[llvm-dev] [RFC] Should we add isa_or_null<>?

[David Greene via llvm-dev]

Bruno Ricci via llvm-dev <llvm-dev at lists.llvm.org> writes:

> On 07/04/2019 14:13, via llvm-dev wrote:
>> I have to say `not_null(v)` reads more like an assertion than a
>> predicate, in which case `isa<T>(not_null(v))` reads like it has the
>> exact same semantics that `isa<T>(v)` has currently—asserts that `v`
>> is not null.
>> 
>> I don't dispute that you can *make* it have the desired semantics, it just won't *look* that way.
>> 
>>  
>> 
>> maybe `isaT_or_null<Foo>(v)` ? Still looks awkward but maybe less naively misleading.
>> 
>
> ... or we keep using "v && isa<T>(v)" (which is not even longer!), which is unambiguous for everyone.
> In the rare special case where the pattern "someExpensiveCall() && isa<T>(someExpensiveCall())" is used,
> just assign the result of "someExpensiveCall()" to a variable.

+1.

                           -David