[Issue 12555] Incorrect error ungagging for speculatively instantiated class

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=12555

--- Comment #2 from Kenji Hara <k.hara.pg at gmail.com> ---
New PR:
https://github.com/D-Programming-Language/dmd/pull/3384

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