[clang][dataflow] Refactor PropagateResultObject() with a switch st…

…atement. (#88865)

See also discussion in #88726.

clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp

@@ -414,25 +414,52 @@ class ResultObjectVisitor : public RecursiveASTVisitor<ResultObjectVisitor> {
 
     ResultObjectMap[E] = Loc;
 
+    switch (E->getStmtClass()) {
     // The following AST node kinds are "original initializers": They are the
     // lowest-level AST node that initializes a given object, and nothing
     // below them can initialize the same object (or part of it).
-    if (isa<CXXConstructExpr>(E) || isa<CallExpr>(E) || isa<LambdaExpr>(E) ||
-        isa<CXXDefaultArgExpr>(E) || isa<CXXDefaultInitExpr>(E) ||
-        isa<CXXStdInitializerListExpr>(E) ||
-        // We treat `BuiltinBitCastExpr` as an "original initializer" too as
-        // it may not even be casting from a record type -- and even if it is,
-        // the two objects are in general of unrelated type.
-        isa<BuiltinBitCastExpr>(E)) {
+    case Stmt::CXXConstructExprClass:
+    case Stmt::CallExprClass:
+    case Stmt::LambdaExprClass:
+    case Stmt::CXXDefaultArgExprClass:
+    case Stmt::CXXDefaultInitExprClass:
+    case Stmt::CXXStdInitializerListExprClass:
+    // We treat `BuiltinBitCastExpr` as an "original initializer" too as it may
+    // not even be casting from a record type -- and even if it is, the two
+    // objects are in general of unrelated type.
+    case Stmt::BuiltinBitCastExprClass:
+      return;
+    case Stmt::BinaryOperatorClass: {
+      auto *Op = cast<BinaryOperator>(E);
+      if (Op->getOpcode() == BO_Cmp) {
+        // Builtin `<=>` returns a `std::strong_ordering` object. We
+        // consider this to be an "original" initializer too (see above).
+        return;
+      }
+      if (Op->isCommaOp()) {
+        PropagateResultObject(Op->getRHS(), Loc);
+        return;
+      }
+      // We don't expect any other binary operators to produce a record
+      // prvalue, so if we get here, we've hit some case we don't know
+      // about.
+      assert(false);
       return;
     }
-    if (auto *Op = dyn_cast<BinaryOperator>(E);
-        Op && Op->getOpcode() == BO_Cmp) {
-      // Builtin `<=>` returns a `std::strong_ordering` object.
+    case Stmt::BinaryConditionalOperatorClass:
+    case Stmt::ConditionalOperatorClass: {
+      auto *Cond = cast<AbstractConditionalOperator>(E);
+      PropagateResultObject(Cond->getTrueExpr(), Loc);
+      PropagateResultObject(Cond->getFalseExpr(), Loc);
       return;
     }
-
-    if (auto *InitList = dyn_cast<InitListExpr>(E)) {
+    case Stmt::StmtExprClass: {
+      auto *SE = cast<StmtExpr>(E);
+      PropagateResultObject(cast<Expr>(SE->getSubStmt()->body_back()), Loc);
+      return;
+    }
+    case Stmt::InitListExprClass: {
+      auto *InitList = cast<InitListExpr>(E);
       if (!InitList->isSemanticForm())
         return;
       if (InitList->isTransparent()) {
@@ -462,33 +489,20 @@ class ResultObjectVisitor : public RecursiveASTVisitor<ResultObjectVisitor> {
       }
       return;
     }
-
-    if (auto *Op = dyn_cast<BinaryOperator>(E); Op && Op->isCommaOp()) {
-      PropagateResultObject(Op->getRHS(), Loc);
+    default: {
+      // All other expression nodes that propagate a record prvalue should
+      // have exactly one child.
+      SmallVector<Stmt *, 1> Children(E->child_begin(), E->child_end());
+      LLVM_DEBUG({
+        if (Children.size() != 1)
+          E->dump();
+      });
+      assert(Children.size() == 1);
+      for (Stmt *S : Children)
+        PropagateResultObject(cast<Expr>(S), Loc);
       return;
     }
-
-    if (auto *Cond = dyn_cast<AbstractConditionalOperator>(E)) {
-      PropagateResultObject(Cond->getTrueExpr(), Loc);
-      PropagateResultObject(Cond->getFalseExpr(), Loc);
-      return;
     }
-
-    if (auto *SE = dyn_cast<StmtExpr>(E)) {
-      PropagateResultObject(cast<Expr>(SE->getSubStmt()->body_back()), Loc);
-      return;
-    }
-
-    // All other expression nodes that propagate a record prvalue should have
-    // exactly one child.
-    SmallVector<Stmt *, 1> Children(E->child_begin(), E->child_end());
-    LLVM_DEBUG({
-      if (Children.size() != 1)
-        E->dump();
-    });
-    assert(Children.size() == 1);
-    for (Stmt *S : Children)
-      PropagateResultObject(cast<Expr>(S), Loc);
   }
 
 private: