Brummel
9c4d195806
Third iteration of spec 0064. Closes false-positive class 2: Term::Let walks its value in Position::Consume, so (let a t (match a …)) over a borrow-mode t consumes t at the binding -> false consume-while-borrowed. Fix: Checker gains a scoped aliases: HashMap<String,String>. A (let a t body) whose value is a bare Var resolving to a tracked binder records a -> root(t) for the body scope and skips the consume walk. A new resolve_alias helper maps a name to its root, PREFERRING a real binder at each chain step -- so an inner binder named `a` (nested let, pattern binder, lam param) automatically shadows the alias with NO change to with_binder/walk_arm/Lam (the shadowing is handled centrally in the resolver, not at three scattered introduction sites). Every binder-state lookup keyed by name resolves through the map first: use_var, the App borrow bump + decrement, callee_arg_modes, and the reuse-as source. Design calls (orchestrator): - Alias REDIRECT, not state clone (spec scope decision 3): consuming the alias marks the single root consumed, so a real double-consume through an alias is still caught -- a clone would miss it (unsound). Pinned by the let_alias_of_owned_double_consume_still_errors unit test. - resolve_alias prefers binders -> shadowing needs no edits to the three binder-introduction sites (simpler, lower-risk than clearing aliases at each). - reuse-as source (linearity.rs:663) is the 4th binder-state-reading site; the spec's Fix 3 named three illustratively. Resolving there too avoids a spurious reuse-as-source-not-bare-var on an aliased Var. Faithful completion of Fix 3, documented as such. Three tasks, RED-first: Task 1 adds examples/c2_let_alias.ail to the harden list (RED: consume-while-borrowed on count's t); Task 2 is the alias mechanism (GREEN) + the soundness unit test; Task 3 closes the design/contracts/0008-memory-model.md:340 let-alias carve-out (was "has not shipped yet") and extends the Ratified-by trailer to name linearity.rs. Diagnostic-only; no schema/type change. plan-recon mapped current post-iter-2 line numbers; parse gate fired on the inlined fixture (RED confirmed). Class 4 (partition_eithers rewrite) remains for the final iteration. refs #57