RustPython · ShaharNaveh · May 11, 2026 · May 11, 2026 · May 11, 2026 · May 11, 2026
diff --git a/Cargo.toml b/Cargo.toml
@@ -343,6 +343,13 @@ unnested_or_patterns = "warn"
 
 # pedantic lints to enforce gradually
 cloned_instead_of_copied = "warn"
+collapsible_else_if = "warn"
+comparison_chain = "warn"
+explicit_into_iter_loop = "warn"
+explicit_iter_loop = "warn"
+filter_map_next = "warn"
+flat_map_option = "warn"
+inconsistent_struct_constructor = "warn"
 manual_is_variant_and = "warn"
 map_unwrap_or = "warn"
 must_use_candidate = "warn"
diff --git a/crates/codegen/src/compile.rs b/crates/codegen/src/compile.rs
@@ -823,7 +823,7 @@ impl Compiler {
             }
         }
 
-        for elt in elts.iter() {
+        for elt in elts {
             if let ast::Expr::Starred(ast::ExprStarred { value, .. }) = elt {
                 // When we hit first star, build sequence with elements so far
                 if !sequence_built {
@@ -11509,7 +11509,7 @@ impl Compiler {
         let mut current_string = Wtf8Buf::new();
         let mut interp_count: u32 = 0;
 
-        for tstring in tstring_value.iter() {
+        for tstring in tstring_value {
             self.collect_tstring_strings(
                 tstring,
                 &mut all_strings,
@@ -11534,7 +11534,7 @@ impl Compiler {
             }
         );
 
-        for tstring in tstring_value.iter() {
+        for tstring in tstring_value {
             self.compile_tstring_interpolations(tstring)?;
         }
 

diff --git a/crates/codegen/src/ir.rs b/crates/codegen/src/ir.rs
@@ -529,7 +529,7 @@ impl CodeInfo {
 
         // Final DCE: truncate instructions after terminal ops in linearized blocks.
         // This catches dead code created by normalize_jumps after the initial DCE.
-        for block in blocks.iter_mut() {
+        for block in &mut blocks {
             if let Some(pos) = block
                 .instructions
                 .iter()
@@ -540,7 +540,7 @@ impl CodeInfo {
         }
 
         // Pre-compute cache_entries for real (non-pseudo) instructions
-        for block in blocks.iter_mut() {
+        for block in &mut blocks {
             for instr in &mut block.instructions {
                 if let AnyInstruction::Real(op) = instr.instr {
                     instr.cache_entries = op.cache_entries() as u32;
@@ -9430,7 +9430,7 @@ impl CodeInfo {
 
         // Fix up handler stack_depth in ExceptHandlerInfo using start_depths
         // computed above: depth = start_depth - 1 - preserve_lasti
-        for block in self.blocks.iter_mut() {
+        for block in &mut self.blocks {
             for ins in &mut block.instructions {
                 if let Some(ref mut handler) = ins.except_handler {
                     let h_start = start_depths[handler.handler_block.idx()];

diff --git a/crates/compiler-core/src/bytecode.rs b/crates/compiler-core/src/bytecode.rs
@@ -652,7 +652,7 @@ impl CodeUnits {
     /// Disable adaptive specialization by setting all counters to unreachable.
     /// Used for CPython-compiled bytecode where specialization may not be safe.
     pub fn disable_specialization(&self) {
-        for counter in self.adaptive_counters.iter() {
+        for counter in &self.adaptive_counters {
             counter.store(UNREACHABLE_BACKOFF, Ordering::Relaxed);
         }
     }

diff --git a/crates/compiler-core/src/marshal.rs b/crates/compiler-core/src/marshal.rs
@@ -928,13 +928,13 @@ pub fn serialize_code<W: Write, C: Constant>(buf: &mut W, code: &CodeObject<C>)
     let total_lp_count = code.varnames.len() + cell_only_names.len() + code.freevars.len();
     buf.write_u8(Type::Tuple as u8);
     write_len(buf, total_lp_count);
-    for n in code.varnames.iter() {
+    for n in &code.varnames {
         write_marshal_str(buf, n.as_ref());
     }
     for &n in &cell_only_names {
         write_marshal_str(buf, n);
     }
-    for n in code.freevars.iter() {
+    for n in &code.freevars {
         write_marshal_str(buf, n.as_ref());
     }
     // 10: co_localspluskinds — use the stored kinds directly

