Add upgrade guide entry about stricter compile-time checks

Closes #1048, closes #1052.

[skip ci]
This commit is contained in:
Dean Moldovan 2017-09-02 14:46:32 +02:00
parent 1ad2227d3c
commit 91b42c8174

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@ -225,6 +225,33 @@ should be used directly instead: ``borrowed_t{}`` and ``stolen_t{}``
(`#771 <https://github.com/pybind/pybind11/pull/771>`_).
Stricter compile-time error checking
------------------------------------
Some error checks have been moved from run time to compile time. Notably,
automatic conversion of ``std::shared_ptr<T>`` is not possible when ``T`` is
not directly registered with ``py::class_<T>`` (e.g. ``std::shared_ptr<int>``
or ``std::shared_ptr<std::vector<T>>`` are not automatically convertible).
Attempting to bind a function with such arguments now results in a compile-time
error instead of waiting to fail at run time.
``py::init<...>()`` constructor definitions are also stricter and now prevent
bindings which could cause unexpected behavior:
.. code-block:: cpp
struct Example {
Example(int &);
};
py::class_<Example>(m, "Example")
.def(py::init<int &>()); // OK, exact match
// .def(py::init<int>()); // compile-time error, mismatch
A non-``const`` lvalue reference is not allowed to bind to an rvalue. However,
note that a constructor taking ``const T &`` can still be registered using
``py::init<T>()`` because a ``const`` lvalue reference can bind to an rvalue.
v2.1
====