Enum rustc_middle::ty::VarianceDiagInfo

pub enum VarianceDiagInfo<'tcx> {
    None,
    Invariant {
        ty: Ty<'tcx>,
        param_index: u32,
    },
}

Extra information about why we ended up with a particular variance. This is only used to add more information to error messages, and has no effect on soundness. While choosing the ‘wrong’ VarianceDiagInfo may lead to confusing notes in error messages, it will never cause a miscompilation or unsoundness.

When in doubt, use VarianceDiagInfo::default()

Variants

None

No additional information - this is the default. We will not add any additional information to error messages.

Invariant

We switched our variance because a generic argument occurs inside the invariant generic argument of another type.

Fields

ty: Ty<'tcx>

The generic type containing the generic parameter that changes the variance (e.g. *mut T, MyStruct<T>)

param_index: u32

The index of the generic parameter being used (e.g. 0 for *mut T, 1 for MyStruct<'CovariantParam, 'InvariantParam>)

Implementations

impl<'tcx> VarianceDiagInfo<'tcx>

pub fn xform(self, other: VarianceDiagInfo<'tcx>) -> VarianceDiagInfo<'tcx>

Mirrors Variance::xform - used to ‘combine’ the existing and new VarianceDiagInfos when our variance changes.

Trait Implementations

impl<'tcx> Clone for VarianceDiagInfo<'tcx>

fn clone(&self) -> VarianceDiagInfo<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for VarianceDiagInfo<'tcx>

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

Formats the value using the given formatter.

impl<'tcx> Default for VarianceDiagInfo<'tcx>

fn default() -> VarianceDiagInfo<'tcx>

Returns the “default value” for a type.

impl<'tcx> PartialEq for VarianceDiagInfo<'tcx>

fn eq(&self, other: &VarianceDiagInfo<'tcx>) -> 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<'tcx> Copy for VarianceDiagInfo<'tcx>

impl<'tcx> Eq for VarianceDiagInfo<'tcx>

impl<'tcx> StructuralPartialEq for VarianceDiagInfo<'tcx>

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: 16 bytes

Size for each variant:

• None: 0 bytes
• Invariant: 12 bytes