From ab1ad7c18b281b024401327bbe6c24a312be4c1d Mon Sep 17 00:00:00 2001
From: Florian Verdonck <florian.verdonck@outlook.com>
Date: Sat, 29 May 2021 13:36:07 +0200
Subject: [PATCH] Print trivia after arrow in last clause. Fixes #1759. (#1760)

---
 src/Fantomas.Tests/KeepIndentInBranchTests.fs | 39 +++++++++++++++++++
 src/Fantomas/CodePrinter.fs                   |  6 ++-
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/Fantomas.Tests/KeepIndentInBranchTests.fs b/src/Fantomas.Tests/KeepIndentInBranchTests.fs
index f3db95650c..57d3a0bbbb 100644
--- a/src/Fantomas.Tests/KeepIndentInBranchTests.fs
+++ b/src/Fantomas.Tests/KeepIndentInBranchTests.fs
@@ -1689,3 +1689,42 @@ module Foo =
 
         0
 """
+
+[<Test>]
+let ``comment after arrow, 1759`` () =
+    formatSourceString
+        false
+        """
+let mapOperationToWebPart (operation: OpenApiOperationDescription) : SynExpr =
+    let verb = mkIdentExpr (operation.Method.ToUpper())
+    let route =
+        match operation with
+        | _ -> // no route parameters
+            let route = mkAppNonAtomicExpr (mkIdentExpr "route") (mkStringExprConst operation.Path)
+            let responseHttpFunc =
+                mkLambdaExpr [ ] unitExpr
+                |> mkParenExpr
+            infixFish route responseHttpFunc
+
+    infixFish verb route
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+let mapOperationToWebPart (operation: OpenApiOperationDescription) : SynExpr =
+    let verb = mkIdentExpr (operation.Method.ToUpper())
+
+    let route =
+        match operation with
+        | _ -> // no route parameters
+
+        let route =
+            mkAppNonAtomicExpr (mkIdentExpr "route") (mkStringExprConst operation.Path)
+
+        let responseHttpFunc = mkLambdaExpr [] unitExpr |> mkParenExpr
+        infixFish route responseHttpFunc
+
+    infixFish verb route
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 2d677cb459..00cd8e7627 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -5314,7 +5314,11 @@ and genLastClauseKeepIdent (astContext: ASTContext) (Clause (pat, expr, whenExpr
     +> genPat astContext pat
     +> sepSpace
     +> optSingle (genExpr astContext) whenExpr
-    +> sepArrowFixed
+    +> (fun ctx ->
+        let arrowRange =
+            ctx.MkRange pat.Range.End expr.Range.Start
+
+        tokN arrowRange FsTokenType.RARROW sepArrowFixed ctx)
     +> sepNln
     +> (let t, r = synExprToFsAstType expr in sepNlnConsideringTriviaContentBeforeForMainNode t r)
     +> genExprKeepIndentInBranch astContext expr