chore: Enable eslint rule no-unnecessary-type-assertion

.eslintrc.cjs

@@ -35,6 +35,9 @@ module.exports = {
     {
       files: ["**/*.ts"],
       parser: "@typescript-eslint/parser",
+      parserOptions: {
+        project: "./tsconfig.json",
+      },
       plugins: ["@typescript-eslint"],
       rules: {
         "no-unused-vars": "off",
@@ -61,6 +64,7 @@ module.exports = {
             allowNamedExports: true,
           },
         ],
+        "@typescript-eslint/no-unnecessary-type-assertion": "error",
       },
     },
     {

package.json

@@ -39,8 +39,8 @@
     "@rollup/plugin-node-resolve": "^13.3.0",
     "@rollup/plugin-replace": "^4.0.0",
     "@types/node": "^18.11.7",
-    "@typescript-eslint/eslint-plugin": "^5.41.0",
-    "@typescript-eslint/parser": "^5.41.0",
+    "@typescript-eslint/eslint-plugin": "^5.46.0",
+    "@typescript-eslint/parser": "^5.46.0",
     "babel-plugin-transform-charcodes": "^0.2.0",
     "c8": "^7.12.0",
     "chalk": "^5.0.0",

packages/babel-cli/src/babel/watcher.ts

@@ -123,7 +123,7 @@ export function updateExternalDependencies(
 }
 
 function removeFileDependency(filename: string, dep: string) {
-  const deps = depToFiles.get(dep) as Set<string>;
+  const deps = depToFiles.get(dep);
   deps.delete(filename);
 
   if (deps.size === 0) {

packages/babel-core/src/config/files/configuration.ts

@@ -226,7 +226,7 @@ export function* findRelativeConfig(
         envName,
         caller,
         packageData.pkg?.dirname === loc
-          ? packageToBabelConfig(packageData.pkg as ConfigFile)
+          ? packageToBabelConfig(packageData.pkg)
           : null,
       );
     }

packages/babel-core/src/config/files/module-types.ts

@@ -59,7 +59,7 @@ function guessJSModuleType(filename: string): "cjs" | "mjs" | "unknown" {
 }
 
 function loadCjsDefault(filepath: string, fallbackToTranspiledModule: boolean) {
-  const module = endHiddenCallStack(require)(filepath) as any;
+  const module = endHiddenCallStack(require)(filepath);
   return module?.__esModule
     ? // TODO (Babel 8): Remove "module" and "undefined" fallback
       module.default || (fallbackToTranspiledModule ? module : undefined)

packages/babel-core/src/gensync-utils/async.ts

@@ -28,7 +28,7 @@ export function maybeAsync<Args extends unknown[], Return>(
 ): Gensync<Args, Return> {
   return gensync({
     sync(...args) {
-      const result = fn.apply(this, args) as Return;
+      const result = fn.apply(this, args);
       if (isThenable(result)) throw new Error(message);
       return result;
     },

packages/babel-core/src/transformation/normalize-file.ts

@@ -45,7 +45,7 @@ export default function* normalizeFile(
     }
 
     if (options.cloneInputAst) {
-      ast = cloneDeep(ast) as t.File;
+      ast = cloneDeep(ast);
     }
   } else {
     // @ts-expect-error todo: use babel-types ast typings in Babel parser

packages/babel-helper-create-class-features-plugin/src/fields.ts

@@ -487,6 +487,7 @@ const privateNameHandlerLoose: Handler<PrivateNameState> = {
   boundGet(member) {
     return t.callExpression(
       t.memberExpression(this.get(member), t.identifier("bind")),
+      // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
       [t.cloneNode(member.node.object as t.Expression)],
     );
   },
@@ -1045,7 +1046,7 @@ export function buildFieldsInitNodes(
         // We special-case the single expression case to avoid the iife, since
         // it's common.
         if (blockBody.length === 1 && t.isExpressionStatement(blockBody[0])) {
-          staticNodes.push(blockBody[0] as t.ExpressionStatement);
+          staticNodes.push(blockBody[0]);
         } else {
           staticNodes.push(template.statement.ast`(() => { ${blockBody} })()`);
         }

packages/babel-helper-create-class-features-plugin/src/index.ts

@@ -190,7 +190,7 @@ export function createClassFeaturePlugin({
         const privateNamesMap = buildPrivateNamesMap(props);
         const privateNamesNodes = buildPrivateNamesNodes(
           privateNamesMap,
-          (privateFieldsAsProperties ?? loose) as boolean,
+          privateFieldsAsProperties ?? loose,
           file,
         );
 
