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[SR-8247] Associated type inheriting from generic class with Self as a parameter prints canonical type in errors #50779

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huonw mannequin opened this issue Jul 13, 2018 · 4 comments · Fixed by #71354
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[SR-8247] Associated type inheriting from generic class with Self as a parameter prints canonical type in errors #50779

huonw mannequin opened this issue Jul 13, 2018 · 4 comments · Fixed by #71354
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@slavapestov
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself conformances Feature → protocol: protocol conformances diagnostics QoI Bug: Diagnostics Quality of Implementation protocol Feature → type declarations: Protocol declarations Self in protocol Feature → types: The 'Self' type in protocols swift 5.10 type checker Area → compiler: Semantic analysis

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@huonw
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Mannequin

huonw mannequin commented Jul 13, 2018

Previous ID SR-8247
Radar None
Original Reporter @huonw
Type Bug
Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, DiagnosticsQoI
Assignee @slavapestov
Priority Medium

md5: a7f630ed225df1f60e8817ca991f4aa5

cloned from:

  • SR-8028 Protocol with where class constraint fails to compile, but same extension succeeds

relates to:

  • SR-10612 Illegal Instruction: 4 when compiling with Xcode 10.2.1
  • SR-10712 Cannot conform to protocol with associated type constrained to generic class specialised by associated type

Issue Description:

Apologies if the sample a little noisy, tried cleaning it up as much as could in available time. The following fails to build, but replaced with commented lines does compile. Intentional? Why?
@huonw
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huonw mannequin commented Jul 13, 2018 •
edited by AnthonyLatsis

The following is a correctly not-accepted version of the reduction of #50561:

protocol SecureCodingProvider {
    associatedtype T : Generic<Self>
}

class Generic<Value> {}

internal struct Foo {}

extension Foo: SecureCodingProvider {
    class T {}
}

The error message is:

sr8028.swift:9:1: error: type 'Foo' does not conform to protocol 'SecureCodingProvider'
extension Foo: SecureCodingProvider {
^
sr8028.swift:10:11: note: possibly intended match 'Foo.T' does not inherit from 'Generic<τ_0_0>'
    class T {}
          ^
sr8028.swift:2:20: note: protocol requires nested type 'T'; do you want to add it?
    associatedtype T : Generic<Self>
                   ^

The Generic<τ_0_0> should be either Generic<Self> to at least match the protocol, or, better, Generic<Foo>.

@belkadan
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Looks like we made it to Generic<Self> in Swift 5, at least.

@slavapestov
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I looked at this recently and IIRC its still failing to apply the right substitutions somewhere.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@slavapestov
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Generic superclass requirements in protocols were fixed by #71354.

@slavapestov slavapestov mentioned this issue Feb 3, 2024
Merged
@AnthonyLatsis AnthonyLatsis added type checker Area → compiler: Semantic analysis conformances Feature → protocol: protocol conformances swift 5.10 protocol Feature → type declarations: Protocol declarations Self in protocol Feature → types: The 'Self' type in protocols labels Feb 7, 2024
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@slavapestov slavapestov

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself conformances Feature → protocol: protocol conformances diagnostics QoI Bug: Diagnostics Quality of Implementation protocol Feature → type declarations: Protocol declarations Self in protocol Feature → types: The 'Self' type in protocols swift 5.10 type checker Area → compiler: Semantic analysis
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Sema: Fix problems with checkTypeWitness() slavapestov/swift
3 participants
@slavapestov @belkadan @AnthonyLatsis