From 71402c3aa7a61fdacb82922d0811a9d705d284fc Mon Sep 17 00:00:00 2001
From: Ryan McConnell <rammcconnell@gmail.com>
Date: Wed, 27 Nov 2024 00:15:18 -0500
Subject: [PATCH] compsite typclass

---
 compiler/concepts.nim          |  3 ++-
 tests/concepts/tconceptsv2.nim | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/compiler/concepts.nim b/compiler/concepts.nim
index 8c52909fbbd8..b063a764fd00 100644
--- a/compiler/concepts.nim
+++ b/compiler/concepts.nim
@@ -187,7 +187,8 @@ proc matchType(c: PContext; f, a: PType; m: var MatchCon): bool =
       ak = last(a)
     result = matchType(c, last(f), ak, m)
   of tyCompositeTypeClass:
-    result = matchType(c, last(f), a, m)
+    var ak = if a.kind == tyCompositeTypeClass: a.last else: a
+    result = matchType(c, last(f), ak, m)
   of tyArray, tyTuple, tyVarargs, tyOpenArray, tyRange, tySequence, tyRef, tyPtr,
      tyGenericInst:
     # ^ XXX Rewrite this logic, it's more complex than it needs to be.
diff --git a/tests/concepts/tconceptsv2.nim b/tests/concepts/tconceptsv2.nim
index 5934ec439e49..178e58aac162 100644
--- a/tests/concepts/tconceptsv2.nim
+++ b/tests/concepts/tconceptsv2.nim
@@ -77,3 +77,17 @@ block:
   proc p(a: Buffer)=discard
   var buffer = ArrayBuffer[5]()
   p(buffer)
+
+block: # composite typeclass matching
+  type
+    A[T] = object
+    Buffer = concept
+      proc put(s: Self, i: A)
+    BufferImpl = object
+    WritableImpl = object
+
+  proc launch(a: var Buffer)=discard
+  proc put(x: BufferImpl, i: A)=discard
+
+  var a = BufferImpl()
+  launch(a)