3 files changed, 87 insertions, 7 deletions

diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 5e4d49ffb..f7a35f05b 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -54,6 +54,24 @@ pub fn infer(db: &impl HirDatabase, func: Function) -> Arc<InferenceResult> {
     Arc::new(ctx.resolve_all())
 }
 
+#[derive(Debug, Copy, Clone)]
+enum ExprOrPatId {
+    Expr(ExprId),
+    Pat(PatId),
+}
+
+impl From<ExprId> for ExprOrPatId {
+    fn from(id: ExprId) -> Self {
+        ExprOrPatId::Expr(id)
+    }
+}
+
+impl From<PatId> for ExprOrPatId {
+    fn from(id: PatId) -> Self {
+        ExprOrPatId::Pat(id)
+    }
+}
+
 /// The result of type inference: A mapping from expressions and patterns to types.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct InferenceResult {
@@ -61,6 +79,8 @@ pub struct InferenceResult {
     method_resolutions: FxHashMap<ExprId, Function>,
     /// For each field access expr, records the field it resolves to.
     field_resolutions: FxHashMap<ExprId, StructField>,
+    /// For each associated function call expr, records the function it resolves to
+    assoc_fn_resolutions: FxHashMap<ExprId, Function>,
     pub(super) type_of_expr: ArenaMap<ExprId, Ty>,
     pub(super) type_of_pat: ArenaMap<PatId, Ty>,
 }
@@ -72,6 +92,9 @@ impl InferenceResult {
     pub fn field_resolution(&self, expr: ExprId) -> Option<StructField> {
         self.field_resolutions.get(&expr).map(|it| *it)
     }
+    pub fn assoc_fn_resolutions(&self, expr: ExprId) -> Option<Function> {
+        self.assoc_fn_resolutions.get(&expr).map(|it| *it)
+    }
 }
 
 impl Index<ExprId> for InferenceResult {
@@ -99,6 +122,7 @@ struct InferenceContext<'a, D: HirDatabase> {
     var_unification_table: InPlaceUnificationTable<TypeVarId>,
     method_resolutions: FxHashMap<ExprId, Function>,
     field_resolutions: FxHashMap<ExprId, StructField>,
+    assoc_fn_resolutions: FxHashMap<ExprId, Function>,
     type_of_expr: ArenaMap<ExprId, Ty>,
     type_of_pat: ArenaMap<PatId, Ty>,
     /// The return type of the function being inferred.
@@ -110,6 +134,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         InferenceContext {
             method_resolutions: FxHashMap::default(),
             field_resolutions: FxHashMap::default(),
+            assoc_fn_resolutions: FxHashMap::default(),
             type_of_expr: ArenaMap::default(),
             type_of_pat: ArenaMap::default(),
             var_unification_table: InPlaceUnificationTable::new(),
@@ -135,6 +160,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         InferenceResult {
             method_resolutions: self.method_resolutions,
             field_resolutions: self.field_resolutions,
+            assoc_fn_resolutions: self.assoc_fn_resolutions,
             type_of_expr: expr_types,
             type_of_pat: pat_types,
         }
@@ -152,6 +178,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.field_resolutions.insert(expr, field);
     }
 
+    fn write_assoc_fn_resolution(&mut self, expr: ExprId, func: Function) {
+        self.assoc_fn_resolutions.insert(expr, func);
+    }
+
     fn write_pat_ty(&mut self, pat: PatId, ty: Ty) {
         self.type_of_pat.insert(pat, ty);
     }
@@ -341,7 +371,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         })
     }
 
-    fn infer_path_expr(&mut self, resolver: &Resolver, path: &Path) -> Option<Ty> {
+    fn infer_path_expr(&mut self, resolver: &Resolver, path: &Path, id: ExprOrPatId) -> Option<Ty> {
         let resolved = resolver.resolve_path_segments(self.db, &path);
 
         let (def, remaining_index) = resolved.into_inner();
@@ -421,6 +451,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let typable: Option<TypableDef> = def.into();
                 let typable = typable?;
 
