Two provably-wrong cases the inference already has the facts for, closing the
last RFC 0006 open question:
- Calling a non-function. At an :invoke whose callee is provably :num or :str
(the only non-callable types — keywords/maps/vectors/sets are IFn), report
"cannot call a number as a function". Default level (no closed-world: the
callee type is inferred at the call site). Covers (5 1), ("hi" 0),
((+ 1 2) :k), a let-bound number, and a var holding a number (via vtype-box
in direct-link). A union is non-callable only when every member is, so
((if c 1 :k) x) is accepted (:kw is callable). Verified zero false positives
on the ray tracer, which calls maps/keywords/vectors as fns throughout.
- Wrong arity to a user fn. The registered single-fixed-arity sig (jolt-zo1)
makes a mismatched arg count provably throw; reported under the
JOLT_TYPE_CHECK_USER opt-in (same closed-world boundary; ^:redef/variadic
skipped). Caught at compile time before the runtime arity error.
Both fold into the existing infer walk, carry :pos for file:line:col, and keep
no-false-positives. Gate green, suite 4718, conformance 335/335, runtime bench
even (compile-time only).
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