Struct Transparent 

pub struct Transparent<T> { /* private fields */ }

A type that transparently implements PartialEq and Hash, to be used in structs that carry additional data that should not be relevant in comparisons.

It additionally supports creating dummy values and they will also compare equal to all other and hash identically.

The use of a Transparent<_> as a field of a struct should be understood to convey the following intent: this field is useful only for diagnostics and is never relevant for decisions. This makes Transparent::forge suitable for use in unit tests where said diagnostic data may not be available and we still want the computation to be unaffected.

In fact the computation is guaranteed to be unaffected because Transparent provides no peeking method, and the only way to extract data is unwrap that will panic if the inner value was forged.

Implementations

impl<T> Transparent<T>

pub fn unwrap(self) -> T

Assert that the value was not forged and get its contents.

Panics

fails if self was obtainedy by Transparent::forge().

pub fn forge(loc: &'static str) -> Self

Create a dummy value.

It is recommended to use the loc parameter as a way to track the location where it was forged so that if it is accidentally unwrapped the error message is more readable, e.g. by using either an identifying string or even better the output of the here!() macro that gives the location in the source code.

impl<T> Transparent<Option<T>>

pub fn try_override_inner(&mut self, t: T)

If there is not already data, add it. This is a noop if the contents were not forged.

impl<T> Transparent<Transparent<T>>

pub fn flatten(self) -> Transparent<T>

Remove the outer Transparent

impl<T> Transparent<Option<T>>

pub fn flatten(self) -> Option<Transparent<T>>

Remove the outer Transparent

impl<T> Transparent<T>

pub fn from(inner: T) -> Self

Wrap in a transparent.

impl Transparent<Span>

pub fn join(self, other: Self) -> Option<Self>

Map join to the inner spans

Trait Implementations

impl<T: Clone> Clone for Transparent<T>

fn clone(&self) -> Transparent<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> Debug for Transparent<T>

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

Formats the value using the given formatter.

impl<T: Display> Display for Transparent<T>

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

Almost transparent wrapper for display.

impl<T> Hash for Transparent<T>

fn hash<H: Hasher>(&self, _: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> PartialEq for Transparent<T>

fn eq(&self, _: &Self) -> bool

Trivial equality. All Transparent are indistinguishable from each other.

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

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

impl<T: TrySpan> TrySpan for Transparent<T>

fn try_span(&self) -> Option<Span>

Sp always has a span, so TrySpan is guaranteed to succeed.

impl<T: Copy> Copy for Transparent<T>

impl<T> Eq for Transparent<T>