The callee part is separated from #24697 for further investigation 

When typing a function literal's expression to infer the callee type, we
now create placeholder tree for each argument, and make sure the
function part does not refer to any parameter. This ensures that
references in the expression won't incorrectly resolve to outer scope
variables with the same names as the parameters.

Fix the following test:

```scala
def foo[T <: (B => Unit)](f: T) = ???
def transfer(in: A): Unit =
  foo(in => transfer(in)) // error: Found: (in : B) Required: A
def transfer(in: B): Unit = ???
```