Support aliases and Self in struct literals

Fixes #3306.

Author: flodiebold

crates/ra_hir_ty/src/infer.rs

@@ -425,7 +425,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
         // FIXME: this should resolve assoc items as well, see this example:
         // https://play.rust-lang.org/?gist=087992e9e22495446c01c0d4e2d69521
-        match resolver.resolve_path_in_type_ns_fully(self.db, path.mod_path()) {
+        return match resolver.resolve_path_in_type_ns_fully(self.db, path.mod_path()) {
             Some(TypeNs::AdtId(AdtId::StructId(strukt))) => {
                 let substs = Ty::substs_from_path(&ctx, path, strukt.into());
                 let ty = self.db.ty(strukt.into());
@@ -438,7 +438,33 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let ty = self.insert_type_vars(ty.subst(&substs));
                 (ty, Some(var.into()))
             }
+            Some(TypeNs::SelfType(impl_id)) => {
+                let generics = crate::utils::generics(self.db, impl_id.into());
+                let substs = Substs::type_params_for_generics(&generics);
+                let ty = self.db.impl_self_ty(impl_id).subst(&substs);
+                let variant = ty_variant(&ty);
+                (ty, variant)
+            }
+            Some(TypeNs::TypeAliasId(it)) => {
+                let substs = Substs::build_for_def(self.db, it)
+                    .fill(std::iter::repeat_with(|| self.table.new_type_var()))
+                    .build();
+                let ty = self.db.ty(it.into()).subst(&substs);
+                let variant = ty_variant(&ty);
+                (ty, variant)
+            }
             Some(_) | None => (Ty::Unknown, None),
+        };
+
+        fn ty_variant(ty: &Ty) -> Option<VariantId> {
+            ty.as_adt().and_then(|(adt_id, _)| match adt_id {
+                AdtId::StructId(s) => Some(VariantId::StructId(s)),
+                AdtId::UnionId(u) => Some(VariantId::UnionId(u)),
+                AdtId::EnumId(_) => {
+                    // Error E0071, expected struct, variant or union type, found enum `Foo`
+                    None
+                }
+            })
         }
     }
 

crates/ra_hir_ty/src/tests/simple.rs

@@ -50,6 +50,47 @@ fn test() {
     assert_eq!("Nat", type_at_pos(&db, pos));
 }
 
+#[test]
+fn self_in_struct_lit() {
+    assert_snapshot!(infer(
+        r#"
+//- /main.rs
+struct S<T> { x: T }
+
+impl S<u32> {
+    fn foo() {
+        Self { x: 1 };
+    }
+}
+"#,
+    ), @r###"
+    [63; 93) '{     ...     }': ()
+    [73; 86) 'Self { x: 1 }': S<u32>
+    [83; 84) '1': u32
+    "###);
+}
+
+#[test]
+fn type_alias_in_struct_lit() {
+    assert_snapshot!(infer(
+        r#"
+//- /main.rs
+struct S<T> { x: T }
+
+type SS = S<u32>;
+
+fn foo() {
+    SS { x: 1 };
+}
+
+"#,
+    ), @r###"
+    [64; 84) '{     ...1 }; }': ()
+    [70; 81) 'SS { x: 1 }': S<u32>
+    [78; 79) '1': u32
+    "###);
+}
+
 #[test]
 fn infer_ranges() {
     let (db, pos) = TestDB::with_position(

crates/ra_ide/src/diagnostics.rs

@@ -472,6 +472,33 @@ mod tests {
         check_apply_diagnostic_fix(before, after);
     }
 
+    #[test]
+    fn test_fill_struct_fields_self() {
+        let before = r"
+            struct TestStruct {
+                one: i32,
+            }
+
+            impl TestStruct {
+                fn test_fn() {
+                    let s = Self {};
+                }
+            }
+        ";
+        let after = r"
+            struct TestStruct {
+                one: i32,
+            }
+
+            impl TestStruct {
+                fn test_fn() {
+                    let s = Self { one: ()};
+                }
+            }
+        ";
+        check_apply_diagnostic_fix(before, after);
+    }
+
     #[test]
     fn test_fill_struct_fields_enum() {
         let before = r"