Enforce rawType to be a Class in ParameterizedTypeImpl

[panic08]

There is a JDK-6255169 issue that states that getRawType() in ParameterizedType should return Class and not Type. However, this issue is closed, it was explained by the fact that there is no way to fix it due to backward compatibility. Our TODO specifies a related issue JDK-8250659 which calls to comment out that getRawType() always returns Class as Type

Accordingly, looking at all this, we implement ParameterizedType and assume that rawType will always be Class. However, in our implementation class in the constructor we can throw under rawType more than just Class, which is not the right thing to do

Here I tried to solve this problem by throwing the IllegalArgumentException(“rawType must be a Class type”) exception

[eamonnmcmanus]

I think we should probably just change the type of the rawType parameter of newParameterizedTypeWithOwner and of the ParameterizedTypeImpl constructor from Type to Class<?>. That then requires two casts in $Gson$Types itself and one change from rawType to the already-existing rawClass in TypeToken. I think it's fine to get a ClassCastException in the supposedly-impossible case that these Type instances are not actually instances of Class.

Ordinarily we wouldn't change parameter types in a public API, but in this case the API is doubly marked as internal: it has .internal. in its package name and it has those funky $ signs in its name. I do see a few references in GitHub search that might conceivably be broken by this change but I'm relatively unsympathetic. If they are indeed affected then the fix is just inserting a cast. I tried making a change along these lines and running it against all of Google's internal tests (including lots of third-party code) and did not discover any problems.

[panic08]

I agree with you. I did what you suggested, in this case in $Gson$Types itself I needed to make casts to Class<?>, and also changed the description of the rawType field in TypeToken from Type to Class.

I also directly removed a small piece of code in TypeTokenTest that checks for an error if Type is not passed in Class.

Also, am I correct that we can ignore the error “Check API compatibility / check-api-compatibility (pull_request) Failed after 1m”?

[eamonnmcmanus]

Oh, we can't change the signature of this method. It is part of the public API and it is not internal. So I think you want to undo the changes in this method, and just change rawType to rawClass in the return statement.

[eamonnmcmanus]

I would undo these changes too.

[eamonnmcmanus]

Thanks, this is great!