Fix 23767 - ImportC: ternary with null constant has wrong pointer type

[dkorpel]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	23767	normal	ImportC: ternary with null constant has wrong pointer type

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#14980"

[maxhaton]

Is there a way to change the way the types are merged rather than rewriting them? Not sure if you have the scope available but you could always just have a different function for finding the common types of C.

The C behaviour (in a sense) was almost what D used to do before I fixed it a while back.

[dkorpel]

void* + T* merges to void* in general, both in C and D, only in C there is special treatment when the void* is the NULL constant

[maxhaton]

Previously it went to T* until I fixed it (I think ldc 1.30 still has this bug)

Could potentially use TypeNull

[dkorpel]

I am rewriting (void*)0 to use TypeNull