 2b47e908912..b26b37b0466 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -508,7 +508,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let mut resolutions = self.expect_full_res_from_use(id).fuse();
                 // We want to return *something* from this function, so hold onto the first item
                 // for later.
-                let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
+                let ret_res = smallvec![self.lower_res(resolutions.next().unwrap_or(Res::Err))];
 
                 // Here, we are looping over namespaces, if they exist for the definition
                 // being imported. We only handle type and value namespaces because we
@@ -538,8 +538,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let span = path.span;
 
                     self.with_hir_id_owner(new_node_id, |this| {
-                        let res = this.lower_res(res);
-                        let path = this.lower_path_extra(res, &path, ParamMode::Explicit);
+                        let res = smallvec![this.lower_res(res)];
+                        let path = this.lower_use_path(res, &path, ParamMode::Explicit);
                         let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
                         if let Some(attrs) = attrs {
                             this.attrs.insert(hir::ItemLocalId::new(0), attrs);
@@ -556,15 +556,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     });
                 }
 
-                let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit);
+                let path = self.lower_use_path(ret_res, &path, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::Single)
             }
             UseTreeKind::Glob => {
-                let path = self.lower_path(
-                    id,
-                    &Path { segments, span: path.span, tokens: None },
-                    ParamMode::Explicit,
-                );
+                let res = self.expect_full_res(id);
+                let res = smallvec![self.lower_res(res)];
+                let path = Path { segments, span: path.span, tokens: None };
+                let path = self.lower_use_path(res, &path, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::Glob)
             }
             UseTreeKind::Nested(ref trees) => {
@@ -635,8 +634,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
 
                 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
-                let res = self.lower_res(res);
-                let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit);
+                let res = smallvec![self.lower_res(res)];
+                let path = self.lower_use_path(res, &prefix, ParamMode::Explicit);
                 hir::ItemKind::Use(path, hir::UseKind::ListStem)
             }
         }
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index dc85b5e95ea..8d23c26e603 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -12,7 +12,7 @@ use rustc_hir::GenericArg;
 use rustc_span::symbol::{kw, Ident};
 use rustc_span::{BytePos, Span, DUMMY_SP};
 
-use smallvec::smallvec;
+use smallvec::{smallvec, SmallVec};
 
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
     #[instrument(level = "trace", skip(self))]
@@ -144,13 +144,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         );
     }
 
-    pub(crate) fn lower_path_extra(
+    pub(crate) fn lower_use_path(
         &mut self,
-        res: Res,
+        res: SmallVec<[Res; 3]>,
         p: &Path,
         param_mode: ParamMode,
-    ) -> &'hir hir::Path<'hir> {
-        self.arena.alloc(hir::Path {
+    ) -> &'hir hir::UsePath<'hir> {
+        self.arena.alloc(hir::UsePath {
             res,
             segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
                 self.lower_path_segment(
@@ -165,17 +165,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         })
     }
 
-    pub(crate) fn lower_path(
-        &mut self,
-        id: NodeId,
-        p: &Path,
-        param_mode: ParamMode,
-    ) -> &'hir hir::Path<'hir> {
-        let res = self.expect_full_res(id);
-        let res = self.lower_res(res);
-        self.lower_path_extra(res, p, param_mode)
-    }
-
     pub(crate) fn lower_path_segment(
         &mut self,
         path_span: Span,