[SR-7449] Conditional conformances: Execute extension function with wrong type

[swift-ci]

Previous ID	SR-7449
Radar	rdar://problem/39492423
Original Reporter	tarunon (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

Xcode Version 9.3 (9E145)
Apple Swift version 4.1 (swiftlang-902.0.48 clang-902.0.37.1)
Target: x86_64-apple-darwin17.5.0

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, ConditionalConformance, Miscompile
Assignee	None
Priority	Medium

md5: f5969e1fb4d1fd509d68980e7803ceef

Issue Description:

protocol A {
    static func foo()
}

extension Dictionary: A where Key == Value {
    static func foo() {
        print(type(of: self))
    }
}

extension Array where Element: A {
    static func foo() {
        Element.foo()
    }
}

[String: String].foo() // Dictionary<String, String>
[[String: String]].foo() // Dictionary<Dictionary<String, String>, Dictionary<String, String>>

1. Make conditional conformance with equivement 2 generics parameter.
2. Extend other generics parameter while the protocol that used on [1.]

[swift-ci]

Comment by Taketo Sano (JIRA)

I suspect this is the same cause of the EXC_BAD_ACCESS problem I was suffering from. (currently commented out)

https://github.com/taketo1024/SwiftyMath/blob/master/Sources/SwiftyMath/Abstract/Map.swift#L58

[belkadan]

Yikes! Thanks, Nobuo.

@swift-ci create

[huonw]

Element is the correct type, but it's being passed off strangely to foo.

protocol A {
    static func foo()
}
func callFoo<T: A>(_: T.Type) {
    print("** callfoo")
    print(T.self)
    T.foo()
}

extension Dictionary: A where Key == Value {
    static func foo() {
        print("** Dictionary.foo")
        print(type(of: self))
    }
}

extension Array where Element: A {
    static func foo() {
        print("** Array.foo")
        print(type(of: self))
        print(Element.self)
        Element.foo()
        callFoo(Element.self)
    }
}

[String: String].foo()
[[String: String]].foo()

** Dictionary.foo
Dictionary<String, String>.Type
** Array.foo
Array<Dictionary<String, String>>.Type
Dictionary<String, String>
** Dictionary.foo
Dictionary<Dictionary<String, String>, Dictionary<String, String>>.Type
** callfoo
Dictionary<String, String>
** Dictionary.foo
Dictionary<Dictionary<String, String>, Dictionary<String, String>>.Type

[huonw]

This was fixed by #15960