cstage types the binding ty_u8; the wwstage single-binder arm peeled
the element only for slice/array iterables, so a str scrutinee fell to
the N_FORRANGE fallback decl and exprtype stamped the binding str.
The stamp-keyed call-arg marshal then pushed the 3-word str ABI for a
1-word scalar, and an uncast compare on the binding was falsely
rejected. Route str through the same synthetic-N_LET binder with a u8
element. Graduates r940_str_forrange_arg.
Hojun-Cho
06c20dbec4