add-syntax

Attribute macros that prepend or append arbitrary syntax. Useful with [cfg_attr].

This crate provides two attribute macros, [prepend] and [append], that add the tokens passed to them to the start or end of the item to which the attribute is applied, respectively. This is particularly useful with [cfg_attr].

Example

Conditionally applying unsafe when #[may_dangle] is used:

```rust

[cfgattr(feature = "dropckeyepatch", add_syntax::prepend(unsafe))]

impl<#[cfgattr(feature = "dropckeyepatch", may_dangle)] T> Drop for Foo { fn drop(&mut self) { /* ... */ } } ```

If the hypothetical feature dropck_eyepatch is enabled, the code above is equivalent to:

rust unsafe impl<#[may_dangle] T> Drop for Foo<T> { fn drop(&mut self) { /* ... */ } }

Otherwise, if the feature is not enabled, the code is equivalent to:

rust impl<T> Drop for Foo<T> { fn drop(&mut self) { /* ... */ } }