diff --git a/crates/stdlib/src/faulthandler.rs b/crates/stdlib/src/faulthandler.rs
@@ -609,7 +609,7 @@ mod decl {
         // Disable SIGSEGV handler for access violations to avoid double output
         if code == 0xC0000005 {
             unsafe {
-                for handler in FAULTHANDLER_HANDLERS.iter_mut() {
+                for handler in &mut FAULTHANDLER_HANDLERS {
                     if handler.signum == libc::SIGSEGV {
                         faulthandler_disable_fatal_handler(handler);
                         break;
@@ -632,7 +632,7 @@ mod decl {
         }
 
         unsafe {
-            for handler in FAULTHANDLER_HANDLERS.iter_mut() {
+            for handler in &mut FAULTHANDLER_HANDLERS {
                 if handler.enabled {
                     continue;
                 }
@@ -661,7 +661,7 @@ mod decl {
         }
 
         unsafe {
-            for handler in FAULTHANDLER_HANDLERS.iter_mut() {
+            for handler in &mut FAULTHANDLER_HANDLERS {
                 if handler.enabled {
                     continue;
                 }
@@ -700,7 +700,7 @@ mod decl {
         }
 
         unsafe {
-            for handler in FAULTHANDLER_HANDLERS.iter_mut() {
+            for handler in &mut FAULTHANDLER_HANDLERS {
                 faulthandler_disable_fatal_handler(handler);
             }
         }

diff --git a/crates/stdlib/src/ssl/cert.rs b/crates/stdlib/src/ssl/cert.rs
@@ -473,7 +473,7 @@ pub(super) fn cert_der_to_dict_helper(
         if let Some(ext) = ext_map.get(&OID_X509_EXT_CRL_DISTRIBUTION_POINTS)
             && let ParsedExtension::CRLDistributionPoints(cdp) = &ext.parsed_extension()
         {
-            for dp in cdp.points.iter() {
+            for dp in &cdp.points {
                 if let Some(dist_point) = &dp.distribution_point {
                     use x509_parser::extensions::DistributionPointName;
                     if let DistributionPointName::FullName(names) = dist_point {
@@ -583,7 +583,7 @@ pub(super) fn build_verified_chain(
         let issuer_name = last_cert.issuer();
         let mut found_issuer = false;
 
-        for ca_der in ca_certs_der.iter() {
+        for ca_der in ca_certs_der {
             let (_, ca_cert) = match X509Certificate::from_der(ca_der) {
                 Ok(parsed) => parsed,
                 Err(_) => continue,

diff --git a/crates/vm/src/builtins/namespace.rs b/crates/vm/src/builtins/namespace.rs
@@ -99,7 +99,7 @@ impl Initializer for PyNamespace {
             };
 
             // Validate keys are strings and set attributes
-            for (key, value) in dict.into_iter() {
+            for (key, value) in dict {
                 let key_str = key
                     .downcast_ref::<crate::builtins::PyStr>()
                     .ok_or_else(|| {

diff --git a/crates/vm/src/builtins/template.rs b/crates/vm/src/builtins/template.rs
@@ -55,7 +55,7 @@ impl Constructor for PyTemplate {
         let mut interpolations: Vec<PyObjectRef> = Vec::new();
         let mut last_was_str = false;
 
-        for item in args.args.iter() {
+        for item in &args.args {
             if let Ok(s) = item.clone().downcast::<PyStr>() {
                 if last_was_str {
                     // Concatenate adjacent strings

diff --git a/crates/vm/src/builtins/type.rs b/crates/vm/src/builtins/type.rs
@@ -824,7 +824,7 @@ impl PyType {
     pub(crate) fn init_slots(&self, ctx: &Context) {
         // Inherit slots from MRO (mro[0] is self, so skip it)
         let mro: Vec<_> = self.mro.read()[1..].to_vec();
-        for base in mro.iter() {
+        for base in &mro {
             self.inherit_slots(base);
         }
 
