Avoid stack overflow in Sequentials pattern

src/Compiler/Service/ServiceInterfaceStubGenerator.fs

@@ -6,6 +6,7 @@ open System
 open System.Diagnostics
 open Internal.Utilities.Library
 open FSharp.Compiler.CodeAnalysis
+open FSharp.Compiler.EditorServices.ParsedInput
 open FSharp.Compiler.Symbols
 open FSharp.Compiler.Syntax
 open FSharp.Compiler.SyntaxTreeOps
@@ -47,13 +48,6 @@ module internal CodeGenerationUtils =
                 stringWriter.Dispose()
                 indentWriter.Dispose()
 
-    /// An recursive pattern that collect all sequential expressions to avoid StackOverflowException
-    let rec (|Sequentials|_|) =
-        function
-        | SynExpr.Sequential (_, _, e, Sequentials es, _) -> Some(e :: es)
-        | SynExpr.Sequential (_, _, e1, e2, _) -> Some [ e1; e2 ]
-        | _ -> None
-
     /// Represent environment where a captured identifier should be renamed
     type NamesWithIndices = Map<string, Set<int>>
 

src/Compiler/Service/ServiceParsedInputOps.fs

@@ -233,6 +233,19 @@ module Entity =
 
 module ParsedInput =
 
+    /// A pattern that collects all sequential expressions to avoid StackOverflowException
+    let internal (|Sequentials|_|) expr =
+
+        let rec collect expr acc =
+            match expr with
+            | SynExpr.Sequential (_, _, e1, (SynExpr.Sequential _ as e2), _) -> collect e2 (e1 :: acc)
+            | SynExpr.Sequential (_, _, e1, e2, _) -> e2 :: e1 :: acc
+            | _ -> acc
+
+        match collect expr [] with
+        | [] -> None
+        | exprs -> Some(List.rev exprs)
+
     let emptyStringSet = HashSet<string>()
 
     let GetRangeOfExprLeftOfDot (pos: pos, parsedInput) =
@@ -558,13 +571,6 @@ module ParsedInput =
             | SynArgPats.Pats ps -> ps
             | SynArgPats.NamePatPairs (pats = xs) -> List.map (fun (_, _, pat) -> pat) xs
 
-        /// A recursive pattern that collect all sequential expressions to avoid StackOverflowException
-        let rec (|Sequentials|_|) expr =
-            match expr with
-            | SynExpr.Sequential (_, _, e, Sequentials es, _) -> Some(e :: es)
-            | SynExpr.Sequential (_, _, e1, e2, _) -> Some [ e1; e2 ]
-            | _ -> None
-
         let inline isPosInRange range = rangeContainsPos range pos
 
         let inline ifPosInRange range f =
@@ -1557,13 +1563,6 @@ module ParsedInput =
         SyntaxTraversal.Traverse(pos, parsedInput, visitor) |> ignore
         path |> List.map (fun x -> x.idText) |> List.toArray
 
-    /// An recursive pattern that collect all sequential expressions to avoid StackOverflowException
-    let rec (|Sequentials|_|) expr =
-        match expr with
-        | SynExpr.Sequential (_, _, e, Sequentials es, _) -> Some(e :: es)
-        | SynExpr.Sequential (_, _, e1, e2, _) -> Some [ e1; e2 ]
-        | _ -> None
-
     let (|ConstructorPats|) pats =
         match pats with
         | SynArgPats.Pats ps -> ps

src/Compiler/Service/ServiceParsedInputOps.fsi

@@ -120,6 +120,9 @@ type public InsertionContextEntity =
 
 /// Operations querying the entire syntax tree
 module public ParsedInput =
+    /// A pattern that collects all sequential expressions to avoid StackOverflowException
+    val internal (|Sequentials|_|): SynExpr -> SynExpr list option
+
     val TryFindExpressionASTLeftOfDotLeftOfCursor: pos: pos * parsedInput: ParsedInput -> (pos * bool) option
 
     val GetRangeOfExprLeftOfDot: pos: pos * parsedInput: ParsedInput -> range option