Bug 1677092: add `constexpr` `AnyOf`. r=sg

The STL supports it only with C++20.

Differential Revision: https://phabricator.services.mozilla.com/D97123

mfbt/Algorithm.h

@@ -28,6 +28,18 @@ constexpr bool AllOf(Iter aFirst, Iter aLast, Pred aPred) {
   return true;
 }
 
+// Like C++20's `std::any_of`.
+template <typename Iter, typename Pred>
+constexpr bool AnyOf(Iter aFirst, Iter aLast, Pred aPred) {
+  for (; aFirst != aLast; ++aFirst) {
+    if (aPred(*aFirst)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 namespace detail {
 template <typename Transform, typename SrcIter>
 using ArrayElementTransformType = typename std::invoke_result_t<

mfbt/tests/TestAlgorithm.cpp

@@ -7,13 +7,16 @@
 #include "mozilla/Algorithm.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Assertions.h"
+
+#include <array>
 #include <iterator>
 
 static constexpr bool even(int32_t n) { return !(n & 1); }
 static constexpr bool odd(int32_t n) { return (n & 1); }
 
+using namespace mozilla;
+
 void TestAllOf() {
-  using namespace mozilla;
   using std::begin;
   using std::end;
 
@@ -36,7 +39,29 @@ void TestAllOf() {
   static_assert(!AllOf(arr3, arr3 + ArrayLength(arr3), odd), "3-2");
 }
 
+void TestAnyOf() {
+  using std::begin;
+  using std::end;
+
+  constexpr std::array<int32_t, 0> arr1{};
+  static_assert(!AnyOf(begin(arr1), end(arr1), even));
+  static_assert(!AnyOf(begin(arr1), end(arr1), odd));
+
+  constexpr int32_t arr2[] = {1};
+  static_assert(!AnyOf(begin(arr2), end(arr2), even));
+  static_assert(AnyOf(begin(arr2), end(arr2), odd));
+
+  constexpr int32_t arr3[] = {2};
+  static_assert(AnyOf(begin(arr3), end(arr3), even));
+  static_assert(!AnyOf(begin(arr3), end(arr3), odd));
+
+  constexpr int32_t arr4[] = {1, 2};
+  static_assert(AnyOf(begin(arr4), end(arr4), even));
+  static_assert(AnyOf(begin(arr4), end(arr4), odd));
+}
+
 int main() {
   TestAllOf();
+  TestAnyOf();
   return 0;
 }