FAKE (4.7.2) breaks with

[robertpi]

The following script breaks FAKE (4.7.2):
#r @"..\packages\FAKE\tools\FakeLib.dll"

open Fake
open RegistryHelper

let configure () =
    let dlls = seq { yield "" } 
    let tabName = sprintf "%s" ""
    for _ in dlls do
        setRegistryValue RegistryBaseKey.HKEYLocalMachine "" "" tabName

The output is:
C:\code\rfq-hub
>packages\FAKE\tools\FAKE.exe scripts\build.fsx

F# Interactive for F# 4.0 (private)
Freely distributed under the Apache 2.0 Open Source License

For help type #help;;

> [Loading C:\code\rfq-hub\scripts\build.fsx]



scripts\build.fsx(12,65): error FS0971: Undefined value 'tabName : string'

Very strange little bug, if you inline the dlls identifier, it works. If you use a list instead of a sequence it works. If you call some other function than setRegistryValue, it works.

[lulu-berlin]

I was worried I might have broken something in the merged pull requests #976 and #980, but I haven't changed setRegistryValue.

So, this issue has nothing to do with the Registry and is only about disappearing identifier weirdness?

[robertpi]

No, actually the repo can be reduced to:

open Fake
open RegistryHelper

let configure () =
    let dlls = seq { yield "" } 
    let tabName = sprintf "%s" ""
    for _ in dlls do
        Console.WriteLine(tabName)

Definitely not a FAKE problem, it's an issue in FSharp.Compiler.Services.

[lulu-berlin]

Phew :)

I'm wondering: I don't understand FCS very deeply, but I saw that it can't find the binding of identifiers starting with an underscore (or an underscore, for that matter): fsprojects-archive/zzarchive-VisualFSharpPowerTools#1032 and fsharp/fsharp-compiler-docs#422

Is your issue related to that issue?

[robertpi]

Don't think so, the bug occurs whether the for loop uses an underscore or not.

I think it's more like to relate to an optimization tries to convert strings to contants, but does take into account dynamically allocated strings. I say that, as if you change let tableTab to be a string constant, rather than the result of a sprintf, everything works ok.

[dsyme]

FCS 1.4.2.3 has been pushed with a fix for this integrated. I believe you should be able to update FAKE to use this.

[dsyme]

Closing old issue