Parser should report ambiguous givens syntax

[WojciechMazur]

Compiler version

3.6

Minimized example

trait Arg
trait Ret

given what: () => Arg => Ret = ??? // error
// ambigious but not handled

given what1: () => (Arg => Ret) = ??? 
// implicit def what(): (Arg => Ret) = ???

given what2: (() => Arg) => Ret = ??? 
// implicit def what(ctx: () => Arg): Ret = ???

given what3: (() => Arg => Ret) = ???
// implicit lazy val: (() => Arg => Ret) = ???

Output Error/Warning message

-- Error: /Users/wmazur/projects/scala/sandbox/test.scala:4:22 ---------------------------------------------------------------------------------------------------------------------------------------------
4 |given what: () => Arg => Ret = ??? // error
  |                      ^^
  |                      end of toplevel definition expected but '=>' found

Why this Error/Warning was not helpful

No context on how to fix the code

Suggested improvement

Inform that given definition is ambigious, recommend placing using paranthesis to fix the expression