[ASTPrinter] Print typealias generic parameters

Author: benlangmuir

lib/AST/ASTPrinter.cpp

@@ -1915,6 +1915,8 @@ void PrintAST::visitTypeAliasDecl(TypeAliasDecl *decl) {
   recordDeclLoc(decl,
     [&]{
       Printer.printName(decl->getName());
+    }, [&]{ // Signature
+      printGenericParams(decl->getGenericParams());
     });
   bool ShouldPrint = true;
   Type Ty;

test/IDE/print_ast_tc_decls.swift

@@ -1348,3 +1348,9 @@ extension ProtocolToExtend where Self.Assoc == Int {}
 // PASS_PRINT_AST: #elseif
 // PASS_PRINT_AST: #else
 // PASS_PRINT_AST: #endif
+
+public struct MyPair<A, B> { var a: A, b: B }
+public typealias MyPairI<B> = MyPair<Int, B>
+// PASS_PRINT_AST: public typealias MyPairI<B> = MyPair<Int, B>
+public typealias MyPairAlias<T, U> = MyPair<T, U>
+// PASS_PRINT_AST: public typealias MyPairAlias<T, U> = MyPair<T, U>