Make the declaration of ``ConstantExpr`` the last declared ``Expr``

sub-class rather than the first. Whilst I'm here clang-format the
moved code.

The motivation for this is that ``ConstantExpr`` may need to refer to a
type that cannot be forward declared (e.g. some kind of enum) in the
other ``Expr`` sub-classes.

For example if an Expr sub-class is ever introduced that has contains an
enum that is used for its constructor then the previous ordering would prevent
a Constant evaluation method (e.g. ``ConstantExpr::MyNewExprType(const
ref<ConstantExpr> &RHS, MyNewType::SpecialEnum p)``) from being
implemented because the ``MyNewType::SpecialEnum`` type has not yet been
declared.

0 files changed, 0 insertions, 0 deletions