Generalized type erasure of concept types with or without heap allocation #356
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Use the Fn concepts instead and templatize the Split iterators. This avoids holding a pointer to a possibly-temporary function object.
Generalize Box<DynError>::from(Error auto) to work with any DynConcept type erasure, with Box<DynC>::from(C auto).
The reference may be an rvalue and it may need to be used as an rvalue in order to get the desired type from it.
This can be useful when it lives on the stack in order to extend its lifetime.
Now that everything can be constexpr we can just max_by and min_by in the implementation of them.
…ifiers appear in subdoc
On clang 16 (but not after for some reason) the concept will not match
any type `F` that is pure virtual. This prevented FnMut from matching
against DynFnMut.
More precisely:
```
template <class T>
concept C = requires(T t) { t.foo(); }
```
This won't match a pure virtual `T` with a mutable `foo()` on clang 16.
It works on 17+ and with GCC 13 and MSVC (at least one version).
`requires(T& t)` does the right thing universally, as in:
```
template <class T>
concept C = requires(T& t) { t.foo(); }
```
Add a rule to STYLE.md and update all concepts that wrote a value type
in a rule to be reference types.
danakj
changed the title
Also test it more!
Use Box<DynFn> instead.
These are superceded by the general concept-type-erasure mechanism of DynConcept and the DynFn/Mut/Once type-erasure support types.
Box::with_args() will pass the args to the ctor of T to construct it directly on the heap.
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The
dyn()function requires a template parameter of the type erasure classDynCof conceptCcurrently.Whereas
into()does not, since it constructs a marker type and then uses type deduction to determine what to construct.We should in theory be able to do the same with
Dynand have it defer choosing the reference type until the operator is called, but it may be tricky to maintain const correctness.Here's a test demo envionment in which this could be explored: https://godbolt.org/z/Y5nGe4E16
Filed #358 for this enchancement.