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Use stricter brace initialization

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This updates the `py::init` constructors to only use brace
initialization for aggregate initiailization if there is no constructor
with the given arguments.

This, in particular, fixes the regression in #1247 where the presence of
a `std::initializer_list<T>` constructor started being invoked for
constructor invocations in 2.2 even when there was a specific
constructor of the desired type.

The added test case demonstrates: without this change, it fails to
compile because the `.def(py::init<std::vector<int>>())` constructor
tries to invoke the `T(std::initializer_list<std::vector<int>>)`
constructor rather than the `T(std::vector<int>)` constructor.

By only using `new T{...}`-style construction when a `T(...)`
constructor doesn't exist, we should bypass this by while still allowing
`py::init<...>` to be used for aggregate type initialization (since such
types, by definition, don't have a user-declared constructor).
This commit is contained in:
Jason Rhinelander
2018-01-11 13:22:13 -04:00
parent 326deef2ae
commit adbc8111bc
3 changed files with 37 additions and 5 deletions
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16
tests/test_class.cpp
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@@ -10,6 +10,16 @@
#include "pybind11_tests.h"
#include "constructor_stats.h"
#include "local_bindings.h"
#include <pybind11/stl.h>
// test_brace_initialization
struct NoBraceInitialization {
NoBraceInitialization(std::vector<int> v) : vec{std::move(v)} {}
template <typename T>
NoBraceInitialization(std::initializer_list<T> l) : vec(l) {}
std::vector<int> vec;
};
TEST_SUBMODULE(class_, m) {
// test_instance
@@ -299,6 +309,12 @@ TEST_SUBMODULE(class_, m) {
.def(py::init<int, const std::string &>())
.def_readwrite("field1", &BraceInitialization::field1)
.def_readwrite("field2", &BraceInitialization::field2);
// We *don't* want to construct using braces when the given constructor argument maps to a
// constructor, because brace initialization could go to the wrong place (in particular when
// there is also an `initializer_list<T>`-accept constructor):
py::class_<NoBraceInitialization>(m, "NoBraceInitialization")
.def(py::init<std::vector<int>>())
.def_readonly("vec", &NoBraceInitialization::vec);
// test_reentrant_implicit_conversion_failure
// #1035: issue with runaway reentrant implicit conversion