fixes #3452

tests/concepts/tgraph.nim

@@ -0,0 +1,29 @@
+discard """
+  output: '''XY is Node
+MyGraph is Graph'''
+"""
+# bug #3452
+import math
+
+type
+    Node* = concept n
+        `==`(n, n) is bool
+
+    Graph* = concept g
+        var x: Node
+        distance(g, x, x) is float
+
+    XY* = tuple[x, y: int]
+
+    MyGraph* = object
+        points: seq[XY]
+
+if XY is Node:
+    echo "XY is Node"
+
+proc distance*( g: MyGraph, a, b: XY): float =
+    sqrt( pow(float(a.x - b.x), 2) + pow(float(a.y - b.y), 2) )
+
+if MyGraph is Graph:
+    echo "MyGraph is Graph"
+