[Clang] [Sema] Fix dependence of DREs in lambdas with an explicit object parameter (#84473)

This fixes some problems wrt dependence of captures in lambdas with
an explicit object parameter.

[temp.dep.expr] states that
> An id-expression is type-dependent if [...] its terminal name is
>   - associated by name lookup with an entity captured by copy
>     ([expr.prim.lambda.capture]) in a lambda-expression that has
>     an explicit object parameter whose type is dependent [dcl.fct].

There were several issues with our implementation of this:
1. we were treating by-reference captures as dependent rather than
   by-value captures;
2. tree transform wasn't checking whether referring to such a
   by-value capture should make a DRE dependent;
3. when checking whether a DRE refers to such a by-value capture, we
   were only looking at the immediately enclosing lambda, and not
   at any parent lambdas;
4. we also forgot to check for implicit by-value captures;
5. lastly, we were attempting to determine whether a lambda has an
   explicit object parameter by checking the `LambdaScopeInfo`'s
   `ExplicitObjectParameter`, but it seems that that simply wasn't
   set (yet) by the time we got to the check.

All of these should be fixed now.

This fixes #70604, #79754, #84163, #84425, #86054, #86398, and #86399.

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/lib/AST/ComputeDependence.cpp b/clang/lib/AST/ComputeDependence.cpp
index 86b77b4..5ec3013 100644
--- a/clang/lib/AST/ComputeDependence.cpp
+++ b/clang/lib/AST/ComputeDependence.cpp
@@ -310,6 +310,16 @@ ExprDependence clang::computeDependence(CXXThisExpr *E) {
   // 'this' is type-dependent if the class type of the enclosing
   // member function is dependent (C++ [temp.dep.expr]p2)
   auto D = toExprDependenceForImpliedType(E->getType()->getDependence());
+
+  // If a lambda with an explicit object parameter captures '*this', then
+  // 'this' now refers to the captured copy of lambda, and if the lambda
+  // is type-dependent, so is the object and thus 'this'.
+  //
+  // Note: The standard does not mention this case explicitly, but we need
+  // to do this so we can mark NSDM accesses as dependent.
+  if (E->isCapturedByCopyInLambdaWithExplicitObjectParameter())
+    D |= ExprDependence::Type;
+
   assert(!(D & ExprDependence::UnexpandedPack));
   return D;
 }