ImportC: add __check(assign-expression) extension

[WalterBright]

Trying to use assert in ImportC without the preprocessor gets tiresome, so I added __assert as an extension.

[dlang-bot]

Thanks for your pull request, @WalterBright!

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[huglovefan]

the name __assert is already used for the assert failure function on some platforms (see druntime core.stdc.assert for a list)

if it's made a keyword, the assert header and uses of the macro will fail to parse

$ cpp /usr/include/assert.h > assert.i
$ dmd -verrors=context assert.i
/usr/include/assert.h(81): Error: identifier or `(` expected
extern void __assert (const char *__assertion, const char *__file, int __line)
            ^

[WalterBright]

Curses! Any ideas for a replacement keyword for __assert ?

[PetarKirov]

How about _Assert?

[WalterBright]

Changed __assert to __check

[ljmf00]

Changed __assert to __check

I already dumped my thoughts on using known keywords for reserved identifiers in C when __import got merged. __ is reserved and we better have a tiny prefix to avoid such conflicts, but well we got to deal with it someday.

[RazvanN7]

ping @WalterBright

[salihdb]

I want to make a new suggestion to you; if the English meaning is not contradictory!

"ascertain" that can't introduce new conflicts never?

  assert(true);
  ascertain(true);

Sounds good, huh? Okay, it's 3 letters more but it is better than underscore typed by double key press.:)

SDB@79

[RazvanN7]

@WalterBright what is the status of this PR?

[RazvanN7]

@WalterBright is this good to go?

[WalterBright]

Ready to merge

[ibuclaw]

@WalterBright @RazvanN7 How do we know this works? The test is never ran by the testsuite!