The success checker fired only against core-fn error domains (stable, not
redefinable). This adds reporting of a call that passes a provably-wrong
type to a USER fn whose body requires otherwise — e.g. a fn that only does
arithmetic on a param, called with a string.
As check-walk sees defs it registers each non-redefinable single-fixed-arity
user fn's {:params :body} in module state (user-sig-box, accumulating across
forms like rtenv-box — a def must precede its call). At a call site (strict
mode only) the body is re-checked with ONE parameter bound to its concrete
argument type, others :any; if that produces a diagnostic the all-:any body
did not, the argument alone is provably wrong and the call is reported.
Monotonic — binding a concrete type can only add error-domain hits — so still
no false positives. A cycle guard (checking-box) terminates mutual recursion.
Gated behind JOLT_TYPE_CHECK_USER (orthogonal to the warn/error level)
because it rests on the closed-world assumption, weaker than the core-fn
case. check-form gains a strict? arity; the default path is unchanged and
user-fn code runs only when the checker is enabled. ^:redef/^:dynamic and
multi/variadic fns are not registered (their body is no stable requirement).
Gate green, suite 4718, conformance 335/335.
The success checker (RFC 0006) used to lose differing if-branches to :any
and accept the use. (inc (if c "a" :k)) typed the if as :any — sound but
imprecise, since the value is provably {:str | :kw}, every member of which
is in inc's error domain.
Adds {:union #{T...}} to the lattice: join-t forms a scalar union of
differing branches instead of collapsing to :any, capped at 4 distinct
scalars (the member space is the five scalar tags, so the lattice stays
finite and the inter-procedural fixpoint still terminates). The checker's
not-number?/not-seqable? report a union only when EVERY member is in the
error domain — any valid member accepts the call, so still no false
positives. type-name renders "a string or a keyword".
Unions are scalar-only and carry no :struct/:vec/:set key, so every
structural predicate already treats them as opaque — specialization sees
them exactly as :any and codegen is unchanged. Gate green, suite 4718,
conformance 335/335, bench even.
Reuse the structural inference from RFC 0005 as a loose type checker. It reports
a core-fn call only when an argument's inferred type is concrete and lies in
that op's throwing error domain, and accepts everything ambiguous (:any, a
union that joined to :any, :truthy). By construction it never produces a false
positive: a correct program has nothing to report even in error mode.
The curated error-domain table starts with the clearest throwing cases:
arithmetic on a provable non-number, and count/first/rest/next/seq/nth on a
provable non-seqable scalar. Lenient operations like (get 5 :k) and (:k 5),
which return nil rather than throw, are deliberately not listed.
Checking is decoupled from specialization: it runs whenever JOLT_TYPE_CHECK is
warn or error, regardless of :inline?, reading the knob at compile time so no
rebuild is needed. warn prints to stderr, error fails the form's compilation,
off (the default) skips it entirely. Core init stays clean under the flag.
jolt-y3b
