No; warnings are for behavior that is likely to be incorrect, not (usually) for issues of stylistic preference, and in general you should not simply choose to ignore them. In any language, but especially in Rust, you should try to make your code compile with no warnings.
Adding new syntax, however trivial, makes the language and the compiler more complicated. Adding syntax that is not recommended and simultaneously adding a warning to discourage actually using that syntax would be counterproductive. (And as noted in other comments, this syntax is not as trivial as it may appear!)