fixes #3706

tests/metatype/tmodulo.nim

@@ -0,0 +1,20 @@
+discard """
+  output: '''1 mod 7'''
+"""
+
+# bug #3706
+
+type Modulo[M: static[int]] = distinct int
+
+proc modulo(a: int, M: static[int]): Modulo[M] = Modulo[M](a %% M)
+
+proc `+`[M: static[int]](a, b: Modulo[M]): Modulo[M] = (a.int + b.int).modulo(M)
+
+proc `$`*[M: static[int]](a: Modulo[M]): string = $(a.int) & " mod " & $(M)
+
+when isMainModule:
+  let
+    a = 3.modulo(7)
+    b = 5.modulo(7)
+  echo a + b
+