Visible type application (VTA) and datatype contexts are incompatible
Consider
data Ord a => T a = MkT (Maybe a)
foo = MkT @Int
Currently we get
Foo.hs:8:7: error:
• Cannot apply expression of type ‘Maybe a0 -> T a0’
to a visible type argument ‘Int’
• In the expression: MkT @Int
In an equation for ‘foo’: foo = MkT @Int
|
8 | foo = MkT @Int
| ^^^^^^^^
This a known infelicity, and perhaps not an important one.
But it turns out to be easy to fix as part of other work on #18481 (closed)