[clang][dataflow] Don't propagate result objects in unevaluated contexts (reland #90438) (#91172)

This relands #90348 with a fix for a [buildbot
failure](https://lab.llvm.org/buildbot/#/builders/216/builds/38446)
caused by the test being run with `-fno-rtti`.

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
index d79e734..cb6c8b2 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -350,6 +350,17 @@ public:
     return RecursiveASTVisitor<ResultObjectVisitor>::TraverseDecl(D);
   }
 
+  // Don't traverse expressions in unevaluated contexts, as we don't model
+  // fields that are only used in these.
+  // Note: The operand of the `noexcept` operator is an unevaluated operand, but
+  // nevertheless it appears in the Clang CFG, so we don't exclude it here.
+  bool TraverseDecltypeTypeLoc(DecltypeTypeLoc) { return true; }
+  bool TraverseTypeOfExprTypeLoc(TypeOfExprTypeLoc) { return true; }
+  bool TraverseCXXTypeidExpr(CXXTypeidExpr *) { return true; }
+  bool TraverseUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *) {
+    return true;
+  }
+
   bool TraverseBindingDecl(BindingDecl *BD) {
     // `RecursiveASTVisitor` doesn't traverse holding variables for
     // `BindingDecl`s by itself, so we need to tell it to.