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`#[cfg]`s are frequently used to gate crate content behind cargo features. This can lead to very confusing errors when features are missing. For example, `serde` doesn't have the `derive` feature by default. Therefore, `serde::Serialize` fails to resolve with a generic error, even though the macro is present in the docs. This commit adds a list of all stripped item names to metadata. This is filled during macro expansion and then, through a fed query, persisted in metadata. The downstream resolver can then access the metadata to look at possible candidates for mentioning in the errors. This slightly increases metadata (800k->809k for the feature-heavy windows crate), but not enough to really matter. |
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| Cargo.toml | ||
| README.md | ||
The rustc_ast crate contains those things concerned purely with syntax
– that is, the AST ("abstract syntax tree"), along with some definitions for tokens and token streams, data structures/traits for mutating ASTs, and shared definitions for other AST-related parts of the compiler (like the lexer and macro-expansion).
For more information about how these things work in rustc, see the rustc dev guide: