Support nested cfg_attr attributes
#34216
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cc @cgswords |
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@bors: r+ |
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📌 Commit 65d256e has been approved by |
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Jun 16, 2016
Support nested `cfg_attr` attributes
Support arbitrarily deeply nested `cfg_attr` attributes (e.g. `#[cfg_attr(foo, cfg_attr(bar, baz))]`).
This makes configuration idempotent.
Currently, the nighties do not support any `cfg_attr` nesting. Stable and beta support just one level of `cfg_attr` nesting (expect for attributes on macro-expanded nodes, where no nesting is supported).
This is a [breaking-change]. For example, the following would break:
```rust
macro_rules! m { () => {
#[cfg_attr(all(), cfg_attr(all(), cfg(foo)))]
fn f() {}
} }
m!();
fn main() { f() } //~ ERROR unresolved name `f`
```
r? @nrc
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Support arbitrarily deeply nested
cfg_attrattributes (e.g.#[cfg_attr(foo, cfg_attr(bar, baz))]).This makes configuration idempotent.
Currently, the nighties do not support any
cfg_attrnesting. Stable and beta support just one level ofcfg_attrnesting (expect for attributes on macro-expanded nodes, where no nesting is supported).This is a [breaking-change]. For example, the following would break:
r? @nrc