Fix 631

Author: dsyme

src/fsharp/fsi/fsi.fs

@@ -2314,7 +2314,7 @@ let internal DriveFsiEventLoop (fsi: FsiEvaluationSessionHostConfig, fsiConsoleO
 
 /// The primary type, representing a full F# Interactive session, reading from the given
 /// text input, writing to the given text output and error writers.
-type FsiEvaluationSession (fsi: FsiEvaluationSessionHostConfig, argv:string[], inReader:TextReader, outWriter:TextWriter, errorWriter: TextWriter, fsiCollectible: bool, msbuildEnabled: bool, checker: FSharpChecker) = 
+type FsiEvaluationSession (fsi: FsiEvaluationSessionHostConfig, argv:string[], inReader:TextReader, outWriter:TextWriter, errorWriter: TextWriter, fsiCollectible: bool, msbuildEnabled: bool) = 
 #if DYNAMIC_CODE_REWRITES_CONSOLE_WRITE
     do
         Microsoft.FSharp.Core.Printf.setWriter outWriter
@@ -2454,6 +2454,10 @@ type FsiEvaluationSession (fsi: FsiEvaluationSessionHostConfig, argv:string[], i
 
     let fsiConsoleInput = FsiConsoleInput(fsi, fsiOptions, inReader, outWriter)
 
+    /// The single, global interactive checker that can be safely used in conjunction with other operations
+    /// on the FsiEvaluationSession.  
+    let checker = FSharpChecker.Create(msbuildEnabled=msbuildEnabled)
+
     let (tcGlobals,frameworkTcImports,nonFrameworkResolutions,unresolvedReferences) = 
         try 
             let tcConfig = tcConfigP.Get()
@@ -2714,12 +2718,8 @@ type FsiEvaluationSession (fsi: FsiEvaluationSessionHostConfig, argv:string[], i
         GC.KeepAlive fsiInterruptController.EventHandlers
 
 
-    static member Create(fsiConfig, argv, inReader, outWriter, errorWriter, ?collectible, ?msbuildEnabled, ?checker) = 
-        /// The single, global interactive checker that can be safely used in conjunction with other operations
-        /// on the FsiEvaluationSession.  
-        let checker = match checker with None -> FSharpChecker.Create() | Some c -> c
-
-        new FsiEvaluationSession(fsiConfig, argv, inReader, outWriter, errorWriter, defaultArg collectible false, defaultArg msbuildEnabled true, checker)
+    static member Create(fsiConfig, argv, inReader, outWriter, errorWriter, ?collectible, ?msbuildEnabled) = 
+        new FsiEvaluationSession(fsiConfig, argv, inReader, outWriter, errorWriter, defaultArg collectible false, defaultArg msbuildEnabled true)
 
     static member GetDefaultConfiguration(fsiObj:obj) = FsiEvaluationSession.GetDefaultConfiguration(fsiObj, true)
 

src/fsharp/fsi/fsi.fsi

@@ -124,7 +124,7 @@ type FsiEvaluationSession =
     /// <param name="inReader">Read input from the given reader</param>
     /// <param name="outWriter">Write output to the given writer</param>
     /// <param name="collectible">Optionally make the dynamic assmbly for the session collectible</param>
-    static member Create : fsiConfig: FsiEvaluationSessionHostConfig * argv:string[] * inReader:TextReader * outWriter:TextWriter * errorWriter: TextWriter * ?collectible: bool * ?msbuildEnabled: bool * ?checker: FSharpChecker -> FsiEvaluationSession
+    static member Create : fsiConfig: FsiEvaluationSessionHostConfig * argv:string[] * inReader:TextReader * outWriter:TextWriter * errorWriter: TextWriter * ?collectible: bool * ?msbuildEnabled: bool -> FsiEvaluationSession
 
     /// A host calls this to request an interrupt on the evaluation thread.
     member Interrupt : unit -> unit