RustPython · youknowone · Nov 10, 2025 · Nov 9, 2025 · Nov 9, 2025 · Nov 9, 2025
diff --git a/compiler/codegen/src/ir.rs b/compiler/codegen/src/ir.rs
@@ -4,8 +4,8 @@ use crate::{IndexMap, IndexSet, error::InternalError};
 use rustpython_compiler_core::{
     OneIndexed, SourceLocation,
     bytecode::{
-        CodeFlags, CodeObject, CodeUnit, ConstantData, InstrDisplayContext, Instruction, Label,
-        OpArg, PyCodeLocationInfoKind,
+        CodeFlags, CodeObject, CodeUnit, CodeUnits, ConstantData, InstrDisplayContext, Instruction,
+        Label, OpArg, PyCodeLocationInfoKind,
     },
 };
 
@@ -214,7 +214,7 @@ impl CodeInfo {
             qualname: qualname.unwrap_or(obj_name),
 
             max_stackdepth,
-            instructions: instructions.into_boxed_slice(),
+            instructions: CodeUnits::from(instructions),
             locations: locations.into_boxed_slice(),
             constants: constants.into_iter().collect(),
             names: name_cache.into_iter().collect(),

diff --git a/compiler/core/src/bytecode.rs b/compiler/core/src/bytecode.rs
@@ -1,13 +1,16 @@
 //! Implement python as a virtual machine with bytecode. This module
 //! implements bytecode structure.
 
-use crate::{OneIndexed, SourceLocation};
+use crate::{
+    marshal::MarshalError,
+    {OneIndexed, SourceLocation},
+};
 use bitflags::bitflags;
 use itertools::Itertools;
 use malachite_bigint::BigInt;
 use num_complex::Complex64;
 use rustpython_wtf8::{Wtf8, Wtf8Buf};
-use std::{collections::BTreeSet, fmt, hash, marker::PhantomData, mem};
+use std::{collections::BTreeSet, fmt, hash, marker::PhantomData, mem, ops::Deref};
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 #[repr(i8)]
@@ -195,7 +198,7 @@ impl ConstantBag for BasicBag {
 /// a code object. Also a module has a code object.
 #[derive(Clone)]
 pub struct CodeObject<C: Constant = ConstantData> {
-    pub instructions: Box<[CodeUnit]>,
+    pub instructions: CodeUnits,
     pub locations: Box<[SourceLocation]>,
     pub flags: CodeFlags,
     /// Number of positional-only arguments
@@ -257,6 +260,12 @@ impl OpArgByte {
     }
 }
 
+impl From<u8> for OpArgByte {
+    fn from(raw: u8) -> Self {
+        Self(raw)
+    }
+}
+
 impl fmt::Debug for OpArgByte {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.0.fmt(f)
@@ -808,14 +817,14 @@ impl From<Instruction> for u8 {
 }
 
 impl TryFrom<u8> for Instruction {
-    type Error = crate::marshal::MarshalError;
+    type Error = MarshalError;
 
     #[inline]
-    fn try_from(value: u8) -> Result<Self, crate::marshal::MarshalError> {
+    fn try_from(value: u8) -> Result<Self, MarshalError> {
         if value <= u8::from(LAST_INSTRUCTION) {
             Ok(unsafe { std::mem::transmute::<u8, Self>(value) })
         } else {
-            Err(crate::marshal::MarshalError::InvalidBytecode)
+            Err(MarshalError::InvalidBytecode)
         }
     }
 }
@@ -835,6 +844,58 @@ impl CodeUnit {
     }
 }
 
+impl TryFrom<&[u8]> for CodeUnit {
+    type Error = MarshalError;
+
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        match value.len() {
+            2 => Ok(Self::new(value[0].try_into()?, value[1].into())),
+            _ => Err(Self::Error::InvalidBytecode),
+        }
+    }
+}
+
+#[derive(Clone)]
+pub struct CodeUnits(Box<[CodeUnit]>);
+
+impl TryFrom<&[u8]> for CodeUnits {
+    type Error = MarshalError;
+
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        if !value.len().is_multiple_of(2) {
+            return Err(Self::Error::InvalidBytecode);
+        }
+
+        value.chunks_exact(2).map(CodeUnit::try_from).collect()
+    }
+}
+
+impl<const N: usize> From<[CodeUnit; N]> for CodeUnits {
+    fn from(value: [CodeUnit; N]) -> Self {
+        Self(Box::from(value))
+    }
+}
+
+impl From<Vec<CodeUnit>> for CodeUnits {
+    fn from(value: Vec<CodeUnit>) -> Self {
+        Self(value.into_boxed_slice())
+    }
+}
+
+impl FromIterator<CodeUnit> for CodeUnits {
+    fn from_iter<T: IntoIterator<Item = CodeUnit>>(iter: T) -> Self {
+        Self(iter.into_iter().collect())
+    }
+}
+
+impl Deref for CodeUnits {
+    type Target = [CodeUnit];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
 use self::Instruction::*;
 
 bitflags! {

diff --git a/compiler/core/src/marshal.rs b/compiler/core/src/marshal.rs
@@ -165,19 +165,6 @@ impl<'a> ReadBorrowed<'a> for &'a [u8] {
     }
 }
 
