Don't crash graph checking on invalid syntax

docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

@@ -2,12 +2,12 @@
 
 * Code generated files with > 64K methods and generated symbols crash when loaded. Use infered sequence points for debugging. ([Issue #16399](https://github.com/dotnet/fsharp/issues/16399), [#PR 16514](https://github.com/dotnet/fsharp/pull/16514))
 * `nameof Module` expressions and patterns are processed to link files in `--test:GraphBasedChecking`. ([PR #16550](https://github.com/dotnet/fsharp/pull/16550))
-* Graph Based Checking doesn't throw on invalid parsed input so it can be used for IDE scenarios ([PR #16575](https://github.com/dotnet/fsharp/pull/16575))
+* Graph Based Checking doesn't throw on invalid parsed input so it can be used for IDE scenarios ([PR #16575](https://github.com/dotnet/fsharp/pull/16575), [PR #16588](https://github.com/dotnet/fsharp/pull/16588))
 * Keep parens for problematic exprs (`if`, `match`, etc.) in `$"{(…):N0}"`, `$"{(…),-3}"`, etc. ([PR #16578](https://github.com/dotnet/fsharp/pull/16578))
 
 ### Added
 
-* The stackguard depth for ILPdbWriter.unshadowScopes can be modified via the environment variable `FSHARP_ILPdb_UnshadowScopes_StackGuardDepth`([PR #16583](https://github.com/dotnet/fsharp/pull/16583)) 
+* The stackguard depth for ILPdbWriter.unshadowScopes can be modified via the environment variable `FSHARP_ILPdb_UnshadowScopes_StackGuardDepth`([PR #16583](https://github.com/dotnet/fsharp/pull/16583))
 * Parser recovers on complex primary constructor patterns, better tree representation for primary constructor patterns. ([PR #16425](https://github.com/dotnet/fsharp/pull/16425))
 * Name resolution: keep type vars in subsequent checks ([PR #16456](https://github.com/dotnet/fsharp/pull/16456))
 * Higher-order-function-based API for working with the untyped abstract syntax tree. ([PR #16462](https://github.com/dotnet/fsharp/pull/16462))

src/Compiler/Driver/GraphChecking/FileContentMapping.fs

@@ -9,10 +9,9 @@ type Continuations = ((FileContentEntry list -> FileContentEntry list) -> FileCo
 let collectFromOption (mapping: 'T -> 'U list) (t: 'T option) : 'U list = List.collect mapping (Option.toList t)
 
 let longIdentToPath (skipLast: bool) (longId: LongIdent) : LongIdentifier =
-    if skipLast then
-        List.take (longId.Length - 1) longId
-    else
-        longId
+    match skipLast, longId with
+    | true, _ :: _ -> List.take (longId.Length - 1) longId
+    | _ -> longId
     |> List.map (fun ident -> ident.idText)
 
 let synLongIdentToPath (skipLast: bool) (synLongIdent: SynLongIdent) =

src/Compiler/Driver/GraphChecking/GraphProcessing.fs

@@ -230,8 +230,12 @@ let processGraphAsync<'Item, 'Result when 'Item: equality and 'Item: comparison>
 
         let processedCount = IncrementableInt(0)
 
-        let raiseExn (item, ex: exn) =
-            localCts.Cancel()
+        let handleExn (item, ex: exn) =
+            try
+                localCts.Cancel()
+            with :? ObjectDisposedException ->
+                // If it's disposed already, it means that the processing has already finished, most likely due to cancellation or failure in another node.
+                ()
 
             match ex with
             | :? OperationCanceledException -> completionSignal.TrySetCanceled()
@@ -252,7 +256,7 @@ let processGraphAsync<'Item, 'Result when 'Item: equality and 'Item: comparison>
 
                     match res with
                     | Choice1Of2() -> ()
-                    | Choice2Of2 ex -> raiseExn (node.Info.Item, ex)
+                    | Choice2Of2 ex -> handleExn (node.Info.Item, ex)
                 },
                 cts.Token
             )

tests/FSharp.Compiler.ComponentTests/TypeChecks/Graph/FileContentMappingTests.fs

@@ -122,17 +122,36 @@ module B = C
     | [ TopLevelNamespace "" [ PrefixedIdentifier "C" ] ] -> Assert.Pass()
     | content -> Assert.Fail($"Unexpected content: {content}")
 
-[<Test>]
-let ``Invalid nested module should just be ignored`` () =
-    let content =
-        getContent
-            false
-            """
-module A
 
-module B.C
-"""
+module InvalidSyntax =
 
-    match content with
-    | [ TopLevelNamespace "" [] ] -> Assert.Pass()
-    | content -> Assert.Fail($"Unexpected content: {content}")
+    [<Test>]
+    let ``Nested module`` () =
+        let content =
+            getContent
+                false
+                """
+    module A
+
+    module B.C
+    """
+
+        match content with
+        | [ TopLevelNamespace "" [] ] -> Assert.Pass()
+        | content -> Assert.Fail($"Unexpected content: {content}")
+
+
+    [<Test>]
+    let ``Module above namespace`` () =
+        let content =
+            getContent
+                false
+                """
+    module
+
+    namespace A.B.C
+    """
+
+        match content with
+        | [ TopLevelNamespace "" [] ] -> Assert.Pass()
+        | content -> Assert.Fail($"Unexpected content: {content}")

vsintegration/src/FSharp.Editor/LanguageService/WorkspaceExtensions.fs

@@ -447,7 +447,7 @@ module private CheckerExtensions =
             ) =
             cancellableTask {
 
-                if document.Project.UseTransparentCompiler then
+                if checker.UsesTransparentCompiler then
                     return! checker.ParseAndCheckDocumentUsingTransparentCompiler(document, options, userOpName)
                 else
                     let allowStaleResults =