[Sema] haveSameParameterTypes - replace repeated isNull() test with assertions

[RKSimon]

Summary

As reported on https://pvs-studio.com/en/blog/posts/cpp/0771/ (Snippet 2) - (and mentioned on rGdc4259d5a38409) we are repeating the T1.isNull() check instead of checking T2.isNull() as well.

[RKSimon]

clang/lib/Sema/SemaOverload.cpp

9589–9590

@rsmith Can these isNull checks ever fail? Or would we be better off changing them into an assert?

QualType T1 = NextParam(F1, I1, I == 0);
QualType T2 = NextParam(F2, I2, I == 0);
assert(!T1.isNull() && !T2.isNull() && "Unknown types");
if (!Context.hasSameUnqualifiedType(T1, T2))

[RKSimon]

ping - any comments?

[RKSimon]

ping

[xbolva00]

LG. Could be changed to the assert in the future….

[urnathan]

clang/lib/Sema/SemaOverload.cpp

9589–9590

that it's never ICED without checking T2's nullness suggests to me that they're never null. A null type here would seem to be from bad parsing, in which case why are we even checking further? IMHO assert now, there's plenty of time before C14 to revert that.

[RKSimon]

clang/lib/Sema/SemaOverload.cpp

9589–9590

OK - I'll change this to an assertion

[jansvoboda11]

FYI, it seems like a branch containing this patch was accidentally pushed to GitHub: https://github.com/llvm/llvm-project/tree/5357a98c823a

clang/lib/Sema/SemaOverload.cpp

auto NextParam = [&](const FunctionDecl *F, unsigned &I, bool First) {
     assert(I < F->getNumParams());
     return F->getParamDecl(I++)->getType();
   };
 
   unsigned I1 = 0, I2 = 0;
   for (unsigned I = 0; I != NumParams; ++I) {
     QualType T1 = NextParam(F1, I1, I == 0);
     QualType T2 = NextParam(F2, I2, I == 0);
-    if (!T1.isNull() && !T1.isNull() && !Context.hasSameUnqualifiedType(T1, T2))
+    assert(!T1.isNull() && !T2.isNull() && "Unexpected null param types");
+    if (!Context.hasSameUnqualifiedType(T1, T2))
       return false;
   }
   return true;
 }
 
 /// isBetterOverloadCandidate - Determines whether the first overload
 /// candidate is a better candidate than the second (C++ 13.3.3p1).
 bool clang::isBetterOverloadCandidate(