Fix stringifying infinity (#2112)

Co-authored-by: ike709 <ike709@github.com>

Author: ike709

Content.Tests/DMProject/Broken Tests/Expression/Constants/numeral_inf.dm

@@ -0,0 +1,8 @@
+
+/proc/RunTest()
+	var/a = 1#INF
+	var/b = -1#INF
+	var/c = -1#IND
+	ASSERT("[a]" == "inf")
+	ASSERT("[b]" == "-inf")
+	ASSERT("[c]" == "nan")

Content.Tests/DMProject/Tests/Expression/Constants/stringify_inf.dm

@@ -362,6 +362,11 @@ public string Stringify() {
             case DreamValueType.Float:
                 var floatValue = MustGetValueAsFloat();
 
+                if (float.IsInfinity(floatValue)) {
+                    var str = float.IsPositiveInfinity(floatValue) ? "inf" : "-inf";
+                    return str;
+                }
+
                 if (floatValue > 16777216f) {
                     return floatValue.ToString("g6");
                 }
@@ -371,6 +376,8 @@ public string Stringify() {
                     return floatValue.ToString("g8");
                 }
 
+                if (float.IsNaN(floatValue)) return "nan";
+
                 return floatValue.ToString("g6");
 
             case DreamValueType.DreamResource: