[GDScript] Correctly report invalid read-only access

core/variant/variant.cpp

@@ -3515,6 +3515,17 @@ bool Variant::is_shared() const {
 	return is_type_shared(type);
 }
 
+bool Variant::is_read_only() const {
+	switch (type) {
+		case ARRAY:
+			return reinterpret_cast<const Array *>(_data._mem)->is_read_only();
+		case DICTIONARY:
+			return reinterpret_cast<const Dictionary *>(_data._mem)->is_read_only();
+		default:
+			return false;
+	}
+}
+
 void Variant::_variant_call_error(const String &p_method, Callable::CallError &error) {
 	switch (error.error) {
 		case Callable::CallError::CALL_ERROR_INVALID_ARGUMENT: {

core/variant/variant.h

@@ -349,6 +349,7 @@ public:
 	bool is_zero() const;
 	bool is_one() const;
 	bool is_null() const;
+	bool is_read_only() const;
 
 	// Make sure Variant is not implicitly cast when accessing it with bracket notation (GH-49469).
 	Variant &operator[](const Variant &p_key) = delete;

modules/gdscript/gdscript_vm.cpp

@@ -884,6 +884,9 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 #endif
 #ifdef DEBUG_ENABLED
 				if (!valid) {
+					if (dst->is_read_only()) {
+						err_text = "Invalid assignment on read-only value (on base: '" + _get_var_type(dst) + "').";
+					} else {
 						Object *obj = dst->get_validated_object();
 						String v = index->operator String();
 						bool read_only_property = false;
@@ -903,6 +906,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 								err_text = "Invalid assignment of index " + v + " (on base: '" + _get_var_type(dst) + "') with value of type '" + _get_var_type(value) + "'.";
 							}
 						}
+					}
 					OPCODE_BREAK;
 				}
 #endif
@@ -926,6 +930,9 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 
 #ifdef DEBUG_ENABLED
 				if (!valid) {
+					if (dst->is_read_only()) {
+						err_text = "Invalid assignment on read-only value (on base: '" + _get_var_type(dst) + "').";
+					} else {
 						String v = index->operator String();
 						if (!v.is_empty()) {
 							v = "'" + v + "'";
@@ -933,6 +940,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 							v = "of type '" + _get_var_type(index) + "'";
 						}
 						err_text = "Invalid assignment of property or key " + v + " with value of type '" + _get_var_type(value) + "' on a base object of type '" + _get_var_type(dst) + "'.";
+					}
 					OPCODE_BREAK;
 				}
 #endif
@@ -958,6 +966,9 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 
 #ifdef DEBUG_ENABLED
 				if (oob) {
+					if (dst->is_read_only()) {
+						err_text = "Invalid assignment on read-only value (on base: '" + _get_var_type(dst) + "').";
+					} else {
 						String v = index->operator String();
 						if (!v.is_empty()) {
 							v = "'" + v + "'";
@@ -965,6 +976,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 							v = "of type '" + _get_var_type(index) + "'";
 						}
 						err_text = "Out of bounds set index " + v + " (on base: '" + _get_var_type(dst) + "')";
+					}
 					OPCODE_BREAK;
 				}
 #endif
@@ -1092,6 +1104,9 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 
 #ifdef DEBUG_ENABLED
 				if (!valid) {
+					if (dst->is_read_only()) {
+						err_text = "Invalid assignment on read-only value (on base: '" + _get_var_type(dst) + "').";
+					} else {
 						Object *obj = dst->get_validated_object();
 						bool read_only_property = false;
 						if (obj) {
@@ -1102,6 +1117,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 						} else {
 							err_text = "Invalid assignment of property or key '" + String(*index) + "' with value of type '" + _get_var_type(value) + "' on a base object of type '" + _get_var_type(dst) + "'.";
 						}
+					}
 					OPCODE_BREAK;
 				}
 #endif

modules/gdscript/tests/scripts/runtime/errors/constant_array_is_deep.out

@@ -3,4 +3,4 @@ GDTEST_RUNTIME_ERROR
 >> on function: test()
 >> runtime/errors/constant_array_is_deep.gd
 >> 6
->> Invalid assignment of property or key '0' with value of type 'int' on a base object of type 'Dictionary'.
+>> Invalid assignment on read-only value (on base: 'Dictionary').

modules/gdscript/tests/scripts/runtime/errors/constant_dictionary_is_deep.out

@@ -3,4 +3,4 @@ GDTEST_RUNTIME_ERROR
 >> on function: test()
 >> runtime/errors/constant_dictionary_is_deep.gd
 >> 6
->> Invalid assignment of index '0' (on base: 'Array') with value of type 'int'.
+>> Invalid assignment on read-only value (on base: 'Array').

modules/gdscript/tests/scripts/runtime/errors/read_only_dictionary.out

@@ -3,4 +3,4 @@ GDTEST_RUNTIME_ERROR
 >> on function: test()
 >> runtime/errors/read_only_dictionary.gd
 >> 4
->> Invalid assignment of property or key 'a' with value of type 'int' on a base object of type 'Dictionary'.
+>> Invalid assignment on read-only value (on base: 'Dictionary').