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[SR-11642] Runtime crash demangling associated type for type defined in equality-constrained extension #54052

swift-ci opened this issue Oct 20, 2019 · 2 comments


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@swift-ci swift-ci commented Oct 20, 2019

Previous ID SR-11642
Radar rdar://problem/56466693
Original Reporter siemensikkema (JIRA User)
Type Bug
Status Resolved
Resolution Done

Attachment: Download


macOS Catalina

MacBook Pro (15-inch, 2017)

Xcode 11 Version 11.1 (11A1027)

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, Generics, RunTimeCrash, Runtime
Assignee None
Priority Medium

md5: 5e3272992c6dde352a1ca1e2e8d25287

Issue Description:

I found a runtime crash when running the following code (e.g. in a playground):

// MARK: Types

struct Validator<T> {
    let validatorFailureType: Any.Type

protocol ValidatorType {
    associatedtype Data
    associatedtype Failure
    func validator() -> Validator<Data>

extension ValidatorType {
    func validator() -> Validator<Data> {
        .init(validatorFailureType: Failure.self)

// MARK: Failing example

extension Validator where T == String {
    struct V: ValidatorType {
        typealias Data = T // or String
        struct Failure {}

Validator.V().validator() // failed to demangle witness for associated type 'Failure' in conformance '(extension in __lldb_expr_1):__lldb_expr_1.Validator<Swift.String>.V4: ValidatorType' from mangled name '13__lldb_expr_19ValidatorVAASSRszrlE2V4V7FailureVyx__G'

I attached a playground file that contains a few similar but non-crashing examples.

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@belkadan belkadan commented Oct 21, 2019

Looks similar to some of the other same-type-constraint issues we've seen…

@swift-ci create

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@DougGregor DougGregor commented Dec 19, 2019

Fixed by #28869

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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3 participants