May 5, 2025 · Oct 20, 2024 · Oct 20, 2024 · Nov 3, 2024 · Nov 3, 2024 · Nov 3, 2024
diff --git a/eslint.config.mjs b/eslint.config.mjs
        'error',
        { allowConstantLoopConditions: true, checkTypePredicates: true },
      ],
      '@typescript-eslint/no-unnecessary-type-conversion': 'error',
      '@typescript-eslint/no-unnecessary-type-parameters': 'error',
      '@typescript-eslint/no-unused-expressions': 'error',
      '@typescript-eslint/no-unused-vars': [
diff --git a/packages/eslint-plugin/docs/rules/no-unnecessary-type-conversion.mdx b/packages/eslint-plugin/docs/rules/no-unnecessary-type-conversion.mdx
 ---
 description: 'Disallow conversion idioms when they do not change the type or value of the expression.'
 ---

 import Tabs from '@theme/Tabs';
 import TabItem from '@theme/TabItem';

 > 🛑 This file is source code, not the primary documentation location! 🛑
 >
 > See **https://typescript-eslint.io/rules/no-unnecessary-type-conversion** for documentation.

 JavaScript provides several commonly used idioms to convert values to a specific type:

 - Primitive coercion (e.g. `Boolean(value)`, `String(value)`): using a built-in primitive function
 - String concatenation (e.g. `value + ''`): turning a value into a string
 - Unary coercion (e.g. `+value`, `!!value`): using a built-in operator
 - The `.toString()` method defined on many types

 These conversions are unnecessary if the value is already of that type.

 ## Examples

 <Tabs>
 <TabItem value="❌ Incorrect">

 ```ts
 String('123');
 '123'.toString();
 '' + '123';
 '123' + '';

 Number(123);
 +123;
 ~~123;

 Boolean(true);
 !!true;

 BigInt(BigInt(1));

 let str = '123';
 str += '';
 ```

 </TabItem>
 <TabItem value="✅ Correct">

 ```ts
 function foo(bar: string | number) {
  String(bar);
  bar.toString();
  '' + bar;
  bar + '';

  Number(bar);
  +bar;
  ~~bar;

  Boolean(bar);
  !!bar;

  BigInt(1);

  bar += '';
 }
 ```

 </TabItem>
 </Tabs>

 ## When Not To Use It

 If you don't care about having no-op type conversions in your code, then you can turn off this rule.
 If you have types which are not accurate, then this rule might cause you to remove conversions that you actually do need.

