Fix #3543: Missing parentheses around field assignment expression in list initializers

Author: siegfriedpammer

ICSharpCode.Decompiler.Tests/Output/InsertParenthesesVisitorTests.cs

@@ -484,5 +484,32 @@ public void ArrayCreationWithInitializerInIndexer()
 			Assert.That(InsertRequired(expr), Is.EqualTo("new int[1] { 42 } [0]"));
 			Assert.That(InsertReadable(expr), Is.EqualTo("(new int[1] { 42 }) [0]"));
 		}
+
+		[Test]
+		public void AssignmentInObjectOrCollectionInitializer()
+		{
+			Expression expr = new ObjectCreateExpression {
+				Type = AstType.Create("List<int>"),
+				Initializer = new ArrayInitializerExpression {
+					Elements = { new AssignmentExpression(new IdentifierExpression("x"), new PrimitiveExpression(42)) }
+				}
+			};
+			Expression expr2 = new ObjectCreateExpression {
+				Type = AstType.Create("Data"),
+				Initializer = new ArrayInitializerExpression {
+					Elements = { new NamedExpression("X", new PrimitiveExpression(42)) }
+				}
+			};
+			Expression expr3 = new ObjectCreateExpression {
+				Type = AstType.Create("Dictionary<int, string>"),
+				Initializer = new ArrayInitializerExpression {
+					Elements = { new AssignmentExpression(new IndexerExpression(null, new PrimitiveExpression(0)), new PrimitiveExpression("42")) }
+				}
+			};
+
+			Assert.That(InsertRequired(expr), Is.EqualTo("new List<int> { (x = 42) }"));
+			Assert.That(InsertRequired(expr2), Is.EqualTo("new Data { X = 42 }"));
+			Assert.That(InsertRequired(expr3), Is.EqualTo("new Dictionary<int, string> { [0] = \"42\" }"));
+		}
 	}
 }

ICSharpCode.Decompiler/CSharp/OutputVisitor/InsertParenthesesVisitor.cs

@@ -458,6 +458,15 @@ private bool IsConditionalRefExpression(ConditionalExpression conditionalExpress
 
 		public override void VisitAssignmentExpression(AssignmentExpression assignmentExpression)
 		{
+			// Assignments in initializers need additional parentheses to disambiguate assignments
+			// to variables and assignments to members of the initialized object.
+			// This works without access to semantic information, because the ExpressionBuilder
+			// uses NamedExpression for `Member = value` instead of AssignmentExpression.
+			if (assignmentExpression.Parent is ArrayInitializerExpression
+				&& assignmentExpression.Left is not IndexerExpression)
+			{
+				Parenthesize(assignmentExpression);
+			}
 			// assignment is right-associative
 			ParenthesizeIfRequired(assignmentExpression.Left, PrecedenceLevel.Assignment + 1);
 			HandleAssignmentRHS(assignmentExpression.Right);