[SR-15111] “Type of expression is ambiguous” error when initializing a class

[swift-ci]

Previous ID	SR-15111
Radar	rdar://problem/82407752
Original Reporter	elidy (JIRA User)
Type	Bug

Environment

Xcode Version 13.0 beta 4 (13A5201i)

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, StarterBug, TypeChecker
Assignee	elidy (JIRA)
Priority	Medium

md5: 37c1160eb7b2424ea42b3ec849906fef

Issue Description:

When a class is initialized, passing an argument as a property of an optional class instance of incorrect type results in “Type of expression is ambiguous” error.

 class IntClass {
    var int: Int?
    
    init(int: Int?) {
        self.int = int
    }
}

class StringClass {
    var string: String? = "hello"
}

var stringClass: StringClass? = StringClass()

IntClass(int: stringClass?.string)
//Type of expression is ambiguous without more context
//Expected error: Cannot convert value of type 'String?' to expected argument type 'Int?'

var stringValue = stringClass?.string
IntClass(int: stringValue)
//Cannot convert value of type 'String?' to expected argument type 'Int?'

[typesanitizer]

@swift-ci create

[xedin]

elidy (JIRA User) I see that you are assigned for this one, here is a hint - in repairFailures for GenericArgument we could check whether previous element is an ApplyArgToParam and if so record a AllowArgumentMismatch fix.

[LucianoPAlmeida]

@xedin Just an addition, this should be also the case for contextual type as well, for example let _: Int? = stringClass?.string

[xedin]

Sure, if ApplyArgToParam -> AllowArgumentMismatch fix, if ContextualType -> IgnoreContextualMismatch fix.

[pedromotita]

Hello @LucianoPAlmeida are you still working on this issue?

First time contributor here, and got interested in this one. Any insights you could give me?

[AnthonyLatsis]

Reduced set of test cases:

struct S {
  var str: String
}

func test(s: S?) {
  let _: Int? = s?.str

  func f(_: Int?) {}
  f(s?.str)
}

Environment update: Swift version 5.9-dev (LLVM 91080e65df791d6, Swift c1d5118)

[LucianoPAlmeida]

Hello @LucianoPAlmeida are you still working on this issue?

I actually forgot about this one 😆
If you want to take it go for it =]

First time contributor here, and got interested in this one. Any insights you could give me?

I think is exactly what @xedin mentioned in previous comments.

[Rajveer100]

elidy (JIRA User) I see that you are assigned for this one, here is a hint - in repairFailures for GenericArgument we could check whether previous element is an ApplyArgToParam and if so record a AllowArgumentMismatch fix.

@xedin
I suppose you meant the diagnoseFailureFor(...) which is where the type_of_expression_is_ambiguous is called.
If that's the case, we probably check for the condition as you mentioned earlier here?

[xedin]

No, we need this diagnosed in repairFailures, diagnoseFailureFor contains only fallback logic for cases were a fix hasn't been emitted.

[Rajveer100]

Also, if I understand correctly, the last two elements of path refer to the fromType and toType, and they need to exist in order to call the diagnostic, or precisely add to conversionsOrFixes?

[xedin]

Yes, the fixes are produced based on the failing constraint, repairFailures gets the types, the constraint and its location passed by the caller, repairFailures checks what does the location (identified by a locator) represent and based on that emits an appropriate fix, you can take a look at a few other case statements in repairFailures to better understand what is going on there, some of them a quite small.

[LucianoPAlmeida]

@pedromotita Are you still working on this? @Rajveer100 started a PR, so if not actively working on it can we change the assignee for this issue?

[pedromotita]

Already removed myself as the assignee. Keep on keeping on @Rajveer100 👍 😉