[Issue 14557] Check typedef usage at semantic stage

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14557

--- Comment #2 from Dicebot <public at dicebot.lv> ---
`alias` is not a replacement for `typedef`. Cases when we do want to use alias
instead are extremely rare. Proper D2 replacement is struct with `alias this`
but for D1 version of code I need to keep typedef
(https://www.sociomantic.com/blog/2015/04/d1-d2-part-3-magic-module)

Why the pushback if `typedef` remains an error in D2? Only thing I ask about is
checking for this error at later stage so that versioned out code is not
checked.

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