Make asserts property boolean, not undefined (#12167)

2020-10-14 06:56:08 +09:00
parent d49e5507ae
commit a5bed04f55
3 changed files with 11 additions and 8 deletions
--- a/packages/babel-parser/src/plugins/typescript/index.js
+++ b/packages/babel-parser/src/plugins/typescript/index.js
@@ -1039,7 +1039,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
        const t: N.TsTypeAnnotation = this.startNode();
        this.expect(returnToken);

-        const asserts = this.tsTryParse(
+        const asserts = !!this.tsTryParse(
          this.tsParseTypePredicateAsserts.bind(this),
        );