Emit a warning when referencing console applications exe's without a main

Create a solution with two Console Application projects:

ConsoleApplication1\Program.fs:

module SharedValue
let hello = "Hello" |> id

ConsoleApplication2\Program.fs (references ConsoleApplication1)

match SharedValue.hello with
| null -> printfn "SharedValue.hello is null!"
| _    -> printfn "all good"

Expected output: all good
Actual output: SharedValue.hello is null!

needless to say, getting a null value from an F# project is quite surprising.

Changing the type of ConsoleApplication1 to a Library fixes this.

@latkin

i think is the same problem as fsharp/fsharp#326 , the console project doesn't initialize hello because you dont declare/execute the main function.

see @latkin 's comment for detailed explaination and workaround

@latkin @dsyme we need to add a warning? with c# you can reference the console app without problem, so is a bit unintuitive/annoying

Yrs, an explicit Main is required, and this is currently considered by design, for better or worse.

Adding a warning on referencing such a component may well be feasible.

What's best?

warning (error?) if a console app doesnt have a main
warning if a referenced fsharp assembly (discriminate on .exe extension?) doesn't have a main

#2 - emit an attribute or other bit when no main on .exe, and detect that when the component is referenced

🤖 This is an automated response from Repo Assist.

Confirmed this still reproduces at commit 7bcc3aea97ce976a1a6644d9bcceb518acfc5298 (2026-09-24), using the compiler produced by the current Release build's Proto stage:

Microsoft (R) F# Interactive version 15.2.101.0 for F# 11.0
Language Version: 11.0
FSharp.Core: 11.0.0.0
.NET: .NET 11.0.0-rc.1.26420.103
OS: Linux 6.17.0-1022-azure (X64)

I compiled the two-file repro from the issue as separate executables, with the second referencing the first. Both compiler invocations completed with no diagnostics. Running the consumer prints:

SharedValue.hello is null!

So the requested diagnostic is still absent: referencing an F# executable with no explicit entry point does not warn that its top-level bindings will remain uninitialized.

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Emit a warning when referencing console applications exe's without a main #602

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enricosada commented on Aug 25, 2015

dsyme commented on Aug 25, 2015

enricosada commented on Aug 25, 2015

dsyme commented on Aug 25, 2015

dsyme commented on Aug 25, 2015

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github-actions commented on Sep 25, 2026

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