Add inlining special cases for dynamic compound assignments

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -343,11 +343,19 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (parent is ILiftableInstruction liftable && liftable.IsLifted) {
 				return true; // inline into lifted operators
 			}
-			if (parent is NullCoalescingInstruction && NullableType.IsNullable(v.Type)) {
-				return true; // inline nullables into ?? operator
-			}
-			if (parent is NullableUnwrap) {
-				return true; // inline into ?. operator
+			switch (parent.OpCode) {
+				case OpCode.NullCoalescingInstruction:
+					if (NullableType.IsNullable(v.Type))
+						return true; // inline nullables into ?? operator
+					break;
+				case OpCode.NullableUnwrap:
+					return true; // inline into ?. operator
+				case OpCode.DynamicGetMemberInstruction:
+				case OpCode.DynamicGetIndexInstruction:
+				case OpCode.LdObj:
+					if (parent.Parent.OpCode == OpCode.DynamicCompoundAssign)
+						return true; // inline into dynamic compound assignments
+					break;
 			}
 			// decide based on the target into which we are inlining
 			switch (next.OpCode) {