Enum naga::proc::TypeResolution
source · pub enum TypeResolution {
Handle(Handle<Type>),
Value(TypeInner),
}
Expand description
The result of computing an expression’s type.
This is the (Rust) type returned by ResolveContext::resolve
to represent
the (Naga) type it ascribes to some expression.
You might expect such a function to simply return a Handle<Type>
. However,
we want type resolution to be a read-only process, and that would limit the
possible results to types already present in the expression’s associated
UniqueArena<Type>
. Naga IR does have certain expressions whose types are
not certain to be present.
So instead, type resolution returns a TypeResolution
enum: either a
Handle
, referencing some type in the arena, or a Value
, holding a
free-floating TypeInner
. This extends the range to cover anything that
can be represented with a TypeInner
referring to the existing arena.
What sorts of expressions can have types not available in the arena?
-
An
Access
orAccessIndex
expression applied to aVector
orMatrix
must have aScalar
orVector
type. But sinceVector
andMatrix
represent their element and column types implicitly, not via a handle, there may not be a suitable type in the expression’s associated arena. Instead, resolving such an expression returns aTypeResolution::Value(TypeInner::X { ... })
, whereX
isScalar
orVector
. -
Similarly, the type of an
Access
orAccessIndex
expression applied to a pointer to a vector or matrix must produce a pointer to a scalar or vector type. These cannot be represented with aTypeInner::Pointer
, since thePointer
’sbase
must point into the arena, and as before, we cannot assume that a suitable scalar or vector type is there. So we take things one step further and provideTypeInner::ValuePointer
, specifically for the case of pointers to scalars or vectors. This type fits in aTypeInner
and is exactly equivalent to aPointer
to aVector
orScalar
.
So, for example, the type of an Access
expression applied to a value of type:
TypeInner::Matrix { columns, rows, width }
might be:
TypeResolution::Value(TypeInner::Vector {
size: rows,
kind: ScalarKind::Float,
width,
})
and the type of an access to a pointer of address space space
to such a
matrix might be:
TypeResolution::Value(TypeInner::ValuePointer {
size: Some(rows),
kind: ScalarKind::Float,
width,
space,
})
Variants§
Handle(Handle<Type>)
A type stored in the associated arena.
Value(TypeInner)
A free-floating TypeInner
, representing a type that may not be
available in the associated arena. However, the TypeInner
itself may
contain Handle<Type>
values referring to types from the arena.
Implementations§
source§impl TypeResolution
impl TypeResolution
pub const fn handle(&self) -> Option<Handle<Type>>
pub fn inner_with<'a>(&'a self, arena: &'a UniqueArena<Type>) -> &'a TypeInner
Trait Implementations§
source§impl Clone for TypeResolution
impl Clone for TypeResolution
source§impl Debug for TypeResolution
impl Debug for TypeResolution
source§impl PartialEq for TypeResolution
impl PartialEq for TypeResolution
source§fn eq(&self, other: &TypeResolution) -> bool
fn eq(&self, other: &TypeResolution) -> bool
self
and other
values to be equal, and is used
by ==
.