@@ -833,7 +833,7 @@ impl PyType {
         let mut slot_name_set = std::collections::HashSet::new();
 
         // mro[0] is self, so skip it; self.attributes is checked separately below
-        for cls in self.mro.read()[1..].iter() {
+        for cls in &self.mro.read()[1..] {
             for &name in cls.attributes.read().keys() {
                 if name.as_bytes().starts_with(b"__") && name.as_bytes().ends_with(b"__") {
                     slot_name_set.insert(name);

diff --git a/crates/vm/src/class.rs b/crates/vm/src/class.rs
@@ -16,7 +16,7 @@ use rustpython_common::static_cell;
 /// 1. Has a function set in the type's slots
 /// 2. Doesn't already have an attribute in the type's dict
 pub fn add_operators(class: &'static Py<PyType>, ctx: &Context) {
-    for def in SLOT_DEFS.iter() {
+    for def in SLOT_DEFS {
         // Skip __new__ - it has special handling
         if def.name == "__new__" {
             continue;

diff --git a/crates/vm/src/exception_group.rs b/crates/vm/src/exception_group.rs
@@ -405,7 +405,7 @@ pub(super) mod types {
         // If it's a tuple of types
         if let Some(tuple) = condition.downcast_ref::<PyTuple>() {
             let mut types = Vec::new();
-            for item in tuple.iter() {
+            for item in tuple {
                 let typ: PyTypeRef = item.clone().try_into_value(vm).map_err(|_| {
                     vm.new_type_error(
                         "expected a function, exception type or tuple of exception types",

diff --git a/crates/vm/src/frame.rs b/crates/vm/src/frame.rs
@@ -978,7 +978,7 @@ impl Frame {
                 // Non-merged cell: find the name by skipping merged cellvars
                 let mut found_name = None;
                 let mut skip = nonmerged_cell_idx;
-                for cv in code.cellvars.iter() {
+                for cv in &code.cellvars {
                     let is_merged = code.varnames.contains(cv);
                     if !is_merged {
                         if skip == 0 {

diff --git a/crates/vm/src/gc_state.rs b/crates/vm/src/gc_state.rs
@@ -699,7 +699,7 @@ impl GcState {
 
         if debug.contains(GcDebugFlags::SAVEALL) {
             let mut garbage_guard = self.garbage.lock();
-            for obj_ref in truly_dead.iter() {
+            for obj_ref in &truly_dead {
                 garbage_guard.push(obj_ref.clone());
             }
         }
@@ -708,7 +708,7 @@ impl GcState {
             // Break cycles by clearing references (tp_clear)
             // Use deferred drop context to prevent stack overflow.
             rustpython_common::refcount::with_deferred_drops(|| {
-                for obj_ref in truly_dead.iter() {
+                for obj_ref in &truly_dead {
                     if obj_ref.gc_has_clear() {
                         let edges = unsafe { obj_ref.gc_clear() };
                         drop(edges);

diff --git a/crates/vm/src/object/core.rs b/crates/vm/src/object/core.rs
@@ -1828,7 +1828,7 @@ impl PyObject {
             if let Some(dict_ref) = ext.dict.as_ref().and_then(|d| d.replace(None)) {
                 result.push(dict_ref.into());
             }
-            for slot in ext.slots.iter() {
+            for slot in &ext.slots {
                 if let Some(val) = slot.write().take() {
                     result.push(val);
                 }

diff --git a/crates/vm/src/stdlib/_ctypes.rs b/crates/vm/src/stdlib/_ctypes.rs
@@ -882,7 +882,7 @@ pub(crate) mod _ctypes {
             && let Ok(fields) = fields_attr.try_to_value::<Vec<PyObjectRef>>(vm)
         {
             let mut max_align = 1usize;
-            for field in fields.iter() {
+            for field in &fields {
                 if let Some(tuple) = field.downcast_ref::<crate::builtins::PyTuple>()
                     && let Some(field_type) = tuple.get(1)
                 {

diff --git a/crates/vm/src/stdlib/_ctypes/base.rs b/crates/vm/src/stdlib/_ctypes/base.rs
@@ -2540,7 +2540,7 @@ fn make_fields(
         return Err(vm.new_type_error("_fields_ must be a sequence"));
     };
 
