================
@@ -12488,8 +12488,7 @@ static void diagnoseTautologicalComparison(Sema &S,
SourceLocation Loc,
QualType LHSType = LHS->getType();
QualType RHSType = RHS->getType();
if (LHSType->hasFloatingRepresentation() ||
- (LHSType->isBlockPointerType() && !BinaryOperator::isEqualityOp(Opc)) ||
- S.inTemplateInstantiation())
+ (LHSType->isBlockPointerType() && !BinaryOperator::isEqualityOp(Opc)))
----------------
Sirraide wrote:
The entire if statement.
`diagnoseTautologicalComparison()` warns e.g. if you write `true == true` since
that’s a bit pointless since it’s always true. The reason this check is here is
because comparing arrays compares the addresses, not the elements, and thus, if
we know what the arrays are at compile time, we can warn that the comparison
will always be true/false.
Now that C++26 has made this ill-formed, it’d be easiest to just move it out of
`diagnoseTautologicalComparison()`; we should continue to emit the warning in
older language modes, of course, but the code doesn’t need to be in this
function for that, and while there are several places where this is called
from, only the one I pointed out can possibly involve array types I believe.
The reason we check for `inTemplateInstantiation()` here is that we don’t want
to emit tautological comparison warnings if the user writes e.g.
```
template <const int (&a)[3], const int (&b)[3]>
bool f() { return a == b; }
```
and `a` and `b` just happen to refer to the same array when instantiated
(https://godbolt.org/z/bP6Yc61Mn). That check makes sense if all we’re doing is
emitting tautological comparison warnings, but not for deprecated array
comparisons
https://github.com/llvm/llvm-project/pull/191101
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