# iter 23.4-prep — checker prerequisites for prelude free fns

**Date:** 2026-05-11
**Branch:** iter/23.4-prep
**Status:** DONE
**Tasks completed:** 2 of 2

## Summary

Closes two localised checker gaps that BLOCKED iter 23.4 mid-flight:

- **Gap 2 (Task 1):** `linearity::check_module`'s globals-construction
  loop now iterates `Def::Class` methods and registers each method
  type in the globals map. Previously, a borrow-mode fn that
  forwarded its borrow-mode params into a class-method call fired
  `consume-while-borrowed` false positives, because
  `callee_arg_modes` defaulted to `Consume` when it could not find
  the method's `param_modes`. `Def::Instance` stays a no-op:
  instance method bodies are walked separately via `Def::Fn` after
  monomorphisation, per the comment in the new arm.

- **Gap 1 (Task 2):** the `Term::Var { name }` lookup ladder in
  `synth` grows one new branch between the class-method arm and the
  dot-qualified arm. It iterates `env.imports.values()` to find a
  free-fn match in any implicitly-imported module's flat-globals
  table; on hit, it qualifies any owner-module-local Type::Cons via
  the existing `qualify_local_types` helper (mirror of the
  dot-qualified arm). Today the prelude is the only implicit
  import, so single-match-wins is unambiguous; the code comment
  names the future revisit point for multi-implicit-import
  ambiguity.

Both fixes are intra-crate and additive — no schema change, no new
diagnostic, no new workspace plumbing. iter 23.4's five prelude
free fns (`ne`/`lt`/`le`/`gt`/`ge`) can now ship against the
existing plan unchanged.

## Per-task subjects

- iter 23.4-prep.1: linearity — register Def::Class method types in globals
- iter 23.4-prep.2: check — bare-name fall-through to implicit-imported free fns

## Concerns

- No E2E fixture added under `examples/`. The plan's own "Plan
  self-review" identifies the two RED-first tests (one in
  `linearity.rs`, one in `lib.rs`'s `check_workspace`-level test
  module) as the iter-23.4-prep-shaped coverage. The natural E2E
  surface (a fixture calling bare `ne 1 2` against the prelude)
  cannot land until iter 23.4 ships the prelude free fns
  themselves — both `examples/prelude.ail.json` and the consumer
  fixture are out of scope for this iter. iter 23.4's E2E coverage
  is the right place; flagging here so the next iter does not
  inherit "no E2E for the prep iter" as unrecorded debt.

## Known debt

- The Task 2 branch's `mod_name` first-match-wins rule remains
  ambiguous-by-design as long as `prelude` is the singleton
  implicit import. If a second implicit import lands in a future
  milestone, this branch needs a duplicate-detection diagnostic
  ("name `X` resolves through implicit imports `A` and `B`,
  qualify the call"). The code comment names the revisit point.

## Blocked detail

N/A — DONE.

## Commits

c10acf0a..aef4ab84

## Stats

bench/orchestrator-stats/2026-05-11-iter-23.4-prep.json