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[SR-10970] Operators with unrelated precedence incorrectly allowed to be adjacent #53359

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hamishknight opened this issue Jun 19, 2019 · 2 comments
Closed

[SR-10970] Operators with unrelated precedence incorrectly allowed to be adjacent #53359

hamishknight opened this issue Jun 19, 2019 · 2 comments
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@gregomni
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accepts invalid Bug: Accepts invalid bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@hamishknight
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Previous ID SR-10970
Radar None
Original Reporter @hamishknight
Type Bug
Status Closed
Resolution Done
Environment

Apple Swift version 5.1 (swiftlang-1100.0.212.5 clang-1100.0.28.2)

Target: x86_64-apple-darwin19.0.0

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, AcceptsInvalid, TypeChecker
Assignee @gregomni
Priority Medium

md5: d8463e32d8da4bff72b759edb5963e32

Issue Description:

In the following example we correctly diagnose the fact that we're using two adjacent operators with unrelated precedence:

precedencegroup PowerPrecedence {
  lowerThan: BitwiseShiftPrecedence
  higherThan: AdditionPrecedence
  associativity: right
}
infix operator ^^ : PowerPrecedence

extension Int {
  static func ^^ (lhs: Int, rhs: Int) -> Int {
    var result = 1
    for _ in 1...rhs { result *= lhs }
    return result
  }
}

// error: Adjacent operators are in unordered precedence groups
// 'PowerPrecedence' and 'MultiplicationPrecedence'
_ = 1 ^^ 3 * 4

However if we add another application of ^^, the code compiles:

_ = 1 ^^ 2 ^^ 3 * 4 // No error.

I believe this should also be diagnosed with the above error.
@belkadan
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Yikes. And fixing it means a source-break, now…

@gregomni
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@belkadan: It looks like nothing in the current source compatibility suite actually hits this issue. (<https://github.com/apple/swift/pull/26603\>).

I'm not sure what the policy is on source-breaking changes like this. Ought the error in this case be conditional on a version check? Or just a warning? If there's a policy doc or a similar example you could point me at, that'd be very helpful. I haven't done any (purposeful) source-breakage since Swift 3->4 days.

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

Labels
accepts invalid Bug: Accepts invalid bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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@belkadan @hamishknight @gregomni