[ArrayRef] Provide constructors from any type with a data() member (#145735)

The assumption here is that if data() returns a pointer and size()
exists it's something representing contiguous storage.

Modeled after the behavior of C++20 std::span and enables two-way
conversion between std::span (or really any span-like type) and
ArrayRef. Add a unit test that verifies this if std::span is around.

This also means we can get rid of specific conversions for std::vector
and SmallVector.

1 files changed, 18 insertions, 1 deletions

diff --git a/llvm/unittests/ADT/ArrayRefTest.cpp b/llvm/unittests/ADT/ArrayRefTest.cpp
index 39a4a9b..3858d90 100644
--- a/llvm/unittests/ADT/ArrayRefTest.cpp
+++ b/llvm/unittests/ADT/ArrayRefTest.cpp
@@ -8,10 +8,16 @@
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/Allocator.h"
-#include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 #include <limits>
 #include <vector>
+#if __has_include(<version>)
+#include <version>
+#endif
+#ifdef __cpp_lib_span
+#include <span>
+#endif
+
 using namespace llvm;
 
 // Check that the ArrayRef-of-pointer converting constructor only allows adding
@@ -406,4 +412,15 @@ TEST(ArrayRefTest, MutableArrayRefDeductionGuides) {
   }
 }
 
+#ifdef __cpp_lib_span
+static_assert(std::is_constructible_v<ArrayRef<int>, std::span<const int>>,
+              "should be able to construct ArrayRef from const std::span");
+static_assert(std::is_constructible_v<std::span<const int>, ArrayRef<int>>,
+              "should be able to construct const std::span from ArrayRef");
+static_assert(std::is_constructible_v<ArrayRef<int>, std::span<int>>,
+              "should be able to construct ArrayRef from mutable std::span");
+static_assert(!std::is_constructible_v<std::span<int>, ArrayRef<int>>,
+              "cannot construct mutable std::span from ArrayRef");
+#endif
+
 } // end anonymous namespace