Struct member access inside quotation gives compile error

[simoncowen88]

Acccessing members of a struct captured local variable gives spurious "A quotation may not involve an assignment to or taking the address of a captured local variable" errors.

Repro steps

open FSharp.Quotations

[<Struct>]
type S =
    {
        A : int
    }

let go () =
    let s = { A = 1 }
    <@ s.A @>

Expected behavior

go should compile.

Actual behavior

go gives a compile error (squiggly is under s in the quotation) of "A quotation may not involve an assignment to or taking the address of a captured local variable"

Some further examples of quotations that do / don't work:

open FSharp.Quotations

[<Struct>]
type S =
    {
        A : int
    }
    with
    member __.B () = 1
    member __.C () () = 2

let go () =
    let s = { A = 1 }

    // # these do not compile if `S` is a struct

    // Accessing a field of `S`
    let e = <@ s.A @>

    // Invoking a member method of `S`
    let e = <@ s.B () @>


    // # these compile regardless of `S` being a struct

    // Accessing a member method of `S`
    let e = <@ s.B @>
    let e = <@ s.C @>

    // Invoking a curried member method of `S`
    let e = <@ s.C () @>
    let e = <@ s.C () () @>

    // Invoking a member method of `S` by accessing it then using a lambda to invoke it
    let e = <@ (fun f -> f ()) s.B @>

    // Accessing a field of `S` via splicing
    let sExpr = <@ s @>
    let e = <@ (%sExpr).A @>

    // Invoking a member method of `S` via splicing
    let e = <@ (%sExpr).B () @>

    ()

Known workarounds

No known workarounds.

Related information

• Windows
• .NET Framework 4.6.1 and Core 2.0 tested - possibly others

[TIHan]

This should be relatively easy to fix.

[lucasteles]

Same error if I try to use a method inside a LINQ Expression

let getUserById (context: DbContext) (userId: Guid) =
  context.Users.FirstOrDefaultAsync(fun x -> x.Id = userId.ToString())

The userId has "A quotation may not involve an assignment to or taking the address of a captured local variable"