Print trivia before SynExpr.MatchLambda. Fix #1074 (#1078)

src/Fantomas.Tests/PatternMatchingTests.fs

@@ -684,4 +684,30 @@ let private update onSubmit msg model =
                 Map.remove "distance" model.Errors
 
         { model with Errors = errors }, Cmd.none
-"""
+"""
+
+[<Test>]
+let ``keep new line before function match, 1074`` () =
+    formatSourceString false """
+    let (|AndExpr|_|) =
+        let chooser =
+            function
+            | (ExprPat e1, ExprPat e2) -> Some(e1, e2)
+            | _ -> None
+
+        function
+        | ListSplitPick "&&" chooser (e1, e2) -> Some(BoolExpr.And(e1, e2))
+        | _ -> None
+"""  config
+    |> prepend newline
+    |> should equal """
+let (|AndExpr|_|) =
+    let chooser =
+        function
+        | (ExprPat e1, ExprPat e2) -> Some(e1, e2)
+        | _ -> None
+
+    function
+    | ListSplitPick "&&" chooser (e1, e2) -> Some(BoolExpr.And(e1, e2))
+    | _ -> None
+"""

src/Fantomas/CodePrinter.fs

@@ -2083,6 +2083,7 @@ and genExpr astContext synExpr =
         | SynExpr.New _ -> genTriviaFor SynExpr_New synExpr.Range
         | SynExpr.Assert _ -> genTriviaFor SynExpr_Assert synExpr.Range
         | SynExpr.While _ -> genTriviaFor SynExpr_While synExpr.Range
+        | SynExpr.MatchLambda _ -> genTriviaFor SynExpr_MatchLambda synExpr.Range
         | _ -> id)
 
 and genMultilineRecordInstance