csharp: Add implicit conversion from tuples to structs.

Summary:
Also generates implicit conversion for 1-field structs.
Usage examples:

```
// With tuples
Point2D p = (1, 2);
obj.SetPoint((1, 2));

// With 1-field structs
StringWrapper sw = "Must be handled by wrapper.";
```

Due to limitations of MSC compiler, implicit conversions are generated
only if struct has 4 fields or less.

Ref T8489.

Reviewers: brunobelo, cedric, lauromoura, segfaultxavi

Reviewed By: lauromoura

Subscribers: #reviewers, #committers

Tags: #efl

Maniphest Tasks: T8489

Differential Revision: https://phab.enlightenment.org/D10801

4 files changed, 146 insertions, 5 deletions

diff --git a/src/bin/eolian_mono/eolian/mono/struct_definition.hh b/src/bin/eolian_mono/eolian/mono/struct_definition.hh
index d83e91b591..03085335d1 100644
--- a/src/bin/eolian_mono/eolian/mono/struct_definition.hh
+++ b/src/bin/eolian_mono/eolian/mono/struct_definition.hh
@@ -403,6 +403,66 @@ struct struct_internal_definition_generator
 
 struct struct_definition_generator
 {
+  /**
+   * Generates an implicit operator for packing only if the struct has more
+   * than one attribute. Then operator will receive a tuple with the same of
+   * each attribute's type in the same order they were declared.
+   *
+   * Remarks: due to the MCS compiler's limitations, no operator is generated
+   * for structs with more than 4 fields.
+   */
+  template <typename OutputIterator, typename Context>
+  bool generate_implicit_operator(attributes::struct_def const& struct_
+                              , OutputIterator sink
+                              , Context const& context) const
+  {
+     if (struct_.fields.size() <= 1 || struct_.fields.size() > 4)
+       return true;
+
+     auto struct_name = binding_struct_name(struct_);
+     auto const& indent = current_indentation(context);
+
+     if (!as_generator(
+           indent << scope_tab << "/// <summary>Packs tuple into " << struct_name << " object.\n"
+           << indent << scope_tab << "///<para>Since EFL 1.24.</para>\n"
+           << indent << scope_tab << "///</summary>\n"
+        ).generate(sink, attributes::unused, context))
+       return false;
+
+     if (!as_generator(
+          indent << scope_tab << "public static implicit operator " << struct_name << "(\n"
+          << indent << scope_tab << scope_tab << "(\n"
+          << ((indent << scope_tab << scope_tab << " " << field_argument_decl) % ",\n") << "\n"
+          << indent << scope_tab << scope_tab << ") tuple)\n"
+          << indent << scope_tab << "{\n"
+        ).generate(sink, struct_.fields, context))
+       return false;
+
+     // object constructor
+     if (!as_generator(
+          indent << scope_tab << scope_tab << "return new " << struct_name << "{\n"
+        ).generate(sink, attributes::unused, context))
+       return false;
+
+     for (const auto& field: struct_.fields)
+       {
+          auto field_name = name_helpers::to_field_name(field.name);
+
+          if (!as_generator(
+               indent << scope_tab << scope_tab << scope_tab << field_name << " = tuple." << field_name << ",\n"
+             ).generate(sink, attributes::unused, context))
+            return false;
+       }
+
+     if (!as_generator(
+          indent << scope_tab << scope_tab << "};\n"
+          << indent << scope_tab << "}\n"
+        ).generate(sink, attributes::unused, context))
+       return false;
+
+     return true;
+  }
+
   template <typename OutputIterator, typename Context>
   bool generate(OutputIterator sink, attributes::struct_def const& struct_, Context const& context) const
   {
@@ -473,7 +533,10 @@ struct struct_definition_generator
                       << *(indent << scope_tab << scope_tab << field_argument_assignment << ";\n")
                       << indent << scope_tab << "}\n\n")
              .generate(sink, std::make_tuple(struct_.fields, struct_name, struct_.fields, struct_.fields), context))
-              return false;
+            return false;
+
+          if (!generate_implicit_operator(struct_, sink, context))
+            return false;
        }
 
      std::string since_line;
@@ -546,9 +609,9 @@ struct struct_definition_generator
               ).generate(sink, attributes::unused, context))
             return false;
        }
-     
-     
-     if (!as_generator(   
+
+
+     if (!as_generator(
              indent << scope_tab << scope_tab << ";\n"
              << indent << scope_tab << "}\n"
           ).generate(sink, attributes::unused, context))
diff --git a/src/bin/eolian_mono/eolian/mono/struct_fields.hh b/src/bin/eolian_mono/eolian/mono/struct_fields.hh
index b8bb0a231b..76e0f64138 100644
--- a/src/bin/eolian_mono/eolian/mono/struct_fields.hh
+++ b/src/bin/eolian_mono/eolian/mono/struct_fields.hh
@@ -28,6 +28,30 @@
 
