From 58a6efcfe375a7be84cb792e2bf1d338de2e3ddf Mon Sep 17 00:00:00 2001
From: Synvoya <16019863+Synvoya@users.noreply.github.com>
Date: Sat, 4 Jul 2026 16:31:47 +1000
Subject: [PATCH] fix(kotlin): emit implements edge for interface delegation
 (`by`)

class Foo : Bar by baz produced no edge because the delegation_specifier loop only handled constructor_invocation and bare user_type children; the by form wraps user_type in an explicit_delegation node. Add that branch so the implements edge (and generic-arg recovery) fires.
---
 graphify/extract.py      | 11 +++++++++++
 tests/fixtures/sample.kt |  2 ++
 tests/test_languages.py  |  7 +++++++
 3 files changed, 20 insertions(+)

diff --git a/graphify/extract.py b/graphify/extract.py
index f1cb548d6..db1cebaaa 100644
--- a/graphify/extract.py
+++ b/graphify/extract.py
@@ -3648,6 +3648,17 @@ def _php_emit_base(base_name: str, rel: str, at_line: int) -> None:
                             if sub.type == "user_type":
                                 user_type_node = sub
                                 break
+                            # `class Foo : Bar by baz` wraps the delegated
+                            # interface `Bar` in an `explicit_delegation`
+                            # node; grab its first `user_type` descendant so
+                            # the implements edge (and generic-arg recovery)
+                            # still fire.
+                            if sub.type == "explicit_delegation":
+                                for inner in sub.children:
+                                    if inner.type == "user_type":
+                                        user_type_node = inner
+                                        break
+                                break
                         if user_type_node is None:
                             continue
                         base = _kotlin_user_type_name(user_type_node, source)
diff --git a/tests/fixtures/sample.kt b/tests/fixtures/sample.kt
index 5c4489c5d..db3f2810d 100644
--- a/tests/fixtures/sample.kt
+++ b/tests/fixtures/sample.kt
@@ -35,6 +35,8 @@ class DataProcessor : BaseProcessor(), Loggable {
     override fun log() {}
 }
 
+class LoggingList<T>(inner: MutableList<T>) : MutableList<T> by inner
+
 fun createClient(baseUrl: String): HttpClient {
     val config = Config(baseUrl, 30)
     return HttpClient(config)
diff --git a/tests/test_languages.py b/tests/test_languages.py
index ca5169d54..588b42a2f 100644
--- a/tests/test_languages.py
+++ b/tests/test_languages.py
@@ -623,6 +623,13 @@ def test_kotlin_splits_inherits_and_implements():
     assert ("DataProcessor", "Loggable") in _edge_labels(r, "implements")
 
 
+def test_kotlin_interface_delegation_emits_implements():
+    """`class Foo : Bar by baz` wraps the delegated interface in an
+    `explicit_delegation` node — it must still emit an implements edge."""
+    r = extract_kotlin(FIXTURES / "sample.kt")
+    assert ("LoggingList", "MutableList") in _edge_labels(r, "implements")
+
+
 def test_kotlin_parameter_return_generic_and_field_contexts():
     r = extract_kotlin(FIXTURES / "sample.kt")
     assert ("run", "DataProcessor") in _edge_labels(r, "references", "parameter_type")