isAllocator

import std.experimental.allocator.building_blocks.null_allocator : NullAllocator;
import std.experimental.allocator.mallocator : Mallocator;
import std.experimental.allocator.gc_allocator : GCAllocator;
import std.experimental.allocator.mmap_allocator : MmapAllocator;
static assert(isAllocator!NullAllocator);
static assert(isAllocator!Mallocator);
static assert(isAllocator!GCAllocator);
static assert(isAllocator!MmapAllocator);
static assert(!isAllocator!int);