Add a type cast to RCT_ENUM_CONVERTER for C++ compatibility

[jballer]

Motivation

C++ doesn't provide an implicit cast to an enum value from the enum's backing type. When a .mm file calls RCT_ENUM_CONVERTER, we end up with the following compiler error:

Error: cannot initialize return object of type <TypeName> with an rvalue of type NSInteger

Since RCT_ENUM_CONVERTER is a macro, this error will appear whenever we try to expand the macro in a C++ context.

Test Plan

The project compiles and runs as expected when this additional cast is added 😃

[javache]

What type are you trying to convert? [NSNumber getter] should already be giving you the right type.

[jballer]

The C++ compiler expects the enum type ("TypeName" in typedef NS_ENUM(NSInteger, TypeName)…).

The getter (in this case, integerValue) is properly returning the enum's NSInteger backing type. In standard ObjC this will compile without issue, but C++ requires an explicit cast from NSInteger back to the enum type.

More explicitly, the problem in the C++ compiler is that the macro expands to:

+(TypeName)TypeName:(id)json
{
  …
  return [… integerValue]; // fine in ObjC, but in ObjC++ this isn't the same as TypeName
}

[facebook-github-bot]

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