The strict linearity check (use-after-consume / consume-while-borrowed,
linearity.rs) runs today only on the ~45 of 258 all-explicit-mode fns;
its activation gate skips any fn with a bare/Implicit param. Deleting
ParamMode::Implicit (#55) would turn it on universally and surface ~21%
false positives in two classes. This closes both, making the core
ownership analysis sharp across the whole codebase for the first time —
the precondition for #55. Diagnostic-only: no schema, no hash, no
codegen change; the two existing diagnostic codes simply fire on a
smaller, more correct set.
Fix 1 — value-type exemption. A new is_value_type predicate
(ailang-core::primitives) names the unboxed set {Int,Bool,Float,Unit};
BinderState gains an is_value flag seeded from the binder's locally
available type (param signatures, ctor field types for pattern binders,
lam typed-params), and use_var short-circuits the Consume arm for it. A
value type has no refcount and is never consumed, so multi-read is
always legal.
Str is deliberately NOT in the value set, though is_primitive_name
includes it: drop.rs:490-492 lowers only Int/Bool/Float/Unit to
non-ptr; Str is a ptr, RC-dec'd, so a multi-consume of Str without
clone is a real use-after-free. is_value_type is the Str-excluding
subset of is_primitive_name, pinned by a unit test. is_heap_type and
the over-strict-mode lint are left untouched (separate concern).
Fix 2 — application is a borrow. Term::App walks its callee in
Position::Borrow (was Consume). Applying a function value reads it; it
stays live for further applications. Global fn-refs are untracked
(no-op); a tracked function-typed binder (a HOF param) is no longer
consumed by application. This fixes both the own-f-param
use-after-consume and the borrow-f-param consume-while-borrowed in the
recursion-passing HOF shape (map_int f t). Passing a function value as
an arg is unchanged — it follows the callee param_modes.
Scope decision: value-typed let-binders stay conservatively tracked as
heap (their type is inferred, not annotated, and the linearity walk
does not re-run inference). This is soundness-safe — over-strict, never
unsound — and not a measured corpus shape; lifting it would need a full
binder->type table out of the type-checker.
Verification: all three false-positive classes reproduced today against
explicit-mode fns and shipped as RED->GREEN fixtures
(examples/fp_{value,hof,map}.ail); examples/real_consume.ail stays RED
(heap double-consume still fires) to prove the exemption is type-gated.
715 workspace tests green; bench/check.py 0/34 and bench/compile_check.py
0/24 regressed. merge_states carries is_value so the flag survives
branch merges. RED-first verified per task.
closes#56
Brummel
aaa70d4c35