Fix Issue 19415 - return non-copyable struct fails if member function…

… has return attribute

src/dmd/mtype.d

@@ -5506,7 +5506,9 @@ extern (C++) final class TypeStruct : Type
         // Probably should cache this information in sym rather than recompute
         StructDeclaration s = sym;
 
-        sym.size(Loc.initial); // give error for forward references
+        if (sym.members && !sym.determineFields() && sym.type != Type.terror)
+            error(sym.loc, "no size because of forward references");
+
         foreach (VarDeclaration v; s.fields)
         {
             if (v.storage_class & STC.ref_ || v.hasPointers())

test/compilable/test19145.d

@@ -0,0 +1,14 @@
+// https://issues.dlang.org/show_bug.cgi?id=19415
+
+struct S
+{
+   int x;
+   S foo() return { return S(x); }
+   this(this) @disable;
+}
+
+S bar()
+{
+   S s;
+   return s; // Error: struct `S` is not copyable because it is annotated with @disable
+}