 ## Related To

 - [no-unnecessary-type-assertion](./no-unnecessary-type-assertion.mdx)
 - [no-useless-template-literals](./no-useless-template-literals.mdx)
diff --git a/packages/eslint-plugin/src/configs/eslintrc/all.ts b/packages/eslint-plugin/src/configs/eslintrc/all.ts
    '@typescript-eslint/no-unnecessary-type-arguments': 'error',
    '@typescript-eslint/no-unnecessary-type-assertion': 'error',
    '@typescript-eslint/no-unnecessary-type-constraint': 'error',
    '@typescript-eslint/no-unnecessary-type-conversion': 'error',
    '@typescript-eslint/no-unnecessary-type-parameters': 'error',
    '@typescript-eslint/no-unsafe-argument': 'error',
    '@typescript-eslint/no-unsafe-assignment': 'error',
diff --git a/packages/eslint-plugin/src/configs/eslintrc/disable-type-checked.ts b/packages/eslint-plugin/src/configs/eslintrc/disable-type-checked.ts
    '@typescript-eslint/no-unnecessary-template-expression': 'off',
    '@typescript-eslint/no-unnecessary-type-arguments': 'off',
    '@typescript-eslint/no-unnecessary-type-assertion': 'off',
    '@typescript-eslint/no-unnecessary-type-conversion': 'off',
    '@typescript-eslint/no-unnecessary-type-parameters': 'off',
    '@typescript-eslint/no-unsafe-argument': 'off',
    '@typescript-eslint/no-unsafe-assignment': 'off',
diff --git a/packages/eslint-plugin/src/configs/flat/all.ts b/packages/eslint-plugin/src/configs/flat/all.ts
      '@typescript-eslint/no-unnecessary-type-arguments': 'error',
      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
      '@typescript-eslint/no-unnecessary-type-constraint': 'error',
      '@typescript-eslint/no-unnecessary-type-conversion': 'error',
      '@typescript-eslint/no-unnecessary-type-parameters': 'error',
      '@typescript-eslint/no-unsafe-argument': 'error',
      '@typescript-eslint/no-unsafe-assignment': 'error',
diff --git a/packages/eslint-plugin/src/configs/flat/disable-type-checked.ts b/packages/eslint-plugin/src/configs/flat/disable-type-checked.ts
    '@typescript-eslint/no-unnecessary-template-expression': 'off',
    '@typescript-eslint/no-unnecessary-type-arguments': 'off',
    '@typescript-eslint/no-unnecessary-type-assertion': 'off',
    '@typescript-eslint/no-unnecessary-type-conversion': 'off',
    '@typescript-eslint/no-unnecessary-type-parameters': 'off',
    '@typescript-eslint/no-unsafe-argument': 'off',
    '@typescript-eslint/no-unsafe-assignment': 'off',
diff --git a/packages/eslint-plugin/src/rules/adjacent-overload-signatures.ts b/packages/eslint-plugin/src/rules/adjacent-overload-signatures.ts
          return {
            ...getNameFromMember(member, context.sourceCode),
            callSignature: false,
            static:!!member.static,
            static: member.static,
          };
        case AST_NODE_TYPES.TSCallSignatureDeclaration:
          return {
diff --git a/packages/eslint-plugin/src/rules/explicit-function-return-type.ts b/packages/eslint-plugin/src/rules/explicit-function-return-type.ts
            }
          }
        }
        if (!!funcName &&!!options.allowedNames.includes(funcName)) {
        if (!!funcName && options.allowedNames.includes(funcName)) {
          return true;
        }
      }
      if (
        node.type === AST_NODE_TYPES.FunctionDeclaration &&
        node.id &&
 !!options.allowedNames.includes(node.id.name)
        options.allowedNames.includes(node.id.name)
      ) {
        return true;
      }
diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
 import noUnnecessaryTypeArguments from './no-unnecessary-type-arguments';
 import noUnnecessaryTypeAssertion from './no-unnecessary-type-assertion';
 import noUnnecessaryTypeConstraint from './no-unnecessary-type-constraint';
 import noUnnecessaryTypeConversion from './no-unnecessary-type-conversion';
 import noUnnecessaryTypeParameters from './no-unnecessary-type-parameters';
 import noUnsafeArgument from './no-unsafe-argument';
 import noUnsafeAssignment from './no-unsafe-assignment';
  'no-unnecessary-type-arguments': noUnnecessaryTypeArguments,
  'no-unnecessary-type-assertion': noUnnecessaryTypeAssertion,
  'no-unnecessary-type-constraint': noUnnecessaryTypeConstraint,
  'no-unnecessary-type-conversion': noUnnecessaryTypeConversion,
  'no-unnecessary-type-parameters': noUnnecessaryTypeParameters,
  'no-unsafe-argument': noUnsafeArgument,
  'no-unsafe-assignment': noUnsafeAssignment,
diff --git a/packages/eslint-plugin/src/rules/member-ordering.ts b/packages/eslint-plugin/src/rules/member-ordering.ts
    case AST_NODE_TYPES.PropertyDefinition:
    case AST_NODE_TYPES.TSAbstractMethodDefinition:
    case AST_NODE_TYPES.MethodDefinition:
      return!!node.optional;
      return node.optional;
  }
  return false;
 }
diff --git a/packages/eslint-plugin/src/rules/no-duplicate-enum-values.ts b/packages/eslint-plugin/src/rules/no-duplicate-enum-values.ts

          let value: number | string | undefined;
          if (isStringLiteral(member.initializer)) {
            value =String(member.initializer.value);
            value = member.initializer.value;
          } else if (isNumberLiteral(member.initializer)) {
            value =Number(member.initializer.value);
            value = member.initializer.value;
          } else if (isStaticTemplateLiteral(member.initializer)) {
            value = member.initializer.quasis[0].value.cooked;
          }
diff --git a/packages/eslint-plugin/src/rules/no-empty-interface.ts b/packages/eslint-plugin/src/rules/no-empty-interface.ts
              def => def.node.type === AST_NODE_TYPES.ClassDeclaration,
            );

