Internal error of single case active pattern within `let` binding

[ijklam]

Repro steps

Input following code into fsi:

let (|T|) (f: _ -> _) = ();;
match id with T -> ();;
let (T) = id;;

Expected behavior

Both works.

Actual behavior

let way doesn't work.

Known workarounds

Use match.

Related information

Provide any related information (optional):

• Operating system: Windows 11
• .NET Runtime kind (.NET Core, .NET Framework, Mono): .NET 9.0.100-preview.1.24101.2
• Editing Tools (e.g. Visual Studio Version, Visual Studio): Microsoft (R) F# Interactive version F# 8.0 的 12.8.300.0

[edgarfgp]

Looking into this. I think this should not throw an internal error. Found a workaround to make this compile adding unit -> unit

let (|T|) (f: _ -> _) = ()
match id with T -> ()
let (T: unit -> unit) = id

Edit: this will also avoid the internal error

let (|T|) (f: unit -> unit) = f()
match id with T -> ()
let (T) = id


let (|T|) f = f()
match id with T c -> c
let (T) = id

cc @vzarytovskii