[clang][analyzer][NFC] Remove redundant code in StreamChecker

[benshi001]

No description provided.

[steakhal]

I find this alternative less idiomatic (dissimilar to how we implement checks in other checkers), thus I find this less readable.
I'm okay with that amount of redundancy as it was present.

[balazske]

This function has a role like ensureStreamNonNullAndOpened, that would be a better name for it. And it should return the new State, like ensureStreamNonNull.

[balazske]

Suggested change

	if (!basicCheck(Desc, Call, C, State, StreamVal))
	State = ensureStreamNonNullAndOpened(Desc, Call, C, State, StreamVal);
	if (!State)
	return;

[balazske]

The function returns a state that is modified further by the following functions. Otherwise the state changes applied in basicCheck are lost. (ensureStreamNonNull does a state change, ensureStreamOpened does not, but all return a state to make the usage similar.)

[balazske]

With the current code it is a corner case if this change makes the code more readable. Probably it can be useful if new functions are added to the checker. But the rule here is that there is one "ensure" function to check one aspect of the state, and the pre-callbacks call all of the ensure functions that are needed in that case. It would not much more readable if multiple combinations of ensure functions are made, for example ensureStreamNonNullAndOpenedAndNoFilePositionIndeterminate.

[benshi001]

It seems my previous change make little sense, so I reuse this PR for another change.

[balazske]

This change looks not very useful to me. These removed return statements indicate that at the end of the if branch there is no more work to do in this function, and it reduces complexity (less execution paths). The code becomes a bit shorter but not necessarily more easy to understand. Optimizing code for execution speed or binary size is not important because I am sure that compiler optimizations can handle this case.

[benshi001]

How about only remove the second return State ? The removal of the first one may be less readable. But for the second one, it is very near to the final return State. It may looks strange for very near return States.

if () {
   return State;
}
return State;