diff --git a/compiler/bitsets.nim b/compiler/bitsets.nim
index 5454ef5e70dd..6afd1bd78071 100644
--- a/compiler/bitsets.nim
+++ b/compiler/bitsets.nim
@@ -28,6 +28,7 @@ proc bitSetExcl*(x: var TBitSet, elem: BiggestInt)
 proc bitSetIn*(x: TBitSet, e: BiggestInt): bool
 proc bitSetEquals*(x, y: TBitSet): bool
 proc bitSetContains*(x, y: TBitSet): bool
+proc bitSetCard*(x: TBitSet): BiggestInt
 # implementation
 
 proc bitSetIn(x: TBitSet, e: BiggestInt): bool =
@@ -69,3 +70,27 @@ proc bitSetContains(x, y: TBitSet): bool =
     if (x[i] and not y[i]) != int8(0):
       return false
   result = true
+
+# Number of set bits for all values of int8
+const populationCount: array[low(int8)..high(int8), int8] = [
+  1.int8, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 
+  4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, 
+  0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 
+  3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7
+]
+
+proc bitSetCard(x: TBitSet): BiggestInt =
+  for it in x:
+    result.inc populationCount[it]
diff --git a/compiler/nimsets.nim b/compiler/nimsets.nim
index bda753e85f16..8ec4d3c0dd5c 100644
--- a/compiler/nimsets.nim
+++ b/compiler/nimsets.nim
@@ -27,7 +27,7 @@ proc intersectSets*(a, b: PNode): PNode
 proc symdiffSets*(a, b: PNode): PNode
 proc containsSets*(a, b: PNode): bool
 proc equalSets*(a, b: PNode): bool
-proc cardSet*(s: PNode): BiggestInt
+proc cardSet*(a: PNode): BiggestInt
 # implementation
 
 proc inSet(s: PNode, elem: PNode): bool =
@@ -156,16 +156,10 @@ proc deduplicate*(a: PNode): PNode =
   toBitSet(a, x)
   result = toTreeSet(x, a.typ, a.info)
 
-proc cardSet(s: PNode): BiggestInt =
-  # here we can do better than converting it into a compact set
-  # we just count the elements directly
-  result = 0
-  for i in countup(0, sonsLen(s) - 1):
-    if s.sons[i].kind == nkRange:
-      result = result + getOrdValue(s.sons[i].sons[1]) -
-          getOrdValue(s.sons[i].sons[0]) + 1
-    else:
-      inc(result)
+proc cardSet(a: PNode): BiggestInt =
+  var x: TBitSet
+  toBitSet(a, x)
+  result = bitSetCard(x)
 
 proc setHasRange(s: PNode): bool =
   if s.kind != nkCurly:
diff --git a/tests/sets/tsets.nim b/tests/sets/tsets.nim
index 53a955af8cbd..96d5debc79b7 100644
--- a/tests/sets/tsets.nim
+++ b/tests/sets/tsets.nim
@@ -202,3 +202,7 @@ var
 #import compiler.msgs
 
 echo warnUninit in gNotes
+
+# 7555
+doAssert {-1.int8, -2, -2}.card == 2
+doAssert {1, 2, 2, 3..5, 4..6}.card == 6
\ No newline at end of file