iter ctt.1 — Env-overlay shape ratification

Date: 2026-05-12 Started from: 0a36294e61 Status: DONE Tasks completed: 3 of 3

Summary

Ratifies the two-overlay shape of the check environment (env.types

env.ctor_index) and pins its load-bearing consumer. The split decision now has a DESIGN.md anchor (§"Env construction") explaining the owning-index / reverse-index roles, the rationale for not collapsing into one variant-keyed map, and the intentional asymmetry with the mono side (narrowed to types-only at ct.3.2, because its runtime-ctor-lookup consumer story differs from the check side's in-band DuplicateCtor diagnostic). A new behavioural-pin test (crates/ailang-check/tests/duplicate_ctor_pin.rs) asserts code == "duplicate-ctor" plus message-substring coverage for a two-ADT-same-ctor fixture, going red if the per-module rebuild at crates/ailang-check/src/lib.rs:1342-1384 is ever silently removed. Two P2 roadmap todos struck [x] with one-line forward-references to this iter. No production-code edits. cargo test --workspace green.

iter ctt.1.1: New pinning test crates/ailang-check/tests/duplicate_ctor_pin.rs — builds a Workspace inline with one module declaring type Cat = Twins and type Dog = Twins, calls check_workspace, asserts a Diagnostic with code == "duplicate-ctor" plus message substring for Twins / Cat / Dog. PASS on first run, as the plan predicted (behaviour pre-exists).
iter ctt.1.2: Inserted new top-level section ## Env construction in docs/DESIGN.md between ## Convention: qualified cross-module references (line 1941) and ## Data model (now line 1988, was 1959 pre-edit). Three paragraphs: split definition, rationale, check-side / mono-side asymmetry. Cross-references the pinning test.
iter ctt.1.3: Two [ ] → [x] strikes in docs/roadmap.md at lines 79 (overlay shape question) and 183 (per-module overlay narrowing). Each gains a one-line forward-reference suffix on its context: line pointing at iter ctt.1 and the closing artefact.

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bench/orchestrator-stats/2026-05-12-iter-ctt.1.json