[SR-9738] Poor error message when calling @dynamicCallable with incorrect parameter types

[natecook1000]

Previous ID	SR-9738
Radar	None
Original Reporter	@natecook1000
Type	Bug
Status	Closed
Resolution	Done

Environment

Toolchain: swift-5.0-DEVELOPMENT-SNAPSHOT-2018-12-28-a

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, StarterBug, TypeChecker
Assignee	None
Priority	Medium

md5: 93063d6e18bb5003b95809d72d784923

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'

[belkadan]

cc @dan-zheng

[dan-zheng]

This is a nice starter bug!

@dynamicCallable currently only has bare-bones diagnostics (see here). FailureDiagnosis::visitApplyExpr has a lot of machinery for producing good diagnostics for regular ApplyExprs though, one idea is to make use of that machinery for @dynamicCallable.

[swift-ci]

Comment by David Moore (JIRA)

Submitted a PR to improve this diagnostic: #22098.

[swift-ci]

Comment by Hassan ElDesouky (JIRA)

It has been fixed and Merged [here|#22098]