2 files changed, 51 insertions, 1 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 3fb419571..af59aa1b6 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -953,6 +953,16 @@ impl TypeParam {
     pub fn module(self, db: &dyn HirDatabase) -> Module {
         self.id.parent.module(db.upcast()).into()
     }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let resolver = self.id.parent.resolver(db.upcast());
+        let environment = TraitEnvironment::lower(db, &resolver);
+        let ty = Ty::Placeholder(self.id);
+        Type {
+            krate: self.id.parent.module(db.upcast()).krate,
+            ty: InEnvironment { value: ty, environment },
+        }
+    }
 }
 
 // FIXME: rename from `ImplDef` to `Impl`
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index 86bfb416c..a0a0f234b 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -9,6 +9,7 @@ use hir_def::{
     AsMacroCall, TraitId,
 };
 use hir_expand::ExpansionInfo;
+use hir_ty::associated_type_shorthand_candidates;
 use itertools::Itertools;
 use ra_db::{FileId, FileRange};
 use ra_prof::profile;
@@ -24,8 +25,9 @@ use crate::{
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, SourceAnalyzer},
     AssocItem, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef, Module, ModuleDef,
-    Name, Origin, Path, ScopeDef, Trait, Type, TypeParam,
+    Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam,
 };
+use resolver::TypeNs;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum PathResolution {
@@ -40,6 +42,44 @@ pub enum PathResolution {
     AssocItem(AssocItem),
 }
 
+impl PathResolution {
+    fn in_type_ns(&self) -> Option<TypeNs> {
+        match self {
+            PathResolution::Def(ModuleDef::Adt(adt)) => Some(TypeNs::AdtId((*adt).into())),
+            PathResolution::Def(ModuleDef::BuiltinType(builtin)) => {
+                Some(TypeNs::BuiltinType(*builtin))
+            }
+            PathResolution::Def(ModuleDef::Const(_))
+            | PathResolution::Def(ModuleDef::EnumVariant(_))
+            | PathResolution::Def(ModuleDef::Function(_))
+            | PathResolution::Def(ModuleDef::Module(_))
+            | PathResolution::Def(ModuleDef::Static(_))
+            | PathResolution::Def(ModuleDef::Trait(_)) => None,
+            PathResolution::Def(ModuleDef::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+            PathResolution::Local(_) | PathResolution::Macro(_) => None,
+            PathResolution::TypeParam(param) => Some(TypeNs::GenericParam((*param).into())),
+            PathResolution::SelfType(impl_def) => Some(TypeNs::SelfType((*impl_def).into())),
+            PathResolution::AssocItem(AssocItem::Const(_))
+            | PathResolution::AssocItem(AssocItem::Function(_)) => None,
+            PathResolution::AssocItem(AssocItem::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+        }
+    }
+
+    /// Returns an iterator over associated types that may be specified after this path (using
+    /// `Ty::Assoc` syntax).
+    pub fn assoc_type_shorthand_candidates<R>(
+        &self,
+        db: &dyn HirDatabase,
+        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+    ) -> Option<R> {
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+    }
+}
+
 /// Primary API to get semantic information, like types, from syntax trees.
 pub struct Semantics<'db, DB> {
     pub db: &'db DB,