Add hasElaborateCopyConstructor trait

Author: edi33416

src/dmd/id.d

@@ -428,6 +428,7 @@ immutable Msgtable[] msgtable =
     { "isZeroInit" },
     { "getTargetInfo" },
     { "getLocation" },
+    { "hasElaborateCopyConstructor" },
 
     // For C++ mangling
     { "allocator" },

src/dmd/traits.d

@@ -144,6 +144,7 @@ shared static this()
         "isZeroInit",
         "getTargetInfo",
         "getLocation",
+        "hasElaborateCopyConstructor"
     ];
 
     traitsStringTable._init(names.length);
@@ -596,7 +597,8 @@ Expression semanticTraits(TraitsExp e, Scope* sc)
                 sm => sm.isTemplateDeclaration() !is null) != 0;
         });
     }
-    if (e.ident == Id.isPOD)
+    if (e.ident == Id.isPOD ||
+        e.ident == Id.hasElaborateCopyConstructor)
     {
         if (dim != 1)
             return dimError(1);
@@ -613,7 +615,14 @@ Expression semanticTraits(TraitsExp e, Scope* sc)
         Type tb = t.baseElemOf();
         if (auto sd = tb.ty == Tstruct ? (cast(TypeStruct)tb).sym : null)
         {
-            return sd.isPOD() ? True() : False();
+            if (e.ident == Id.isPOD)
+            {
+                return sd.isPOD() ? True() : False();
+            }
+            else if (e.ident == Id.hasElaborateCopyConstructor)
+            {
+                return sd.hasCopyCtor ? True() : False();
+            }
         }
         return True();
     }

test/compilable/traits.d

@@ -86,3 +86,45 @@ struct Outer
 static assert(__traits(getLocation, Outer.Nested)[1] == 82);
 static assert(__traits(getLocation, Outer.method)[1] == 84);
 
+/******************************************/
+// https://issues.dlang.org/show_bug.cgi?id=19902
+// Define hasElaborateCopyConstructor trait
+
+struct S
+{
+    this (ref S rhs) {}
+}
+
+struct OuterS
+{
+    struct S
+    {
+        this (ref S rhs) {}
+    }
+}
+
+void foo(T)()
+{
+    struct S(U)
+    {
+        this (ref S rhs) {}
+    }
+    static assert (__traits(hasElaborateCopyConstructor, S!int));
+}
+
+struct U(T) {
+    this (ref U rhs) {}
+}
+
+struct SPostblit {
+    this(this) {}
+}
+
+static assert(__traits(hasElaborateCopyConstructor, S));
+static assert(__traits(hasElaborateCopyConstructor, OuterS.S));
+static assert(__traits(compiles, foo!int));
+static assert(__traits(compiles, foo!S));
+static assert(__traits(hasElaborateCopyConstructor, U!int));
+static assert(__traits(hasElaborateCopyConstructor, U!S));
+
+static assert(!__traits(hasElaborateCopyConstructor, SPostblit));