csharp: Implement Deconstruct for structs.

Summary:
Usage example:

```
var (x, y) = somePos2D;
```

Not available on Mono environment due to [`mcs` not implementing
it](a3de0304a1/mcs/mcs/tuples.cs (L590)).
To keep tests from breaking because of it, a `MONO` preprocessor variable is
defined and checked during test compilation.

Ref T8489.

Reviewers: brunobelo, lauromoura, segfaultxavi

Reviewed By: lauromoura

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Maniphest Tasks: T8489

Differential Revision: https://phab.enlightenment.org/D10809

src/bin/eolian_mono/eolian/mono/struct_definition.hh

@@ -463,6 +463,61 @@ struct struct_definition_generator
      return true;
   }
 
+  template <typename OutputIterator, typename Context>
+  bool generate_deconstruct_method(OutputIterator sink, attributes::struct_def const& struct_, Context const& context) const
+  {
+     auto const& indent = current_indentation(context);
+     auto struct_name = binding_struct_name(struct_);
+
+     if (!as_generator(
+         indent << scope_tab << "/// <summary>Unpacks " << struct_name << " into tuple.\n"
+         << indent << scope_tab << "/// <para>Since EFL 1.24.</para>\n"
+         << indent << scope_tab << "/// </summary>\n"
+         << indent << scope_tab << "public void Deconstruct(\n"
+         ).generate(sink, attributes::unused, context))
+       return false;
+
+     // parameters
+     {
+        auto i = 0u;
+        for (auto const& field : struct_.fields)
+          {
+             auto field_name = name_helpers::to_field_name(field.name);
+
+             auto suffix = i == struct_.fields.size() - 1 ? "\n" : ",\n";
+
+             if (!as_generator(
+                 indent << scope_tab << scope_tab << "out " << type << " " << field_name << suffix
+                 ).generate(sink, std::make_tuple(field.type), context))
+               return false;
+
+             ++i;
+          }
+     }
+
+     if (!as_generator(
+         indent << scope_tab << ")\n"
+         << indent << scope_tab << "{\n"
+         ).generate(sink, attributes::unused, context))
+       return false;
+
+     // assigments
+     for (auto const& field : struct_.fields)
+       {
+          auto field_name = name_helpers::to_field_name(field.name);
+
+          if (!as_generator(
+              indent << scope_tab << scope_tab << field_name << " = this." << field_name << ";\n"
+              ).generate(sink, attributes::unused, context))
+            return false;
+       }
+
+     // the end
+     return as_generator(
+             indent << scope_tab << "}\n"
+             ).generate(sink, attributes::unused, context);
+  }
+
   template <typename OutputIterator, typename Context>
   bool generate(OutputIterator sink, attributes::struct_def const& struct_, Context const& context) const
   {
@@ -537,6 +592,9 @@ struct struct_definition_generator
 
           if (!generate_implicit_operator(struct_, sink, context))
             return false;
+
+          if (!generate_deconstruct_method(sink, struct_, context))
+            return false;
        }
 
      std::string since_line;

src/bindings/mono/meson.build

@@ -199,12 +199,13 @@ if (get_option('dotnet'))
   )
 
 else
+  extra_cs_args += '-d:MONO'
 
   efl_mono = library('efl_mono',
       mono_generator_target + mono_files + [efl_src],
       install : true,
       install_dir : efl_mono_install_dir,
-      cs_args : extra_cs_args + ['-doc:' + efl_mono_xml_doc, '-warnaserror+']
+      cs_args : extra_cs_args + ['-doc:' + efl_mono_xml_doc, '-warnaserror+'],
   )
 
   meson.add_install_script(join_paths(meson.source_root(), 'meson', 'meson_csharp_docs.sh'),

src/tests/efl_mono/Structs.cs

@@ -419,6 +419,16 @@ internal class TestStructEquality
         Test.AssertNotEquals(a.GetHashCode(), c.GetHashCode());
         Test.AssertNotEquals(a.GetHashCode(), singleDifferentField.GetHashCode());
     }
+
+#if !MONO
+    public static void test_deconstruct() {
+        var p = new Eina.Position2D(1, 2);
+        var (x, y) = p;
+
+        Test.AssertEquals(x, 1);
+        Test.AssertEquals(y, 2);
+    }
+#endif
 }
 
 internal class TestStructTuples