Syntax fails when function declaration return type is on a separate line

[mgthomas99]

TS and JS Grammar Extension version: 0.0.46 / latest

Code

function main(url: string)
: Promise<any> {
    return new Promise((accept, reject) => {
        const text = window.prompt();
        accept(text);
    });
}

In the code snippet above, notice the incorrect syntax highlighting of the function body's first expression (return new Promise(...)). The effect of the incorrect syntax is most visible in Visual Studio Code (notice lines 4 and 11):

Here is the expected syntax highlighting:

Interestingly, the issue on line 4 can be fixed by wrapping the return type in parentheses, but this does not fix the issue on line 11:

Furthermore, it appears as though the syntax highlighting of an arrow function's name and return type is dependent on the arrangement of its parameters:

This bug cannot be attributed to VS Code as it also appears in VS Code Insiders, and continues to appear even after I have disabled all extensions.