Fix #4159: look up the type alias paramter within the context of the parent type alias declaration

src/compiler/declarationEmitter.ts

@@ -750,6 +750,8 @@ namespace ts {
         }
 
         function writeTypeAliasDeclaration(node: TypeAliasDeclaration) {
+            let prevEnclosingDeclaration = enclosingDeclaration;
+            enclosingDeclaration = node;
             emitJsDocComments(node);
             emitModuleElementDeclarationFlags(node);
             write("type ");
@@ -759,6 +761,7 @@ namespace ts {
             emitTypeWithNewGetSymbolAccessibilityDiagnostic(node.type, getTypeAliasDeclarationVisibilityError);
             write(";");
             writeLine();
+            enclosingDeclaration = prevEnclosingDeclaration;
 
             function getTypeAliasDeclarationVisibilityError(symbolAccesibilityResult: SymbolAccessiblityResult): SymbolAccessibilityDiagnostic {
                 return {

tests/baselines/reference/typeAliasDeclarationEmit2.js

@@ -0,0 +1,13 @@
+//// [typeAliasDeclarationEmit2.ts]
+
+export type A<a> = { value: a };
+
+//// [typeAliasDeclarationEmit2.js]
+define(["require", "exports"], function (require, exports) {
+});
+
+
+//// [typeAliasDeclarationEmit2.d.ts]
+export declare type A<a> = {
+    value: a;
+};

tests/baselines/reference/typeAliasDeclarationEmit2.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit2.ts ===
+
+export type A<a> = { value: a };
+>A : Symbol(A, Decl(typeAliasDeclarationEmit2.ts, 0, 0))
+>a : Symbol(a, Decl(typeAliasDeclarationEmit2.ts, 1, 14))
+>value : Symbol(value, Decl(typeAliasDeclarationEmit2.ts, 1, 20))
+>a : Symbol(a, Decl(typeAliasDeclarationEmit2.ts, 1, 14))
+

tests/baselines/reference/typeAliasDeclarationEmit2.types

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit2.ts ===
+
+export type A<a> = { value: a };
+>A : { value: a; }
+>a : a
+>value : a
+>a : a
+

tests/cases/compiler/typeAliasDeclarationEmit2.ts

@@ -0,0 +1,5 @@
+// @target: ES5
+// @module: AMD
+// @declaration: true
+
+export type A<a> = { value: a };