Add parenthesis around lamba in tuple, fixes #450

src/Fantomas.Tests/Fantomas.Tests.fsproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <Import Project="..\netfx.props" />
   <PropertyGroup>
     <Version>3.0.0-beta-001</Version>
@@ -51,6 +51,7 @@
     <Compile Include="SynExprSetTests.fs" />
     <Compile Include="SynConstTests.fs" />
     <Compile Include="FSharpScriptTests.fs" />
+    <Compile Include="TupleTests.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Fantomas\Fantomas.fsproj" />

src/Fantomas.Tests/TupleTests.fs

@@ -0,0 +1,17 @@
+module Fantomas.Tests.TupleTests
+
+open NUnit.Framework
+open FsUnit
+
+open Fantomas.Tests.TestHelper
+
+[<Test>]
+let ``tuple with lamba should add parenthesis`` () =
+    formatSourceString false """
+let private carouselSample =
+    FunctionComponent.Of<obj>(fun _ ->
+        fragment [] []
+    ,"CarouselSample")
+"""  config
+    |> should equal """let private carouselSample = FunctionComponent.Of<obj>((fun _ -> fragment [] []), "CarouselSample")
+"""

src/Fantomas/CodePrinter.fs

@@ -644,7 +644,11 @@ and genAnonRecordFieldName astContext (AnonRecordFieldName(s, e)) =
 and genTuple astContext es =
     atCurrentColumn (coli sepComma es (fun i -> 
             if i = 0 then genExpr astContext else noIndentBreakNln astContext
-            |> addParenWhen (function |ElIf _ -> true |_ -> false) // "if .. then .. else" have precedence over ","
+            |> addParenWhen (fun e ->
+                match e with
+                |ElIf _
+                | SynExpr.Lambda _ -> true
+                |_ -> false) // "if .. then .. else" have precedence over ","
         ))
 
 and genExpr astContext synExpr =