[C++20] Lambdas in unevaluated contexts: wrong conversion from lambda to std::priority_queue #492
Description
C++ Insights link: https://cppinsights.io/s/f1515a7d
void f()
{
std::priority_queue<int,
std::vector<int>,
decltype([](int lhs, int rhs) { return lhs > rhs; })> min_heap;
}
translates into
void f()
{
class __lambda_8_34
{
...
};
std::priority_queue<int, std::vector<int, std::allocator<int> >, __lambda_8_34> min_heap = __lambda_8_34{};
}
which is not valid C++ code:
error: conversion from 'f()::__lambda_8_34' to non-scalar type 'std::priority_queue<int, std::vector<int, std::allocator<int> >, f()::__lambda_8_34>'
A slightly modified function, where the lambda is defined before the std::priority_queue:
void g()
{
auto cmp_greater = [](int lhs, int rhs) { return lhs > rhs; };
std::priority_queue<int,
std::vector<int>,
decltype(cmp_greater)> min_heap;
}
translates into
void g()
{
class __lambda_13_24
{
...
};
__lambda_13_24 cmp_greater = __lambda_13_24{};
std::priority_queue<int, std::vector<int, std::allocator<int> >, __lambda_13_24> min_heap = std::priority_queue<int, std::vector<int, std::allocator<int> >, __lambda_13_24>();
}
which is valid C++ code.