ObjC: Handle boolean fixed type for enum.

Before this commit, we assert failure in ImplicitCastExpr
"unheralded conversion to bool". This commit fixes the assertion by using
the correct cast type when the fixed type is boolean.

This commit also fixes the behavior for Microsoft mode as well, since
Obj-C and Microsoft mode share the same code path.

rdar://24999533


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@264167 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaDecl.cpp

@@ -14146,7 +14146,10 @@ EnumConstantDecl *Sema::CheckEnumConstant(EnumDecl *Enum,
             } else
               Diag(IdLoc, diag::err_enumerator_too_large) << EltTy;
           } else
-            Val = ImpCastExprToType(Val, EltTy, CK_IntegralCast).get();
+            Val = ImpCastExprToType(Val, EltTy,
+                                    EltTy->isBooleanType() ?
+                                    CK_IntegralToBoolean : CK_IntegralCast)
+                    .get();
         } else if (getLangOpts().CPlusPlus) {
           // C++11 [dcl.enum]p5:
           //   If the underlying type is not fixed, the type of each enumerator

test/SemaObjC/enum-fixed-type.m

@@ -38,3 +38,8 @@ int arr3[(long long)Bar == (long long)-1 ? 1 : -1];
 
 typedef enum : Integer { BaseElem } BaseEnum;
 typedef enum : BaseEnum { DerivedElem } DerivedEnum; // expected-error {{non-integral type 'BaseEnum' is an invalid underlying type}}
+
+// <rdar://problem/24999533>
+enum MyEnum : _Bool {
+  MyThing = 0
+};