From 551273d8408ada10aee22eed2f85cd19dcd281e3 Mon Sep 17 00:00:00 2001
From: nojaf <florian.verdonck@outlook.com>
Date: Fri, 3 Jan 2020 10:05:26 +0100
Subject: [PATCH] Add indent when line comment precedes type info, #565

---
 src/Fantomas.Tests/LetBindingTests.fs | 22 ++++++++++++++++++++++
 src/Fantomas/CodePrinter.fs           |  8 +++++++-
 src/Fantomas/TriviaHelpers.fs         |  8 +++++++-
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/Fantomas.Tests/LetBindingTests.fs b/src/Fantomas.Tests/LetBindingTests.fs
index 91bf40758a..85ea864ef0 100644
--- a/src/Fantomas.Tests/LetBindingTests.fs
+++ b/src/Fantomas.Tests/LetBindingTests.fs
@@ -317,4 +317,26 @@ let x =
     elif true then printfn "b"
 
     if true then 1 else 0
+"""
+
+[<Test>]
+let ``line comment before return type info should indent before colon, 565`` () =
+    formatSourceString false """module Bar =
+  let f a
+    // foo
+    : int
+    =
+    0
+"""  ({ config with
+            SpaceAfterComma = false
+            SpaceAfterSemicolon = false
+            SpaceAroundDelimiter = false
+            SpaceBeforeArgument = false })
+    |> prepend newline
+    |> should equal """
+module Bar =
+    let f a
+        // foo
+        : int =
+            0
 """
\ No newline at end of file
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 2d377692a5..24effbed0d 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -489,7 +489,13 @@ and genExprSepEqPrependType astContext prefix (pat:SynPat) e ctx =
                 addSpaceAfterGenericConstructBeforeColon
             | _ -> sepNone
 
-        (prefix +> addExtraSpaceBeforeGenericType +> sepColon +> genType astContext false t +> sepEq
+        let genCommentBeforeColon ctx =
+            let hasLineComment = TriviaHelpers.``has line comment before`` t.Range ctx.Trivia
+            (ifElse hasLineComment indent sepNone +> enterNode t.Range) ctx
+
+        (prefix +> addExtraSpaceBeforeGenericType
+        +> genCommentBeforeColon
+        +> sepColon +> genType astContext false t +> sepEq
         +> breakNlnOrAddSpace astContext (hasTriviaContentAfterEqual || multilineCheck || checkPreserveBreakForExpr e ctx) e) ctx
     | e ->
 
diff --git a/src/Fantomas/TriviaHelpers.fs b/src/Fantomas/TriviaHelpers.fs
index 9089e2eaaa..4edfe1af4d 100644
--- a/src/Fantomas/TriviaHelpers.fs
+++ b/src/Fantomas/TriviaHelpers.fs
@@ -45,4 +45,10 @@ module TriviaHelpers =
             | Comment(LineCommentAfterSourceCode(_)) -> true
             | _ -> false
         )
-        |> (List.isEmpty >> not)
\ No newline at end of file
+        |> (List.isEmpty >> not)
+
+    let internal ``has line comment before`` range triviaNodes =
+        triviaNodes
+        |> List.tryFind (fun tv -> tv.Range = range)
+        |> Option.map (fun tv -> tv.ContentBefore |> List.exists (function | Comment(LineCommentOnSingleLine(_)) -> true | _ -> false))
+        |> Option.defaultValue false
\ No newline at end of file