Can anyone explain the error message?

Alc · 2024-04-13T15:37:15.992Z

I understand that (in this code) I cannot compare generics that differ in types, but I do not understand the error message. Can anyone explain why it says it cannot compare "two 'Struct<String>' operands" when one is a String and other is an Int? I would expect the error message to be something like this

Error message that is intuitive to me (with my current understanding)

error: binary operator '==' cannot be applied to 'Struct<String>' and 'Struct<Int>' operands

Actual error message

error: binary operator '==' cannot be applied to two 'Struct<String>' operands

Code

struct Struct<T: Equatable> {
    let val: T

    init(_ val: T) {
        self.val = val
    }

    static func == (lhs: Struct, rhs: Struct) -> Bool{
        lhs.val == rhs.val
    }
}

print(Struct(0) == Struct(0))  // true
// print(Struct("0") == Struct(0))  // error: binary operator '==' cannot be applied to two 'Struct<String>' operands

jrose · 2024-04-13T16:39:02.602Z

Sounds like a compiler bug to me, not a deliberate message. Worth filing!

Alc · 2024-04-14T02:37:16.515Z

Thank you for replying @jrose, I have created an issue.

github.com/apple/swift

Misleading error message when comparing generics that vary in types

opened 02:34AM - 14 Apr 24 UTC

Alc-Alc

bug triage needed

### Description When the following code is run, the error I get is ``` erro…r: binary operator '==' cannot be applied to two 'MyStruct<String>' operands ``` While it is apparent that generics that differ in types cannot be compared, the error message does not indicate that is indeed the problem here. It says it cannot compare "two `'MyStruct<String>'` operands", however, one is a `MyStruct<String>` and other is a `MyStruct<Int>`. ### Reproduction ```swift struct MyStruct<T: Equatable> { let val: T init(_ val: T) { self.val = val } static func == (lhs: MyStruct, rhs: MyStruct) -> Bool{ lhs.val == rhs.val } } print(MyStruct(0) == MyStruct(0)) // true print(MyStruct("0") == MyStruct(0)) ``` ### Expected behavior I would expect an intuitive error message like so, that shows what exactly is the problem (types are different) ``` error: binary operator '==' cannot be applied to 'MyStruct<String>' and 'MyStruct<Int>' operands ``` ### Environment ``` swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4) Target: arm64-apple-macosx14.0 ``` ### Additional information Asked this in [Swift forums](https://forums.swift.org/t/can-anyone-explain-the-error-message/71240) and I was suggested to file a report here.

PS: deleted the earlier message as I replied to my own question instead of yours apologies for the double pings.