Merge pull request #6406 from edi33416/null_allocator_allocate

Make null_allocator allocate @safe

Author: wilzbach

std/experimental/allocator/building_blocks/null_allocator.d

@@ -12,6 +12,8 @@ composite allocators.
 struct NullAllocator
 {
     import std.typecons : Ternary;
+
+    nothrow @nogc pure @safe:
     /**
     `NullAllocator` advertises a relatively large _alignment equal to 64 KB.
     This is because `NullAllocator` never actually needs to honor this
@@ -33,65 +35,59 @@ struct NullAllocator
     Precondition: $(D b is null). This is because there is no other possible
     legitimate input.
     */
-    pure nothrow @safe @nogc
     bool expand(ref void[] b, size_t s) shared
     { assert(b is null); return s == 0; }
     /// Ditto
-    pure nothrow @nogc
     bool reallocate(ref void[] b, size_t) shared
     { assert(b is null); return false; }
     /// Ditto
-    pure nothrow @nogc
     bool alignedReallocate(ref void[] b, size_t, uint) shared
     { assert(b is null); return false; }
     /// Returns `Ternary.no`.
-    pure nothrow @safe @nogc
     Ternary owns(const void[]) shared const { return Ternary.no; }
     /**
     Returns `Ternary.no`.
     */
-    pure nothrow @safe @nogc
     Ternary resolveInternalPointer(const void*, ref void[]) shared const
     { return Ternary.no; }
     /**
     No-op.
     Precondition: $(D b is null)
     */
-    pure nothrow @nogc
     bool deallocate(void[] b) shared { assert(b is null); return true; }
     /**
     No-op.
     */
-    pure nothrow @safe @nogc
     bool deallocateAll() shared { return true; }
     /**
     Returns `Ternary.yes`.
     */
-    pure nothrow @safe @nogc
     Ternary empty() shared const { return Ternary.yes; }
     /**
     Returns the `shared` global instance of the `NullAllocator`.
     */
     static shared NullAllocator instance;
 }
 
-@system unittest
+nothrow @nogc pure @safe unittest
 {
-    assert(NullAllocator.instance.alignedAllocate(100, 0) is null);
-    assert(NullAllocator.instance.allocateAll() is null);
-    auto b = NullAllocator.instance.allocate(100);
+    alias a = NullAllocator.instance;
+
+    assert(a.alignedAllocate(100, 0) is null);
+    assert(a.allocateAll() is null);
+    auto b = a.allocate(100);
     assert(b is null);
-    assert((() nothrow @safe @nogc => NullAllocator.instance.expand(b, 0))());
-    assert((() nothrow @safe @nogc => !NullAllocator.instance.expand(b, 42))());
-    assert((() nothrow @nogc => !NullAllocator.instance.reallocate(b, 42))());
-    assert((() nothrow @nogc => !NullAllocator.instance.alignedReallocate(b, 42, 0))());
-    assert((() nothrow @nogc => NullAllocator.instance.deallocate(b))());
-    assert((() nothrow @nogc => NullAllocator.instance.deallocateAll())());
+    assert(a.expand(b, 0));
+    assert(!a.expand(b, 42));
+    assert(!a.reallocate(b, 42));
+    assert(!a.alignedReallocate(b, 42, 0));
+    assert(a.deallocate(b));
+    assert(a.deallocateAll());
 
     import std.typecons : Ternary;
-    assert((() nothrow @safe @nogc => NullAllocator.instance.empty)() == Ternary.yes);
-    assert((() nothrow @safe @nogc => NullAllocator.instance.owns(null))() == Ternary.no);
+    assert(a.empty == Ternary.yes);
+    assert(a.owns(null) == Ternary.no);
 
     void[] p;
-    assert((() nothrow @safe @nogc => NullAllocator.instance.resolveInternalPointer(null, p))() == Ternary.no);
+    assert(a.resolveInternalPointer(null, p) == Ternary.no);
 }