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[SR-7903] Generic types with an associated type cannot be a default value in a func #50438

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bscothern opened this issue Jun 6, 2018 · 2 comments
Open

[SR-7903] Generic types with an associated type cannot be a default value in a func #50438

bscothern opened this issue Jun 6, 2018 · 2 comments
Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@bscothern
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Previous ID SR-7903
Radar None
Original Reporter @bscothern
Type Bug
Environment

macOS 10.13.4

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, TypeChecker
Assignee None
Priority Medium

md5: 5e611b1b25ba8f020ac28556fcda7c4d

Issue Description:

The following code fails to compile

func foo<T: StringProtocol>(_ s: T = "Bar") {
    print(s)
}

foo()

Error Message

$ swiftc main.swift

main.swift:5:1: error: generic parameter 'T' could not be inferred
foo()
^
main.swift:1:6: note: in call to function 'foo'
func foo<T: StringProtocol>(_ s: T = "Bar") {

I get this error with these versions of swift:

Apple Swift version 4.1.2 (swiftlang-902.0.54 clang-902.0.39.2)
Target: x86_64-apple-darwin17.5.0

Apple Swift version 4.2-dev (LLVM a38ff55b31, Clang 5272858825, Swift defc3e9073)
Target: x86_64-apple-darwin17.5.0

Apple Swift version 4.2-dev (LLVM 031e148970, Clang b58a7ad218, Swift 0747546bd7)
Target: x86_64-apple-darwin17.5.0
@belkadan
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belkadan commented Jun 6, 2018

I don't think this has anything to do with associated types. Since T conforms to StringProtocol, and StringProtocol inherits from ExpressibleByStringLiteral, I would expect this to work.

@bscothern
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Good point

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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@belkadan @bscothern