It's unrelated to the lazy keyword. Instead it's another feature related to error messages.
The example:
>> 'hello'.toUpperCase()
Traceback (most recent call last):
...
AttributeError: 'str' object has no attribute 'toUpperCase'. Did you mean '.upper'?I’ve often thought it would be funny if instead of an error message for stuff like this, a language could be designed to be “typo-insensitive”. If a method or function call is similar enough to an existing one or a common one from other languages, to just have it silently use that.
In the Rust toolchain we've done the same. It just so happens that rustdoc already has introduced annotations for "aliases" so that when someone searches for push and it doesn't exist, append would show up. Having those annotations already meant that bootstrapping the feature to check the aliases during name resolution errors in rustc was almost trivial. I love it when improving one thing improves another indirectly too.
I really appreciate them going out of their way to do this, being quite aware of the hidden complexity in doing it.