Add tests for top-level modules and fix top-level item resolution in …

…signature files - FCS now failing for a different reason.

tests/ParallelTypeCheckingTests/Code/ASTVisit.fs

@@ -1327,10 +1327,17 @@ module TopModulesExtraction =
                                    range,
                                    synModuleOrNamespaceTrivia) ->
             if mightHaveAutoOpen synAttributeLists then
-                // Contents of a module that's potentially AutoOpen are available everywhere, so treat it as if it had no name ('root' module).
+                // Contents of a module that's potentially AutoOpen are available from its parent without a prefix.
+                // Stay safe and as soon as the parent module is reachable, consider this module reachable as well
                 [| LongIdent.Empty |]
             else
-                synModuleDecls |> moduleSigDecls |> combine longId
+            // 'module A.B' is equivalent to 'namespace A; module B', meaning that 'A' is opened implicitly
+            if
+                synModuleOrNamespaceKind.IsModule && longId.Length > 1
+            then
+                [| longId.GetSlice(None, Some <| longId.Length - 2); longId |]
+            else
+                [| longId |]
 
     and moduleSigDecls (x: SynModuleSigDecl list) : Eit =
         let emptyState = Eit.Nested [||]

tests/ParallelTypeCheckingTests/Code/ParallelTypeChecking.fs

@@ -2,6 +2,7 @@
 
 #nowarn "1182"
 
+open System
 open System.Collections.Concurrent
 open System.Collections.Generic
 open System.IO

tests/ParallelTypeCheckingTests/Tests/TestCompilationFromCmdlineArgs.fs

@@ -89,14 +89,14 @@ let internal codebaseToConfig code method =
         WorkingDir = Some code.WorkDir
     }
 
+/// Before running these tests, you must prepare the codebase by running the script 'FCS.prepare.ps1'
 [<TestCaseSource(nameof (codebases))>]
-[<Explicit("Before running these tests, you must prepare the codebase by running FCS.prepare.ps1")>]
 let ``Test graph-based type-checking`` (code: Codebase) =
     let config = codebaseToConfig code Method.Graph
     TestCompilerFromArgs config
 
 [<TestCaseSource(nameof (codebases))>]
-[<Explicit("Before running these tests, you must prepare the codebase by running FCS.prepare.ps1")>]
+[<Explicit("Slow, only useful as a sanity check that the test codebase is sound and type-checks using the old method")>]
 let ``Test sequential type-checking`` (code: Codebase) =
     let config = codebaseToConfig code Method.Sequential
     TestCompilerFromArgs config

tests/ParallelTypeCheckingTests/Tests/TestDependencyResolution.fs

@@ -10,7 +10,6 @@ open ParallelTypeCheckingTests.Types
 open ParallelTypeCheckingTests.Utils
 open ParallelTypeCheckingTests.DepResolving
 open NUnit.Framework
-open Newtonsoft.Json
 
 let buildFiles (files: (string * string) seq) =
     files
@@ -50,6 +49,84 @@ open A
     let expectedEdges = [ "B.fs", [ "A.fs" ] ]
     assertGraphEqual deps expectedEdges
 
+[<Test>]
+let ``When defining a top-level module, the implicit parent namespace is taken into account when considering references to the file - .fsi pair`` () =
+    let files =
+        [|
+            "A.fsi", """
+module A.B.C1
+type X = X of int
+"""
+            "B.fsi", """
+module A.B.C2
+val x : C1.X -> unit
+"""
+        |] |> buildFiles
+
+    let deps = DependencyResolution.detectFileDependencies files
+
+    let expectedEdges = ["B.fsi", ["A.fsi"]]
+    assertGraphEqual deps expectedEdges
+
+
+[<Test>]
+let ``When defining a top-level module, the implicit parent namespace is taken into account when considering references to the file - .fs, .fsi pair`` () =
+    let files =
+        [|
+            "A.fs", """
+module A.B.C1
+type X = X of int
+"""
+            "B.fsi", """
+module A.B.C2
+val x : C1.X -> unit
+"""
+        |] |> buildFiles
+
+    let deps = DependencyResolution.detectFileDependencies files
+
+    let expectedEdges = ["B.fsi", ["A.fs"]]
+    assertGraphEqual deps expectedEdges
+
+
+[<Test>]
+let ``When defining a top-level module, the implicit parent namespace is taken into account when considering references to the file - .fsi, .fs pair`` () =
+    let files =
+        [|
+            "A.fsi", """
+module A.B.C1
+type X = X of int
+"""
+            "B.fs", """
+module A.B.C2
+let x : C1.X -> unit = failwith ""
+"""
+        |] |> buildFiles
+
+    let deps = DependencyResolution.detectFileDependencies files
+
+    let expectedEdges = ["B.fs", ["A.fsi"]]
+    assertGraphEqual deps expectedEdges
+
+[<Test>]
+let ``When defining a top-level module, the implicit parent namespace is taken into account when considering references to the file - .fs, .fs pair`` () =
+    let files =
+        [|
+            "A.fs", """
+module A.B.C1
+type X = X of int
+"""
+            "B.fs", """
+module A.B.C2
+let x : C1.X -> unit = failwith ""
+"""
+        |] |> buildFiles
+
+    let deps = DependencyResolution.detectFileDependencies files
+
+    let expectedEdges = ["B.fs", ["A.fs"]]
+    assertGraphEqual deps expectedEdges
+
 [<Test>]
 let ``With no references there is no dependency`` () =
     let files =