@@ -230,9 +230,9 @@ export function createClassFeaturePlugin({
                 props,
                 privateNamesMap,
                 file,
-                (setPublicClassFields ?? loose) as boolean,
-                (privateFieldsAsProperties ?? loose) as boolean,
-                (constantSuper ?? loose) as boolean,
+                setPublicClassFields ?? loose,
+                privateFieldsAsProperties ?? loose,
+                constantSuper ?? loose,
                 innerBinding,
               ));
           }
@@ -245,9 +245,9 @@ export function createClassFeaturePlugin({
               props,
               privateNamesMap,
               file,
-              (setPublicClassFields ?? loose) as boolean,
-              (privateFieldsAsProperties ?? loose) as boolean,
-              (constantSuper ?? loose) as boolean,
+              setPublicClassFields ?? loose,
+              privateFieldsAsProperties ?? loose,
+              constantSuper ?? loose,
               innerBinding,
             ));
         }

packages/babel-helper-member-expression-to-functions/src/index.ts

@@ -283,6 +283,7 @@ const handle = {
             "=",
             context,
             // object must not be Super when `context` is an identifier
+            // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
             object as t.Expression,
           );
         }

packages/babel-node/src/_babel-node.ts

@@ -258,7 +258,7 @@ function replStart() {
     useGlobal: true,
     preview: true,
   });
-  const NODE_REPL_HISTORY = process.env.NODE_REPL_HISTORY as string;
+  const NODE_REPL_HISTORY = process.env.NODE_REPL_HISTORY;
   if (process.env.BABEL_8_BREAKING) {
     replServer.setupHistory(NODE_REPL_HISTORY, () => {});
   } else {

packages/babel-node/src/babel-node.ts

@@ -54,7 +54,7 @@ getV8Flags(async function (err, v8Flags) {
       args.push(flag);
       args.push(babelArgs[++i]);
     } else if (aliases.has(flag)) {
-      args.unshift(aliases.get(flag) as string);
+      args.unshift(aliases.get(flag));
     } else if (
       flag === "debug" || // node debug foo.js
       flag === "inspect" ||

packages/babel-parser/src/parser/expression.ts

@@ -63,7 +63,6 @@ import {
   PARAM_RETURN,
   functionFlags,
 } from "../util/production-parameter";
-import type { ParamKind } from "../util/production-parameter";
 import {
   newArrowHeadScope,
   newAsyncArrowScope,
@@ -2558,9 +2557,7 @@ export default abstract class ExpressionParser extends LValParser {
 
       // FunctionBody[Yield, Await]:
       //   StatementList[?Yield, ?Await, +Return] opt
-      this.prodParam.enter(
-        (this.prodParam.currentFlags() | PARAM_RETURN) as ParamKind,
-      );
+      this.prodParam.enter(this.prodParam.currentFlags() | PARAM_RETURN);
       node.body = this.parseBlock(
         true,
         false,

packages/babel-parser/src/parser/util.ts

@@ -175,7 +175,7 @@ export default abstract class UtilParser extends Tokenizer {
         this.state.tokensLength = failState.tokensLength;
         return {
           node,
-          error: failState.errors[oldState.errors.length] as ParseError<any>,
+          error: failState.errors[oldState.errors.length],
           thrown: false,
           aborted: false,
           failState,

packages/babel-parser/src/plugins/estree.ts

@@ -501,7 +501,7 @@ export default (superClass: typeof Parser) =>
           break;
       }
 
