Assert that kernels are called with the right signature (#38361)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38361
Rather than segfaulting, we should show a good error message when in op.call<Return, Args...>(...) the Return type or Args types mismatch the kernel.
This adds an assertion comparing two std::type_index to the call path, but that should be fast. Hashing the function signature is also in the call path and not strictly constexpr, but I checked on godbolt that GCC >=5 and Clang >=3.8 optimize it away and make it constexpr, i.e. it's not part of the assembly.
supersedes D17485438
ghstack-source-id: 106178820
Test Plan: waitforsandcastle
Differential Revision: D21534052
fbshipit-source-id: 6be436a3f20586277a051d764af29e21d5567da0
