Raise value error on large precision values for float, int __format__ (RustPython#3415)

Author: DimitrisJim

Lib/test/test_format.py

@@ -466,7 +466,8 @@ def test_optimisations(self):
         self.assertIs(text % (), text)
         self.assertIs(text.format(), text)
 
-    @unittest.skip("TODO: RUSTPYTHON, chews up RAM")
+    # TODO: RustPython missing complex.__format__ implementation
+    @unittest.expectedFailure
     def test_precision(self):
         f = 1.2
         self.assertEqual(format(f, ".0f"), "1")

vm/src/format.rs

@@ -204,8 +204,11 @@ fn parse_precision(text: &str) -> Result<(Option<usize>, &str), &'static str> {
     Ok(match chars.next() {
         Some('.') => {
             let (size, remaining) = parse_number(chars.as_str())?;
-            if size.is_some() {
-                (size, remaining)
+            if let Some(size) = size {
+                if size > i32::MAX as usize {
+                    return Err("Precision too big");
+                }
+                (Some(size), remaining)
             } else {
                 (None, text)
             }