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no-shadow

Disallow shadowing variables from outer scopes.

Targeted pattern scope​

This rule walks lexical scopes and reports variable declarations that reuse names from parent scopes.

Enum declarations are intentionally ignored.

What this rule reports​

This rule reports variables that reuse names from outer scopes.

Enum declarations are skipped both when evaluating the current declaration and when evaluating potential outer-scope matches.

Why this rule exists​

Shadowing can hide outer bindings and make data flow harder to reason about.

❌ Incorrect​

const x = 1;
function f() {
 const x = 2;
 return x;
}

✅ Correct​

const x = 1;
function f() {
 const y = x + 1;
 return y;
}

Deprecated​

Behavior and migration notes​

This rule is deprecated in favor of @typescript-eslint/no-shadow.

It reports only and does not provide an autofix.

Options​

This rule has no options.

Status​

Use the Deprecated section above for lifecycle details.

Additional examples​

enum Status {
 Ready,
}

function run(Status: number): number {
 return Status;
}
// enum-related declarations are intentionally ignored by this rule.

ESLint flat config example​

import etcMisc from "eslint-plugin-etc-misc";

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/no-shadow": "error",
  },
 },
];

When not to use it​

Disable this rule if shadowed variable names are acceptable in your code style.

Package documentation​

Rule catalog ID: R040

Further reading​

Adoption resources​

  • Start at warning level in CI, then move to error after cleanup.
  • Use focused codemods/autofix batches per package or directory.