WIP try to fix regression

Bisected to dd66eb3.

fsx/Program.fs

@@ -110,9 +110,10 @@ let SplitArgsIntoFsxcArgsAndUserArgs
     |> List.ofArray
     |> userArgsInternal FsxFsxNotFoundYet List.empty List.empty
 
-let InjectBinSubfolderInPath(userScriptPath: string) =
+let InjectBinSubfolderInPath(userScript: FileInfo) =
+    let userScriptPath = userScript.FullName
     if not(userScriptPath.EndsWith ".fsx") then
-        failwithf "Assertion failed: %s should end with .fsx" userScriptPath
+        failwithf "Assertion failed: %s should end with .fsx" userScript.FullName
 
     let binPath =
         match userScriptPath.LastIndexOf Path.DirectorySeparatorChar with
@@ -138,6 +139,7 @@ let fsxcArgs, maybeUserScriptPath, userArgs = SplitArgsIntoFsxcArgsAndUserArgs()
 let fsxcMainArguments =
     match maybeUserScriptPath with
     | Some userScriptPath ->
+        let userScriptFile = FileInfo userScriptPath
         Seq.append fsxcArgs (Seq.singleton userScriptPath) |> Seq.toArray
     | None -> fsxcArgs |> Seq.toArray
 
@@ -149,23 +151,23 @@ match maybeUserScriptPath with
         "Compilation of anything that is not an .fsx should have been rejected by fsx"
         + " and shouldn't have reached this point. Please report this bug."
     )
-| _ -> ()
+| Some userScriptPath ->
+    let userScriptFile = FileInfo userScriptPath
+    let finalLaunch =
+        {
+            Command =
+                (InjectBinSubfolderInPath userScriptFile).FullName
+            Arguments = String.Join(" ", userArgs)
+        }
 
-let finalLaunch =
-    {
-        Command =
-            (InjectBinSubfolderInPath maybeUserScriptPath.Value)
-                .FullName
-        Arguments = String.Join(" ", userArgs)
-    }
+    let finalProc = Process.Execute(finalLaunch, Echo.OutputOnly)
 
-let finalProc = Process.Execute(finalLaunch, Echo.OutputOnly)
 // FIXME: fsx being an F# project instead of a launcher script means that, on
 // Windows (and in Unix when installed via 'dotnet tool install fsx'), fsx will be running the user script as
 // child process, which may make the memory gains of using fsx instead of fsi/fsharpi
 // (as explained in the ReadMe.md file) not as prominent (while in Unix, i.e. Linux and macOS, when the
 // tool is not installed via `dotnet tool install fsx`, they still are what ReadMe.md claims because we use a
 // bash script which uses 'exec') // TODO: measure measure!
-match finalProc.Result with
-| Error(exitCode, _errOutput) -> Environment.Exit exitCode
-| _ -> Environment.Exit 0
+    match finalProc.Result with
+    | Error(exitCode, _errOutput) -> Environment.Exit exitCode
+    | _ -> Environment.Exit 0