VisitorBase::Clone does not handle declaration replacement

[parth-07]

We often use the VisitorBase::Clone function in all the Visitor classes to perform cloning of the original expression. This is mostly used for the cases where we do not need the derivative of primal expression, as in those cases, we use Visit(...) function instead.

VisitorBase::Clone function does not handle declaration replacement, and can thus produce incorrect cloned expressions. In all the Visitor classes, declaration replacement is being handled in VisitDeclRefExpr. Therefore, currently, the only way to get correct cloned expression in all cases is using Visit function.

[ro4i7]

Hello @parth-07 @vgvassilev

To solve this issue, you can modify the VisitorBase::Clone function to handle declaration replacement by calling the VisitDeclRefExpr function for each DeclRefExpr encountered during the cloning process. Here is an example implementation:

clang::Expr* VisitorBase::Clone(const clang::Expr* E) {
  // Create a new expression of the same type as the original.
  clang::Expr* NewExpr = E->Clone(context);
  // Replace declarations in the cloned expression.
  ReplaceDecls(NewExpr);
  return NewExpr;
}

void VisitorBase::ReplaceDecls(clang::Expr* E) {
  if (!E) return;
  switch (E->getStmtClass()) {
    case clang::Stmt::DeclRefExprClass: {
      clang::DeclRefExpr* DRE = llvm::cast<clang::DeclRefExpr>(E);
      clang::ValueDecl* VD = DRE->getDecl();
      if (clang::VarDecl* Var = llvm::dyn_cast<clang::VarDecl>(VD)) {
        if (Var->hasInit()) {
          // Recursively clone the initializer expression.
          clang::Expr* Init = Clone(Var->getInit());
          // Replace the initializer in the cloned expression.
          Var->setInit(Init);
        }
      }
      break;
    }
    default:
      // Recursively replace declarations in child expressions.
      for (auto& Child : E->children()) {
        ReplaceDecls(Child);
      }
      break;
  }
}

This implementation uses a ReplaceDecls function to recursively replace declarations in the cloned expression. It checks each DeclRefExpr encountered during the cloning process and calls Clone on the initializer expression if it exists. Then, it replaces the initializer in the cloned expression. Finally, it recursively replaces declarations in child expressions.

With this modification, you should be able to use VisitorBase::Clone to correctly clone expressions with declaration replacement in all cases.

[vgvassilev]

@ro4i7, please stop commenting under every issue. Select one or two issues and work to solve them, then repeat.

PS: Solving means submit a PR, get a successful review and a merged PR.

[vgvassilev]

Fixed in #655.