[Issue 22033] importC: Add C++ helper function to return Type for given Identifier or string

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22033

--- Comment #2 from Iain Buclaw <ibuclaw at gdcproject.org> ---
(In reply to Walter Bright from comment #1)
> I'm not sure what good this will do. As wchar_t is a macro, it gets replaced
> with a C type by the preprocessor, and ImportC will never see it.
Was thinking about possible portability issues, and I was referring to
internally within the compiler it's a macro "string", which gets parsed and
resolved as the appropriate AST type.

e.g: These are defaults
---
#define WCHAR_TYPE "int"
#define PTRDIFF_TYPE "long int"
#define WINT_TYPE "unsigned int"

Which could be overridden by the backend target.

If these eventually point to their respective special cpp macros
__WCHAR_TYPE__, __PTRDIFF_TYPE__, __WINT_TYPE__, etc... then of course these
will be all be expanded by the preprocessor leaving us not having to deal with
it.

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