Rustc Code Index: Key Data Structures

# Code Index rustc has a lot of important data structures. This is an attempt to give some guidance on where to learn more about some of the key data structures of the compiler. Item | Kind | Short description | Chapter | Declaration ----------------|----------|-----------------------------|--------------------|------------------- `BodyId` | struct | One of four types of HIR node identifiers | [Identifiers in the HIR] | [compiler/rustc_hir/src/hir.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir/struct.BodyId.html) `Compiler` | struct | Represents a compiler session and can be used to drive a compilation. | [The Rustc Driver and Interface] | [compiler/rustc_interface/src/interface.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/struct.Compiler.html) `ast::Crate` | struct | A syntax-level representation of a parsed crate | [The parser] | [compiler/rustc_ast/src/ast.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/ast/struct.Crate.html) `rustc_hir::Crate` | struct | A more abstract, compiler-friendly form of a crate's AST | [The Hir] | [compiler/rustc_hir/src/hir.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir/struct.Crate.html) `DefId` | struct | One of four types of HIR node identifiers | [Identifiers in the HIR] | [compiler/rustc_hir/src/def_id.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/def_id/struct.DefId.html) `Diag` | struct | A struct for a compiler diagnostic, such as an error or lint | [Emitting Diagnostics] | [compiler/rustc_errors/src/diagnostic.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.Diag.html) `DocContext` | struct | A state container used by rustdoc when crawling through a crate to gather its documentation | [Rustdoc] | [src/librustdoc/core.rs](https://github.com/rust-lang/rust/blob/master/src/librustdoc/core.rs) `HirId` | struct | One of four types of HIR node identifiers | [Identifiers in the HIR] | [compiler/rustc_hir/src/hir_id.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir_id/struct.HirId.html) `Lexer` | struct | This is the lexer used during parsing. It consumes characters from the raw source code being compiled and produces a series of tokens for use by the rest of the parser | [The parser] | [compiler/rustc_parse/src/lexer/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_parse/lexer/struct.Lexer.html) `NodeId` | struct | One of four types of HIR node identifiers. Being phased out | [Identifiers in the HIR] | [compiler/rustc_ast/src/ast.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/node_id/struct.NodeId.html) `P` | struct | An owned immutable smart pointer. By contrast, `&T` is not owned, and `Box<T>` is not immutable. | None | [compiler/rustc_ast/src/ptr.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/ptr/struct.P.html) `ParamEnv` | struct | Information about generic parameters or `Self`, useful for working with associated or generic items | [Parameter Environment] | [compiler/rustc_middle/src/ty/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.ParamEnv.html)

This section provides an index of important data structures used in the rustc compiler, including a short description, the relevant chapter in the documentation, and a link to the source code declaration. Structures listed include `BodyId`, `Compiler`, `ast::Crate`, `rustc_hir::Crate`, `DefId`, `Diag`, `DocContext`, `HirId`, `Lexer`, `NodeId`, `P`, and `ParamEnv`.