https://llvm.org/bugs/show_bug.cgi?id=25669
Bug ID: 25669
Summary: Arbitrary overload resolution on template function
instead of "ambiguous overload" error
Product: clang
Version: 3.7
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
The code below is a minimal code sample that exhibits the bug.
The type FindInMap<Map, int>::type should be `void' but Clang thinks it's
`char'.
This works correctly in GCC (tested version 4.8.5) but fails in Clang 3.7.0.
Explanation:
* The first overload of f (templated) is ambiguous (both Value=char and
Value=float match, with the same priority since both require a conversion from
Map* to the respective Pair<...>*) so it should be discarded.
* The second overload of f (non-templated) is the only one that remains and
therefore is the one that should be picked.
What's even more puzzling is that if the non-templated f is commented out, then
Clang displays the ambiguous overload error (which is correct) but for some
reason that's otherwise ignored.
template <typename T, typename U>
struct Pair {};
template <typename M, typename T>
struct FindInMap {
template <typename Value>
static Value f(Pair<T, Value>*);
static void f(void*);
using type = decltype(f((M*)0));
};
struct Map : public Pair<int, float>, Pair<int, char> {};
#include <functional> // Just for std::is_same
static_assert(std::is_same<FindInMap<Map, int>::type, void>::value, "");
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