Create std.traits.classInstanceAlignment

std/traits.d

@@ -2781,6 +2781,43 @@ unittest
 }
 
 
+private template maxAlignment(U...) if(isTypeTuple!U)
+{
+    static if(U.length == 1)
+        enum maxAlignment = U[0].alignof;
+    else
+        enum maxAlignment = max(U[0].alignof, .maxAlignment!(U[1 .. $]));
+}
+
+
+/**
+Returns class instance alignment.
+
+Example:
+---
+class A { byte b; }
+class B { long l; }
+
+// As class instancec always has a hidden pointer
+static assert(classInstanceAlignment!A == (void*).alignof);
+static assert(classInstanceAlignment!B == long.alignof);
+---
+ */
+template classInstanceAlignment(T) if(is(T == class))
+{
+    alias maxAlignment!(void*, typeof(T.tupleof)) classInstanceAlignment;
+}
+
+unittest
+{
+    class A { byte b; }
+    class B { long l; }
+
+    static assert(classInstanceAlignment!A == (void*).alignof);
+    static assert(classInstanceAlignment!B == long.alignof);
+}
+
+
 //::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::://
 // Type Conversion
 //::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::://

std/typecons.d

@@ -3069,7 +3069,7 @@ unittest
         {
             // _d_newclass now use default GC alignment (looks like (void*).sizeof * 2 for
             // small objects). We will just use the maximum of filed alignments.
-            alias maxAlignment!(void*, typeof(T.tupleof)) alignment;
+            alias classInstanceAlignment!T alignment;
 
             static size_t aligned(size_t n)
             {
@@ -3103,14 +3103,6 @@ unittest
     return result;
 }
 
-private template maxAlignment(U...) if(isTypeTuple!U)
-{
-    static if(U.length == 1)
-        enum maxAlignment = U[0].alignof;
-    else
-        enum maxAlignment = max(U[0].alignof, .maxAlignment!(U[1 .. $]));
-}
-
 unittest // Issue 6580 testcase
 {
     enum alignment = (void*).alignof;