[gHashTag]

Summary

Add an expression-level positive-control / characterization test set to
mod tests_compiler_rejects in bootstrap/src/compiler.rs. Where #1123 (Q) pinned
declaration-level rejection and #1130 (T) pinned declaration-level acceptance, this set pins
EXPRESSION-LEVEL lowering: the exact Verilog a valid return-expression lowers to. Pure test
additions; no production code changes.

Motivation

The reject/accept suite covers casts (#1123/#1130) and declaration shapes, but the precise
SHAPE of lowered expressions is not pinned. A refactor of the expression generator could
silently change associativity, parenthesization, or operand handling without any test
failing. This locks the current output so such a change is caught.

Per the project rule, each assertion was written by first observing the current generator
output, then locking it in. These characterize CURRENT behavior; they do not endorse or
prescribe it.

New tests (5)

• lowers_binop_add_characterization -- return x + 1 lowers to add = (x + 1); (no dropped
  body).
• lowers_chained_binop_left_assoc_characterization -- return x + 1 + 2 lowers
  left-associatively to f = ((x + 1) + 2);.
• lowers_redundant_paren_to_operand_characterization -- return (x) strips the redundant
  parenthesis to f = x;.
• lowers_identity_cast_to_operand_characterization -- return x as u8 (u8 fn) lowers to the
  operand f = x; with no dropped body.
• let_binding_falls_back_to_todo_characterization -- a let binding before the return is
  NOT yet lowered; the body falls back to the // TODO: implement stub. Pinned as a visible
  current GAP (named characterization), to be updated deliberately if let lowering is added.

Verification

• tests_compiler_rejects count: 21 -> 26.
• Full suite: 1468 passed, 0 failed, 0 regressions.
• Build warnings unchanged (623; test-only additions).

L6 gf16 SSOT untouched; catalog stays 83; no gen/ edits; ASCII-only added lines; no quality
claim added.

[github-actions]

📓 NotebookLM Notebook linked to this PR

• Notebook ID: b83263109fb055dc
• URL: https://notebooklm.google.com/notebook/b83263109fb055dc

This notebook contains session context, decisions, and artifacts for this work.

[github-actions]

PR Dashboard

Generated at: 2026-06-14 17:54:25 UTC

• compiler.rs: expression-level positive/characterization tests (tests_compiler_rejects 21->26). Closes #1137 #1140 compiler.rs: expression-level positive/characterization tests (tests_compiler_rejects 21->26). Closes #1137 | Created: 2026-06-14 | Updated: 2026-06-14 | 12 failing / 17 total
• fix(gen): untrack stale gen/numeric catalog artifacts (committed gen drifts 77 vs SSOT 83) -- Closes #1120 #1128 fix(gen): untrack stale gen/numeric catalog artifacts (committed gen drifts 77 vs SSOT 83) -- Closes #1120 | Created: 2026-06-14 | Updated: 2026-06-14 | 0 failing / 21 total

Summary

Status	Count
Total Open PRs	2
PRs with Failing Checks	0
PRs with All Checks Green	2
READY	1
FAILING	0
PENDING	0

Seal Status

• ⚠️ STALE -- sha256(compiler.rs)=1953ec73601f != manifest seal=49e55df6d444.
  The committed NMSE numbers were certified against an older compiler.rs.
  Run scripts/reseal-check.sh locally for the two-step reseal command (advisory; not a merge gate).