-/// Parses bytecode bytes into CodeUnit instructions.
-/// Each instruction is 2 bytes: opcode and argument.
-pub fn parse_instructions_from_bytes(bytes: &[u8]) -> Result<Box<[CodeUnit]>> {
-    bytes
-        .chunks_exact(2)
-        .map(|cu| {
-            let op = Instruction::try_from(cu[0])?;
-            let arg = OpArgByte(cu[1]);
-            Ok(CodeUnit { op, arg })
-        })
-        .collect()
-}
-
 pub struct Cursor<B> {
     pub data: B,
     pub position: usize,
@@ -197,8 +184,8 @@ pub fn deserialize_code<R: Read, Bag: ConstantBag>(
     bag: Bag,
 ) -> Result<CodeObject<Bag::Constant>> {
     let len = rdr.read_u32()?;
-    let instructions = rdr.read_slice(len * 2)?;
-    let instructions = parse_instructions_from_bytes(instructions)?;
+    let raw_instructions = rdr.read_slice(len * 2)?;
+    let instructions = CodeUnits::try_from(raw_instructions)?;
 
     let len = rdr.read_u32()?;
     let locations = (0..len)

diff --git a/vm/src/builtins/code.rs b/vm/src/builtins/code.rs
@@ -1,12 +1,10 @@
-/*! Infamous code object. The python class `code`
-
-*/
+//! Infamous code object. The python class `code`
 
 use super::{PyBytesRef, PyStrRef, PyTupleRef, PyType, PyTypeRef};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyResult, VirtualMachine,
     builtins::PyStrInterned,
-    bytecode::{self, AsBag, BorrowedConstant, CodeFlags, CodeUnit, Constant, ConstantBag},
+    bytecode::{self, AsBag, BorrowedConstant, CodeFlags, Constant, ConstantBag},
     class::{PyClassImpl, StaticType},
     convert::ToPyObject,
     frozen,
@@ -15,11 +13,7 @@ use crate::{
 };
 use malachite_bigint::BigInt;
 use num_traits::Zero;
-use rustpython_compiler_core::{
-    OneIndexed,
-    bytecode::PyCodeLocationInfoKind,
-    marshal::{MarshalError, parse_instructions_from_bytes},
-};
+use rustpython_compiler_core::{OneIndexed, bytecode::CodeUnits, bytecode::PyCodeLocationInfoKind};
 use std::{borrow::Borrow, fmt, ops::Deref};
 
 /// State for iterating through code address ranges
@@ -457,7 +451,7 @@ impl Constructor for PyCode {
 
         // Parse and validate bytecode from bytes
         let bytecode_bytes = args.co_code.as_bytes();
-        let instructions = parse_bytecode(bytecode_bytes)
+        let instructions = CodeUnits::try_from(bytecode_bytes)
             .map_err(|e| vm.new_value_error(format!("invalid bytecode: {}", e)))?;
 
         // Convert constants
@@ -925,7 +919,7 @@ impl PyCode {
         let instructions = match co_code {
             OptionalArg::Present(code_bytes) => {
                 // Parse and validate bytecode from bytes
-                parse_bytecode(code_bytes.as_bytes())
+                CodeUnits::try_from(code_bytes.as_bytes())
                     .map_err(|e| vm.new_value_error(format!("invalid bytecode: {}", e)))?
             }
             OptionalArg::Missing => self.code.instructions.clone(),
@@ -1033,19 +1027,6 @@ impl ToPyObject for bytecode::CodeObject {
     }
 }
 
-/// Validates and parses bytecode bytes into CodeUnit instructions.
-/// Returns MarshalError if bytecode is invalid (odd length or contains invalid opcodes).
-/// Note: Returning MarshalError is not necessary at this point because this is not a part of marshalling API.
-/// However, we (temporarily) reuse MarshalError for simplicity.
-fn parse_bytecode(bytecode_bytes: &[u8]) -> Result<Box<[CodeUnit]>, MarshalError> {
-    // Bytecode must have even length (each instruction is 2 bytes)
-    if !bytecode_bytes.len().is_multiple_of(2) {
-        return Err(MarshalError::InvalidBytecode);
-    }
-
-    parse_instructions_from_bytes(bytecode_bytes)
-}
-
 // Helper struct for reading linetable
 struct LineTableReader<'a> {
     data: &'a [u8],