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[SR-11681] Segfault when emitting SIL for Generic specialized to Self #54090

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swift-ci opened this issue Oct 30, 2019 · 4 comments
Closed

[SR-11681] Segfault when emitting SIL for Generic specialized to Self #54090

swift-ci opened this issue Oct 30, 2019 · 4 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software

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@swift-ci
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Previous ID SR-11681
Radar rdar://problem/56747659
Original Reporter benpious (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

Swift 5.1, Xcode 11.1

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

md5: 893a0517d6b87a11744a40e54193a693

Issue Description:

The following code crashes the compiler. It has no dependencies, you can paste it into a file and run `swiftc` to see the bug.

struct S<T> {
    let boxed: T
}

class C {
    private(set) lazy var s = S<Self>(boxed: self as! Self)
}

I originally thought that adding final to C should stop the crashes, but even then the crash still occurs. This gives me hope that maybe this should have been allowed to type-check even without the as!, since I don't see a difference between returning Self and returning S<Self>.

Interestingly, private(set) lazy var s = S<Self>(boxed: self) doesn't type check even when C is final, as the compiler claims that it can't convert a value of type C to type Self, which doesn't make much sense to me, since it isn't even possible for Self to be a subclass of C in that context.
@belkadan
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@swift-ci create

@theblixguy
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On master, I get:

/Users/suyashsrijan/Desktop/test.swift:6:25: error: covariant 'Self' can only appear at the top level of property type
  private(set) lazy var s = S<Self>(boxed: self as! Self)
                        ^
/Users/suyashsrijan/Desktop/test.swift:6:25: error: mutable property cannot have covariant 'Self' type
  private(set) lazy var s = S<Self>(boxed: self as! Self)
                        ^
/Users/suyashsrijan/Desktop/test.swift:6:25: error: covariant 'Self' can only appear at the top level of method result type
  private(set) lazy var s = S<Self>(boxed: self as! Self)
                        ^
/Users/suyashsrijan/Desktop/test.swift:6:25: error: covariant 'Self' can only appear at the top level of property type
  private(set) lazy var s = S<Self>(boxed: self as! Self)
                        ^
/Users/suyashsrijan/Desktop/test.swift:6:25: error: stored property cannot have covariant 'Self' type
  private(set) lazy var s = S<Self>(boxed: self as! Self)

@beccadax
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beccadax commented Nov 1, 2019

Likewise, I can reproduce this in Xcode 11.2 but not in master.

@slavapestov
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#29682

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 2022
This issue was closed.
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software
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@slavapestov @belkadan @beccadax @theblixguy @swift-ci @AnthonyLatsis