[−][src]Struct chalk_engine::FlounderedSubgoal
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
impl<I: Clone + Interner> Clone for FlounderedSubgoal<I>
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fn clone(&self) -> FlounderedSubgoal<I>
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fn clone_from(&mut self, source: &Self)
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impl<I: Debug + Interner> Debug for FlounderedSubgoal<I>
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impl<I: Eq + Interner> Eq for FlounderedSubgoal<I>
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impl<I: Interner, _TI> Fold<I, _TI> for FlounderedSubgoal<I> where
_TI: TargetInterner<I>,
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_TI: TargetInterner<I>,
type Result = FlounderedSubgoal<_TI>
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
fn fold_with<'i>(
&self,
folder: &mut dyn Folder<'i, I, _TI>,
outer_binder: DebruijnIndex
) -> Fallible<Self::Result> where
I: 'i,
_TI: 'i,
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&self,
folder: &mut dyn Folder<'i, I, _TI>,
outer_binder: DebruijnIndex
) -> Fallible<Self::Result> where
I: 'i,
_TI: 'i,
impl<I: Hash + Interner> Hash for FlounderedSubgoal<I>
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fn hash<__H: Hasher>(&self, state: &mut __H)
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fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
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H: Hasher,
impl<I: PartialEq + Interner> PartialEq<FlounderedSubgoal<I>> for FlounderedSubgoal<I>
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fn eq(&self, other: &FlounderedSubgoal<I>) -> bool
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fn ne(&self, other: &FlounderedSubgoal<I>) -> bool
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impl<I: Interner> StructuralEq for FlounderedSubgoal<I>
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impl<I: Interner> StructuralPartialEq for FlounderedSubgoal<I>
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impl<I: Interner> Visit<I> for FlounderedSubgoal<I>
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fn visit_with<'i, R: VisitResult>(
&self,
visitor: &mut dyn Visitor<'i, I, Result = R>,
outer_binder: DebruijnIndex
) -> R where
I: 'i,
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&self,
visitor: &mut dyn Visitor<'i, I, Result = R>,
outer_binder: DebruijnIndex
) -> R where
I: 'i,
Auto Trait Implementations
impl<I> RefUnwindSafe for FlounderedSubgoal<I> where
<I as Interner>::InternedGoal: RefUnwindSafe,
<I as Interner>::InternedProgramClauses: RefUnwindSafe,
<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,
<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,
<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,
<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,
<I as Interner>::InternedGoal: UnwindSafe,
<I as Interner>::InternedProgramClauses: UnwindSafe,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut T
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impl<T> Cast for T
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fn cast<U>(self, interner: &<U as HasInterner>::Interner) -> U where
Self: CastTo<U>,
U: HasInterner,
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Self: CastTo<U>,
U: HasInterner,
impl<Q, K> Equivalent<K> for Q where
K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,
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K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,
pub fn equivalent(&self, key: &K) -> bool
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impl<T> From<T> for T
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impl<T> Instrument for T
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fn instrument(self, span: Span) -> Instrumented<Self>
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fn in_current_span(self) -> Instrumented<Self>
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, I> Shift<I> for T where
I: Interner,
T: Fold<I, I>,
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I: Interner,
T: Fold<I, I>,
pub fn shifted_in(&self, interner: &I) -> <T as Fold<I, I>>::Result
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pub fn shifted_in_from(
&self,
interner: &I,
source_binder: DebruijnIndex
) -> <T as Fold<I, I>>::Result
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&self,
interner: &I,
source_binder: DebruijnIndex
) -> <T as Fold<I, I>>::Result
pub fn shifted_out_to(
&self,
interner: &I,
target_binder: DebruijnIndex
) -> Result<<T as Fold<I, I>>::Result, NoSolution>
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&self,
interner: &I,
target_binder: DebruijnIndex
) -> Result<<T as Fold<I, I>>::Result, NoSolution>
pub fn shifted_out(
&self,
interner: &I
) -> Result<<T as Fold<I, I>>::Result, NoSolution>
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&self,
interner: &I
) -> Result<<T as Fold<I, I>>::Result, NoSolution>
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
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pub fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T, I> VisitExt<I> for T where
I: Interner,
T: Visit<I>,
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I: Interner,
T: Visit<I>,