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TypeScript 3.7 syntax: `asserts this` #10671

thorn0 opened this issue Nov 6, 2019 · 1 comment · Fixed by #10677


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@thorn0 thorn0 commented Nov 6, 2019

Bug Report

Current Behavior
In #10527, it wasn't taken into account that the asserts keyword can be followed by this, not only by an identifier. Now it's a parser error, Unexpected token. Babel REPL.

Input Code

class Test {
    assertIsTest2(): asserts this is Test2 {
        if (this instanceof Test2) return;
        throw new Error();

Expected behavior/code
Should parse. TypeScript playground.


  • Babel version(s): 7.7.0
  • How you are using Babel: @babel/parser

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@babel-bot babel-bot commented Nov 6, 2019

Hey @thorn0! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

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