          const isInAmbientDeclaration = !!(
          const isInAmbientDeclaration =
            isDefinitionFile(context.filename) &&
            scope.type === ScopeType.tsModule &&
            scope.block.declare
          );
            scope.block.declare;

          const useAutoFix = !(
            isInAmbientDeclaration || mergedWithClassDeclaration
diff --git a/packages/eslint-plugin/src/rules/no-redundant-type-constituents.ts b/packages/eslint-plugin/src/rules/no-redundant-type-constituents.ts
 }

 function isNodeInsideReturnType(node: TSESTree.TSUnionType): boolean {
  return!!(
  return (
    node.parent.type === AST_NODE_TYPES.TSTypeAnnotation &&
    isFunctionOrFunctionType(node.parent.parent)
  );
diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts b/packages/eslint-plugin/src/rules/no-unnecessary-template-expression.ts
 // '\\\\$' <- true
 // '\\\\\\$' <- false
 function endsWithUnescapedDollarSign(str: string): boolean {
  return new RegExp(`${String(evenNumOfBackslashesRegExp.source)}\\$$`).test(
    str,
  );
  return new RegExp(`${evenNumOfBackslashesRegExp.source}\\$$`).test(str);
 }

 export default createRule<[], MessageId>({
            // \${ -> \${
            // \\${ -> \\\${
            .replaceAll(
              new RegExp(
                `${String(evenNumOfBackslashesRegExp.source)}(\`|\\\${)`,
                'g',
              ),
              new RegExp(`${evenNumOfBackslashesRegExp.source}(\`|\\\${)`, 'g'),
              '\\$1',
            );
Original file line number	Diff line number	Diff line change
Expand Up		@@ -148,6 +148,7 @@ export default tseslint.config(
		'error',
		{ allowConstantLoopConditions: true, checkTypePredicates: true },
		],
		'@typescript-eslint/no-unnecessary-type-conversion': 'error',
		'@typescript-eslint/no-unnecessary-type-parameters': 'error',
		'@typescript-eslint/no-unused-expressions': 'error',
		'@typescript-eslint/no-unused-vars': [
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,79 @@
		---
		description: 'Disallow conversion idioms when they do not change the type or value of the expression.'
		---

		import Tabs from '@theme/Tabs';
		import TabItem from '@theme/TabItem';

		> 🛑 This file is source code, not the primary documentation location! 🛑
		>
		> See https://typescript-eslint.io/rules/no-unnecessary-type-conversion for documentation.

		JavaScript provides several commonly used idioms to convert values to a specific type:

		- Primitive coercion (e.g. `Boolean(value)`, `String(value)`): using a built-in primitive function
		- String concatenation (e.g. `value + ''`): turning a value into a string
		- Unary coercion (e.g. `+value`, `!!value`): using a built-in operator
		- The `.toString()` method defined on many types

		These conversions are unnecessary if the value is already of that type.

		## Examples

		<Tabs>
		<TabItem value="❌ Incorrect">

		```ts
		String('123');
		'123'.toString();
		'' + '123';
		'123' + '';

		Number(123);
		+123;
		~~123;

		Boolean(true);
		!!true;

		BigInt(BigInt(1));

		let str = '123';
		str += '';
		```

		</TabItem>
		<TabItem value="✅ Correct">

		```ts
		function foo(bar: string \| number) {
		String(bar);
		bar.toString();
		'' + bar;
		bar + '';

		Number(bar);
		+bar;
		~~bar;

		Boolean(bar);
		!!bar;

		BigInt(1);

		bar += '';
		}
		```

		</TabItem>
		</Tabs>

		## When Not To Use It

		If you don't care about having no-op type conversions in your code, then you can turn off this rule.
		If you have types which are not accurate, then this rule might cause you to remove conversions that you actually do need.

