Use regex for cast to int validation.

core/variant.cpp

@@ -39,6 +39,9 @@
 #include "core/variant_parser.h"
 #include "scene/gui/control.h"
 #include "scene/main/node.h"
+#include "modules/regex/regex.h"
+
+RegEx number("^((-?\\d+)(\\.\\d+)?|true|false)$");
 
 String Variant::get_type_name(Variant::Type p_type) {
 	switch (p_type) {
@@ -605,21 +608,9 @@ bool Variant::can_convert(Type p_type_to) const {
 	// If this is a string variant and we are converting to an integer, check if the contents of the string
 	// make sense as an integer
 	if (type == Type::STRING && p_type_to == Type::INT) {
-		// Get a reference to the string
-		String s = operator String();
-
-		// Is the first character a numeral?
-		if (s.length() > 0 && s[0] >= '0' && s[0] <= '9') {
-			return true;
-		}
-
-		// Is the first character '-' and the second character a numeral?
-		if (s.length() > 1 && s[0] == '-' && s[1] >= '0' && s[1] <= '9') {
-			return true;
-		}
-
-		// The string cannot be converted to a valid integer
-		return false;
+		// Use regular expression to validate the string
+		Ref<RegExMatch> match = number.search(operator String());
+		return match != NULL;
 	}
 
 	// Do other type checks