avm2: Allow any i32 in Value::Integer

core/src/avm2/activation.rs

@@ -1962,8 +1962,13 @@ impl<'a, 'gc> Activation<'a, 'gc> {
         let value1 = self.pop_stack();
 
         let sum_value = match (value1, value2) {
-            // note: with not-yet-guaranteed assumption that Integer < 1<<28, this won't overflow.
-            (Value::Integer(n1), Value::Integer(n2)) => (n1 + n2).into(),
+            (Value::Integer(n1), Value::Integer(n2)) => {
+                if let Some(res) = n1.checked_add(n2) {
+                    res.into()
+                } else {
+                    (n1 as f64 + n2 as f64).into()
+                }
+            }
             (Value::Number(n1), Value::Number(n2)) => (n1 + n2).into(),
             (Value::String(s), value2) => Value::String(AvmString::concat(
                 self.gc(),
@@ -2208,8 +2213,13 @@ impl<'a, 'gc> Activation<'a, 'gc> {
         let value1 = self.pop_stack();
 
         let sub_value: Value<'gc> = match (value1, value2) {
-            // note: with not-yet-guaranteed assumption that Integer < 1<<28, this won't underflow.
-            (Value::Integer(n1), Value::Integer(n2)) => (n1 - n2).into(),
+            (Value::Integer(n1), Value::Integer(n2)) => {
+                if let Some(res) = n1.checked_sub(n2) {
+                    res.into()
+                } else {
+                    (n1 as f64 - n2 as f64).into()
+                }
+            }
             (Value::Number(n1), Value::Number(n2)) => (n1 - n2).into(),
             _ => {
                 let value2 = value2.coerce_to_number(self)?;

core/src/avm2/value.rs

@@ -41,11 +41,15 @@ pub enum Value<'gc> {
     Undefined,
     Null,
     Bool(bool),
+
+    /// Numbers that are representable as ints are equivalent to
+    /// [`Value::Integer`]. See [`Value::normalize`] for details.
     Number(f64),
-    // note: this value should never reach +/- 1<<28; this is currently not enforced (TODO).
-    // Ruffle currently won't break if you break that invariant,
-    // but some FP compatibility edge cases depend on it, so we should do this at some point.
+
+    /// All integers are equivalent to [`Value::Number`].
+    /// See [`Value::normalize`] for details.
     Integer(i32),
+
     String(AvmString<'gc>),
     Object(Object<'gc>),
 }
@@ -118,18 +122,14 @@ impl From<u16> for Value<'_> {
 
 impl From<i32> for Value<'_> {
     fn from(value: i32) -> Self {
-        if fits_in_value_integer_i32(value) {
-            Value::Integer(value)
-        } else {
-            Value::Number(value as f64)
-        }
+        Value::Integer(value)
     }
 }
 
 impl From<u32> for Value<'_> {
     fn from(value: u32) -> Self {
-        if fits_in_value_integer_u32(value) {
-            Value::Integer(value as i32)
+        if let Some(value) = value.to_i32() {
+            Value::Integer(value)
         } else {
             Value::Number(value as f64)
         }
@@ -163,10 +163,6 @@ fn fits_in_value_integer_i32(value: i32) -> bool {
     value < (1 << 28) && value >= -(1 << 28)
 }
 
-fn fits_in_value_integer_u32(value: u32) -> bool {
-    value < (1 << 28)
-}
-
 /// Strips leading whitespace.
 fn skip_spaces(s: &mut &WStr) {
     *s = s.trim_start_matches(|c| {