george.karpenkov added inline comments.
================
Comment at: lib/StaticAnalyzer/Checkers/DynamicTypePropagation.cpp:587
if (TrackedType &&
+ !isa<ExplicitCastExpr>(CE) &&
!ASTCtxt.canAssignObjCInterfaces(DestObjectPtrType, *TrackedType) &&
----------------
dcoughlin wrote:
> xazax.hun wrote:
> > george.karpenkov wrote:
> > > Should it check that we are actually casting to the right type? Also it's
> > > a bit strange that isa<> check on line 569 did not catch this case, maybe
> > > that if- branch should be generalized instead?
> > I agree, line 569 supposed to handle this case and also update the state
> > accordingly.
> For suppressive casts, I am worried about updating the state to reflect
> destination type.
>
> Programmers use a suppressive cast when they know a better invariant about
> the contents of a collection -- at a particular point in time -- than the
> analysis infers. It is not a promise that the invariant will hold at all
> later program points. I'm particularly worried that adding one suppressive
> cast would require the programmer to add other, different suppressive casts
> later in the program. For this reason I don't think it make sense to update
> the specialized type args map with the destination type of the cast.
>
> Gabor: what do you think about the alternative of always removing the
> inferred specialized type args information for an unspecialized symbol on an
> explicit cast? After an explicit cast we would essentially treat the value as
> unspecialized and so not warn about later uses until the analyzer infers more
> information. Essentially this would be an acknowledgement that an explicit
> cast means the programmer had an invariant in mind that couldn't be
> represented in the type system and so the analyzer should back off.
Sounds reasonable, though actual examples would be even more helpful.
https://reviews.llvm.org/D39711
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