Fix #4194: emit type paramters in type alias declaration

src/compiler/declarationEmitter.ts

@@ -754,6 +754,7 @@ namespace ts {
             emitModuleElementDeclarationFlags(node);
             write("type ");
             writeTextOfNode(currentSourceFile, node.name);
+            emitTypeParameters(node.typeParameters);
             write(" = ");
             emitTypeWithNewGetSymbolAccessibilityDiagnostic(node.type, getTypeAliasDeclarationVisibilityError);
             write(";");

src/compiler/types.ts

@@ -1786,10 +1786,10 @@ namespace ts {
         ObjectType = Class | Interface | Reference | Tuple | Anonymous,
         UnionOrIntersection = Union | Intersection,
         StructuredType = ObjectType | Union | Intersection,
-        /* @internal */
+        /* @internal */
         RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
         /* @internal */
-        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
+        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
     }
 
     // Properties common to all types

tests/baselines/reference/typeAliasDeclarationEmit.js

@@ -0,0 +1,14 @@
+//// [typeAliasDeclarationEmit.ts]
+
+export type callback<T> = () => T;
+
+export type CallbackArray<T extends callback> = () => T;
+
+//// [typeAliasDeclarationEmit.js]
+define(["require", "exports"], function (require, exports) {
+});
+
+
+//// [typeAliasDeclarationEmit.d.ts]
+export declare type callback<T> = () => T;
+export declare type CallbackArray<T extends callback> = () => T;

tests/baselines/reference/typeAliasDeclarationEmit.symbols

@@ -0,0 +1,13 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit.ts ===
+
+export type callback<T> = () => T;
+>callback : Symbol(callback, Decl(typeAliasDeclarationEmit.ts, 0, 0))
+>T : Symbol(T, Decl(typeAliasDeclarationEmit.ts, 1, 21))
+>T : Symbol(T, Decl(typeAliasDeclarationEmit.ts, 1, 21))
+
+export type CallbackArray<T extends callback> = () => T;
+>CallbackArray : Symbol(CallbackArray, Decl(typeAliasDeclarationEmit.ts, 1, 34))
+>T : Symbol(T, Decl(typeAliasDeclarationEmit.ts, 3, 26))
+>callback : Symbol(callback, Decl(typeAliasDeclarationEmit.ts, 0, 0))
+>T : Symbol(T, Decl(typeAliasDeclarationEmit.ts, 3, 26))
+

tests/baselines/reference/typeAliasDeclarationEmit.types

@@ -0,0 +1,13 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit.ts ===
+
+export type callback<T> = () => T;
+>callback : () => T
+>T : T
+>T : T
+
+export type CallbackArray<T extends callback> = () => T;
+>CallbackArray : () => T
+>T : T
+>callback : () => T
+>T : T
+

tests/cases/compiler/typeAliasDeclarationEmit.ts

@@ -0,0 +1,7 @@
+// @target: ES5
+// @module: AMD
+// @declaration: true
+
+export type callback<T> = () => T;
+
+export type CallbackArray<T extends callback> = () => T;