Compiler crash when using function expression as RHS in assignment

[bbrk24]

Consider this code, nearly identical to the default code added when scaffolding a new project:

function add(a: i32, b: i32): i32 {
    return a + b;
}

export {
    add
};

It works just fine. However, in JavaScript it's often more idiomatic to assign a function to a const rather than using it directly. So I do:

const add = function add(a: i32, b: i32): i32 {
    return a + b;
};

export {
    add
};

And suddenly the compiler crashes, with the following backtrace:

▌ C:\[...]\node_modules\assemblyscript\std\portable\index.js:200
▌     throw new AssertionError(message);
▌           ^
▌ 
▌ AssertionError: assertion failed
▌     at null.q.assert (C:\[...]\node_modules\assemblyscript\std\portable\index.js:200:11)
▌     at Nr.toTypeScriptType (C:\[...]\node_modules\assemblyscript\src\bindings\tsd.ts:239:21)
▌     at Nr.visitGlobal (C:\[...]\node_modules\assemblyscript\src\bindings\tsd.ts:55:23)
▌     at Nr.visitElement (C:\[...]\node_modules\assemblyscript\src\bindings\util.ts:82:52)
▌     at Nr.visitFile (C:\[...]\node_modules\assemblyscript\src\bindings\util.ts:59:14)
▌     at Nr.walk (C:\[...]\node_modules\assemblyscript\src\bindings\util.ts:47:65)
▌     at Nr.build (C:\[...]\node_modules\assemblyscript\src\bindings\tsd.ts:189:10)
▌     at Function.build (C:\[...]\node_modules\assemblyscript\src\bindings\tsd.ts:37:41)
▌     at Module.JS (C:\[...]\node_modules\assemblyscript\src\index-wasm.ts:330:21)
▌     at Module.Ue (C:\[...]\node_modules\assemblyscript\cli\index.js:954:35)

Using an arrow function, as follows, crashes in the same way.

const add = (a: i32, b: i32): i32 => {
    return a + b;
};

export {
    add
};