Remove 'no module' restriction on .fsx files

Remove restriction that main .fsx file mustn't define a module

Dotnet fsi fails if the main .fsx file defines a module:

module Hello
printfn "Hello world"

> dotnet fsi Hello.fsx
Hello.fsx(3,1): error FS0010: Unexpected start of structured construct in definition. Expected '=' or other token.

What is allowed is

module Hello =
    printfn "Hello world"

or just

printfn "Hello world"

A full-fledged F# project however does not have this restriction.

This makes it impractical to experiment with interactive workspaces, because one always has to remove the module definition before testing a single file with fsi and then put it back if one wishes to reference the file from somewhere else.

I would therefore propose to remove this 'no module' restriction.

This is based on report: https://github.com/dotnet/fsharp/issues/11699

Pros and Cons

The advantages of making this adjustment to F# are

• makes it more convenient for people to run files interactively
• makes interactive mode behave same as normal projects.

The disadvantages of making this adjustment to F# are

• none

Extra information

Estimated cost (XS, S, M, L, XL, XXL): S

Related suggestions: none that I know

Affidavit (please submit!)

Please tick this by placing a cross in the box:

• This is not a question (e.g. like one you might ask on stackoverflow) and I have searched stackoverflow for discussions of this issue
• I have searched both open and closed suggestions on this site and believe this is not a duplicate
• This is not something which has obviously "already been decided" in previous versions of F#. If you're questioning a fundamental design decision that has obviously already been taken (e.g. "Make F# untyped") then please don't submit it.

Please tick all that apply:

• This is not a breaking change to the F# language design
• I or my company would be willing to help implement and/or test this

For Readers

If you would like to see this issue implemented, please click the 👍 emoji on this issue. These counts are used to generally order the suggestions by engagement.

Start by reproducing the restriction with dotnet fsi Hello.fsx and the module-based example shown in the issue. Identify the compiler or FSI entry point that rejects a top-level module, then verify that the file runs without the workaround while existing script forms continue to work.