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typescript/no-complex-declarator-type

Disallow complex inferred declarator types without explicit annotation.

Targeted pattern scope​

This rule targets variable declarators whose identifier has no explicit type annotation.

It is intended to catch complex inferred declarators and prompt an explicit annotation (or as const, where appropriate).

What this rule reports​

This rule reports variable declarators with complex assertions/inference when no explicit type annotation is present.

Why this rule exists​

Complex inferred declarations can obscure the intended variable contract, especially when assertions are involved.

❌ Incorrect​

const value = (() => 1) as () => number;

✅ Correct​

const value: () => number = (() => 1) as () => number;

Behavior and migration notes​

This rule reports only and does not provide an autofix.

Migration is usually adding an explicit annotation to the declarator identifier.

Options​

This rule has no options.

Additional examples​

const model = {
 run() {
  return 1;
 },
} as {
 run(): number;
};
// ❌ reported without an explicit declarator annotation

const typedModel: { run(): number } = {
 run() {
  return 1;
 },
};
// ✅ valid

ESLint flat config example​

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

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/typescript/no-complex-declarator-type": "error",
  },
 },
];

When not to use it​

Disable this rule if your project allows complex inferred declarator types without annotations.

Package documentation​

Rule catalog ID: R086

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.