[fpc-pascal] Checking assignment compatibility

[Mark Morgan Lloyd]

Michael Van Canneyt wrote:
> On Sun, 5 Jan 2014, Mark Morgan Lloyd wrote:
> 
>> Simulating a C-style conditional, I can do this
>>
>> function tf(const q: qword; const qt, qf: TObject): TObject; inline;
>>
>> begin
>>  Assert(TypeOf(qt) = TypeOf(result));
> 
> This is always true. Everything descends from TOBject.
> 
> But assuming the result is not TObject, it would be
> 
> Assert((qt=Nil) or (qt.Inheritsfrom(TheResultClass))

So again skipping the nil check for simplicity, this compiles but are 
the semantics right?

Assert(qt.ClassType.InheritsFrom(result.ClassType));

> Although that is still radically different from what the C style macro 
> does.

Yes, understood and being watched out for.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

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