Keep discard with when on long arms (#1624)

closes #1620

Author: belav

Src/CSharpier.Core/CSharp/SyntaxPrinter/SyntaxNodePrinters/WhenClause.cs

@@ -9,7 +9,9 @@ public static Doc Print(WhenClauseSyntax node, PrintingContext context)
     {
         return Doc.Group(
             Doc.Indent(
-                Doc.Line,
+                node.Parent is SwitchExpressionArmSyntax { Pattern: DiscardPatternSyntax }
+                    ? " "
+                    : Doc.Line,
                 Token.PrintWithSuffix(node.WhenKeyword, " ", context),
                 Node.Print(node.Condition, context)
             )

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/SwitchExpressions.test

@@ -41,6 +41,14 @@ class ClassName
             ),
             VeryLongObject_______________________________________________________________
                 when count > 0 => CallSomeMethod(someValue),
+            _ when KeepWhenWithDiscard() => "",
+            _ when KeepWhenWithDiscard_________________(
+                    SomeObject_______________________________________________
+                ) => "",
+            _ when KeepWhenWithDiscard_________________(
+                    SomeObject_______________________________________________
+                ) =>
+                "LongString_____________________________________________________________________",
             OneMore => "someStrings"
                 + "moreStrings"
                 + "andMoreStrings_________________________________________",