Empty parameters error

[cstjean]

This is a regression:

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julia> type Empty end

julia> f(::Empty{}) = 3
ERROR: TypeError: Type{...} expression: expected UnionAll, got Type{Empty}

[yuyichao]

What do you want?

[cstjean]

In 0.5, Empty{} === Empty, and that's convenient for writing generic code. Besides, it's inconsistent that 0.6 accepts type Empty{} end, but Empty{} is an error in other contexts.

[yuyichao]

The Empty{} === Empty was seen as a bug that's fixed by the change. I don't really see why you want this in generic code since the two behaves very differently anyway. type Empty{} end is not applying type parameters and is a declaration so it is allowed. We can certainly make it a syntax error though.

[yuyichao]

Ref #17943

[StefanKarpinski]

There is something elegant about viewing non-parametric types just as parametric types with no type parameters. It would significantly reduce the number of different kinds of things in the language.