[Issue 8262] ICE(mtype.c) alias this to alias of an expression tuple

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=8262

--- Comment #5 from hsteoh at quickfur.ath.cx ---
And the reason is because aliasthisOf() does not expect a TypeTuple; it expects
a variable declaration, a function, an enum, or a template. Normally,
TypeTuples cannot appear in an alias this due to the current grammar, but there
is a loophole where they can be masked by another layer of alias, as in the
code given here, so it leads into this unhandled case.

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