Type tests

Enter this branch when the acceptance criterion is compiler behavior: inference, assignability, rejection, overload selection, generic constraints, or a displayed public type. Use pnpm check for ordinary declaration edits whose compiler behavior is not independently under test. A runtime bug in generic code needs a runtime regression test, not a type test, when its type contract is unchanged.

Inspect nearby .tst.ts files and use their imports and assertion style. Use ordinary Tstyche assertions such as toBe for structural equality and choose a specific assertion for the inference or assignability contract under test.

Structural equality does not verify editor quick-info rendering. For internal aliases, unsimplified intersections, or other displayed-type regressions, read displayed-types.md.

Run targeted pnpm test-types <filename>; the root command covers every configured TypeScript version. For a regression fix, confirm the assertion fails against the pre-fix type. This branch is complete when the assertion proves the intended contract and the target passes.