Tooltip in IDE suggests wrong type of parameter or even multiple types

[BoundedChenn31]

Repro steps

type U1 = { Name: string }
type U2 = { Age: int; Name: string }

let test =
    seq<U1 -> string> {
        fun u -> u.Name
    }
    |> Seq.map (fun (f: U1 -> string) -> [| f |])

1. Hover over u parameter. Tooltip says that it's type is U2 but it is U1 actually.

2. Also, for .Name-part tooltip shows both types U1 and U2. I would expect to see only one type.

As far as I can see code compiles and runs correctly without runtime errors, IL doesn't mention U2 type besides declaration.

I suspect these problems are related but tell me if I should create separate issue for each one :)

Related information

• .NET SDK 8.0.204
• VS 17.9.6 and also Rider 2024.1, probably not specific to IDE.

[brianrourkeboll]

The same thing also shows with Ionide in VS Code:

Recording.2024-04-12.144420.mp4

[BoundedChenn31]

Noticed that the same code fails to compile with 7.0.202 SDK. Compiler treats u as U2 and doesn't see seq<U1 -> string> when deducing:

Error FS0193 : Type constraint mismatch. The type 
    'U2 -> string'    
is not compatible with type
    'U1 -> string'

Really hope that it's not a regression, I don't want to write fun (u: U1) -> u.Name again in the future 😆