Precondition for #55 (eliminate ParamMode::Implicit, spec 0062). The
strict linearity check (use-after-consume / consume-while-borrowed)
runs today only on the ~45 of 258 all-explicit-mode fns; deleting
Implicit turns it on universally and surfaces ~21% false positives in
two classes — value-type params (Int/Bool/Float/Unit, never consumed)
and applied function params in HOFs (application is a borrow).
Two design questions settled against the live tool, not the model:
- Str is heap, NOT a value type for consume-tracking. 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. The
value-type set is the unboxed {Int,Bool,Float,Unit}, narrower than
is_primitive_name (which includes Str).
- Applying a function value is a borrow; passing it as an arg follows
callee param_modes (unchanged). The recursion-passing HOF pattern is
then consistent under a borrow f-param.
All three false-positive classes reproduced today against explicit-mode
fns (testable without #55) and recorded as RED fixtures; a heap
double-consume fixture stays RED to prove the exemption is type-gated.
grounding-check PASS. refs #56
