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[SR-11491] Misleading error message when inserting [T] into Set<T> #53891

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swift-ci opened this issue Sep 19, 2019 · 4 comments
Closed

[SR-11491] Misleading error message when inserting [T] into Set<T> #53891

swift-ci opened this issue Sep 19, 2019 · 4 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

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@swift-ci
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Previous ID SR-11491
Radar rdar://problem/55593998
Original Reporter apaszke (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

Apple Swift version 5.1 (swiftlang-1100.0.257.2 clang-1100.0.31.3)

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

md5: f505094c443eea2740b92e6ff1ed8831

Issue Description:

This code:

let something = ["a"]
var s = Set<String>()
s.insert(something)

produces the following diagnostic:

error.swift:5:3: error: referencing instance method 'insert' on 'Set' requires the types 'String' and 'AnyHashable' be equivalent
s.insert(something)
  ^
Swift.Set<τ_0_0>:1:11: note: where 'Element' = 'String'
extension Set where Element == AnyHashable {
          ^

The error is quite simple – you can't insert a list of elements as an element of a set, but those error messages were confusing enough that it took me some time to find what the error really was. Also IIUC it's not true that `insert` works only if `Element == AnyHashable`, so the message seems false as well.
@theblixguy
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cc @xedin @hborla

@xedin
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xedin commented Sep 22, 2019

This is actually pretty interesting because if `s` was indeed a `Set<AnyHashable>` `s.insert(something)` would be a valid call. We produce 2 fixes in this case - one for contextual mismatch between `String` and `Set<String>` as an argument and another one for mismatched requirement for `Element` to be equal to `AnyHashable`, and the latter one wins because it's currently considered as having less of an impact impact. It looks like we should re-evaluate our strategy here and consider fixes for methods from conditional extensions like this much being much heavy.

@xedin
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xedin commented Sep 22, 2019

@swift-ci create

@xedin
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xedin commented Oct 1, 2019

Resolved by #27390 apaszke (JIRA User) Please use next available nightly snapshot of master to verify and close.

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