Merge branch 'topic/fix_interface_internal' into 'master'

Generic interface: ignore internal properties when looking for implementation.

Closes #909

See merge request eng/libadalang/langkit!1329

langkit/generic_interface.py

@@ -287,7 +287,8 @@ def find_implementations_of_method(
         )
         for m in class_members:
             if (
-                m.original_name not in implementations
+                not m.is_internal
+                and m.original_name not in implementations
                 and m.implements == method
             ):
                 implementations[m.original_name] = m

testsuite/tests/generic_interfaces/env_spec/foo.lkt

@@ -0,0 +1,25 @@
+# Defining an env spec in a class implementing an interface used to cause a
+# compilation error.
+
+import lexer_example
+
+grammar foo_grammar {
+    @main_rule main_rule <- BarNode("example")
+}
+
+@generic_interface()
+trait Interface {
+    fun method(): Bool
+}
+
+class FooNode implements Node[FooNode] {
+}
+
+class BarNode: FooNode implements Interface {
+    @exported
+    fun prop(): Bool implements Interface.method = true
+
+    env_spec {
+        add_env()
+    }
+}

testsuite/tests/generic_interfaces/env_spec/test.out

@@ -0,0 +1,4 @@
+== foo.lkt ==
+Code generation was successful
+
+lkt_compile: Done

testsuite/tests/generic_interfaces/env_spec/test.yaml

@@ -0,0 +1 @@
+driver: lkt_compile