Visual Studio objects with the following:
```
AST/AnyRequest.h(243): error: C2580: 'swift::AnyRequest::AnyRequest(const swift::AnyRequest &)': multiple versions of a defaulted special member functions are not allowed
AST/AnyRequest(243): warning C4521: 'swift::AnyRequest': multiple copy constructors specified
```
Remove the non-const implementation, the default'ed definition should be
sufficient. Additionally, remove the nonsense const move constructor.
Because we cannot explicitly control which constructor is used, and Visual
Studio also instantiates the templated constructor (even with the copy and move
constructors available, we end up with ambiguity in the constructor when trying
to instantiate a `llvm::SetVector<AnyRequest>` in the Evaluator.
```
swift\include\swift\AST\AnyRequest.h(98): error C2027: use of undefined type 'swift::TypeID<Request>'
with
[
Request=ValueType
]
swift\include\swift\AST\AnyRequest.h(98): note: see declaration of 'swift::TypeID<Request>'
with
[
Request=ValueType
]
swift\include\swift\AST\AnyRequest.h(97): note: while compiling class template member function 'swift::AnyRequest::Holder<ValueType>::Holder(const Request &)'
with
[
Request=ValueType
]
swift\include\swift\AST\AnyRequest.h(167): note: see reference to function template instantiation 'swift::AnyRequest::Holder<ValueType>::Holder(const Request &)' being compiled
with
[
Request=ValueType
]
swift\include\swift\AST\AnyRequest.h(168): note: see reference to class template instantiation 'swift::AnyRequest::Holder<ValueType>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\xmemory0(917): note: see reference to function template instantiation 'swift::AnyRequest::AnyRequest<T&>(swift::AnyRequest&)' being compiled
with
[
T=swift::AnyRequest
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\xmemory(120): note: see reference to function template instantiation 'void std::_Default_allocator_traits<_Alloc>::construct<_Ty,T&>(_Alloc &,_Objty *const ,T &)' being compiled
with
[
_Alloc=std::allocator<swift::AnyRequest>,
_Ty=swift::AnyRequest,
T=swift::AnyRequest,
_Objty=swift::AnyRequest
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\xmemory(120): note: see reference to function template instantiation 'void std::_Default_allocator_traits<_Alloc>::construct<_Ty,T&>(_Alloc &,_Objty *const ,T &)' being compiled
with
[
_Alloc=std::allocator<swift::AnyRequest>,
_Ty=swift::AnyRequest,
T=swift::AnyRequest,
_Objty=swift::AnyRequest
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\xmemory(153): note: see reference to function template instantiation '_FwdIt std::_Uninitialized_copy_al_unchecked<_Iter,_Iter,_Alloc>(_InIt,_InIt,_FwdIt,_Alloc &,std::_General_ptr_iterator_tag,std::_Any_tag)' being compiled
with
[
_FwdIt=swift::AnyRequest *,
_Iter=swift::AnyRequest *,
_Alloc=std::allocator<swift::AnyRequest>,
_InIt=swift::AnyRequest *
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\vector(1939): note: see reference to function template instantiation '_FwdIt *std::_Uninitialized_copy<swift::AnyRequest*,swift::AnyRequest*,std::allocator<_Ty>>(_InIt,_InIt,_FwdIt,_Alloc &)' being compiled
with
[
_FwdIt=swift::AnyRequest *,
_Ty=swift::AnyRequest,
_InIt=swift::AnyRequest *,
_Alloc=std::allocator<swift::AnyRequest>
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\vector(1938): note: while compiling class template member function 'void std::vector<T,std::allocator<_Ty>>::_Umove_if_noexcept1(swift::AnyRequest *,swift::AnyRequest *,swift::AnyRequest *,std::false_type)'
with
[
T=swift::AnyRequest,
_Ty=swift::AnyRequest
]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.13.26128\include\vector(1944): note: see reference to function template instantiation 'void std::vector<T,std::allocator<_Ty>>::_Umove_if_noexcept1(swift::AnyRequest *,swift::AnyRequest *,swift::AnyRequest *,std::false_type)' being compiled
with
[
T=swift::AnyRequest,
_Ty=swift::AnyRequest
]
llvm\include\llvm\ADT\SetVector.h(49): note: see reference to class template instantiation 'std::vector<T,std::allocator<_Ty>>' being compiled
with
[
T=swift::AnyRequest,
_Ty=swift::AnyRequest
]
swift\include\swift\AST\Evaluator.h(208): note: see reference to class template instantiation 'llvm::SetVector<swift::AnyRequest,std::vector<T,std::allocator<_Ty>>,llvm::DenseSet<T,llvm::DenseMapInfo<swift::AnyRequest>>>' being compiled
with
[
T=swift::AnyRequest,
_Ty=swift::AnyRequest
]
swift\include\swift\AST\AnyRequest.h(97): error C2065: 'value': undeclared identifier
```
Hoist the type alias into the template specialization so that we can use that
in the SFINAE expression rather than duplicating it.
The default move constructor and move assignment operator of AnyRequest
would leave the source object in an odd state that’s destructible but
does not maintain the invariant that all “normal” states store a real
instance. This state breaks DenseMap, which assumes that a moved-from
object is still washable.
Introduce another form of debugging dump for the evaluator, rendering the
complete dependency graph using GraphViz, including all dependencies and
values cached within the evaluator.
Introduce a CRTP base class, SimpleRequest, which simplifies the task of
defining a new request kind by handling the storage of the values (in a
std::tuple), their hashing, equality, printing, etc. The values are passed
along to the subclass’s operator() so they’re mostly treated as (const)
parameters, making mutation of the request state impossible.
Extend AnyValue and AnyRequest with printing logic, so we can print any
request for debugging purposes, and
Meant as a replacement for the barely-started iterative type checker,
introduce a simpler "evaluator" that can evaluate individual requests
(essentially, function objects with some additional API), caching
results as appropriate and detecting cycles.
