Add GDScript warning for standalone expression

This makes the error message clearer as it might be used to call
functions with side effects.

modules/gdscript/gdscript.cpp

@@ -2051,6 +2051,9 @@ String GDScriptWarning::get_message() const {
 			CHECK_SYMBOLS(2);
 			return "The '" + symbols[0] + "' keyword is deprecated and will be removed in a future release, please replace its uses by '" + symbols[1] + "'.";
 		} break;
+		case STANDALONE_TERNARY: {
+			return "Standalone ternary conditional operator: the return value is being discarded.";
+		}
 		case WARNING_MAX: break; // Can't happen, but silences warning
 	}
 	ERR_FAIL_V_MSG(String(), "Invalid GDScript warning code: " + get_name_from_code(code) + ".");
@@ -2092,6 +2095,7 @@ String GDScriptWarning::get_name_from_code(Code p_code) {
 		"UNSAFE_CAST",
 		"UNSAFE_CALL_ARGUMENT",
 		"DEPRECATED_KEYWORD",
+		"STANDALONE_TERNARY",
 		NULL
 	};
 

modules/gdscript/gdscript.h

@@ -297,6 +297,7 @@ struct GDScriptWarning {
 		UNSAFE_CAST, // Cast used in an unknown type
 		UNSAFE_CALL_ARGUMENT, // Function call argument is of a supertype of the require argument
 		DEPRECATED_KEYWORD, // The keyword is deprecated and should be replaced
+		STANDALONE_TERNARY, // Return value of ternary expression is discarded
 		WARNING_MAX,
 	} code;
 	Vector<String> symbols;

modules/gdscript/gdscript_parser.cpp

@@ -8274,7 +8274,11 @@ void GDScriptParser::_check_block_types(BlockNode *p_block) {
 						_mark_line_as_safe(op->line);
 						_reduce_node_type(op); // Test for safety anyway
 #ifdef DEBUG_ENABLED
-						_add_warning(GDScriptWarning::STANDALONE_EXPRESSION, statement->line);
+						if (op->op == OperatorNode::OP_TERNARY_IF) {
+							_add_warning(GDScriptWarning::STANDALONE_TERNARY, statement->line);
+						} else {
+							_add_warning(GDScriptWarning::STANDALONE_EXPRESSION, statement->line);
+						}
 #endif // DEBUG_ENABLED
 					}
 				}