support input strings longer than u16::MAX chars

src/main.rs

@@ -13,7 +13,40 @@ fn main() {
     );
 }
 
-fn string_with_fromcodepoint(s: &str) -> String {
+fn string_with_fromcodepoint(mut s: &str) -> String {
+    const ARG_LIMIT: usize = u16::MAX as usize - 3000; // without this 3000, it sometimes throws a call stack overflow error
+
+    if s.is_empty() {
+        return "[]+[]".to_owned();
+    }
+
+    let mut out = String::new();
+    loop {
+        if s.is_empty() {
+            break;
+        }
+
+        let split_point = if s.len() < ARG_LIMIT {
+            s.len()
+        } else {
+            let mut i = ARG_LIMIT;
+            loop {
+                if s.is_char_boundary(i) {
+                    break i;
+                }
+                i -= 1;
+            }
+        };
+
+        out.push_str(&short_string_with_fromcodepoint(&s[..split_point]));
+        out.push('+');
+        s = &s[split_point..];
+    }
+    out.pop(); // remove the last `+`
+    out
+}
+
+fn short_string_with_fromcodepoint(s: &str) -> String {
     let mut out = String::new();
     out.push_str(&function_constructor());
     out.push('(');