Struct rustc_middle::ty::ClosureArgs
source · pub struct ClosureArgs<I>where
I: Interner,{
pub args: <I as Interner>::GenericArgs,
}
Expand description
A closure can be modeled as a struct that looks like:
struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
where:
- ’l0…’li and T0…Tj are the generic parameters in scope on the function that defined the closure,
- CK represents the closure kind (Fn vs FnMut vs FnOnce). This
is rather hackily encoded via a scalar type. See
Ty::to_opt_closure_kind
for details. - CS represents the closure signature, representing as a
fn()
type. For example,fn(u32, u32) -> u32
would mean that the closure implementsCK<(u32, u32), Output = u32>
, whereCK
is the trait specified above. - U is a type parameter representing the types of its upvars, tupled up
(borrowed, if appropriate; that is, if a U field represents a by-ref upvar,
and the up-var has the type
Foo
, then that field of U will be&Foo
).
So, for example, given this function:
fn foo<'a, T>(data: &'a mut T) {
do(|| data.count += 1)
}
the type of the closure would be something like:
struct Closure<'a, T, U>(...U);
Note that the type of the upvar is not specified in the struct. You may wonder how the impl would then be able to use the upvar, if it doesn’t know it’s type? The answer is that the impl is (conceptually) not fully generic over Closure but rather tied to instances with the expected upvar types:
impl<'b, 'a, T> FnMut() for Closure<'a, T, (&'b mut &'a mut T,)> {
...
}
You can see that the impl fully specified the type of the upvar
and thus knows full well that data
has type &'b mut &'a mut T
.
(Here, I am assuming that data
is mut-borrowed.)
Now, the last question you may ask is: Why include the upvar types
in an extra type parameter? The reason for this design is that the
upvar types can reference lifetimes that are internal to the
creating function. In my example above, for example, the lifetime
'b
represents the scope of the closure itself; this is some
subset of foo
, probably just the scope of the call to the to
do()
. If we just had the lifetime/type parameters from the
enclosing function, we couldn’t name this lifetime 'b
. Note that
there can also be lifetimes in the types of the upvars themselves,
if one of them happens to be a reference to something that the
creating fn owns.
OK, you say, so why not create a more minimal set of parameters that just includes the extra lifetime parameters? The answer is primarily that it would be hard — we don’t know at the time when we create the closure type what the full types of the upvars are, nor do we know which are borrowed and which are not. In this design, we can just supply a fresh type parameter and figure that out later.
All right, you say, but why include the type parameters from the
original function then? The answer is that codegen may need them
when monomorphizing, and they may not appear in the upvars. A
closure could capture no variables but still make use of some
in-scope type parameter with a bound (e.g., if our example above
had an extra U: Default
, and the closure called U::default()
).
There is another reason. This design (implicitly) prohibits closures from capturing themselves (except via a trait object). This simplifies closure inference considerably, since it means that when we infer the kind of a closure or its upvars, we don’t have to handle cycles where the decisions we make for closure C wind up influencing the decisions we ought to make for closure C (which would then require fixed point iteration to handle). Plus it fixes an ICE. :P
§Coroutines
Coroutines are handled similarly in CoroutineArgs
. The set of
type parameters is similar, but CK
and CS
are replaced by the
following type parameters:
GS
: The coroutine’s “resume type”, which is the type of the argument passed toresume
, and the type ofyield
expressions inside the coroutine.GY
: The “yield type”, which is the type of values passed toyield
inside the coroutine.GR
: The “return type”, which is the type of value returned upon completion of the coroutine.GW
: The “coroutine witness”.
Fields§
§args: <I as Interner>::GenericArgs
Lifetime and type parameters from the enclosing function, concatenated with a tuple containing the types of the upvars.
These are separated out because codegen wants to pass them around when monomorphizing.
Implementations§
source§impl<I> ClosureArgs<I>where
I: Interner,
impl<I> ClosureArgs<I>where
I: Interner,
sourcepub fn new(cx: I, parts: ClosureArgsParts<I>) -> ClosureArgs<I>
pub fn new(cx: I, parts: ClosureArgsParts<I>) -> ClosureArgs<I>
Construct ClosureArgs
from ClosureArgsParts
, containing Args
for the closure parent, alongside additional closure-specific components.
sourcepub fn parent_args(self) -> <I as Interner>::GenericArgsSlice
pub fn parent_args(self) -> <I as Interner>::GenericArgsSlice
Returns the generic parameters of the closure’s parent.
