MATCH_SELF

compiler/codegen/src/compile.rs

@@ -36,7 +36,7 @@ use rustpython_compiler_core::{
     Mode, OneIndexed, SourceFile, SourceLocation,
     bytecode::{
         self, Arg as OpArgMarker, BinaryOperator, CodeObject, ComparisonOperator, ConstantData,
-        Instruction, OpArg, OpArgType, TestOperator, UnpackExArgs,
+        Instruction, OpArg, OpArgType, UnpackExArgs,
     },
 };
 use rustpython_wtf8::Wtf8Buf;
@@ -3484,7 +3484,7 @@ impl Compiler {
 
         // Process each sub-pattern.
         for subpattern in patterns.iter().chain(kwd_patterns.iter()) {
-            // Decrement the on_top counter BEFORE processing each sub-pattern
+            // Decrement the on_top counter before processing each sub-pattern
             pc.on_top -= 1;
 
             // Check if this is a true wildcard (underscore pattern without name binding)
@@ -3557,6 +3557,7 @@ impl Compiler {
             // Check if the mapping has at least 'size' keys
             emit!(self, Instruction::GetLen);
             self.emit_load_const(ConstantData::Integer { value: size.into() });
+            // Stack: [subject, len, size]
             emit!(
                 self,
                 Instruction::CompareOperation {
@@ -3564,6 +3565,7 @@ impl Compiler {
                 }
             );
             self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse)?;
+            // Stack: [subject]
         }
 
         // Check for overflow (INT_MAX < size - 1)
@@ -3606,9 +3608,8 @@ impl Compiler {
 
                 self.compile_expression(key)?;
             }
-            // Stack: [subject, key1, key2, ..., keyn]
         }
-        // Stack: [subject] if size==0, or [subject, key1, ..., keyn] if size>0
+        // Stack: [subject, key1, key2, ..., key_n]
 
         // Build tuple of keys (empty tuple if size==0)
         emit!(self, Instruction::BuildTuple { size });
@@ -3628,7 +3629,7 @@ impl Compiler {
         emit!(
             self,
             Instruction::TestOperation {
-                op: TestOperator::IsNot
+                op: bytecode::TestOperator::IsNot
             }
         );
         // Stack: [subject, keys_tuple, values_tuple, bool]
@@ -3924,8 +3925,7 @@ impl Compiler {
             Singleton::False => ConstantData::Boolean { value: false },
             Singleton::True => ConstantData::Boolean { value: true },
         });
-        // Compare using the "Is" operator (identity check, not equality).
-        // This is important: False should not match 0, even though False == 0
+        // Compare using the "Is" operator.
         emit!(
             self,
             Instruction::TestOperation {

vm/src/builtins/bool.rs

@@ -109,7 +109,7 @@ impl Constructor for PyBool {
     }
 }
 
-#[pyclass(with(Constructor, AsNumber, Representable))]
+#[pyclass(with(Constructor, AsNumber, Representable), flags(_MATCH_SELF))]
 impl PyBool {
     #[pymethod]
     fn __format__(obj: PyObjectRef, spec: PyStrRef, vm: &VirtualMachine) -> PyResult<String> {

vm/src/builtins/bytearray.rs

@@ -170,7 +170,7 @@ impl PyByteArray {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(
         Py,
         PyRef,

vm/src/builtins/bytes.rs

@@ -132,7 +132,7 @@ impl PyRef<PyBytes> {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(
         Py,
         PyRef,

vm/src/builtins/dict.rs

@@ -176,7 +176,7 @@ impl PyDict {
         AsMapping,
         Representable
     ),
-    flags(BASETYPE, MAPPING)
+    flags(BASETYPE, MAPPING, _MATCH_SELF)
 )]
 impl PyDict {
     #[pyclassmethod]

vm/src/builtins/float.rs

@@ -201,7 +201,7 @@ fn float_from_string(val: PyObjectRef, vm: &VirtualMachine) -> PyResult<f64> {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(Comparable, Hashable, Constructor, AsNumber, Representable)
 )]
 impl PyFloat {

vm/src/builtins/int.rs

@@ -317,7 +317,7 @@ impl PyInt {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(PyRef, Comparable, Hashable, Constructor, AsNumber, Representable)
 )]
 impl PyInt {

vm/src/builtins/list.rs

@@ -109,7 +109,7 @@ pub type PyListRef = PyRef<PyList>;
         AsSequence,
         Representable
     ),
-    flags(BASETYPE, SEQUENCE)
+    flags(BASETYPE, SEQUENCE, _MATCH_SELF)
 )]
 impl PyList {
     #[pymethod]

vm/src/builtins/set.rs

@@ -529,7 +529,7 @@ fn reduce_set(
         AsNumber,
         Representable
     ),
-    flags(BASETYPE)
+    flags(BASETYPE, _MATCH_SELF)
 )]
 impl PySet {
     #[pymethod]
@@ -946,7 +946,7 @@ impl Constructor for PyFrozenSet {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(
         Constructor,
         AsSequence,

vm/src/builtins/str.rs

@@ -521,7 +521,7 @@ impl Py<PyStr> {
 }
 
 #[pyclass(
-    flags(BASETYPE),
+    flags(BASETYPE, _MATCH_SELF),
     with(
         PyRef,
         AsMapping,

vm/src/builtins/tuple.rs

@@ -244,7 +244,7 @@ impl<T> PyTuple<PyRef<T>> {
 }
 
 #[pyclass(
-    flags(BASETYPE, SEQUENCE),
+    flags(BASETYPE, SEQUENCE, _MATCH_SELF),
     with(
         AsMapping,
         AsSequence,

vm/src/frame.rs

@@ -702,19 +702,17 @@ impl ExecutingFrame<'_> {
             }
             bytecode::Instruction::Swap { index } => {
                 let len = self.state.stack.len();
-                if len == 0 {
-                    return Err(vm.new_runtime_error("stack underflow in SWAP".to_string()));
-                }
+                debug_assert!(len > 0, "stack underflow in SWAP");
                 let i = len - 1; // TOS index
                 let index_val = index.get(arg) as usize;
                 // CPython: SWAP(n) swaps TOS with PEEK(n) where PEEK(n) = stack_pointer[-n]
                 // This means swap TOS with the element at index (len - n)
-                if index_val > len {
-                    return Err(vm.new_runtime_error(format!(
-                        "SWAP index {} exceeds stack size {}",
-                        index_val, len
-                    )));
-                }
+                debug_assert!(
+                    index_val <= len,
+                    "SWAP index {} exceeds stack size {}",
+                    index_val,
+                    len
+                );
                 let j = len - index_val;
                 self.state.stack.swap(i, j);
                 Ok(None)
@@ -1433,17 +1431,9 @@ impl ExecutingFrame<'_> {
                             // No __match_args__, check if this is a type with MATCH_SELF behavior
                             // For built-in types like bool, int, str, list, tuple, dict, etc.
                             // they match the subject itself as the single positional argument
-                            let is_match_self_type = cls.is(vm.ctx.types.bool_type)
-                                || cls.is(vm.ctx.types.int_type)
-                                || cls.is(vm.ctx.types.float_type)
-                                || cls.is(vm.ctx.types.str_type)
-                                || cls.is(vm.ctx.types.bytes_type)
-                                || cls.is(vm.ctx.types.bytearray_type)
-                                || cls.is(vm.ctx.types.list_type)
-                                || cls.is(vm.ctx.types.tuple_type)
-                                || cls.is(vm.ctx.types.dict_type)
-                                || cls.is(vm.ctx.types.set_type)
-                                || cls.is(vm.ctx.types.frozenset_type);
+                            let is_match_self_type = cls
+                                .downcast::<PyType>()
+                                .is_ok_and(|t| t.slots.flags.contains(PyTypeFlags::_MATCH_SELF));
 
                             if is_match_self_type {
                                 if nargs_val == 1 {

vm/src/types/slot.rs

@@ -129,6 +129,10 @@ bitflags! {
         const HEAPTYPE = 1 << 9;
         const BASETYPE = 1 << 10;
         const METHOD_DESCRIPTOR = 1 << 17;
+        // For built-in types that match the subject itself in pattern matching
+        // (bool, int, float, str, bytes, bytearray, list, tuple, dict, set, frozenset)
+        // This is not a stable API
+        const _MATCH_SELF = 1 << 22;
         const HAS_DICT = 1 << 40;
 
         #[cfg(debug_assertions)]