introduce module interface declaration (#28408)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28408
This enable interface to defined on a nn.Module, and the InterfaceType
now have a field of is_module_ to distinguish if it's a module interface
or a normal interface (This is similar to what ClassType distinguish on
module and torchscript classes).
The module interface can be assigned with any ScriptModule that has the
compatible signatures on schemas. A normal object that is not a
ScriptModule will not be able to assigned to an module interface and
will error out when user explicitly doing so. Assigning a ScriptModule
to class interface will make it only available in attribute_list, not
module_list. More details on subtyping relationship documented in the
jit_type.h
If you declare an module interface inside an nn.Module that is being
compiled to a ScriptModule, behavior to our internal compilation will
be:
1. ConcreteModuleType will record it as an module attribute and add to
the attributes_ list.
2. JitType that is created from the ConcreteModuleType will record it as
an attribute and pre-genenerate the slot. The slot will be marked as
EntityType::MODULE still to make sure JitType record it as a Module
slot
3. cpp_module will also register it as a Module as the Slot type is the
source of truth
Since JitType will record it as attribute as store its type, it will
behave normally as the class interface attribute behave now. This means
the submodule assigned to this module interface is not getting inlined
into the graph as the normal `Module::attr` behave, it will generate
interface callMethod and allow us to later swap this with another
ScriptModule that implicitly implements this module interface.
Test Plan: Imported from OSS
Differential Revision: D18284311
fbshipit-source-id: e0b8f6e8c34b2087fab337a969e5ea3fb37ec209
