+ case StringConv:
+ /* op must be string, result is number */
+ propagate_types(b->left, c, ok, Tstr, 0);
+ if (!type_compat(type, Tnum, 0))
+ type_err(c,
+ "error: Can only convert string to number, not %1",
+ prog, type, 0, NULL);
+ return Tnum;
+