SERVER-26025 Smart pointer with clone on copy

This clonable pointer works like a unique_ptr, but upon
copy it invokes a customizable cloning function.  A `clone`
member function is used by default.  There exist several
customization points.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/mongo/base/concept/convertible_to.h b/src/mongo/base/concept/convertible_to.h
new file mode 100644
index 00000000000..57e733418cf
--- /dev/null
+++ b/src/mongo/base/concept/convertible_to.h
@@ -0,0 +1,14 @@
+#pragma once
+
+namespace mongo {
+namespace concept {
+/**
+ * The ConvertibleTo concept models a type which can be converted implicitly into a `T`.
+ * The code: `T x; x= ConvertibleTo< T >{};` should be valid.
+ */
+template <typename T>
+struct ConvertibleTo {
+    operator T();
+}
+}  // namespace concept
+}  // namespace mongo