cloned to:

• TF-232 [Sema] Improve @dynamicCallable diagnostics for calls with incorrect parameter types

Issue Description:

If you call a dynamicCallable type as a function with the wrong type of parameters, it gives the message "Cannot call value of non-function type 'Foo'". The error message should be more akin to the message when you call a regular function with incorrect parameter types: "Cannot convert value of type 'String' to expected argument type 'Int'".

@dynamicCallable
struct Foo {
  func dynamicallyCall(withArguments args: [Int]) -> Int {
    return args.count
  }
}


let foo = Foo()
let c: Int = foo(1, 2, 3)     // ok
let d = foo("abc")            // Cannot call value of non-function type 'Foo'
// this error message is okay:
let e: String = foo(1, 2, 3)  // Cannot convert value of type 'Int' to specified type 'String'