Index: lib/Sema/SemaChecking.cpp =================================================================== --- lib/Sema/SemaChecking.cpp +++ lib/Sema/SemaChecking.cpp @@ -8172,7 +8172,8 @@ if (const EnumType *ET = dyn_cast(T)) { EnumDecl *Enum = ET->getDecl(); if (!Enum->isCompleteDefinition()) - return IntRange(C.getIntWidth(QualType(T, 0)), false); + return IntRange(C.getIntWidth(QualType(T, 0)), + !ET->isSignedIntegerOrEnumerationType()); unsigned NumPositive = Enum->getNumPositiveBits(); unsigned NumNegative = Enum->getNumNegativeBits(); Index: test/SemaCXX/sign-conversion.cpp =================================================================== --- /dev/null +++ test/SemaCXX/sign-conversion.cpp @@ -0,0 +1,21 @@ +// RUN: %clang_cc1 -fsyntax-only -verify -Wsign-conversion -std=c++11 %s + +unsigned int test() { + short foo; + return foo; // expected-warning {{implicit conversion changes signedness}} + +} + +unsigned int test3() { + // For a non-defined enum, use the underlying type. + enum u8 : char; + u8 foo{static_cast(0)}; + return foo; // expected-warning {{implicit conversion changes signedness}} + +} +unsigned int test2() { + // For a non-defined enum, use the underlying type. + enum u8 : unsigned char; + u8 foo{static_cast(0)}; + return foo; +}