fixes #2404

tests/concepts/mvarconcept.nim

@@ -0,0 +1,13 @@
+type RNG* = concept var rng
+  rng.randomUint32() is uint32
+
+type MersenneTwister* = object
+
+proc randomUint32*(self: var MersenneTwister): uint32 = 5
+
+proc randomInt*(rng: var RNG; max: Positive): Natural = 5
+
+var mersenneTwisterInst = MersenneTwister()
+
+proc randomInt*(max: Positive): Natural =
+  mersenneTwisterInst.randomInt(max)

tests/concepts/tvarconcept.nim

@@ -1,15 +1,9 @@
+discard """
+  output: "5"
+"""
 
-# bug #2346
+# bug #2346, bug #2404
 
-type RNG64 = concept var rng
-  rng.randomUint64() is uint64
+import mvarconcept
 
-proc randomInt*(rng: var RNG64; max: int): int = 4
-
-
-type MyRNG* = object
-
-proc randomUint64*(self: var MyRNG): uint64 = 4
-
-var r = MyRNG()
-echo r.randomInt(5)
+echo randomInt(5)