[Issue 20920] Typedef!int + Typedef!int => int? is this a typedef overlook?

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20920

--- Comment #3 from mw <mingwu at gmail.com> ---
Comment on attachment 1894
  --> https://issues.dlang.org/attachment.cgi?id=1894
s7.i.gz attached. dmd s7.i shows the same error.

wrong operation, this is for issue #24187

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