Fixes #2889. Merges *tostring tests in tests/system.

tests/system/toString.nim

@@ -1,9 +1,42 @@
 discard """
   output:'''@[23, 45]
-@[, foo, bar]'''
+@[, foo, bar]
+{a, b, c}
+2.3242
+2.982
+123912.1
+123912.1823
+5.0
+1e+100
+inf
+-inf
+nan
+nil
+nil'''
 """
 
 echo($(@[23, 45]))
 echo($(@["", "foo", "bar"]))
 #echo($(["", "foo", "bar"]))
 #echo($([23, 45]))
+
+# bug #2395
+
+let alphaSet: set[char] = {'a'..'c'}
+echo alphaSet
+
+echo($(2.3242))
+echo($(2.982))
+echo($(123912.1))
+echo($(123912.1823))
+echo($(5.0))
+echo($(1e100))
+echo($(1e1000000))
+echo($(-1e1000000))
+echo($(0.0/0.0))
+
+# nil tests
+var x: seq[string]
+var y: string
+echo(x)
+echo(y)