Implement Display trait

bindgen/templates/ObjectTemplate.cs

@@ -57,6 +57,16 @@ public class {{ type_name }}: FFIObject<{{ safe_handle_type }}>, I{{ type_name }
     {% endmatch %}
     {% endfor %}
 
+    {%- for tm in obj.uniffi_traits() -%}
+    {%- match tm %}
+    {%- when UniffiTrait::Display { fmt } %}
+    public override string ToString() {
+        return {{ Type::String.borrow()|lift_fn }}({%- call cs::to_ffi_call_with_prefix("this.GetHandle()", fmt) %});
+    }
+    {%- else %}
+    {%- endmatch %}
+    {%- endfor %}
+
     {% if !obj.alternate_constructors().is_empty() -%}
     {% for cons in obj.alternate_constructors() -%}
     {%- call cs::docstring(cons, 4) %}

dotnet-tests/UniffiCS.binding_tests/TestTraitMethod.cs

@@ -0,0 +1,22 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+using uniffi.trait_methods;
+
+public class TestTraitMethods {
+    [Fact]
+    public void TraitMethodsWork() {
+        using (var methods = new TraitMethods("yo")) {
+            Assert.Equal("TraitMethods(yo)", methods.ToString());
+        }
+    }
+
+    [Fact]
+    public void TraitMethodsProcMacro() {
+        using (var methods = new ProcTraitMethods("yo")) {
+            Assert.Equal("ProcTraitMethods(yo)", methods.ToString());
+        }
+    }
+}
+

fixtures/Cargo.toml

@@ -23,3 +23,4 @@ uniffi-fixture-callbacks = { path = "../3rd-party/uniffi-rs/fixtures/callbacks"
 uniffi-fixture-coverall = { path = "../3rd-party/uniffi-rs/fixtures/coverall" }
 uniffi-fixture-docstring = { path = "../3rd-party/uniffi-rs/fixtures/docstring" }
 uniffi-fixture-time = { path = "../3rd-party/uniffi-rs/fixtures/uniffi-fixture-time" }
+uniffi-fixture-trait-methods = { path = "../3rd-party/uniffi-rs/fixtures/trait-methods" }

fixtures/src/lib.rs

@@ -15,6 +15,7 @@ mod uniffi_fixtures {
     uniffi_coverall::uniffi_reexport_scaffolding!();
     uniffi_fixture_callbacks::uniffi_reexport_scaffolding!();
     uniffi_fixture_docstring::uniffi_reexport_scaffolding!();
+    uniffi_trait_methods::uniffi_reexport_scaffolding!();
 
     global_methods_class_name::uniffi_reexport_scaffolding!();
     uniffi_cs_custom_types_builtin::uniffi_reexport_scaffolding!();