llvm-project/clang-tools-extra/docs/clang-tidy/checks/llvm-prefer-isa-or-dyn-cast-in-conditionals.rst

.. title:: clang-tidy - llvm-prefer-isa-or-dyn-cast-in-conditionals

llvm-prefer-isa-or-dyn-cast-in-conditionals
===========================================

Looks at conditionals and finds and replaces cases of ``cast<>``,
which will assert rather than return a null pointer, and
``dyn_cast<>`` where the return value is not captured. Additionally,
finds and replaces cases that match the pattern ``var &&
isa<X>(var)``, where ``var`` is evaluated twice.

.. code-block:: c++

  // Finds these:
  if (auto x = cast<X>(y)) {}
  // is replaced by:
  if (auto x = dyn_cast<X>(y)) {}

  if (cast<X>(y)) {}
  // is replaced by:
  if (isa<X>(y)) {}

  if (dyn_cast<X>(y)) {}
  // is replaced by:
  if (isa<X>(y)) {}

  if (var && isa<T>(var)) {}
  // is replaced by:
  if (isa_and_nonnull<T>(var.foo())) {}

  // Other cases are ignored, e.g.:
  if (auto f = cast<Z>(y)->foo()) {}
  if (cast<Z>(y)->foo()) {}
  if (X.cast(y)) {}