ast: set inferred argument field types before checking argument types in call

[fridis]

This ensures that failure to infer the argument type due to incompatible actual arguments as in the exampe from #5560

f(v) => say v
f "a"
f 1

will be reported first and the type of the argument will be set to t_ERROR such that no subsequent error will be shown for the actual arguments passed to the call.

This required explicitly checking the called feature's types first and making Feature.checkTypes() re-entrant.

The stricter checking required a minor change in a loop in Sieve_Cache that can no longer use auto-unwrap.

fix #5560.