[AST] Remove the static_assert check in ObjCMethodDecl::ObjCMethodDecl

[bricci]

Summary

This check was introduced by r338641
but this broke some builds. For now remove it.

[erichkeane]

@bricci : This likely needs to be moved into the bitfield section I think. We had a couple of other static-asserts that moved, so this is likely one of them.

[bricci]

@erichkeane

The static_assert itself cannot be in the bitfield since the whole point is to avoid including Basic/IdentifierTable.h just for this.

I originally put the static_assert in ObjCMethodDecl and everything worked just fine when tested with GCC but I then saw just
after you committed it that it broke some builds. Therefore for the moment I just removed it (and had to beg someone on IRC to commit it )

The problem was not the location of the static_assert, but the fact that
even though the member ObjCMethodDeclBits is protected the nested class ObjCMethodDeclBitfields is private. Therefore I used ObjCMethodDeclBits.ObjCMethodFamilyBitWidth which was fine with GCC but not with clang. Unfortunately I did everything with GCC and thus this slipped through. However I think that we can just use something like

static_assert(decltype(ObjCMethodDeclBits)::ObjCMethodFamilyBitWidth == ObjCMethodFamilyBitWidth, "blablabla")

with a comment both in the bitfield and in ObjCMethodDecl explaining why we check this.

lib/AST/DeclObjC.cpp

ObjCMethodDecl::ObjCMethodDecl(SourceLocation beginLoc, SourceLocation endLoc,
                                DeclContext *contextDecl, bool isInstance,
                                bool isVariadic, bool isPropertyAccessor,
                                bool isImplicitlyDeclared, bool isDefined,
                                ImplementationControl impControl,
                                bool HasRelatedResultType)
     : NamedDecl(ObjCMethod, contextDecl, beginLoc, SelInfo),
       DeclContext(ObjCMethod), MethodDeclType(T), ReturnTInfo(ReturnTInfo),
       DeclEndLoc(endLoc) {
-  // See the comment in ObjCMethodFamilyBitfields about
-  // ObjCMethodFamilyBitWidth for why we check this.
-  static_assert(
-      static_cast<unsigned>(ObjCMethodDeclBits.ObjCMethodFamilyBitWidth) ==
-          static_cast<unsigned>(ObjCMethodFamilyBitWidth),
-      "ObjCMethodDeclBitfields::ObjCMethodFamilyBitWidth and "
-      "ObjCMethodFamilyBitWidth do not match!");
 
   // Initialized the bits stored in DeclContext.
   ObjCMethodDeclBits.Family =
       static_cast<ObjCMethodFamily>(InvalidObjCMethodFamily);
   setInstanceMethod(isInstance);
   setVariadic(isVariadic);
   setPropertyAccessor(isPropertyAccessor);
   setDefined(isDefined);