[−][src]Enum rustc_typeck::check::Expectation
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)
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When type-checking an expression, we propagate downward
whatever type hint we are able in the form of an Expectation
.
Variants
NoExpectation
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We know nothing about what type this expression should have.
ExpectIfCondition
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This expression is an if
condition, it must resolve to bool
.
ExpectHasType(Ty<'tcx>)
🔬 This is a nightly-only experimental API. (rustc_private
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This expression should have the type given (or some subtype)
ExpectCastableToType(Ty<'tcx>)
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This expression will be cast to the Ty
ExpectRvalueLikeUnsized(Ty<'tcx>)
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)
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This rvalue expression will be wrapped in &
or Box
and coerced
to &Ty
or Box<Ty>
, respectively. Ty
is [A]
or Trait
.
Methods
impl<'a, 'gcx, 'tcx> Expectation<'tcx>
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impl<'a, 'gcx, 'tcx> Expectation<'tcx>
fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx>
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fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx>
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fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx>
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fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx>
🔬 This is a nightly-only experimental API. (rustc_private
)
this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml
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Provide an expectation for an rvalue expression given an optional
hint, which is not required for type safety (the resulting type might
be checked higher up, as is the case with &expr
and box expr
), but
is useful in determining the concrete type.
The primary use case is where the expected type is a fat pointer,
like &[isize]
. For example, consider the following statement:
let x: &[isize] = &[1, 2, 3];
In this case, the expected type for the &[1, 2, 3]
expression is
&[isize]
. If however we were to say that [1, 2, 3]
has the
expectation ExpectHasType([isize])
, that would be too strong --
[1, 2, 3]
does not have the type [isize]
but rather [isize; 3]
.
It is only the &[1, 2, 3]
expression as a whole that can be coerced
to the type &[isize]
. Therefore, we propagate this more limited hint,
which still is useful, because it informs integer literals and the like.
See the test case test/run-pass/coerce-expect-unsized.rs
and #20169
for examples of where this comes up,.
fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx>
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fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx>
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fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>>
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fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>>
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fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>>
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fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>>
🔬 This is a nightly-only experimental API. (rustc_private
)
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It sometimes happens that we want to turn an expectation into
a hard constraint (i.e., something that must be satisfied
for the program to type-check). only_has_type
will return
such a constraint, if it exists.
fn coercion_target_type(
self,
fcx: &FnCtxt<'a, 'gcx, 'tcx>,
span: Span
) -> Ty<'tcx>
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fn coercion_target_type(
self,
fcx: &FnCtxt<'a, 'gcx, 'tcx>,
span: Span
) -> Ty<'tcx>
🔬 This is a nightly-only experimental API. (rustc_private
)
this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml
instead?
Like only_has_type
, but instead of returning None
if no
hard constraint exists, creates a fresh type variable.
Trait Implementations
impl<'tcx> Copy for Expectation<'tcx>
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impl<'tcx> Copy for Expectation<'tcx>
impl<'tcx> Clone for Expectation<'tcx>
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impl<'tcx> Clone for Expectation<'tcx>
fn clone(&self) -> Expectation<'tcx>
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fn clone(&self) -> Expectation<'tcx>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0[src]
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
impl<'tcx> Debug for Expectation<'tcx>
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impl<'tcx> Debug for Expectation<'tcx>
Auto Trait Implementations
impl<'tcx> !Send for Expectation<'tcx>
impl<'tcx> !Send for Expectation<'tcx>
impl<'tcx> !Sync for Expectation<'tcx>
impl<'tcx> !Sync for Expectation<'tcx>
Blanket Implementations
impl<T> ToOwned for T where
T: Clone,
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impl<T> ToOwned for T where
T: Clone,
type Owned = T
fn to_owned(&self) -> T
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fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
fn clone_into(&self, target: &mut T)
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fn clone_into(&self, target: &mut T)
🔬 This is a nightly-only experimental API. (toowned_clone_into
)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
impl<T> From for T
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impl<T> From for T
impl<T, U> Into for T where
U: From<T>,
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impl<T, U> Into for T where
U: From<T>,
impl<T, U> TryFrom for T where
T: From<U>,
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impl<T, U> TryFrom for T where
T: From<U>,
type Error = !
try_from
)The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
try_from
)Performs the conversion.
impl<T> Borrow for T where
T: ?Sized,
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impl<T> Borrow for T where
T: ?Sized,
ⓘImportant traits for &'a mut Rfn borrow(&self) -> &T
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fn borrow(&self) -> &T
Immutably borrows from an owned value. Read more
impl<T, U> TryInto for T where
U: TryFrom<T>,
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impl<T, U> TryInto for T where
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
try_from
)The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
try_from
)Performs the conversion.
impl<T> BorrowMut for T where
T: ?Sized,
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impl<T> BorrowMut for T where
T: ?Sized,
ⓘImportant traits for &'a mut Rfn borrow_mut(&mut self) -> &mut T
[src]
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
impl<T> Any for T where
T: 'static + ?Sized,
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impl<T> Any for T where
T: 'static + ?Sized,
fn get_type_id(&self) -> TypeId
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fn get_type_id(&self) -> TypeId
🔬 This is a nightly-only experimental API. (get_type_id
)
this method will likely be replaced by an associated static
Gets the TypeId
of self
. Read more
impl<E> SpecializationError for E
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impl<E> SpecializationError for E
fn not_found<S, T>(trait_name: &'static str, method_name: &'static str) -> E where
T: ?Sized,
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fn not_found<S, T>(trait_name: &'static str, method_name: &'static str) -> E where
T: ?Sized,
🔬 This is a nightly-only experimental API. (rustc_private
)
this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml
instead?
Create an error for a missing method specialization. Defaults to panicking with type, trait & method names. S
is the encoder/decoder state type, T
is the type being encoded/decoded, and the arguments are the names of the trait and method that should've been overridden. Read more
impl<T> Erased for T
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impl<T> Erased for T
impl<T> Send for T where
T: ?Sized,
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impl<T> Send for T where
T: ?Sized,
impl<T> Sync for T where
T: ?Sized,
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impl<T> Sync for T where
T: ?Sized,
impl<T> Erased for T
impl<T> Erased for T
impl<T> MaybeResult for T
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impl<T> MaybeResult for T
fn from_ok(x: T) -> T
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fn from_ok(x: T) -> T
🔬 This is a nightly-only experimental API. (rustc_private
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fn map_same<F>(self, f: F) -> T where
F: FnOnce(T) -> T,
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fn map_same<F>(self, f: F) -> T where
F: FnOnce(T) -> T,
🔬 This is a nightly-only experimental API. (rustc_private
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impl<'a, T> Captures for T where
T: ?Sized,
[src]
impl<'a, T> Captures for T where
T: ?Sized,