chore: type check tests via lint:tsc

[cryptodev-2s]

Top of stack #331, on #333. Opts this package into the progressive test type checking rollout core is doing (16 of its 100 packages so far).

Tests were not type checked at all

Verified by injecting const deliberateTypeError: number = "a string" into a test file:

Check	Result
yarn build	passes, tsconfig.build.json excludes tests
yarn test:source	passes, see below
yarn test:types	passes, tsd only reads *.test-d.ts
yarn lint	passes

test:source can never catch it: isolatedModules puts ts-jest on its transpileModule path, which erases types without checking them.

The change

lint:tsc = tsc --noEmit --project tsconfig.lint.json     ← added to `lint`

tsconfig.lint.json extends tsconfig.json (which already covers everything the build does not) and adds skipLibCheck, because dependency declarations do not satisfy the strict flags used here.

Why *.test-d.ts is excluded

Those belong to tsd, which checks them itself via yarn test:types (fixed in #322). Including them here pulls tsd's own types into the program, and those reach type-fest, whose basic.d.ts carries /// <reference lib="esnext" />. That silently widens built in types past this package's lib, producing a spurious failure where FrozenSet no longer satisfies ReadonlySet because of Set methods we do not target. Traced with tsc --explainFiles.

Why this stacks on ES2022

With lib: ES2020 a tsc pass over the tests reports 11 errors, nearly all Property 'cause' does not exist. With lib: ES2022, zero. #333 has to land first.

Confirmed not vacuous

A deliberate type error in a test file now exits non-zero with TS2322, and tsd still independently catches a bad expectAssignable in a .test-d.ts file.

---

Note

Low Risk
Dev-only lint and TypeScript config changes; no runtime or shipped library behavior changes.

Overview
yarn lint now runs TypeScript on test and other non-build code through a new lint:tsc script, closing a gap where tsconfig.build.json and transpile-only Jest never validated types in *.test.ts files.

A new tsconfig.lint.json extends the root config with skipLibCheck, incremental emitDeclarationOnly output under .tsc-lint-cache/ (gitignored and ignored by ESLint), and an exclude for *.test-d.ts so tsd-owned type tests are not double-checked or polluted by tsd’s wider lib types.

^{Reviewed by Cursor Bugbot for commit 670fa8a. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cryptodev-2s]

@metamaskbot publish-preview

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[cryptodev-2s]

@metamaskbot publish-preview

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[mcmire]

LGTM!