g++ 4.7 evaluates operator "" as sibling to macro expansion

I'm moving some code over to GCC 4.7 (from 4.6) and ran into a few compiler errors and found the problem documented in the GCC 4.7 porting guide:

User-defined literals and whitespace

The C++ compiler in ISO C11 mode std={c++11,c++0x,gnu++11,gnu++0x} supports user defined literals, which are incompatible with some valid ISO C++03 code.

In particular, whitespace is now needed after a string literal and before something that could be a valid user defined literal. Take the valid ISO C++03 code

const char *p = "foobar"__TIME__;

In C++03, the TIME macro expands to some string literal and is concatenated with the other one. In C++11 __TIME__ isn't expanded, instead operator "" __TIME__ is being looked up, resulting in the following diagnostic:

error: unable to find string literal operator  ‘operator"" __TIME__’

This applies to any string literal followed without whitespace by some macro. To fix, just add some whitespace between the string literal and the macro name.

While I could fix the errors, I'd like to know why I must do this. __TIME__ is a macro, so "something"__TIME__ would change into "something""15:52:03" (or similar) in the preprocessing stage, so the compiler would never have the opportunity to see it as operator "".

Is this behavior standards-approved or is it a bug?