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`alloc`: make `vec!` unavailable under `no_global_oom_handling` `alloc`: make `vec!` unavailable under `no_global_oom_handling` The `vec!` macro has 3 rules, but two are not usable under `no_global_oom_handling` builds of the standard library (even with a zero size): ```rust let _ = vec![42]; // Error: requires `exchange_malloc` lang_item. let _ = vec![42; 0]; // Error: cannot find function `from_elem`. ``` Thus those two rules should not be available to begin with. The remaining one, with an empty matcher, is just a shorthand for `new()` and may not make as much sense to have alone, since the idea behind `vec!` is to enable `Vec`s to be defined with the same syntax as array expressions. Furthermore, the documentation can be confusing since it shows the other rules. Thus perhaps it is better and simpler to disable `vec!` entirely under `no_global_oom_handling` environments, and let users call `new()` instead: ```rust let _: Vec<i32> = vec![]; let _: Vec<i32> = Vec::new(); ``` Notwithstanding this, a `try_vec!` macro would be useful, such as the one introduced in https://github.com/rust-lang/rust/pull/95051. If the shorthand for `new()` is deemed worth keeping on its own, then it may be interesting to have a separate `vec!` macro with a single rule and different, simpler documentation. Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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