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[SR-6623] Bad diagnostic passing array to vararg parameter with base type #49172

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NachoSoto opened this issue Dec 15, 2017 · 5 comments
Closed

[SR-6623] Bad diagnostic passing array to vararg parameter with base type #49172

NachoSoto opened this issue Dec 15, 2017 · 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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@NachoSoto
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Previous ID SR-6623
Radar rdar://problem/36078499
Original Reporter @NachoSoto
Type Bug
Status Resolved
Resolution Done
Environment

Apple Swift version 4.0.3 (swiftlang-900.0.74.1 clang-900.0.39.2)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, TypeChecker
Assignee owenvoorhees (JIRA)
Priority Medium

md5: 4239ebe3d957159933a87a3d7dd0aeed

Issue Description:

class Base {}
class A: Base {}
class B: Base {}

func f(_ a: [Base]) {}
func g(_ a: Base...) {}

// Works:
f([A(), B()])

// Fails with a bad diagnostic:
g([A(), B()])
error: repl.swift:10:3: error: contextual type 'Base' cannot be used with array literal
g([A(), B()])
  ^~~~~~~~~~
@NachoSoto
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Actually this fails passing Base too:

g([Base()])
error: repl.swift:10:3: error: contextual type 'Base' cannot be used with array literal
g([Base()])
  ^~~~~~~~

@jckarter
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@swift-ci create

@jckarter
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The diagnostic should probably say something more specific like "cannot pass an array [T] as a vararg T..." or at least "got a [T], expected a T".

@CodaFi
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CodaFi commented Dec 15, 2017

#13471 gets this to diagnose as "cannot convert value of type '[Base]' to expected argument type 'Base'" but the real solution here would probably involve adding a new ContextualTypePurpose for variadic parameter arguments to diagnose it as a more specific kind of conversion failure.

@swift-ci
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Comment by Owen Voorhees (JIRA)

Resolved in [[Diagnostics] Improve diagnostic when attempting to pass an Array to a variadic argument|#26207]

@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 type checker Area → compiler: Semantic analysis
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@jckarter @NachoSoto @CodaFi @swift-ci