[SR-677] Infinite recursion instead of compiler error - overwritten function

[swift-ci]

Previous ID	SR-677
Radar	None
Original Reporter	roman.kriz (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

OS X: 10.11.4 Beta (15E33e)
Swift 2.1.1 (Xcode 7.2.1 (7C1002)) and also in 2.2 (Xcode 7.3 beta (7D129n))

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug
Assignee	@CodaFi
Priority

md5: 80de1a1ee66b648a64a4bc5c1d474510

relates to:

• SR-626 No diagnostic for unconditional recursion

Issue Description:

I found pretty weird bug in this example code:

func tr(key key: String) -> String? {
    return key
}

func tr(key: String) -> String {
    return tr(key) ?? key
}

tr("abc")

This code is causing infinite loop because

• first function

  tr(key:)
  

  has label for first argument

• second function

  tr(_:)
  

  has no label and is naively calling the first function because it returns optional (but writer of this code forgot about the label)

Since the operator ?? can be used when left value is non-optional this is complete valid expression, but there should be at least warning for that case, right?

[belkadan]

I think you meant "naively calling the second function". @jopamer, here's an example of where "implicit conversion to optional from non-optional" is a problem!

(We could also warn on infinite recursion, like Clang does, but that wouldn't catch all instances of this mistake—say, within the body of an if statement.)

[CodaFi]

Resolved by the merge of #11869.