Struct chalk_engine::FlounderedSubgoal
source · [−]pub struct FlounderedSubgoal<I: Interner> {
pub floundered_literal: Literal<I>,
pub floundered_time: TimeStamp,
}
Expand description
A “floundered” subgoal is one that contains unbound existential variables for which it cannot produce a value. The classic example of floundering is a negative subgoal:
not { Implemented(?T: Foo) }
The way the prolog solver works, it basically enumerates all the
ways that a given goal can be true. But we can’t use this
technique to find all the ways that ?T: Foo
can be false – so
we call it floundered. In other words, we can evaluate a negative
goal, but only if we know what ?T
is – we can’t use the
negative goal to help us figuring out ?T
.
In addition to negative goals, we use floundering to prevent the
trait solver from trying to enumerate very large goals with tons
of answers. For example, we consider a goal like ?T: Sized
to
“flounder”, since we can’t hope to enumerate all types that are
Sized
. The same is true for other special traits like Clone
.
Floundering can also occur indirectly. For example:
trait Foo { }
impl<T> Foo for T { }
trying to solve ?T: Foo
would immediately require solving ?T: Sized
, and hence would flounder.
Fields
floundered_literal: Literal<I>
Literal that floundered.
floundered_time: TimeStamp
Current value of the strand’s clock at the time of floundering.
Trait Implementations
sourceimpl<I: Clone + Interner> Clone for FlounderedSubgoal<I>
impl<I: Clone + Interner> Clone for FlounderedSubgoal<I>
sourcefn clone(&self) -> FlounderedSubgoal<I>
fn clone(&self) -> FlounderedSubgoal<I>
Returns a copy of the value. Read more
1.0.0 · sourcefn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
sourceimpl<I: Debug + Interner> Debug for FlounderedSubgoal<I>
impl<I: Debug + Interner> Debug for FlounderedSubgoal<I>
sourceimpl<I: Interner> Fold<I> for FlounderedSubgoal<I>
impl<I: Interner> Fold<I> for FlounderedSubgoal<I>
type Result = FlounderedSubgoal<I>
type Result = FlounderedSubgoal<I>
The type of value that will be produced once folding is done.
Typically this is Self
, unless Self
contains borrowed
values, in which case owned values are produced (for example,
one can fold over a &T
value where T: Fold
, in which case
you get back a T
, not a &T
). Read more
sourcefn fold_with<E>(
self,
folder: &mut dyn Folder<I, Error = E>,
outer_binder: DebruijnIndex
) -> Result<Self::Result, E>
fn fold_with<E>(
self,
folder: &mut dyn Folder<I, Error = E>,
outer_binder: DebruijnIndex
) -> Result<Self::Result, E>
Apply the given folder folder
to self
; binders
is the
number of binders that are in scope when beginning the
folder. Typically binders
starts as 0, but is adjusted when
we encounter Binders<T>
in the IR or other similar
constructs. Read more
sourceimpl<I: Hash + Interner> Hash for FlounderedSubgoal<I>
impl<I: Hash + Interner> Hash for FlounderedSubgoal<I>
sourceimpl<I: PartialEq + Interner> PartialEq<FlounderedSubgoal<I>> for FlounderedSubgoal<I>
impl<I: PartialEq + Interner> PartialEq<FlounderedSubgoal<I>> for FlounderedSubgoal<I>
sourcefn eq(&self, other: &FlounderedSubgoal<I>) -> bool
fn eq(&self, other: &FlounderedSubgoal<I>) -> bool
This method tests for self
and other
values to be equal, and is used
by ==
. Read more
sourcefn ne(&self, other: &FlounderedSubgoal<I>) -> bool
fn ne(&self, other: &FlounderedSubgoal<I>) -> bool
This method tests for !=
.
