clang accepts 'enum struct' in C mode with warning despite being unusable

[llvmbot]

Bugzilla Link	43027
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@WonHoYoo,@DougGregor,@garfr,@zygoloid

Extended Description

In C mode, Clang accepts this code with a warning:

enum struct Foo {
A
};

However, it is useless. None of the members seem to be accessible.

I've tried typedefs, ::, :, ., ->, casts, but nothing seems to allow me to access A.

Either these should be allowed as a documented extension with ::, or treated as a syntax error.

[WonHoYoo]

I guess the diagnose is for letting programmers know the C++11 features, so no problem at all.

I don't find any problem with the option -std=c++11.

[AaronBallman]

This is almost certainly a bug -- we're accepting scoped enumerations as a language extension but there's no way to access the enumeration constant by name.

[llvmbot]

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