+                if let ExprOrPatId::Expr(expr) = id {
+                    match typable {
+                        TypableDef::Function(func) => self.write_assoc_fn_resolution(expr, func),
+                        _ => {}
+                    };
+                }
+
                 let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
                 let ty = self.db.type_for_def(typable, Namespace::Values).apply_substs(substs);
                 let ty = self.insert_type_vars(ty);
@@ -572,7 +609,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Pat::Path(path) => {
                 // TODO use correct resolver for the surrounding expression
                 let resolver = self.resolver.clone();
-                self.infer_path_expr(&resolver, &path).unwrap_or(Ty::Unknown)
+                self.infer_path_expr(&resolver, &path, pat.into()).unwrap_or(Ty::Unknown)
             }
             Pat::Bind { mode, name: _name, subpat } => {
                 let inner_ty = if let Some(subpat) = subpat {
@@ -782,7 +819,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::Path(p) => {
                 // TODO this could be more efficient...
                 let resolver = expr::resolver_for_expr(self.body.clone(), self.db, tgt_expr);
-                self.infer_path_expr(&resolver, p).unwrap_or(Ty::Unknown)
+                self.infer_path_expr(&resolver, p, tgt_expr.into()).unwrap_or(Ty::Unknown)
             }
             Expr::Continue => Ty::Never,
             Expr::Break { expr } => {
diff --git a/crates/ra_ide_api/src/goto_definition.rs b/crates/ra_ide_api/src/goto_definition.rs
index 9ec179593..e4febe8cc 100644
--- a/crates/ra_ide_api/src/goto_definition.rs
+++ b/crates/ra_ide_api/src/goto_definition.rs
@@ -47,9 +47,10 @@ pub(crate) fn reference_definition(
     name_ref: &ast::NameRef,
 ) -> ReferenceResult {
     use self::ReferenceResult::*;
-    if let Some(function) =
-        hir::source_binder::function_from_child_node(db, file_id, name_ref.syntax())
-    {
+
+    let function = hir::source_binder::function_from_child_node(db, file_id, name_ref.syntax());
+
+    if let Some(function) = function {
         // Check if it is a method
         if let Some(method_call) = name_ref.syntax().parent().and_then(ast::MethodCallExpr::cast) {
             tested_by!(goto_definition_works_for_methods);
@@ -122,9 +123,29 @@ pub(crate) fn reference_definition(
             Some(Resolution::SelfType(_impl_block)) => {
                 // TODO: go to the implemented type
             }
-            None => {}
+            None => {
+                // If we failed to resolve then check associated items
+                if let Some(function) = function {
+                    // Should we do this above and then grab path from the PathExpr?
+                    if let Some(path_expr) =
+                        name_ref.syntax().ancestors().find_map(ast::PathExpr::cast)
+                    {
+                        let infer_result = function.infer(db);
+                        let syntax_mapping = function.body_syntax_mapping(db);
+                        let expr = ast::Expr::cast(path_expr.syntax()).unwrap();
+
+                        if let Some(func) = syntax_mapping
+                            .node_expr(expr)
+                            .and_then(|it| infer_result.assoc_fn_resolutions(it))
+                        {
+                            return Exact(NavigationTarget::from_function(db, func));
+                        }
+                    }
+                }
+            }
         }
     }
+
     // If that fails try the index based approach.
     let navs = crate::symbol_index::index_resolve(db, name_ref)
         .into_iter()
diff --git a/crates/ra_ide_api/src/hover.rs b/crates/ra_ide_api/src/hover.rs
index 8ec60090d..0f13777d7 100644
--- a/crates/ra_ide_api/src/hover.rs
+++ b/crates/ra_ide_api/src/hover.rs
@@ -512,4 +512,26 @@ mod tests {
         let hover = analysis.hover(position).unwrap().unwrap();
         assert_eq!(trim_markup_opt(hover.info.first()), Some("Thing"));
     }
+
+    #[test]
+    fn test_hover_infer_associated_method_exact() {
+        let (analysis, position) = single_file_with_position(
+            "
+            struct Thing { x: u32 }
+
+            impl Thing {
+                fn new() -> Thing {
+                    Thing { x: 0 }
+                }
+            }
+
+            fn main() {
+                let foo_test = Thing::new<|>();
+            }
+            ",
+        );
+        let hover = analysis.hover(position).unwrap().unwrap();
+        assert_eq!(hover.info.first(), Some("```rust\nfn new() -> Thing\n```"));
+        assert_eq!(hover.info.is_exact(), true);
+    }
 }