chore: enable prefer-for-of rule internally (#4977)

.eslintrc.js

@@ -64,6 +64,7 @@ module.exports = {
     '@typescript-eslint/no-explicit-any': 'error',
     '@typescript-eslint/no-non-null-assertion': 'off',
     '@typescript-eslint/no-var-requires': 'off',
+    '@typescript-eslint/prefer-for-of': 'error',
     '@typescript-eslint/prefer-nullish-coalescing': 'error',
     '@typescript-eslint/prefer-optional-chain': 'error',
     '@typescript-eslint/unbound-method': 'off',

packages/eslint-plugin/src/rules/no-unsafe-argument.ts

@@ -176,9 +176,7 @@ export default util.createRule<[], MessageIds>({
           return;
         }
 
-        for (let i = 0; i < node.arguments.length; i += 1) {
-          const argument = node.arguments[i];
-
+        for (const argument of node.arguments) {
           switch (argument.type) {
             // spreads consume
             case AST_NODE_TYPES.SpreadElement: {
@@ -204,8 +202,7 @@ export default util.createRule<[], MessageIds>({
                 // foo(...[tuple1, tuple2])
                 const spreadTypeArguments =
                   checker.getTypeArguments(spreadArgType);
-                for (let j = 0; j < spreadTypeArguments.length; j += 1) {
-                  const tupleType = spreadTypeArguments[j];
+                for (const tupleType of spreadTypeArguments) {
                   const parameterType = signature.getNextParameterType();
                   if (parameterType == null) {
                     continue;

packages/eslint-plugin/src/rules/no-unsafe-assignment.ts

@@ -164,12 +164,7 @@ export default util.createRule({
       );
 
       let didReport = false;
-      for (
-        let receiverIndex = 0;
-        receiverIndex < receiverNode.properties.length;
-        receiverIndex += 1
-      ) {
-        const receiverProperty = receiverNode.properties[receiverIndex];
+      for (const receiverProperty of receiverNode.properties) {
         if (receiverProperty.type === AST_NODE_TYPES.RestElement) {
           // don't bother checking rest
           continue;

packages/eslint-plugin/src/rules/no-unused-vars.ts

@@ -419,9 +419,7 @@ export default util.createRule<Options, MessageIds>({
 
         const unusedVars = collectUnusedVariables();
 
-        for (let i = 0, l = unusedVars.length; i < l; ++i) {
-          const unusedVar = unusedVars[i];
-
+        for (const unusedVar of unusedVars) {
           // Report the first declaration.
           if (unusedVar.defs.length > 0) {
             context.report({

packages/scope-manager/src/ScopeManager.ts

@@ -132,17 +132,9 @@ class ScopeManager {
           return scope;
         }
       }
-    } else {
-      for (let i = 0; i < scopes.length; ++i) {
-        const scope = scopes[i];
-
-        if (predicate(scope)) {
-          return scope;
-        }
-      }
+      return null;
     }
-
-    return null;
+    return scopes.find(predicate) ?? null;
   }
 
   protected nestScope<T extends Scope>(scope: T): T;

packages/scope-manager/src/scope/ScopeBase.ts

@@ -81,9 +81,7 @@ function isStrictScope(
   }
 
   // Search 'use strict' directive.
-  for (let i = 0; i < body.body.length; ++i) {
-    const stmt = body.body[i];
-
+  for (const stmt of body.body) {
     if (stmt.type !== AST_NODE_TYPES.ExpressionStatement) {
       break;
     }
@@ -358,7 +356,7 @@ abstract class ScopeBase<
   };
 
   public close(scopeManager: ScopeManager): Scope | null {
-    let closeRef;
+    let closeRef: (ref: Reference, scopeManager: ScopeManager) => void;
 
     if (this.shouldStaticallyClose()) {
       closeRef = this.#staticCloseRef;
@@ -370,11 +368,7 @@ abstract class ScopeBase<
 
     // Try Resolving all references in this scope.
     assert(this.leftToResolve);
-    for (let i = 0; i < this.leftToResolve.length; ++i) {
-      const ref = this.leftToResolve[i];
-
-      closeRef(ref, scopeManager);
-    }
+    this.leftToResolve.forEach(ref => closeRef(ref, scopeManager));
     this.leftToResolve = null;
 
     return this.upper;

packages/scope-manager/src/scope/WithScope.ts

@@ -22,10 +22,7 @@ class WithScope extends ScopeBase<
       return super.close(scopeManager);
     }
     assert(this.leftToResolve);
-    for (let i = 0; i < this.leftToResolve.length; ++i) {
-      const ref = this.leftToResolve[i];
-      this.delegateToUpperScope(ref);
-    }
+    this.leftToResolve.forEach(ref => this.delegateToUpperScope(ref));
     this.leftToResolve = null;
     return this.upper;
   }

packages/typescript-estree/src/convert.ts

@@ -692,8 +692,7 @@ export class Converter {
      * to the result, we remove them from the array, so that they
      * are not handled twice.
      */
-    for (let i = 0; i < modifiers.length; i++) {
-      const modifier = modifiers[i];
+    for (const modifier of modifiers) {
       switch (modifier.kind) {
         /**
          * Ignore ExportKeyword and DefaultKeyword, they are handled

packages/typescript-estree/src/node-utils.ts

@@ -278,8 +278,7 @@ export function getTSNodeAccessibility(
   if (!modifiers) {
     return null;
   }
-  for (let i = 0; i < modifiers.length; i++) {
-    const modifier = modifiers[i];
+  for (const modifier of modifiers) {
     switch (modifier.kind) {
       case SyntaxKind.PublicKeyword:
         return 'public';

packages/typescript-estree/tests/ast-alignment/utils.ts

@@ -240,8 +240,7 @@ export function preprocessBabylonAST(ast: File): any {
        * @see https://github.com/babel/babel/blob/381277a/eslint/babel-eslint-parser/src/convert/convertAST.cjs#L81-L102
        */
       TemplateLiteral(node: any) {
-        for (let j = 0; j < node.quasis.length; j++) {
-          const q = node.quasis[j];
+        for (const q of node.quasis) {
           q.range[0] -= 1;
           q.loc.start.column -= 1;
           if (q.tail) {