Fix Bugzilla 3538 - Default value of alias template parameter is inst…

[ntrel]

…antiated only once

The original bug there was fixed long ago, but it was reopened with this case: https://issues.dlang.org/show_bug.cgi?id=3538#c3

@RazvanN7 suggested committing just this fix here: https://github.com/dlang/dmd/pull/13352/files/05a0dc3b4e2a35b872b8f15f59c94c1c70e64093#r794354512

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	3538	critical	Default value of alias template parameter is instantiated only once.

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 "master + dmd#16805"

[ntrel]

Error, unsure if related:

failed to build 'D:\a\dmd\dmd\compiler\test\test_results\d_do_test.exe'
d_do_test-ut.obj : fatal error LNK1179: invalid or corrupt file: duplicate COMDAT '_D3std9algorithm9searching__T8skipOverZ__TQnTAyaTQeZQxFNaNfKQpQrZb'

Update: possibly caused by https://issues.dlang.org/show_bug.cgi?id=16687

[RazvanN7]

Unfortunately, it's probably related since now you are probably ending up with multiple template instances that might overlap with existing non-template function declarations... urgh...