 namespace eolian_mono {
 
+struct field_argument_name_generator
+{
+   template<typename OutputIterator, typename Context>
+   bool generate(OutputIterator sink, attributes::struct_field_def const& field, Context const& context) const
+   {
+       if (!as_generator(name_helpers::to_field_name(field.name))
+               .generate(sink, attributes::unused, context))
+           return false;
+       return true;
+   }
+} const field_argument_name {};
+
+struct field_argument_decl_generator
+{
+   template<typename OutputIterator, typename Context>
+   bool generate(OutputIterator sink, attributes::struct_field_def const& field, Context const& context) const
+   {
+       if (!as_generator(type << " " << string)
+               .generate(sink, std::make_tuple(field.type, name_helpers::to_field_name(field.name)), context))
+           return false;
+       return true;
+   }
+} const field_argument_decl {};
+
 struct field_argument_default_generator
 {
    template<typename OutputIterator, typename Context>
@@ -70,6 +94,16 @@ struct field_argument_docs_generator
 namespace efl { namespace eolian { namespace grammar {
 
 template<>
+struct is_eager_generator< ::eolian_mono::field_argument_name_generator> : std::true_type {};
+template<>
+struct is_generator< ::eolian_mono::field_argument_name_generator> : std::true_type {};
+
+template<>
+struct is_eager_generator< ::eolian_mono::field_argument_decl_generator> : std::true_type {};
+template<>
+struct is_generator< ::eolian_mono::field_argument_decl_generator> : std::true_type {};
+
+template<>
 struct is_eager_generator< ::eolian_mono::field_argument_default_generator> : std::true_type {};
 template<>
 struct is_generator< ::eolian_mono::field_argument_default_generator> : std::true_type {};
@@ -87,6 +121,12 @@ struct is_generator< ::eolian_mono::field_argument_docs_generator> : std::true_t
 namespace type_traits {
 
 template <>
+struct attributes_needed< ::eolian_mono::field_argument_name_generator> : std::integral_constant<int, 1> {};
+
+template <>
+struct attributes_needed< ::eolian_mono::field_argument_decl_generator> : std::integral_constant<int, 1> {};
+
+template <>
 struct attributes_needed< ::eolian_mono::field_argument_default_generator> : std::integral_constant<int, 1> {};
 
 template <>
diff --git a/src/lib/eolian_cxx/grammar/klass_def.hpp b/src/lib/eolian_cxx/grammar/klass_def.hpp
index d6969315e7..ad3b6eecbd 100644
--- a/src/lib/eolian_cxx/grammar/klass_def.hpp
+++ b/src/lib/eolian_cxx/grammar/klass_def.hpp
@@ -1816,7 +1816,7 @@ template <>
 struct is_tuple<attributes::parameter_def> : std::true_type {};
 template <>
 struct is_tuple<attributes::event_def> : std::true_type {};
-  
+
 }
 
 } } }
diff --git a/src/tests/efl_mono/Structs.cs b/src/tests/efl_mono/Structs.cs
index 60be42eea5..521d39ba35 100644
--- a/src/tests/efl_mono/Structs.cs
+++ b/src/tests/efl_mono/Structs.cs
@@ -421,4 +421,42 @@ internal class TestStructEquality
     }
 }
 
+internal class TestStructTuples
+{
+    private static Eina.Position2D simulate_position_usage(Eina.Position2D p) {
+        return p;
+    }
+
+    public static void test_same_type_fields_assign_conversion() {
+        Eina.Position2D p = (1, 2);
+        Test.AssertEquals(p.X, 1);
+        Test.AssertEquals(p.Y, 2);
+    }
+
+    public static void test_same_type_fields_call_conversion() {
+        var p = simulate_position_usage((1, 2));
+        Test.AssertEquals(p.X, 1);
+        Test.AssertEquals(p.Y, 2);
+    }
+
+    public static void test_different_type_fields_assign_conversion() {
+        Efl.Ui.FormatValue v = (1, "Format");
+        Test.AssertEquals(v.Value, 1);
+        Test.AssertEquals(v.Text, "Format");
+    }
+
+    public static void test_complex_fields_assign_conversion() {
+        var pos = new Eina.Position2D(1, 2);
+        var action = Efl.Ui.SelectionAction.Unknown;
+        var format = Efl.Ui.SelectionFormat.None;
+        var item = null as Efl.Canvas.Vg.Object;
+
+        Efl.Dnd.DragPos attr = (pos, action, format, item);
+        Test.AssertEquals(attr.Pos, pos);
+        Test.AssertEquals(attr.Action, action);
+        Test.AssertEquals(attr.Format, format);
+        Test.AssertEquals(attr.Item, item);
+    }
+}
+
 }