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

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

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>)

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

Implementations

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

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns the “default value” for a type. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

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

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

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