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.

Environment

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