-    for pair in fieldlist.iter() {
+    for pair in &fieldlist {
         let field_tuple = pair
             .downcast_ref::<PyTuple>()
             .ok_or_else(|| vm.new_type_error("_fields_ must contain tuples"))?;
@@ -2599,7 +2599,7 @@ pub(super) fn make_anon_fields(cls: &Py<PyType>, vm: &VirtualMachine) -> PyResul
         return Err(vm.new_type_error("_anonymous_ must be a sequence"));
     };
 
-    for fname_obj in anon_names.iter() {
+    for fname_obj in &anon_names {
         let fname = fname_obj
             .downcast_ref::<PyStr>()
             .ok_or_else(|| vm.new_type_error("_anonymous_ items must be strings"))?;

diff --git a/crates/vm/src/stdlib/_ctypes/structure.rs b/crates/vm/src/stdlib/_ctypes/structure.rs
@@ -16,7 +16,7 @@ pub(super) fn calculate_struct_size(cls: &Py<PyType>, vm: &VirtualMachine) -> Py
         let fields: Vec<PyObjectRef> = fields_attr.try_to_value(vm)?;
         let mut total_size = 0usize;
 
-        for field in fields.iter() {
+        for field in &fields {
             if let Some(tuple) = field.downcast_ref::<PyTuple>()
                 && let Some(field_type) = tuple.get(1)
             {
@@ -738,7 +738,7 @@ impl PyCStructure {
         if let Some(fields_attr) = type_obj.get_direct_attr(vm.ctx.intern_str("_fields_")) {
             let fields: Vec<PyObjectRef> = fields_attr.try_to_value(vm)?;
 
-            for field in fields.iter() {
+            for field in &fields {
                 if current_index >= args.len() {
                     break;
                 }
@@ -786,7 +786,7 @@ impl Initializer for PyCStructure {
         }
 
         // 2. Process keyword arguments
-        for (key, value) in args.kwargs.iter() {
+        for (key, value) in &args.kwargs {
             zelf.as_object()
                 .set_attr(vm.ctx.intern_str(key.as_str()), value.clone(), vm)?;
         }

diff --git a/crates/vm/src/stdlib/_ctypes/union.rs b/crates/vm/src/stdlib/_ctypes/union.rs
@@ -16,7 +16,7 @@ pub(super) fn calculate_union_size(cls: &Py<PyType>, vm: &VirtualMachine) -> PyR
         let fields: Vec<PyObjectRef> = fields_attr.try_to_value(vm)?;
         let mut max_size = 0usize;
 
-        for field in fields.iter() {
+        for field in &fields {
             if let Some(tuple) = field.downcast_ref::<PyTuple>()
                 && let Some(field_type) = tuple.get(1)
             {
@@ -609,7 +609,7 @@ impl PyCUnion {
         if let Some(fields_attr) = type_obj.get_direct_attr(vm.ctx.intern_str("_fields_")) {
             let fields: Vec<PyObjectRef> = fields_attr.try_to_value(vm)?;
 
-            for field in fields.iter() {
+            for field in &fields {
                 if current_index >= args.len() {
                     break;
                 }
@@ -656,7 +656,7 @@ impl Initializer for PyCUnion {
         }
 
         // 2. Process keyword arguments
-        for (key, value) in args.kwargs.iter() {
+        for (key, value) in &args.kwargs {
             zelf.as_object()
                 .set_attr(vm.ctx.intern_str(key.as_str()), value.clone(), vm)?;
         }

diff --git a/crates/vm/src/stdlib/_io.rs b/crates/vm/src/stdlib/_io.rs
@@ -4532,7 +4532,7 @@ mod _io {
                 let dict_ref: PyRef<PyDict> = dict.clone().try_into_value(vm)?;
                 if let Some(obj_dict) = zelf.as_object().dict() {
                     obj_dict.clear();
-                    for (key, value) in dict_ref.into_iter() {
+                    for (key, value) in dict_ref {
                         obj_dict.set_item(&*key, value, vm)?;
                     }
                 }
@@ -4774,7 +4774,7 @@ mod _io {
                 let dict_ref: PyRef<PyDict> = dict.clone().try_into_value(vm)?;
                 if let Some(obj_dict) = zelf.as_object().dict() {
                     obj_dict.clear();
-                    for (key, value) in dict_ref.into_iter() {
+                    for (key, value) in dict_ref {
                         obj_dict.set_item(&*key, value, vm)?;
                     }
                 }

