Polymorphic function parameter types not inferred

[LPTK]

minimized code

val f: [A] => A => A = a => a

// same with:

val f: [A] => A => A = [A] => a => a

Weirdly, the error is reported as a "Syntax Error":

[error] -- [E081] Syntax Error: infer.scala:6:25 
[error] 6 |  val f: [A] => A => A = a => a
[error]   |                         ^
[error]   |                         Missing parameter type
[error]   |                         
[error]   |                         I could not infer the type of the parameter a.
[error] one error found

[smarter]

While the error message is weird, this is a feature request (which I'm planning to implement eventually) not a bug, so labelling it as such.

[Blaisorblade]

Weirdly, the error is reported as a "Syntax Error":

One-liner fix in #7654.

[Atry]

The inference will be extremely useful if it supports implicit parameters as well.

type F = [A, B] => quoted.Expr[_ <: A] => (given quoted.Type[A]) => B

val f: F = { a =>
  a
}