Docs: Integers prootion to float documented.

Author: dylan-sutton-chavez

compiler/README.md

@@ -74,7 +74,7 @@ print(counter)
 
 ### Value Representation
 
-NaN-boxed 64-bit: integers are 48-bit signed ($\pm 2^{47}$), overflow promotes to float. Heap index is 28-bit ($2^{28}$ objects max, returns `MemoryError` beyond).
+NaN-boxed 64-bit: integers are 48-bit signed ($\pm 2^{47}$), overflow promotes to float (Gudeman, 1993). Results exceeding 48-bit range lose integer precision, consistent with Lua 5.3 and PHP 8. Heap index is 28-bit ($2^{28}$ objects max, returns `MemoryError` beyond).
 
 ### Building for WebAssembly
 

compiler/src/modules/parser/stmt.rs

@@ -318,6 +318,15 @@ impl<'src, I: Iterator<Item = Token>> Parser<'src, I> {
                     self.expr();
                     self.chunk.emit(OpCode::StoreItem, 0);
                     false
+                } else if self.peek().and_then(|tok| Self::augmented_op(&tok)).is_some() {
+                    let op = Self::augmented_op(&self.peek().unwrap()).unwrap();
+                    self.advance();
+                    self.chunk.emit(OpCode::Dup2, 0);
+                    self.chunk.emit(OpCode::GetItem, 0);
+                    self.expr();
+                    self.chunk.emit(op, 0);
+                    self.chunk.emit(OpCode::StoreItem, 0);
+                    false
                 } else {
                     self.chunk.emit(OpCode::GetItem, 0);
                     self.expr_tails();

compiler/src/modules/parser/types.rs

@@ -22,7 +22,7 @@ pub enum OpCode {
     BuildSlice, MakeClass, SetupExcept, PopExcept, Raise, Import, ImportFrom, BitAnd, BitOr, BitXor, 
     BitNot, Shl, Shr, In, NotIn, Is, IsNot, UnpackSequence, BuildTuple, SetupWith, ExitWith, Yield, 
     Del, Assert, Global, Nonlocal, UnpackArgs, ListComp, SetComp, DictComp, BuildSet, RaiseFrom, 
-    UnpackEx, LoadEllipsis, GenExpr, Await, MakeCoroutine, YieldFrom, TypeAlias, StoreItem
+    UnpackEx, LoadEllipsis, GenExpr, Await, MakeCoroutine, YieldFrom, TypeAlias, StoreItem, Dup2
 }
 
 /*

compiler/src/modules/vm/mod.rs

@@ -375,6 +375,12 @@ impl<'a> VM<'a> {
                     ip = target;
                 }
                 OpCode::PopTop => { self.pop()?; }
+                OpCode::Dup2 => {
+                    let b = self.pop()?;
+                    let a = self.pop()?;
+                    self.push(a); self.push(b);
+                    self.push(a); self.push(b);
+                }
                 OpCode::ReturnValue => {
                     let result = if self.stack.is_empty() { Val::none() } else { self.pop()? };
                     self.live_slots.truncate(slots_base);