Merge pull request #5028 from somzzz/issue_16542

fix issue 16542 -  makeArray not usable with const initializer

std/experimental/allocator/package.d

@@ -1031,8 +1031,7 @@ private enum hasPureDtor(T) = !hasElaborateDestructor!T ||
 private enum canSafelyDeallocPostRewind(T) = hasPurePostblit!T && hasPureDtor!T;
 
 /// Ditto
-T[] makeArray(T, Allocator)(auto ref Allocator alloc, size_t length,
-    auto ref T init)
+T[] makeArray(T, Allocator)(auto ref Allocator alloc, size_t length, T init)
 {
     if (!length) return null;
     auto m = alloc.allocate(T.sizeof * length);
@@ -1094,6 +1093,18 @@ T[] makeArray(T, Allocator)(auto ref Allocator alloc, size_t length,
     test!(immutable int)();
 }
 
+@system unittest
+{
+    void test(T)(in T initialValue)
+    {
+        auto t = theAllocator.makeArray!T(100, initialValue);
+        //auto t = theAllocator.makeArray(100, initialValue); // works well with the old code
+    }
+
+    const int init = 3;
+    test(init);
+}
+
 @system unittest
 {
     void test(A)(auto ref A alloc)