Module rustc_ast::ast

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The Rust abstract syntax tree module.

This module contains common structures forming the language AST. Two main entities in the module are Item (which represents an AST element with additional metadata), and ItemKind (which represents a concrete type and contains information specific to the type of the item).

Other module items worth mentioning:


pub use crate::util::parser::ExprPrecedence;
pub use crate::node_id::NodeId;
pub use crate::node_id::CRATE_NODE_ID;
pub use crate::node_id::DUMMY_NODE_ID;
pub use GenericArgs::*;
pub use UnsafeSource::*;



A path like Foo<'a, T>.
A constant (expression) that’s not an item or associated item, but needs its own DefId for type-checking, const-eval, etc. These are usually found nested inside types (e.g., array lengths) or expressions (e.g., repeat counts), and also used to define explicit discriminant values for enum variants.
An arm of a ‘match’.
A constraint on an associated type (e.g., A = Bar in Foo<A = Bar> or A: TraitA + TraitB in Foo<A: TraitA + TraitB>).
Metadata associated with an item.
Explicit binding annotations given in the HIR for a binding. Note that this is not the final binding mode that we infer after type inference.
A block ({ .. }).
Delimited arguments, as used in #[attr()/[]/{}] or mac!()/[]/{}.
An expression.
A single field in a struct expression, e.g. x: value and y in Foo { x: value, y }.
Field definition in a struct, variant or union.
A signature (not the body) of a function declaration.
A function header.
Represents a function’s signature in a trait declaration, trait implementation, or free function.
Foreign module declaration.
Represents lifetime, type and const parameters attached to a declaration of a function, enum, trait, etc.
Inline assembly.
Inline assembly symbol operands get their own AST node that is somewhat similar to AnonConst.
An item definition.
A “Label” is an identifier of some point in sources, e.g. in the following code:
A “Lifetime” is an annotation of the scope in which variable can be used, e.g. 'a in &'a i32.
An AST literal.
Local represents a let statement, e.g., let <pat>:<ty> = <expr>;.
Represents a macro invocation. The path indicates which macro is being invoked, and the args are arguments passed to it.
Represents a macro definition.
A spanned compile-time attribute item.
A method call (e.g.<Bar, Baz>(a, b, c)).
A parameter in a function header.
A path like Foo(A, B) -> C.
A match pattern.
A single field in a struct pattern.
A “Path” is essentially Rust’s notion of a name.
A segment of a path: an identifier, an optional lifetime, and a set of types.
The explicit Self type in a “qualified path”. The actual path, including the trait and the associated item, is stored separately. position represents the index of the associated item qualified with this Self type.
A statement
Same as Lit, but restricted to string literals.
TraitRefs appear in impls.
The location of a where clause on a TyAlias (Span) and whether there was a where keyword (bool). This is split out from WhereClause, since there are two locations for where clause on type aliases, but their predicates are concatenated together.
A tree of paths sharing common prefixes. Used in use items both at top-level and inside of braces in import groups.
Enum variant.
A type bound.
A where-clause in a definition.
An equality predicate (unsupported).
A lifetime predicate.


Either an argument for a parameter e.g., 'a, Vec<u8>, 0, or a constraint on an associated item, e.g., Item = String or Item: Bound.
The kinds of an AssocConstraint.
Represents associated item kinds.
Arguments passed to an attribute macro.
Distinguishes between Attributes that decorate items and Attributes that are contained as statements within items. These two cases need to be distinguished for pretty-printing.
The kind of borrow in an AddrOf expression, e.g., &place or &raw const place.
A capture clause used in closures and async blocks.
Closure lifetime binder, for<'a, 'b> in for<'a, 'b> |_: &'a (), _: &'b ()|.
Item defaultness. For details see the RFC #2532.
extern qualifier on a function item or function type.
An item in extern block.
Concrete argument in the sequence of generic args.
The arguments of a path segment.
The AST represents all type param bounds as types. typeck::collect::compute_bounds matches these against the “special” built-in traits (see middle::lang_items) and detects Copy, Send and Sync.
Inline assembly operand.
Inline assembly operand explicit register or register class.
Is the trait definition an auto trait?
Type of the float literal based on provided suffix.
Type of the integer literal based on provided suffix.
Note that the entire literal (including the suffix) is considered when deciding the LitKind. This means that float literals like 1f32 are classified by this type as Float. This is different to token::LitKind which does not consider the suffix.
A compile-time attribute item.
Module item kind.
The movability of a generator / closure literal: whether a generator contains self-references, causing it to be !Unpin.
Possible values inside of compile-time attribute lists.
Specifies the enforced ordering for generic parameters. In the future, if we wanted to relax this order, we could override PartialEq and PartialOrd, to allow the kinds to be unordered.
All the different flavors of pattern that Rust recognizes.
Limit types of a range (inclusive or exclusive)
Alternative representation for Args describing self parameter of methods.
The kinds of an AssocConstraint.
A modifier on a bound, e.g., ?Trait or ~const Trait.
Syntax used to declare a trait object.
The various kinds of type recognized by the compiler.
Unary operator.
Part of use item to the right of its prefix.
Fields and constructor ids of enum variants and structs.
A single predicate in a where-clause.

Type Definitions

Represents associated items. These include items in impl and trait definitions.
A list of attributes.