Enum rustc_ast_lowering::ImplTraitContext

pub(crate) enum ImplTraitContext {
    Universal,
    ReturnPositionOpaqueTy {
        origin: OpaqueTyOrigin,
        in_trait: bool,
    },
    TypeAliasesOpaqueTy,
    FeatureGated(ImplTraitPosition, Symbol),
    Disallowed(ImplTraitPosition),
}

Context of impl Trait in code, which determines whether it is allowed in an HIR subtree, and if so, what meaning it has.

Variants

Universal

Treat impl Trait as shorthand for a new universal generic parameter. Example: fn foo(x: impl Debug), where impl Debug is conceptually equivalent to a fresh universal parameter like fn foo<T: Debug>(x: T).

Newly generated parameters should be inserted into the given Vec.

ReturnPositionOpaqueTy

Fields

origin: OpaqueTyOrigin

Origin: Either OpaqueTyOrigin::FnReturn or OpaqueTyOrigin::AsyncFn,

in_trait: bool

Treat impl Trait as shorthand for a new opaque type. Example: fn foo() -> impl Debug, where impl Debug is conceptually equivalent to a new opaque type like type T = impl Debug; fn foo() -> T.

TypeAliasesOpaqueTy

Impl trait in type aliases.

FeatureGated(ImplTraitPosition, Symbol)

impl Trait is unstably accepted in this position.

Disallowed(ImplTraitPosition)

impl Trait is not accepted in this position.

Trait Implementations

impl Clone for ImplTraitContext

fn clone(&self) -> ImplTraitContext

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ImplTraitContext

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

Formats the value using the given formatter.

impl PartialEq<ImplTraitContext> for ImplTraitContext

fn eq(&self, other: &ImplTraitContext) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for ImplTraitContext

impl Eq for ImplTraitContext

impl StructuralEq for ImplTraitContext

impl StructuralPartialEq for ImplTraitContext

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

Size: 12 bytes

Size for each variant:

• Universal: 0 bytes
• ReturnPositionOpaqueTy: 12 bytes
• TypeAliasesOpaqueTy: 0 bytes
• FeatureGated: 12 bytes
• Disallowed: 5 bytes