convert to non-varargs Tuple ignores trailing element mismatch

[vtjnash]

this should be an error, since a 3-element tuple can't be converted to a 1-element tuple, but instead it just ignored the trailing elements:

julia> convert(Tuple{Int}, (1.0, 2.0, 3.0))
(1,2.0,3.0)

[JeffBezanson]

Worked in 0.4. This is absurd.

[JeffBezanson]

Reduction:

julia> f(::Type{Tuple}) = 0

julia> methods(f, (Type{Tuple{}},))
# 1 method for generic function "f":
f(::Type{Tuple}) at REPL[5]:1

Though interestingly f(Tuple{}) fails with a method error, while convert(Tuple{}, (1, 2)) goes through.

[vtjnash]

More reduced:

julia> typeintersect(Type{Tuple}, Type{Tuple{}})
Type{Tuple{}}

and

julia> Type{Tuple{}} <: Type{Tuple}
true

[Keno]

This issue seems familiar. Did we something related before?

[timholy]

Just from knowing the code that implements this, I'd guess #11242 is to blame---advance apologies. I can take a peek sometime in the next day or so.

[timholy]

Good evidence that when the type-system rewrite gets underway, a good first step will be to look over our tests and see what's wrong/missing.