Wobbling ty constraint order

TY_CONSTRAINT_SET_ORDER perturbs both the builder-local TDD-variable order and the local typevar order used to orient typevar-to-typevar constraints. The setting is fixed for the lifetime of each test process.

• unset/0: normal ordering;
• reverse: reverse both orderings;
• an integer: XOR each local ID with that mask. Small masks immediately perturb dense arena IDs: 1 swaps adjacent IDs, 3 reverses blocks of four, and powers of two exchange neighboring blocks.

This deliberately changes internal TDD shape. Run mdtests only: graph-structure unit snapshots are expected to differ. Never enable snapshot updates for a wobble run, since updating would hide the failures being sought.

Run

From the Ruff root, first establish the normal baseline, then run the reversed and XOR-masked orders sequentially. Set TY_CONSTRAINT_ORDER_LOG_DIR to retain logs in a particular writable directory; otherwise mktemp chooses an appropriate temporary directory (respecting the environment's temporary-directory configuration).

set -u