Add more specific return type for getTypeParameters()

Author: andy-ms

src/services/services.ts

@@ -412,7 +412,7 @@ namespace ts {
         getDeclaration(): SignatureDeclaration {
             return this.declaration;
         }
-        getTypeParameters(): Type[] {
+        getTypeParameters(): TypeParameter[] {
             return this.typeParameters;
         }
         getParameters(): Symbol[] {

src/services/types.ts

@@ -39,7 +39,7 @@ namespace ts {
 
     export interface Signature {
         getDeclaration(): SignatureDeclaration;
-        getTypeParameters(): Type[];
+        getTypeParameters(): TypeParameter[];
         getParameters(): Symbol[];
         getReturnType(): Type;
         getDocumentationComment(): SymbolDisplayPart[];