[spec] .tupleof can be used on a struct/class type (#3824)

Don't list it under 'instance properties'.
It gives a symbol sequence, which is an lvalue sequence when used on an
instance.
Add link to hidden fields.

Author: ntrel

spec/class.dd

@@ -164,6 +164,12 @@ void foo(B b)
 
 $(H2 $(LNAME2 class_properties, Class Properties))
 
+$(TABLE2 Class Properties,
+$(THEAD Property, Description)
+$(TROW $(RELATIVE_LINK2 tupleof, `.tupleof`),
+    Symbol sequence of fields in the class.)
+)
+
 $(TABLE2 Class Instance Properties,
 $(THEAD Property, Description)
 $(TROW $(DDSUBLINK spec/property, classinfo, $(D .classinfo)),
@@ -172,16 +178,19 @@ $(TROW $(RELATIVE_LINK2 outer-property, `.outer`), $(ARGS For
         a nested class instance, provides either the parent class instance,
         or the parent function's context pointer when there is no parent
         class.))
-$(TROW $(D .tupleof), See below.)
 )
 
 $(H3 $(LNAME2 tupleof, `.tupleof`))
 
-        $(P The $(D .tupleof) property is an
-        $(DDSUBLINK spec/template, lvalue-sequences, lvalue sequence)
-        of all the non-static fields in the class, excluding the hidden fields and
-        the fields in the base class.)
+        $(P The $(D .tupleof) property provides a symbol sequence
+        of all the non-static fields in the class, excluding the
+        $(RELATIVE_LINK2 hidden-fields, hidden fields) and
+        the fields in the base class.
+        When used on an instance, `.tupleof` gives an
+        $(DDSUBLINK spec/template, lvalue-sequences, lvalue sequence).)
+
         $(P The order of the fields in the tuple matches the order in which the fields are declared.)
+
         $(NOTE `.tupleof` is not available for `extern(Objective-C)` classes due to
         their fields having a dynamic offset.
         )

spec/struct.dd

@@ -599,20 +599,14 @@ assert(u.c == false); // no overlap
 ---
 )
 
-$(H2 $(LNAME2 struct_properties, Struct Properties))
+$(H2 $(LEGACY_LNAME2 struct_instance_properties, struct_properties, Struct Properties))
 
-$(TABLE2 Struct Type Properties,
+$(TABLE
 $(THEAD Name, Description)
 $(TROW $(D .alignof), Size boundary struct needs to be aligned on)
-)
-
-$(H3 $(LNAME2 struct_instance_properties, Struct Instance Properties))
-
-$(TABLE2 Struct Instance Properties,
-$(THEAD Name, Description)
-$(TROW $(D .tupleof), An $(DDSUBLINK spec/template, lvalue-sequences, lvalue sequence)
+$(TROW $(D .tupleof), A $(DDSUBLINK spec/template, variadic-templates, symbol sequence)
     of all struct fields - see
-    $(DDSUBLINK spec/class, tupleof, here) for a class-based example.)
+    $(DDSUBLINK spec/class, tupleof, class `.tupleof`) for more details.)
 )
 
 $(H3 $(LNAME2 struct_field_properties, Struct Field Properties))