-      return node as N.AnyExport;
+      return node;
     }
 
     parseSubscript(

packages/babel-parser/src/plugins/jsx/index.ts

@@ -480,15 +480,10 @@ export default (superClass: typeof Parser) =>
               this.setContext(tc.brace);
               this.next();
               if (this.match(tt.ellipsis)) {
-                children.push(
-                  this.jsxParseSpreadChild(node as Undone<N.JSXSpreadChild>),
-                );
+                children.push(this.jsxParseSpreadChild(node));
               } else {
                 children.push(
-                  this.jsxParseExpressionContainer(
-                    node as Undone<N.JSXExpressionContainer>,
-                    tc.j_expr,
-                  ),
+                  this.jsxParseExpressionContainer(node, tc.j_expr),
                 );
               }
 

packages/babel-parser/src/plugins/typescript/index.ts

@@ -1097,7 +1097,7 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
           !type.typeParameters &&
           type.typeName.type === "Identifier"
         ) {
-          labeledNode.label = type.typeName as N.Identifier;
+          labeledNode.label = type.typeName;
         } else {
           this.raise(TSErrors.InvalidTupleMemberLabel, { at: type });
           // @ts-expect-error This produces an invalid AST, but at least we don't drop
@@ -1482,13 +1482,13 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
           // if it turns out to be a `TSThisType`, wrap it with `TSTypePredicate`
           // : asserts this
           if (thisTypePredicate.type === "TSThisType") {
-            node.parameterName = thisTypePredicate as N.TsThisType;
+            node.parameterName = thisTypePredicate;
             node.asserts = true;
             (node as N.TsTypePredicate).typeAnnotation = null;
             thisTypePredicate = this.finishNode(node, "TSTypePredicate");
           } else {
             this.resetStartLocationFromNode(thisTypePredicate, node);
-            (thisTypePredicate as N.TsTypePredicate).asserts = true;
+            thisTypePredicate.asserts = true;
           }
           t.typeAnnotation = thisTypePredicate;
           return this.finishNode(t, "TSTypeAnnotation");
@@ -2094,7 +2094,7 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
           if (this.match(tt.braceL)) {
             this.scope.enter(SCOPE_TS_MODULE);
             this.prodParam.enter(PARAM);
-            const mod = node as Undone<N.TsModuleDeclaration>;
+            const mod = node;
             mod.global = true;
             mod.id = expr;
             mod.body = this.tsParseModuleBlock();
@@ -2880,10 +2880,7 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
               at: this.state.curPosition(),
             });
           }
-          super.parseClassStaticBlock(
-            classBody,
-            member as any as N.StaticBlock,
-          );
+          super.parseClassStaticBlock(classBody, member as N.StaticBlock);
         } else {
           this.parseClassMemberWithIsStatic(
             classBody,

packages/babel-parser/src/util/production-parameter.ts

@@ -75,6 +75,5 @@ export function functionFlags(
   isAsync: boolean,
   isGenerator: boolean,
 ): ParamKind {
-  return ((isAsync ? PARAM_AWAIT : 0) |
-    (isGenerator ? PARAM_YIELD : 0)) as ParamKind;
+  return (isAsync ? PARAM_AWAIT : 0) | (isGenerator ? PARAM_YIELD : 0);
 }

packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/src/index.ts

@@ -7,8 +7,8 @@ import type * as t from "@babel/types";
 export default declare(api => {
   api.assertVersion(7);
 
-  const noDocumentAll = (api.assumption("noDocumentAll") ?? false) as boolean;
-  const pureGetters = (api.assumption("pureGetters") ?? false) as boolean;
+  const noDocumentAll = api.assumption("noDocumentAll") ?? false;
+  const pureGetters = api.assumption("pureGetters") ?? false;
 
   return {
     name: "bugfix-v8-spread-parameters-in-optional-chaining",

packages/babel-plugin-proposal-class-static-block/src/index.ts

@@ -7,7 +7,6 @@ import {
   FEATURES,
 } from "@babel/helper-create-class-features-plugin";
 
-import type * as t from "@babel/types";
 /**
  * Generate a uid that is not in `denyList`
  *
@@ -65,7 +64,7 @@ export default declare(({ types: t, template, assertVersion }) => {
           // We special-case the single expression case to avoid the iife, since
           // it's common.
           if (blockBody.length === 1 && t.isExpressionStatement(blockBody[0])) {
-            replacement = (blockBody[0] as t.ExpressionStatement).expression;
+            replacement = blockBody[0].expression;
           } else {
             replacement = template.expression.ast`(() => { ${blockBody} })()`;
           }

packages/babel-plugin-proposal-decorators/src/transformer-2022-03.ts

@@ -610,7 +610,7 @@ function transformClass(
       let name = "computedKey";
 
       if (isPrivate) {
-        name = (key as t.PrivateName).id.name;
+        name = key.id.name;
       } else if (!isComputed && key.type === "Identifier") {
         name = key.name;
       }
@@ -653,7 +653,7 @@ function transformClass(
               `set_${name}`,
             );
 