sourcepub fn upvar_tys(self) -> <I as Interner>::Tys
pub fn upvar_tys(self) -> <I as Interner>::Tys
Returns an iterator over the list of types of captured paths by the closure. In case there was a type error in figuring out the types of the captured path, an empty iterator is returned.
sourcepub fn tupled_upvars_ty(self) -> <I as Interner>::Ty
pub fn tupled_upvars_ty(self) -> <I as Interner>::Ty
Returns the tuple type representing the upvars for this closure.
sourcepub fn kind_ty(self) -> <I as Interner>::Ty
pub fn kind_ty(self) -> <I as Interner>::Ty
Returns the closure kind for this closure; may return a type
variable during inference. To get the closure kind during
inference, use infcx.closure_kind(args)
.
sourcepub fn sig_as_fn_ptr_ty(self) -> <I as Interner>::Ty
pub fn sig_as_fn_ptr_ty(self) -> <I as Interner>::Ty
Returns the fn
pointer type representing the closure signature for this
closure.
sourcepub fn kind(self) -> ClosureKind
pub fn kind(self) -> ClosureKind
Returns the closure kind for this closure; only usable outside of an inference context, because in that context we know that there are no type variables.
If you have an inference context, use infcx.closure_kind()
.
Trait Implementations§
source§impl<I> Clone for ClosureArgs<I>where
I: Interner,
impl<I> Clone for ClosureArgs<I>where
I: Interner,
source§fn clone(&self) -> ClosureArgs<I>
fn clone(&self) -> ClosureArgs<I>
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl<I> Debug for ClosureArgs<I>where
I: Interner,
impl<I> Debug for ClosureArgs<I>where
I: Interner,
source§impl<I> Hash for ClosureArgs<I>where
I: Interner,
impl<I> Hash for ClosureArgs<I>where
I: Interner,
source§impl<I, J> Lift<J> for ClosureArgs<I>where
I: Interner,
J: Interner,
<I as Interner>::GenericArgs: Lift<J, Lifted = <J as Interner>::GenericArgs>,
impl<I, J> Lift<J> for ClosureArgs<I>where
I: Interner,
J: Interner,
<I as Interner>::GenericArgs: Lift<J, Lifted = <J as Interner>::GenericArgs>,
type Lifted = ClosureArgs<J>
fn lift_to_interner(self, interner: J) -> Option<ClosureArgs<J>>
source§impl<I> PartialEq for ClosureArgs<I>where
I: Interner,
impl<I> PartialEq for ClosureArgs<I>where
I: Interner,
source§fn eq(&self, other: &ClosureArgs<I>) -> bool
fn eq(&self, other: &ClosureArgs<I>) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl<I> TypeFoldable<I> for ClosureArgs<I>
impl<I> TypeFoldable<I> for ClosureArgs<I>
source§fn try_fold_with<__F>(
self,
__folder: &mut __F,
) -> Result<ClosureArgs<I>, <__F as FallibleTypeFolder<I>>::Error>where
__F: FallibleTypeFolder<I>,
fn try_fold_with<__F>(
self,
__folder: &mut __F,
) -> Result<ClosureArgs<I>, <__F as FallibleTypeFolder<I>>::Error>where
__F: FallibleTypeFolder<I>,
source§fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
try_fold_with
for use with infallible
folders. Do not override this method, to ensure coherence with
try_fold_with
.source§impl<I> TypeVisitable<I> for ClosureArgs<I>
impl<I> TypeVisitable<I> for ClosureArgs<I>
source§fn visit_with<__V>(
&self,
__visitor: &mut __V,
) -> <__V as TypeVisitor<I>>::Resultwhere
__V: TypeVisitor<I>,
fn visit_with<__V>(
&self,
__visitor: &mut __V,
) -> <__V as TypeVisitor<I>>::Resultwhere
__V: TypeVisitor<I>,
impl<I> Copy for ClosureArgs<I>where
I: Interner,
impl<I> Eq for ClosureArgs<I>where
I: Interner,
Auto Trait Implementations§
impl<I> Freeze for ClosureArgs<I>
impl<I> RefUnwindSafe for ClosureArgs<I>
impl<I> Send for ClosureArgs<I>
impl<I> Sync for ClosureArgs<I>
impl<I> Unpin for ClosureArgs<I>
impl<I> UnwindSafe for ClosureArgs<I>
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impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere
T: Copy,
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fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'a mut [T]
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fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'a mut [T]
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T: ?Sized,
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T: ?Sized,
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fn borrow_mut(&mut self) -> &mut T
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