Add placeholder for stringifying arrays of unknown type

metamethods/cord.c

@@ -85,6 +85,7 @@ static CORD vas_cord(void *x, const char **fmt, va_list args)
 			void *arg = va_arg(args, void*);
 			return fn(x, arg);
 		}
+		case ' ': return "?";
 		default: errx(1, "Unsupported format specifier: '%c'", c);
 	}
 	errx(1, "Unreachable");

nextlang.h

@@ -39,6 +39,7 @@ CORD as_cord(void *x, const char *fmt, ...);
                          double: CORD_asprintf("%g", x), float: CORD_asprintf("%g", x), \
                          CORD: x, \
                          char*: (CORD)({ const char *__str = x; __str && __str[0] ? __str : CORD_EMPTY;}), \
+                         array_t: as_cord(&(x), "[ ]"), \
                          default: "???")
 #define __heap(x) (__typeof(x)*)memcpy(GC_MALLOC(sizeof(x)), (__typeof(x)[1]){x}, sizeof(x))
 #define __stack(x) &(x)