Fix printing of enum casts with suppressed tags

[nick.sumner]

Summary

Allow C style casts of enums to be printed correctly when the incoming PrintingPolicy suppresses tags. This can happen, when casts to enums occur during the initialization of an anonymous struct. Given the code:

enum Foo { FOO = 0 };
struct {
    enum Foo foo;
} anon = {(enum Foo)0};

The type of the enum is suppressed when printing the initializer, so the cast is printed as:

} anon = {()0};

With the patch, the initialization is printed as:

} anon = {(enum Foo)0};

lib/AST/StmtPrinter.cpp

void StmtPrinter::VisitExtVectorElementExpr(ExtVectorElementExpr *Node) {
   PrintExpr(Node->getBase());
   OS << ".";
   OS << Node->getAccessor().getName();
 }
 void StmtPrinter::VisitCStyleCastExpr(CStyleCastExpr *Node) {
   OS << '(';
   PrintingPolicy SubPolicy(Policy);
   SubPolicy.SuppressSpecifiers = false;
+  SubPolicy.SuppressTag = false;
   Node->getTypeAsWritten().print(OS, SubPolicy);
   OS << ')';
   PrintExpr(Node->getSubExpr());
 }
 void StmtPrinter::VisitCompoundLiteralExpr(CompoundLiteralExpr *Node) {
   OS << '(';
   Node->getType().print(OS, Policy);
   OS << ')';

test/Sema/ast-print.c

 };
 
 // CHECK: struct pair_t p = {a: 3, .b = 4};
 struct pair_t p = {a: 3, .b = 4};
 
 void cast() {
 // CHECK: int *x = ((void *)0), *y = ((void *)0);
   int *x = ((void *)0), *y = ((void *)0);
+
+  enum Foo { FOO = 0 };
+  struct {
+    enum Foo foo;
+// CHECK: } anon = {(enum Foo)0};
+  } anon = {(enum Foo)0};
 }
 
 void stmtExpr() {
   int a, b = ({
 // CHECK: int c = 1;
     int c = 1;
     c;
   });
 }
 
 // CHECK: char c = '\x80';
 char c = '\200';