		## Related To

		- [no-unnecessary-type-assertion](./no-unnecessary-type-assertion.mdx)
		- [no-useless-template-literals](./no-useless-template-literals.mdx)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -98,6 +98,7 @@ export = {
		'@typescript-eslint/no-unnecessary-type-arguments': 'error',
		'@typescript-eslint/no-unnecessary-type-assertion': 'error',
		'@typescript-eslint/no-unnecessary-type-constraint': 'error',
		'@typescript-eslint/no-unnecessary-type-conversion': 'error',
		'@typescript-eslint/no-unnecessary-type-parameters': 'error',
		'@typescript-eslint/no-unsafe-argument': 'error',
		'@typescript-eslint/no-unsafe-assignment': 'error',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -34,6 +34,7 @@ export = {
		'@typescript-eslint/no-unnecessary-template-expression': 'off',
		'@typescript-eslint/no-unnecessary-type-arguments': 'off',
		'@typescript-eslint/no-unnecessary-type-assertion': 'off',
		'@typescript-eslint/no-unnecessary-type-conversion': 'off',
		'@typescript-eslint/no-unnecessary-type-parameters': 'off',
		'@typescript-eslint/no-unsafe-argument': 'off',
		'@typescript-eslint/no-unsafe-assignment': 'off',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -112,6 +112,7 @@ export default (
		'@typescript-eslint/no-unnecessary-type-arguments': 'error',
		'@typescript-eslint/no-unnecessary-type-assertion': 'error',
		'@typescript-eslint/no-unnecessary-type-constraint': 'error',
		'@typescript-eslint/no-unnecessary-type-conversion': 'error',
		'@typescript-eslint/no-unnecessary-type-parameters': 'error',
		'@typescript-eslint/no-unsafe-argument': 'error',
		'@typescript-eslint/no-unsafe-assignment': 'error',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -41,6 +41,7 @@ export default (
		'@typescript-eslint/no-unnecessary-template-expression': 'off',
		'@typescript-eslint/no-unnecessary-type-arguments': 'off',
		'@typescript-eslint/no-unnecessary-type-assertion': 'off',
		'@typescript-eslint/no-unnecessary-type-conversion': 'off',
		'@typescript-eslint/no-unnecessary-type-parameters': 'off',
		'@typescript-eslint/no-unsafe-argument': 'off',
		'@typescript-eslint/no-unsafe-assignment': 'off',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -79,7 +79,7 @@ export default createRule({
		return {
		...getNameFromMember(member, context.sourceCode),
		callSignature: false,
		static:!!member.static,
		static: member.static,
		};
		case AST_NODE_TYPES.TSCallSignatureDeclaration:
		return {
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -169,14 +169,14 @@ export default createRule<Options, MessageIds>({
		}
		}
		}
		if (!!funcName &&!!options.allowedNames.includes(funcName)) {
		if (!!funcName && options.allowedNames.includes(funcName)) {
		return true;
		}
		}
		if (
		node.type === AST_NODE_TYPES.FunctionDeclaration &&
		node.id &&
		!!options.allowedNames.includes(node.id.name)
		options.allowedNames.includes(node.id.name)
		) {
		return true;
		}
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -75,6 +75,7 @@ import noUnnecessaryTemplateExpression from './no-unnecessary-template-expressio
		import noUnnecessaryTypeArguments from './no-unnecessary-type-arguments';
		import noUnnecessaryTypeAssertion from './no-unnecessary-type-assertion';
		import noUnnecessaryTypeConstraint from './no-unnecessary-type-constraint';
		import noUnnecessaryTypeConversion from './no-unnecessary-type-conversion';
		import noUnnecessaryTypeParameters from './no-unnecessary-type-parameters';
		import noUnsafeArgument from './no-unsafe-argument';
		import noUnsafeAssignment from './no-unsafe-assignment';
Expand DownExpand Up		@@ -208,6 +209,7 @@ const rules = {
		'no-unnecessary-type-arguments': noUnnecessaryTypeArguments,
		'no-unnecessary-type-assertion': noUnnecessaryTypeAssertion,
		'no-unnecessary-type-constraint': noUnnecessaryTypeConstraint,
		'no-unnecessary-type-conversion': noUnnecessaryTypeConversion,
		'no-unnecessary-type-parameters': noUnnecessaryTypeParameters,
		'no-unsafe-argument': noUnsafeArgument,
		'no-unsafe-assignment': noUnsafeAssignment,
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -488,7 +488,7 @@ function isMemberOptional(node: Member): boolean {
		case AST_NODE_TYPES.PropertyDefinition:
		case AST_NODE_TYPES.TSAbstractMethodDefinition:
		case AST_NODE_TYPES.MethodDefinition:
		return!!node.optional;
		return node.optional;
		}
		return false;
		}
Expand Down