diff --git a/crates/vm/src/stdlib/_typing.rs b/crates/vm/src/stdlib/_typing.rs
@@ -164,7 +164,7 @@ pub(crate) mod decl {
     fn typing_type_repr_value(value: &PyObjectRef, vm: &VirtualMachine) -> PyResult {
         if let Ok(tuple) = value.try_to_ref::<PyTuple>(vm) {
             let mut parts = Vec::with_capacity(tuple.len());
-            for item in tuple.iter() {
+            for item in tuple {
                 parts.push(typing_type_repr(item, vm)?);
             }
             let inner = if parts.len() == 1 {

diff --git a/crates/vm/src/stdlib/atexit.rs b/crates/vm/src/stdlib/atexit.rs
@@ -69,7 +69,7 @@ mod atexit {
     pub fn _run_exitfuncs(vm: &VirtualMachine) {
         let funcs: Vec<_> = core::mem::take(&mut *vm.state.atexit_funcs.lock());
         // Callbacks stored in LIFO order, iterate forward
-        for entry in funcs.into_iter() {
+        for entry in funcs {
             let (func, args) = *entry;
             if let Err(e) = func.call(args, vm) {
                 let exit = e.fast_isinstance(vm.ctx.exceptions.system_exit);

diff --git a/crates/vm/src/stdlib/gc.rs b/crates/vm/src/stdlib/gc.rs
@@ -133,7 +133,7 @@ mod gc {
         let stats = gc_state::gc_state().get_stats();
         let mut result = Vec::with_capacity(3);
 
-        for stat in stats.iter() {
+        for stat in &stats {
             let dict = vm.ctx.new_dict();
             dict.set_item("collections", vm.ctx.new_int(stat.collections).into(), vm)?;
             dict.set_item("collected", vm.ctx.new_int(stat.collected).into(), vm)?;

diff --git a/crates/vm/src/stdlib/marshal.rs b/crates/vm/src/stdlib/marshal.rs
@@ -293,7 +293,7 @@ mod decl {
             }
         } else if let Some(d) = obj.downcast_ref::<PyDict>() {
             buf.write_u8(b'{');
-            for (k, v) in d.into_iter() {
+            for (k, v) in d {
                 write_object_depth(buf, &k, refs, version, vm, depth - 1)?;
                 write_object_depth(buf, &v, refs, version, vm, depth - 1)?;
             }
@@ -572,7 +572,7 @@ mod decl {
                 check_no_code(&elem, vm)?;
             }
         } else if let Some(dict) = obj.downcast_ref::<PyDict>() {
-            for (k, v) in dict.into_iter() {
+            for (k, v) in dict {
                 check_no_code(&k, vm)?;
                 check_no_code(&v, vm)?;
             }

diff --git a/crates/vm/src/stdlib/nt.rs b/crates/vm/src/stdlib/nt.rs
@@ -1074,7 +1074,7 @@ pub(crate) mod module {
 
         // Build environment strings as "KEY=VALUE\0" wide strings
         let mut env_strings: Vec<widestring::WideCString> = Vec::new();
-        for (key, value) in env.into_iter() {
+        for (key, value) in env {
             let key = FsPath::try_from_path_like(key, true, vm)?;
             let value = FsPath::try_from_path_like(value, true, vm)?;
             let key_str = key.to_string_lossy();
@@ -1192,7 +1192,7 @@ pub(crate) mod module {
         let env = crate::stdlib::os::envobj_to_dict(env, vm)?;
         // Build environment strings as "KEY=VALUE\0" wide strings
         let mut env_strings: Vec<widestring::WideCString> = Vec::new();
-        for (key, value) in env.into_iter() {
+        for (key, value) in env {
             let key = PyStrRef::try_from_object(vm, key)?;
             let value = PyStrRef::try_from_object(vm, value)?;
             let key_str = key.expect_str();