missing compile error for returning an error from an async function that does not return an error

[andrewrk]

const std = @import("std");

export fn entry() void {
    const p = async(std.debug.global_allocator) amain() catch unreachable;
}

async fn amain() void {
    return error.ShouldBeCompileError;
}

this builds, but it should be compile error: expected void, found error
it gets tricked because of the possible coro allocation frame failure.