Struct TraitDecl

pub struct TraitDecl {
    pub def_id: TraitDeclId,
    pub item_meta: ItemMeta,
    pub generics: GenericParams,
    pub parent_clauses: Vector<TraitClauseId, TraitClause>,
    pub consts: Vec<(TraitItemName, Ty)>,
    pub const_defaults: HashMap<TraitItemName, GlobalDeclRef>,
    pub types: Vec<TraitItemName>,
    pub type_defaults: HashMap<TraitItemName, Ty>,
    pub type_clauses: Vec<(TraitItemName, Vector<TraitClauseId, TraitClause>)>,
    pub required_methods: Vec<(TraitItemName, FunDeclId)>,
    pub provided_methods: Vec<(TraitItemName, FunDeclId)>,
}

A trait declaration.

For instance:

trait Foo {
  type Bar;

  fn baz(...); // required method (see below)

  fn test() -> bool { true } // provided method (see below)
}

In case of a trait declaration, we don’t include the provided methods (the methods with a default implementation): they will be translated on a per-need basis. This is important for two reasons:

• this makes the trait definitions a lot smaller (the Iterator trait has one declared function and more than 70 provided functions)
• this is important for the external traits, whose provided methods often use features we don’t support yet

Remark: In Aeneas, we still translate the provided methods on an individual basis, and in such a way thay they take as input a trait instance. This means that we can use default methods but:

• implementations of required methods shoudln’t call default methods
• trait implementations shouldn’t redefine required methods The use case we have in mind is std::iter::Iterator: it declares one required method (next) that should be implemented for every iterator, and defines many helpers like all, map, etc. that shouldn’t be re-implemented. Of course, this forbids other useful use cases such as visitors implemented by means of traits.

Fields

def_id: TraitDeclId

item_meta: ItemMeta

generics: GenericParams

parent_clauses: Vector<TraitClauseId, TraitClause>

The “parent” clauses: the supertraits.

Supertraits are actually regular where clauses, but we decided to have a custom treatment.

trait Foo : Bar {
            ^^^
        supertrait, that we treat as a parent predicate
}

TODO: actually, as of today, we consider that all trait clauses of trait declarations are parent clauses.

consts: Vec<(TraitItemName, Ty)>

The associated constants declared in the trait, along with their type.

const_defaults: HashMap<TraitItemName, GlobalDeclRef>

Records associated constants that have a default value.

types: Vec<TraitItemName>

The associated types declared in the trait.

type_defaults: HashMap<TraitItemName, Ty>

Records associated types that have a default value.

type_clauses: Vec<(TraitItemName, Vector<TraitClauseId, TraitClause>)>

List of trait clauses that apply to each associated type. This is used during translation, but the lift_associated_item_clauses pass moves them to be parent clauses later. Hence this is empty after that pass. TODO: Do this as we translate to avoid the need to store this vector.

required_methods: Vec<(TraitItemName, FunDeclId)>

The required methods.

The required methods are the methods declared by the trait but with no default implementation. The corresponding FunDecls don’t have a body.

provided_methods: Vec<(TraitItemName, FunDeclId)>

The provided methods.

The provided methods are the methods with a default implementation. The corresponding FunDecls may have a body, according to the usual rules for extracting function bodies.

Trait Implementations

impl Clone for TraitDecl

fn clone(&self) -> TraitDecl

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TraitDecl

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for TraitDecl

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Drive for TraitDecl

fn drive<V: Visitor>(&self, visitor: &mut V)

impl DriveMut for TraitDecl

fn drive_mut<V: VisitorMut>(&mut self, visitor: &mut V)

impl<C: AstFormatter> FmtWithCtx<C> for TraitDecl

fn fmt_with_ctx(&self, ctx: &C) -> String

fn fmt_with_ctx_and_indent(&self, _tab: &str, _ctx: &C) -> String

fn with_ctx<'a>(&'a self, ctx: &'a C) -> impl Display + 'a

Returns a struct that implements Display. This allows the following:

impl<'a> Formatter<&TraitDecl> for FmtCtx<'a>

fn format_object(&self, def: &TraitDecl) -> String

impl Serialize for TraitDecl

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.