Back parser state exportedIdentifiers by set (#13406)

packages/babel-parser/src/parser/base.js

@@ -18,6 +18,9 @@ export default class BaseParser {
   declare expressionScope: ExpressionScopeHandler;
   declare plugins: PluginsMap;
   declare filename: ?string;
+  // Names of exports store. `default` is stored as a name for both
+  // `export default foo;` and `export { foo as default };`.
+  declare exportedIdentifiers: Set<string>;
   sawUnambiguousESM: boolean = false;
   ambiguousScriptDifferentAst: boolean = false;
 

packages/babel-parser/src/parser/statement.js

@@ -2114,7 +2114,7 @@ export default class StatementParser extends ExpressionParser {
       | N.ExportDefaultSpecifier,
     name: string,
   ): void {
-    if (this.state.exportedIdentifiers.indexOf(name) > -1) {
+    if (this.exportedIdentifiers.has(name)) {
       this.raise(
         node.start,
         name === "default"
@@ -2123,7 +2123,7 @@ export default class StatementParser extends ExpressionParser {
         name,
       );
     }
-    this.state.exportedIdentifiers.push(name);
+    this.exportedIdentifiers.add(name);
   }
 
   // Parses a comma-separated list of module exports.

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

@@ -349,8 +349,8 @@ export default class UtilParser extends Tokenizer {
     const oldLabels = this.state.labels;
     this.state.labels = [];
 
-    const oldExportedIdentifiers = this.state.exportedIdentifiers;
-    this.state.exportedIdentifiers = [];
+    const oldExportedIdentifiers = this.exportedIdentifiers;
+    this.exportedIdentifiers = new Set();
 
     // initialize scopes
     const oldInModule = this.inModule;
@@ -372,7 +372,7 @@ export default class UtilParser extends Tokenizer {
     return () => {
       // Revert state
       this.state.labels = oldLabels;
-      this.state.exportedIdentifiers = oldExportedIdentifiers;
+      this.exportedIdentifiers = oldExportedIdentifiers;
 
       // Revert scopes
       this.inModule = oldInModule;

packages/babel-parser/src/tokenizer/state.js

@@ -148,10 +148,6 @@ export default class State {
   // after a non-directive is parsed
   strictErrors: Map<number, ErrorTemplate> = new Map();
 
-  // Names of exports store. `default` is stored as a name for both
-  // `export default foo;` and `export { foo as default };`.
-  exportedIdentifiers: Array<string> = [];
-
   // Tokens length in token store
   tokensLength: number = 0;