Add failing scenario.

Author: nojaf

src/Compiler/Driver/ParseAndCheckInputs.fs

@@ -1479,7 +1479,8 @@ let CheckOneInputAux'
                 // printfn $"Finished Processing Sig {file.FileName}"
                 return
                     fun isFinalFold tcState ->
-                        // printfn $"Applying Sig {file.FileName}"
+                        printfn $"Applying Sig {file.FileName} (final: {isFinalFold})"
+
                         let fsiPartialResult, tcState =
                             let rootSigs = Zmap.add qualNameOfFile sigFileType tcState.tcsRootSigs
 
@@ -1504,6 +1505,9 @@ let CheckOneInputAux'
                         if isFinalFold then
                             fsiPartialResult, tcState
                         else
+                            // Train of thought: I'm not sure you want to add the results to the tcState,
+                            // when this function is called right before it will check the implementation file.
+
                             // Update the TcEnv of implementation files to also contain the signature data.
                             let _ccuSigForFile, tcState =
                                 AddCheckResultsToTcState

tests/ParallelTypeCheckingTests/Tests/Scenarios.fs

@@ -549,4 +549,32 @@ let fn (a: A) = ()
 """
                     (set [| 0 |])
             ]
+        scenario
+            "Implementation uses something defined above and in signature"
+            [
+                sourceFile
+                    "A.fsi"
+                    """
+module Bar
+
+type Bar =
+    new: unit -> Bar
+    static member Foo: unit -> unit
+
+val Foo: unit -> unit
+"""
+                    Set.empty
+                sourceFile
+                    "B.fs"
+                    """
+module Barry
+
+type Barry() =
+    static member Foo () : unit =
+        failwith ""
+
+let Foo () : unit = 
+    Barry.Foo ()
+"""
+                    (set [| 0 |])
     ]

tests/ParallelTypeCheckingTests/Tests/TestCompilation.fs

@@ -303,6 +303,20 @@ let ``Compile a valid scenario using graph-based type-checking`` (scenario: Scen
             Project = project
         }
 
+[<TestCaseSource(nameof scenarios)>]
+let ``Compile a valid scenario using parallel backed implementation files type-checking`` (scenario: Scenario) =
+    let project =
+        scenario.Files
+        |> Array.map (fun (f: FileInScenario) -> f.FileWithAST.File, f.Content)
+        |> List.ofArray
+        |> FProject.Make CompileOutput.Library
+
+    compileAValidProject
+        {
+            Method = Method.ParallelCheckingOfBackedImplFiles
+            Project = project
+        }
+
 [<TestCaseSource(nameof scenarios)>]
 let ``Compile a valid scenario using sequential type-checking`` (scenario: Scenario) =
     let project =