sourceimpl<I: Interner> Visit<I> for FlounderedSubgoal<I>
impl<I: Interner> Visit<I> for FlounderedSubgoal<I>
sourcefn visit_with<B>(
&self,
visitor: &mut dyn Visitor<I, BreakTy = B>,
outer_binder: DebruijnIndex
) -> ControlFlow<B>
fn visit_with<B>(
&self,
visitor: &mut dyn Visitor<I, BreakTy = B>,
outer_binder: DebruijnIndex
) -> ControlFlow<B>
Apply the given visitor visitor
to self
; binders
is the
number of binders that are in scope when beginning the
visitor. Typically binders
starts as 0, but is adjusted when
we encounter Binders<T>
in the IR or other similar
constructs. Read more
impl<I: Eq + Interner> Eq for FlounderedSubgoal<I>
impl<I: Interner> StructuralEq for FlounderedSubgoal<I>
impl<I: Interner> StructuralPartialEq for FlounderedSubgoal<I>
Auto Trait Implementations
impl<I> RefUnwindSafe for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: RefUnwindSafe,
<I as Interner>::InternedProgramClauses: RefUnwindSafe,
impl<I> Send for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: Send,
<I as Interner>::InternedProgramClauses: Send,
impl<I> Sync for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: Sync,
<I as Interner>::InternedProgramClauses: Sync,
impl<I> Unpin for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: Unpin,
<I as Interner>::InternedProgramClauses: Unpin,
impl<I> UnwindSafe for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: UnwindSafe,
<I as Interner>::InternedProgramClauses: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcepub fn borrow_mut(&mut self) -> &mut T
pub fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> Cast for T
impl<T> Cast for T
sourcefn cast<U>(self, interner: <U as HasInterner>::Interner) -> U where
Self: CastTo<U>,
U: HasInterner,
fn cast<U>(self, interner: <U as HasInterner>::Interner) -> U where
Self: CastTo<U>,
U: HasInterner,
Cast a value to type U
using CastTo
.
sourceimpl<Q, K> Equivalent<K> for Q where
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
impl<Q, K> Equivalent<K> for Q where
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
sourcepub fn equivalent(&self, key: &K) -> bool
pub fn equivalent(&self, key: &K) -> bool
Compare self to key
and return true
if they are equal.
sourceimpl<T> Instrument for T
impl<T> Instrument for T
sourcefn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
sourcefn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
sourceimpl<T, I> Shift<I> for T where
T: Fold<I>,
I: Interner,
impl<T, I> Shift<I> for T where
T: Fold<I>,
I: Interner,
sourcepub fn shifted_in(self, interner: I) -> <T as Fold<I>>::Result
pub fn shifted_in(self, interner: I) -> <T as Fold<I>>::Result
Shifts this term in one level of binders.
sourcepub fn shifted_in_from(
self,
interner: I,
source_binder: DebruijnIndex
) -> <T as Fold<I>>::Result
pub fn shifted_in_from(
self,
interner: I,
source_binder: DebruijnIndex
) -> <T as Fold<I>>::Result
Shifts a term valid at outer_binder
so that it is
valid at the innermost binder. See DebruijnIndex::shifted_in_from
for a detailed explanation. Read more
sourcepub fn shifted_out_to(
self,
interner: I,
target_binder: DebruijnIndex
) -> Result<<T as Fold<I>>::Result, NoSolution>
pub fn shifted_out_to(
self,
interner: I,
target_binder: DebruijnIndex
) -> Result<<T as Fold<I>>::Result, NoSolution>
Shifts a term valid at the innermost binder so that it is
valid at outer_binder
. See DebruijnIndex::shifted_out_to
for a detailed explanation. Read more
sourcepub fn shifted_out(
self,
interner: I
) -> Result<<T as Fold<I>>::Result, NoSolution>
pub fn shifted_out(
self,
interner: I
) -> Result<<T as Fold<I>>::Result, NoSolution>
Shifts this term out one level of binders.
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcepub fn to_owned(&self) -> T
pub fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
sourcepub fn clone_into(&self, target: &mut T)
pub fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more
sourceimpl<T, I> VisitExt<I> for T where
I: Interner,
T: Visit<I>,
impl<T, I> VisitExt<I> for T where
I: Interner,
T: Visit<I>,
sourcefn has_free_vars(&self, interner: I) -> bool
fn has_free_vars(&self, interner: I) -> bool
Check whether there are free (non-bound) variables.
sourceimpl<T> WithSubscriber for T
impl<T> WithSubscriber for T
sourcefn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self> where
S: Into<Dispatch>,
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self> where
S: Into<Dispatch>,
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
sourcefn with_current_subscriber(self) -> WithDispatch<Self>
fn with_current_subscriber(self) -> WithDispatch<Self>
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more