Fix: Don't make variable const if modified using array accessor.

E.g.
mat2 m = ...;  // Shouldn't make const!
m[1].x *= 2.0;

Author: DeanEdisGG

ShaderShrinker/Shrinker.Parser/Optimizations/DetectConstantsExtension.cs

@@ -52,7 +52,7 @@ public static bool DetectConstants(this SyntaxNode rootNode)
                     var uses = nodesInScope
                         .Where(o => o.Token?.Content.StartsWithVarName(defCandidate.Name) == true)
                         .ToList();
-                    var isModified = uses.Any(o => o.Next?.Token?.IsAnyOf(SymbolOperatorToken.ModifyingOperator) == true);
+                    var isModified = uses.Any(IsModifiedByOperator);
 
                     // ...or '++i' ?
                     if (!isModified)
@@ -93,5 +93,18 @@ public static bool DetectConstants(this SyntaxNode rootNode)
 
             return repeatSimplifications;
         }
+
+        private static bool IsModifiedByOperator(SyntaxNode node)
+        {
+            // Could be node[index]
+            if (node.Next is SquareBracketSyntaxNode)
+                node = node.Next;
+
+            // Could be node.rgb
+            if (node.Next?.Token is DotToken)
+                node = node.Next?.Next;
+
+            return node.Next?.Token?.IsAnyOf(SymbolOperatorToken.ModifyingOperator) == true;
+        }
     }
 }

ShaderShrinker/UnitTests/ShrinkerTests.cs

@@ -2032,7 +2032,7 @@ public void CheckFullOptimizationDoesNotCorruptArrays(
             [Values(
                        "int main() { const int arr[2] = int[2](23, 32); return arr[0]; }",
                        "int main() { int arr[2]; arr[0] = 1; }",
-                       "int main() { const int arr[] = int[](1); arr[0] *= 2; }",
+                       "int main() { int arr[] = int[](1); arr[0] *= 2; }",
                        "int main() { int arr[] = int[](1); arr[0] = arr[1] * 2; }",
                        "int main() { const int arr[2] = int[2](23, 32); return arr[1]; }")] string expected)
         {