Add test for class from external module is used in union

tests/baselines/reference/metadataOfClassFromAlias.js

@@ -0,0 +1,49 @@
+//// [tests/cases/compiler/metadataOfClassFromAlias.ts] ////
+
+//// [auxiliry.ts]
+
+export class SomeClass {
+    field: string;
+}
+
+//// [test.ts]
+import { SomeClass } from './auxiliry';
+function annotation(): PropertyDecorator {
+    return (target: any): void => { };
+}
+export class ClassA {
+    @annotation() array: SomeClass | null;
+}
+
+//// [auxiliry.js]
+"use strict";
+var SomeClass = (function () {
+    function SomeClass() {
+    }
+    return SomeClass;
+}());
+exports.SomeClass = SomeClass;
+//// [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 annotation() {
+    return function (target) { };
+}
+var ClassA = (function () {
+    function ClassA() {
+    }
+    return ClassA;
+}());
+__decorate([
+    annotation(),
+    __metadata("design:type", auxiliry_1.SomeClass)
+], ClassA.prototype, "array", void 0);
+exports.ClassA = ClassA;

tests/baselines/reference/metadataOfClassFromAlias.symbols

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+=== tests/cases/compiler/auxiliry.ts ===
+
+export class SomeClass {
+>SomeClass : Symbol(SomeClass, Decl(auxiliry.ts, 0, 0))
+
+    field: string;
+>field : Symbol(SomeClass.field, Decl(auxiliry.ts, 1, 24))
+}
+
+=== tests/cases/compiler/test.ts ===
+import { SomeClass } from './auxiliry';
+>SomeClass : Symbol(SomeClass, Decl(test.ts, 0, 8))
+
+function annotation(): PropertyDecorator {
+>annotation : Symbol(annotation, Decl(test.ts, 0, 39))
+>PropertyDecorator : Symbol(PropertyDecorator, Decl(lib.d.ts, --, --))
+
+    return (target: any): void => { };
+>target : Symbol(target, Decl(test.ts, 2, 12))
+}
+export class ClassA {
+>ClassA : Symbol(ClassA, Decl(test.ts, 3, 1))
+
+    @annotation() array: SomeClass | null;
+>annotation : Symbol(annotation, Decl(test.ts, 0, 39))
+>array : Symbol(ClassA.array, Decl(test.ts, 4, 21))
+>SomeClass : Symbol(SomeClass, Decl(test.ts, 0, 8))
+}

tests/baselines/reference/metadataOfClassFromAlias.types

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+=== tests/cases/compiler/auxiliry.ts ===
+
+export class SomeClass {
+>SomeClass : SomeClass
+
+    field: string;
+>field : string
+}
+
+=== tests/cases/compiler/test.ts ===
+import { SomeClass } from './auxiliry';
+>SomeClass : typeof SomeClass
+
+function annotation(): PropertyDecorator {
+>annotation : () => PropertyDecorator
+>PropertyDecorator : PropertyDecorator
+
+    return (target: any): void => { };
+>(target: any): void => { } : (target: any) => void
+>target : any
+}
+export class ClassA {
+>ClassA : ClassA
+
+    @annotation() array: SomeClass | null;
+>annotation() : PropertyDecorator
+>annotation : () => PropertyDecorator
+>array : SomeClass
+>SomeClass : SomeClass
+>null : null
+}

tests/cases/compiler/metadataOfClassFromAlias.ts

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+// @experimentalDecorators: true
+// @emitDecoratorMetadata: true
+// @target: es5
+// @module: commonjs
+
+// @filename: auxiliry.ts
+export class SomeClass {
+    field: string;
+}
+
+//@filename: test.ts
+import { SomeClass } from './auxiliry';
+function annotation(): PropertyDecorator {
+    return (target: any): void => { };
+}
+export class ClassA {
+    @annotation() array: SomeClass | null;
+}