Merge pull request #4086 from icsharpcode/fix/ref-conditional-assignment-parens

Parenthesize a ref-conditional assignment target

ICSharpCode.Decompiler.Tests/TestCases/Pretty/RefLocalsAndReturns.cs

@@ -343,6 +343,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			RefReassignment(ref reference.GetHashCode() == 4 ? ref reference : ref s);
 		}
 
+		public static void ConditionalRefAssignment(bool c, ref int a, ref int b)
+		{
+			(c ? ref a : ref b) = 3;
+			(c ? ref a : ref b) += 10;
+			(c ? ref b : ref a)++;
+		}
+
 		public static void Main(string[] args)
 		{
 			DoubleNumber(ref args.Length == 1 ? ref numbers[0] : ref DefaultInt);

ICSharpCode.Decompiler/CSharp/OutputVisitor/InsertParenthesesVisitor.cs

@@ -475,8 +475,10 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			{
 				Parenthesize(assignmentExpression);
 			}
-			// assignment is right-associative
-			ParenthesizeIfRequired(assignmentExpression.Left, PrecedenceLevel.Assignment + 1);
+			// assignment is right-associative. A ref-conditional target (cond ? ref a : ref b)
+			// has conditional precedence and would otherwise re-parse as cond ? ref a : (ref b = value),
+			// so the target needs precedence above ?: to keep its parentheses.
+			ParenthesizeIfRequired(assignmentExpression.Left, PrecedenceLevel.Conditional + 1);
 			HandleAssignmentRHS(assignmentExpression.Right);
 			base.VisitAssignmentExpression(assignmentExpression);
 		}