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[SR-10066] Unhelpful diagnostic when keypath types don't match #52468

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hamishknight opened this issue Mar 8, 2019 · 3 comments
Closed

[SR-10066] Unhelpful diagnostic when keypath types don't match #52468

hamishknight opened this issue Mar 8, 2019 · 3 comments
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 key paths Feature: key paths (both native and Objective-C) type checker Area → compiler: Semantic analysis

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@hamishknight
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Previous ID SR-10066
Radar None
Original Reporter @hamishknight
Type Bug
Status Closed
Resolution Done
Environment

Swift version 5.0-dev (LLVM 94d957ca75, Swift a699f84c0f)
Target: x86_64-apple-darwin18.2.0

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

md5: 32d36056c6f2a654e480dd34153dafee

Issue Description:

For the following code:

struct C {
  func get<Root, Value>(
    _ root: Root, _ keyPath: KeyPath<Root, Value?>
  ) -> Value? {
    return nil
  }
}

struct S {
  var foo: Int {
    return C().get(self, \.foo)
  }
}

We emit the following diagnostic:

/Users/hamishknight/Desktop/Stochastic Projects/lets build associated objects/lets build associated objects/main.swift:22:28: error: type '_' has no member 'foo'
    return C().get(self, \.foo)
                           ^
Swift.Bool:1:15: note: did you mean 'Bool'?
public struct Bool {

This could be improved to point to the actual source of the error, which is that we're trying to pass a KeyPath<C, Int> argument to a KeyPath<C, Value?> parameter.
@belkadan
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cc @xedin

@LucianoPAlmeida
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@hamishknight This seems fixed on master
Here is what I'm seeing on the latest snapshot

struct C {
  func get<Root, Value>(
    _ root: Root, _ keyPath: KeyPath<Root, Value?>
  ) -> Value? {
    return nil
  }
}

struct S {
  var foo: Int {
    return C().get(self, \.foo) //Key path value type 'Int' cannot be converted to contextual type 'Int?' 
    // Cannot convert return expression of type 'Int?' to return type 'Int'
  }
}

@hamishknight
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Thanks for checking @LucianoPAlmeida!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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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 key paths Feature: key paths (both native and Objective-C) type checker Area → compiler: Semantic analysis
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@belkadan @LucianoPAlmeida @hamishknight