InvalidProgramException on string interpolation

[bent-rasmussen]

Please provide a succinct description of the issue.

Repro steps

Provide the steps required to reproduce the problem:

1. Create a console project with this code

type Foo() =

    let sb = System.Text.StringBuilder()

    member _.Bar(s: System.ReadOnlySpan<char>) = sb.Append(s) |> ignore

let foo = Foo()
let foos = "foo"
foo.Bar($"{foos} is bar")

2. Build and run the project

Expected behavior

InvalidProgramException

Actual behavior

InvalidProgramException

Known workarounds

• Use let binding for interpolated string and use that in function call
• Use string instead of ReadOnlySpan<char>
• Do not use string interpolation

Related information

Provide any related information (optional):

• Windows 11
• .NET 9 RC1
• Version 17.12.0 Preview 2.0

[vzarytovskii]

Yes, we should probably disallow byreflikes when we work with interpolation until we have good escape analysis.

[T-Gro]

Workaround: Adding "AsSpan()" at the callsite fixes the runtime error:

https://sharplab.io/#v2:DYLgZgzgNAJiDUAfA9gBwKYDsAEBlAnhAC7oC2AsAFBVH4bYBiyyAFAJTYC8VV2f2wdEWwQARlzyESpAHQAVdAA8iM3EQBOAS0wBzAEIBXTcBjp17HpX7ZSZUWewB9GXoCG5iCEnEyMgErorjAA8pjA+LiorpgAPADGABbuAHwcnCKiMgCCqBiYMCwQHIjJ2Jo6mMjq6JaCwmDMEkysbFR12A3IEBIARJ09VJ0u7iwAJD0A3p0QAL5l3aLuPdkQkdHsbEA==

[vzarytovskii]

Also <LangVersion>8</LangVersion> fixes it