Undo a refactor-o and base the bitfield-truncation warning on the

uncoerced value.  Also, whitelist bool bitfields, which aren't
really a truncation.

llvm-svn: 118778

clang/lib/Sema/SemaChecking.cpp

@@ -2617,12 +2617,16 @@ bool AnalyzeBitFieldAssignment(Sema &S, FieldDecl *Bitfield, Expr *Init,
   if (Bitfield->isInvalidDecl())
     return false;
 
+  // White-list bool bitfields.
+  if (Bitfield->getType()->isBooleanType())
+    return false;
+
   Expr *OriginalInit = Init->IgnoreParenImpCasts();
 
   llvm::APSInt Width(32);
   Expr::EvalResult InitValue;
   if (!Bitfield->getBitWidth()->isIntegerConstantExpr(Width, S.Context) ||
-      !Init->Evaluate(InitValue, S.Context) ||
+      !OriginalInit->Evaluate(InitValue, S.Context) ||
       !InitValue.Val.isInt())
     return false;
 

clang/test/Sema/constant-conversion.c

@@ -37,3 +37,21 @@ void test3() {
   struct A d = (struct A) { 10, 0 }; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 10 to 2}}
   struct A e = { .foo = 10 };        // expected-warning {{implicit truncation from 'int' to bitfield changes value from 10 to 2}}
 }
+
+void test4() {
+  struct A {
+    char c : 2;
+  } a;
+
+  a.c = 0x101; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 257 to 1}}
+}
+
+void test5() {
+  struct A {
+    _Bool b : 1;
+  } a;
+
+  // Don't warn about this implicit conversion to bool, or at least
+  // don't warn about it just because it's a bitfield.
+  a.b = 100;
+}