Use the value symbol for decorator purpose only if it is same as type symbol

src/compiler/checker.ts

@@ -20518,18 +20518,21 @@ namespace ts {
         function getTypeReferenceSerializationKind(typeName: EntityName, location?: Node): TypeReferenceSerializationKind {
             // Resolve the symbol as a value to ensure the type can be reached at runtime during emit.
             const valueSymbol = resolveEntityName(typeName, SymbolFlags.Value, /*ignoreErrors*/ true, /*dontResolveAlias*/ false, location);
-            const globalPromiseSymbol = tryGetGlobalPromiseConstructorSymbol();
-            if (globalPromiseSymbol && valueSymbol === globalPromiseSymbol) {
-                return TypeReferenceSerializationKind.Promise;
-            }
-
-            const constructorType = valueSymbol ? getTypeOfSymbol(valueSymbol) : undefined;
-            if (constructorType && isConstructorType(constructorType)) {
-                return TypeReferenceSerializationKind.TypeWithConstructSignatureAndValue;
-            }
 
             // Resolve the symbol as a type so that we can provide a more useful hint for the type serializer.
             const typeSymbol = resolveEntityName(typeName, SymbolFlags.Type, /*ignoreErrors*/ true, /*dontResolveAlias*/ false, location);
+            if (valueSymbol && valueSymbol === typeSymbol) {
+                const globalPromiseSymbol = tryGetGlobalPromiseConstructorSymbol();
+                if (globalPromiseSymbol && valueSymbol === globalPromiseSymbol) {
+                    return TypeReferenceSerializationKind.Promise;
+                }
+
+                const constructorType = getTypeOfSymbol(valueSymbol);
+                if (constructorType && isConstructorType(constructorType)) {
+                    return TypeReferenceSerializationKind.TypeWithConstructSignatureAndValue;
+                }
+            }
+
             // We might not be able to resolve type symbol so use unknown type in that case (eg error case)
             if (!typeSymbol) {
                 return TypeReferenceSerializationKind.ObjectType;

tests/baselines/reference/metadataOfEventAlias.js

@@ -0,0 +1,38 @@
+//// [tests/cases/compiler/metadataOfEventAlias.ts] ////
+
+//// [event.ts]
+
+export interface Event { title: string };
+
+//// [test.ts]
+import { Event } from './event';
+function Input(target: any, key: string): void { }
+export class SomeClass {
+    @Input event: Event;
+}
+
+//// [event.js]
+"use strict";
+;
+//// [test.js]
+"use strict";
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+var __metadata = (this && this.__metadata) || function (k, v) {
+    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
+};
+function Input(target, key) { }
+var SomeClass = (function () {
+    function SomeClass() {
+    }
+    return SomeClass;
+}());
+__decorate([
+    Input,
+    __metadata("design:type", Object)
+], SomeClass.prototype, "event", void 0);
+exports.SomeClass = SomeClass;

tests/baselines/reference/metadataOfEventAlias.symbols

@@ -0,0 +1,23 @@
+=== tests/cases/compiler/event.ts ===
+
+export interface Event { title: string };
+>Event : Symbol(Event, Decl(event.ts, 0, 0))
+>title : Symbol(Event.title, Decl(event.ts, 1, 24))
+
+=== tests/cases/compiler/test.ts ===
+import { Event } from './event';
+>Event : Symbol(Event, Decl(test.ts, 0, 8))
+
+function Input(target: any, key: string): void { }
+>Input : Symbol(Input, Decl(test.ts, 0, 32))
+>target : Symbol(target, Decl(test.ts, 1, 15))
+>key : Symbol(key, Decl(test.ts, 1, 27))
+
+export class SomeClass {
+>SomeClass : Symbol(SomeClass, Decl(test.ts, 1, 50))
+
+    @Input event: Event;
+>Input : Symbol(Input, Decl(test.ts, 0, 32))
+>event : Symbol(SomeClass.event, Decl(test.ts, 2, 24))
+>Event : Symbol(Event, Decl(test.ts, 0, 8))
+}

tests/baselines/reference/metadataOfEventAlias.types

@@ -0,0 +1,23 @@
+=== tests/cases/compiler/event.ts ===
+
+export interface Event { title: string };
+>Event : Event
+>title : string
+
+=== tests/cases/compiler/test.ts ===
+import { Event } from './event';
+>Event : any
+
+function Input(target: any, key: string): void { }
+>Input : (target: any, key: string) => void
+>target : any
+>key : string
+
+export class SomeClass {
+>SomeClass : SomeClass
+
+    @Input event: Event;
+>Input : (target: any, key: string) => void
+>event : Event
+>Event : Event
+}

tests/cases/compiler/metadataOfEventAlias.ts

@@ -0,0 +1,14 @@
+// @experimentalDecorators: true
+// @emitDecoratorMetadata: true
+// @target: es5
+// @includeBuiltFile: lib.d.ts
+
+// @filename: event.ts
+export interface Event { title: string };
+
+// @filename: test.ts
+import { Event } from './event';
+function Input(target: any, key: string): void { }
+export class SomeClass {
+    @Input event: Event;
+}