gir: Fix assignable_to for interface implementations

Part of #29

blueprintcompiler/gir.py

@@ -257,9 +257,11 @@ class Class(GirNode, GirType):
             return True
         elif self.parent and self.parent.assignable_to(other):
             return True
-        elif other in self.implements:
-            return True
         else:
+            for iface in self.implements:
+                if self.get_containing(Namespace).lookup_type(iface).assignable_to(other):
+                    return True
+
             return False
 
 

tests/sample_errors/does_not_implement.blp

@@ -0,0 +1,7 @@
+using Gtk 4.0;
+
+Label label {}
+
+DropDown {
+  model: label;
+}

tests/sample_errors/does_not_implement.err

@@ -0,0 +1 @@
+6,10,5,Cannot assign Gtk.Label to Gio.ListModel

tests/samples/string_list.blp

@@ -1,8 +1,12 @@
 using Gtk 4.0;
 
-StringList {
+StringList greetings {
   strings [
     "Hello, world!",
     _("Hello!"),
   ]
 }
+
+Gtk.DropDown {
+  model: greetings;
+}

tests/samples/string_list.ui

@@ -1,10 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
   <requires lib="gtk" version="4.0"/>
-  <object class="GtkStringList">
+  <object class="GtkStringList" id="greetings">
     <items>
       <item>Hello, world!</item>
       <item translatable="true">Hello!</item>
     </items>
   </object>
+  <object class="GtkDropDown">
+    <property name="model">greetings</property>
+  </object>
 </interface>

tests/test_samples.py

@@ -144,6 +144,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample_error("class_assign")
         self.assert_sample_error("class_dne")
         self.assert_sample_error("consecutive_unexpected_tokens")
+        self.assert_sample_error("does_not_implement")
         self.assert_sample_error("duplicate_obj_id")
         self.assert_sample_error("enum_member_dne")
         self.assert_sample_error("filters_in_non_file_filter")