Excluded ExprAppWithLambdaNode in Chain.

src/Fantomas.Core.Tests/LambdaTests.fs

@@ -1497,3 +1497,29 @@ let _ =
 b\"      )
     |> List.length
 "
+
+[<Test>]
+let ``lambda with generic argument in function identifier, 2699`` () =
+    formatSourceString
+        false
+        """
+MailboxProcessor<string>.Start
+    (fun inbox ->
+        async {
+            while true do
+                let! msg = inbox.Receive()
+                do! sw.WriteLineAsync(msg) |> Async.AwaitTask
+        })
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+MailboxProcessor<string>.Start(fun inbox ->
+    async {
+        while true do
+            let! msg = inbox.Receive()
+            do! sw.WriteLineAsync(msg) |> Async.AwaitTask
+    })
+"""

src/Fantomas.Core/ASTTransformer.fs

@@ -840,6 +840,13 @@ let (|ChainExpr|_|) (e: SynExpr) : LinkExpr list option =
         | other -> continuation [ LinkExpr.Expr other ]
 
     match e with
+    // An identifier only application with a parenthesis lambda expression.
+    // ex: `List.map (fun n -> n)` or `MailboxProcessor<string>.Start (fun n -> n)
+    // Because the identifier is not complex we don't consider it a chain.
+    | SynExpr.App(
+        isInfix = false
+        funcExpr = SynExpr.LongIdent _ | SynExpr.Ident _ | SynExpr.DotGet(expr = SynExpr.TypeApp(expr = SynExpr.Ident _))
+        argExpr = ParenExpr(_, SynExpr.Lambda _, _, _)) -> None
     | SynExpr.App(
         isInfix = false
         funcExpr = SynExpr.DotGet _ | SynExpr.TypeApp(expr = SynExpr.DotGet _)