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[SR-13898] "redundant conformance constraint" warning shows up (again?) #56296

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ffried opened this issue Nov 25, 2020 · 5 comments
Closed

[SR-13898] "redundant conformance constraint" warning shows up (again?) #56296

ffried opened this issue Nov 25, 2020 · 5 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis

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@ffried
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ffried commented Nov 25, 2020

Previous ID SR-13898
Radar rdar://problem/71914018
Original Reporter @ffried
Type Bug
Environment

Apple Swift version 5.3.1 (swiftlang-1200.0.41 clang-1200.0.32.8)
Target: x86_64-apple-darwin20.1.0

Additional Detail from JIRA
Votes 3
Component/s Compiler
Labels Bug, DiagnosticsQoI, TypeChecker
Assignee None
Priority Medium

md5: c4edde1e87bd6db408682d93071bb508

relates to:

  • SR-5753 Remove "redundant same-type constraints" warnings

Issue Description:

I'm not 100% sure, but I think this should have been removed by resolving SR-5753.

The following code triggers a warning on associcatedtype Y: P0 which can be inferred by the Z.X == Y requirement on associatedtype Z: P1 just beneath. While this is technically true, the warnings is not of much help, because it's hard to see this requirement of Y: P0, especially if P0 and P1 are defined in completely different modules.

protocol P0 {}

protocol P1 {
   associatedtype X: P0
}

protocol P2 {
   associatedtype Y: P0
   associatedtype Z: P1 where Z.X == Y
}

Output:

TooMuchWarning.swift:8:22: warning: redundant conformance constraint 'Self.Y': 'P0'
   associatedtype Y: P0
                     ^
TooMuchWarning.swift:9:22: note: conformance constraint 'Self.Y': 'P0' implied here
   associatedtype Z: P1 where Z.X == Y
                     ^
@swift-ci
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Comment by Danila Shikulin (JIRA)

Is there a workaround?

@ffried
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ffried commented Nov 25, 2020

Yes and no.
To remove the warning, you can simply remove the : P0 requirement. But that’s not really solving the issue that then the requirement is no longer visible and hidden behind a same type requirement.
Otherwise you could ignore the warning, but that’s not really ideal either. And won’t work if you treat warnings as errors.

@typesanitizer
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@swift-ci create

@swift-ci
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swift-ci commented Jan 5, 2022

Comment by Galen Rhodes (JIRA)

Even if we could get an option or flag to turn this off. That would be nice.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@slavapestov
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Redundant requirement warnings are now disabled by default.

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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation type checker Area → compiler: Semantic analysis
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@slavapestov @ffried @typesanitizer @swift-ci