Missing --unstable flag gives non-obvious errors

[cknight]

Errors for use of non stable APIs are non-obvious. For example:

$ deno run --allow-read --allow-write main.ts
Compile file:///dev/deno/main.ts
Download https://deno.land/std@0.50.0/fs/copy.ts
Download https://deno.land/std@0.50.0/fs/ensure_dir.ts
Download https://deno.land/std@0.50.0/fs/_util.ts
error: TS2339 [ERROR]: Property 'utime' does not exist on type 'typeof Deno'.
    await Deno.utime(dest, statInfo.atime, statInfo.mtime);
               ~~~~~
    at https://deno.land/std@0.50.0/fs/copy.ts:90:16

Is there a way that we could include the unstable types at runtime where they could be checked (but not used) when errors of type Property xyz does not exist... occur to provide a more helpful error message?

That would allow us to output something like:

$ deno run --allow-read --allow-write main.ts
Compile file:///dev/deno/main.ts
Download https://deno.land/std@0.50.0/fs/copy.ts
Download https://deno.land/std@0.50.0/fs/ensure_dir.ts
Download https://deno.land/std@0.50.0/fs/_util.ts
error: TS2339 [ERROR]: Property 'utime' does not exist on type 'typeof Deno'.  
'utime' is an unstable property of Deno.  Add the --unstable flag to enable use.
    await Deno.utime(dest, statInfo.atime, statInfo.mtime);
               ~~~~~
    at https://deno.land/std@0.50.0/fs/copy.ts:90:16

[lucacasonato]

Duplicate of #5175. Ref #5503

[cknight]

Thanks @lucacasonato , closing in favor of those.