RFR: 8313249: Fix -Wconversion warnings in verifier code [v2]

[Coleen Phillimore]

On Sun, 30 Jul 2023 11:52:57 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> To me, the two lines serves two purposes:
>> 
>> 
>> assert(appends > 0 && appends < 4, "Invalid append amount");
>> 
>> This is the input expected by this function.
>> 
>> 
>>     return static_cast<u1>(251 + appends);
>> 
>> 
>> This is a mechanical check that the code is actually correctly written (i.e., you didn't mess up and wrote (253 + appends). That way the reader doesn't have do the math in order to trust this code.
>
> True - the assert is checking a precondition; the checked_cast would be checking a postcondition.

What Ioi said.  The explicit assert gives a better, more helpful error message than

  assert(static_cast<T1>(result) == thing, "must be");

And so in this case I always choose an existing assert rather than checked_cast.  I'll change it to static_cast<> instead of the C style cast.  I always find static_cast<> a noisier and mentally more effort than the C style cast, but it doesn't matter.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15056#discussion_r1279237899