Improved type system

src/errors/ParameterCountMismatch.go

@@ -0,0 +1,19 @@
+package errors
+
+import "fmt"
+
+// ParameterCountMismatch error is created when the number of parameters doesn't match the function prototype.
+type ParameterCountMismatch struct {
+	Function      string
+	Count         int
+	ExpectedCount int
+}
+
+// Error generates the string representation.
+func (err *ParameterCountMismatch) Error() string {
+	if err.Count > err.ExpectedCount {
+		return fmt.Sprintf("Too many parameters in '%s' function call", err.Function)
+	}
+
+	return fmt.Sprintf("Not enough parameters in '%s' function call", err.Function)
+}