-            addCallAccessorsFor(newPath, key as t.PrivateName, getId, setId);
+            addCallAccessorsFor(newPath, key, getId, setId);
 
             locals = [newFieldInitId, getId, setId];
           } else {
@@ -678,12 +678,12 @@ function transformClass(
           locals = initId;
 
           if (isPrivate) {
-            privateMethods = extractProxyAccessorsFor(key as t.PrivateName);
+            privateMethods = extractProxyAccessorsFor(key);
           }
         } else if (isPrivate) {
           locals = element.scope.parent.generateDeclaredUidIdentifier(
             `call_${name}`,
-          ) as t.Identifier;
+          );
 
           const replaceSupers = new ReplaceSupers({
             constantSuper,
@@ -712,7 +712,7 @@ function transformClass(
           if (kind === GETTER || kind === SETTER) {
             movePrivateAccessor(
               element as NodePath<t.ClassPrivateMethod>,
-              t.cloneNode(key as t.PrivateName),
+              t.cloneNode(key),
               t.cloneNode(locals),
               isStatic,
             );
@@ -721,15 +721,10 @@ function transformClass(
 
             // Unshift
             path.node.body.body.unshift(
-              t.classPrivateProperty(
-                key as t.PrivateName,
-                t.cloneNode(locals),
-                [],
-                node.static,
-              ),
+              t.classPrivateProperty(key, t.cloneNode(locals), [], node.static),
             );
 
-            decoratedPrivateMethods.add((key as t.PrivateName).id.name);
+            decoratedPrivateMethods.add(key.id.name);
 
             element.remove();
           }

packages/babel-plugin-proposal-logical-assignment-operators/src/index.ts

@@ -28,6 +28,7 @@ export default declare(api => {
               "=",
               t.cloneNode(memo),
               // object must not be Super when `memo` is an identifier
+              // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
               object as t.Expression,
             );
           }

packages/babel-plugin-proposal-object-rest-spread/src/index.ts

@@ -412,8 +412,7 @@ export default declare((api, opts: Options) => {
             if (path.isObjectProperty()) {
               refPropertyPath.unshift(path);
             } else if (path.isVariableDeclarator()) {
-              kind = (path.parentPath as NodePath<t.VariableDeclaration>).node
-                .kind;
+              kind = path.parentPath.node.kind;
               return true;
             }
           });

packages/babel-plugin-proposal-optional-chaining/src/index.ts

@@ -11,8 +11,8 @@ export default declare((api, options: Options) => {
   api.assertVersion(7);
 
   const { loose = false } = options;
-  const noDocumentAll = (api.assumption("noDocumentAll") ?? loose) as boolean;
-  const pureGetters = (api.assumption("pureGetters") ?? loose) as boolean;
+  const noDocumentAll = api.assumption("noDocumentAll") ?? loose;
+  const pureGetters = api.assumption("pureGetters") ?? loose;
 
   return {
     name: "proposal-optional-chaining",

packages/babel-plugin-proposal-optional-chaining/src/transform.ts

@@ -141,6 +141,7 @@ export function transform(
           // Here `chainWithTypes` MUST NOT be cloned because it could be
           // updated when generating the memoised context of a call
           // expression. It must be an Expression when `ref` is an identifier
+          // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
           chainWithTypes as t.Expression,
         );
 
@@ -189,7 +190,8 @@ export function transform(
       // object must not be Super as super?.foo is invalid
       const object = skipTransparentExprWrapperNodes(
         replacement.object,
-      ) as t.Expression;
+        // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
+      ) as any as t.Expression;
       let baseRef;
       if (!pureGetters || !isSimpleMemberExpression(object)) {
         // memoize the context object when getters are not always pure