Rules

ttsc is the standalone TypeScript-Go compiler — see Setup if you haven’t installed it yet.

The full catalog by category. Each rule maps to an ESLint name where one exists. Severity in lint.config.ts is one of "error" (fails the build), "warning" (prints, exit code 0), "off" (skipped).

If you’re skimming: the error-severity defaults at the bottom of this page are what most projects end up with.

Authoritative source: the canonical rule-name union lives at packages/lint/src/structures/TtscLintRule.ts. This page documents what each rule does and when to keep it on.

Variable declarations

Rule	Effect
`no-var`	Reject `var`. Use `let` or `const`. Autofixable.
`prefer-const`	When a `let` is never reassigned, demand `const`. Autofixable for single declarations.

Equality and comparison

Rule	Effect
`eqeqeq`	Reject `==` and `!=`. Autofixable when both operands are typed.
`no-self-compare`	Reject `x === x` and friends.
`no-self-assign`	Reject `x = x`, including destructured forms.

Suggestions

Rule	Effect
`no-explicit-any`	Reject `any` annotations. Typically `"warning"` during migrations.
`prefer-as-const`	Reject `as Literal` when `as const` would do. Autofixable.
`object-shorthand`	Reject `{ foo: foo }`. Autofixable.
`no-useless-rename`	Reject `{ x: x }` in destructuring. Autofixable.
`no-extra-non-null-assertion`	Reject `x!!`. Autofixable.
`no-unnecessary-type-constraint`	Reject `<T extends unknown>` and similar. Autofixable.
`prefer-namespace-keyword`	Use `namespace` not `module`. Autofixable.

Strings and literals

Rule	Effect
`no-useless-escape`	Reject `\.` and friends when not required. Autofixable.
`no-octal`	Reject octal literals.
`no-octal-escape`	Reject `\08`-style escapes.
`no-template-curly-in-string`	Reject `${}` inside non-template strings (probably a bug).

Wrapper objects and prototypes

Rule	Effect
`no-wrapper-object-types`	Reject `String` / `Number` / `Boolean` / `Symbol` / `BigInt`. Autofixable. `Object` stays detection-only.
`no-proto`	Reject `obj.__proto__`.
`no-prototype-builtins`	Reject `obj.hasOwnProperty(...)`; use `Object.prototype.hasOwnProperty.call`.

Loops

Rule	Effect
`no-constant-condition`	Reject `while (true)` and other constant test expressions.
`for-direction`	`for (i = 0; i < 10; i--)` → fail.
`prefer-for-of`	Prefer `for..of` when the index is unused.

Imports and exports

Rule	Effect
`no-import-type-side-effects`	Hoist inline `type` modifiers into a single `import type {}`. Autofixable.
`consistent-type-imports`	Prefer `import type {}` when imports are types-only.
`no-require-imports`	Reject `require(...)` outside CommonJS modules.

Promises and async

Rule	Effect
`await-thenable`	Reject `await` on non-thenable operands. Type-aware — uses the Checker. Autofixable (drops the `await`).
`no-async-promise-executor`	Reject `new Promise(async (...) => ...)`.
`no-promise-executor-return`	Reject `return` inside a Promise executor.

Throw and control flow

Rule	Effect
`no-throw-literal`	`throw "boom"` → fail. Use `throw new Error(...)`.
`no-fallthrough`	Reject `switch` case fall-through without an explicit comment.
`no-unsafe-finally`	Reject `return` / `throw` inside a `finally`.

Parameters

Rule	Effect
`default-param-last`	`(req, opt = 1, req2)` → fail.
`no-dupe-args`	Function declared with two parameters of the same name.

Duplicates

Rule	Effect
`no-dupe-keys`	`{ a: 1, a: 2 }`.
`no-duplicate-case`	Same case label twice in a `switch`.
`no-dupe-else-if`	`if (a) ... else if (a) ...`.

Miscellaneous

Rule	Effect
`no-debugger`	Reject `debugger`.
`no-empty`	Reject `if (x) {}`, `while (x) {}`, etc.
`no-empty-function`	Reject `function f() {}`.
`no-with`	Reject `with (...)`.
`no-multi-assign`	Reject `a = b = 0` chains.

Format

The format rules (format/*) cover Prettier’s territory. They live on their own page — Format rules.

A common starter set

Most projects start here. Add and remove as you go.


// lint.config.ts
import type { TtscLintConfig } from "@ttsc/lint";
 
export default {
  rules: {
    // Variables
    "no-var": "error",
    "prefer-const": "error",
 
    // Comparison
    "eqeqeq": "error",
    "no-self-compare": "error",
 
    // Suggestions
    "no-explicit-any": "warning",
    "prefer-as-const": "error",
    "object-shorthand": "error",
    "no-useless-rename": "error",
 
    // Imports
    "no-import-type-side-effects": "error",
    "consistent-type-imports": "error",
 
    // Misc safety
    "no-debugger": "error",
    "no-throw-literal": "error",
    "await-thenable": "error",
 
    // Format (see /docs/lint/format)
    "format/semi": "error",
    "format/quotes": ["error", { prefer: "double" }],
    "format/trailing-comma": "error",
    "format/print-width": ["error", { printWidth: 80 }],
  },
} satisfies TtscLintConfig;

Autofix coverage at a glance

ttsc fix autofixes a subset. Native fixers cover:

no-var, single-declaration prefer-const, ESLint-safe eqeqeq
no-wrapper-object-types (primitives only; Object is detection-only)
prefer-as-const, no-useless-rename, object-shorthand, no-extra-non-null-assertion
no-unnecessary-type-constraint, prefer-namespace-keyword, no-useless-escape
no-import-type-side-effects (hoists inline type modifiers)
await-thenable (type-aware — drops await on non-thenable operands)
Every format rule

With an eslint.config.* file and ESLint installed, ttsc fix delegates non-native fixers to ESLint, then reloads the program.