Bump version to 0.0.35

.pre-commit-config.yaml

@@ -1,5 +1,5 @@
 repos:
   - repo: https://github.com/charliermarsh/ruff
-    rev: v0.0.32
+    rev: v0.0.35
     hooks:
       - id: lint

Cargo.lock

@@ -1744,7 +1744,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.32"
+version = "0.0.35"
 dependencies = [
  "anyhow",
  "bincode",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.32"
+version = "0.0.35"
 edition = "2021"
 
 [lib]

README.md

@@ -57,7 +57,7 @@ ruff also works with [Pre-Commit](https://pre-commit.com) (requires Cargo on sys
 ```yaml
 repos:
 - repo: https://github.com/charliermarsh/ruff
-  rev: v0.0.32
+  rev: v0.0.35
   hooks:
     - id: lint
 ```
@@ -86,7 +86,7 @@ ruff path/to/code/ --select F401 F403
 See `ruff --help` for more:
 
 ```shell
-ruff (v0.0.32)
+ruff (v0.0.35)
 An extremely fast Python linter.
 
 USAGE:
@@ -96,16 +96,17 @@ ARGS:
     <FILES>...
 
 OPTIONS:
-    -e, --exit-zero             Exit with status code "0", even upon detecting errors
-    -f, --fix                   Attempt to automatically fix lint errors
-    -h, --help                  Print help information
-        --ignore <IGNORE>...    Comma-separated list of error codes to ignore
-    -n, --no-cache              Disable cache reads
-    -q, --quiet                 Disable all logging (but still exit with status code "1" upon
-                                detecting errors)
-        --select <SELECT>...    Comma-separated list of error codes to enable
-    -v, --verbose               Enable verbose logging
-    -w, --watch                 Run in watch mode by re-running whenever files change
+    -e, --exit-zero               Exit with status code "0", even upon detecting errors
+        --exclude <EXCLUDE>...    List of file and/or directory patterns to exclude from checks
+    -f, --fix                     Attempt to automatically fix lint errors
+    -h, --help                    Print help information
+        --ignore <IGNORE>...      List of error codes to ignore
+    -n, --no-cache                Disable cache reads
+    -q, --quiet                   Disable all logging (but still exit with status code "1" upon
+                                  detecting errors)
+        --select <SELECT>...      List of error codes to enable
+    -v, --verbose                 Enable verbose logging
+    -w, --watch                   Run in watch mode by re-running whenever files change
 ```
 
 ### Compatibility with Black
@@ -123,7 +124,7 @@ ruff's goal is to achieve feature-parity with Flake8 when used (1) without any p
 stylistic checks; limiting to Python 3 obviates the need for certain compatibility checks.)
 
 Under those conditions, Flake8 implements about 58 rules, give or take. At time of writing, ruff
-implements 28 rules. (Note that these 28 rules likely cover a disproportionate share of errors:
+implements 33 rules. (Note that these 33 rules likely cover a disproportionate share of errors:
 unused imports, undefined variables, etc.)
 
 Of the unimplemented rules, ruff is missing:
@@ -152,9 +153,14 @@ Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis F
 | E713 | NotInTest | Test for membership should be `not in` |
 | E714 | NotIsTest | Test for object identity should be `is not` |
 | E731 | DoNotAssignLambda | Do not assign a lambda expression, use a def |
+| E741 | AmbiguousVariableName | ambiguous variable name '...' |
+| E742 | AmbiguousClassName | ambiguous class name '...' |
+| E743 | AmbiguousFunctionName | ambiguous function name '...' |
 | E902 | IOError | No such file or directory: `...` |
 | F401 | UnusedImport | `...` imported but unused |
 | F403 | ImportStarUsage | Unable to detect undefined names |
+| F404 | LateFutureImport | from __future__ imports must occur at the beginning of the file |
+| F407 | FutureFeatureNotDefined | future feature '...' is not defined |
 | F541 | FStringMissingPlaceholders | f-string without any placeholders |
 | F601 | MultiValueRepeatedKeyLiteral | Dictionary key literal repeated |
 | F602 | MultiValueRepeatedKeyVariable | Dictionary key `...` repeated |
@@ -206,7 +212,7 @@ git clone --branch 3.10 https://github.com/python/cpython.git resources/test/cpy
 Add this `pyproject.toml` to the CPython directory:
 
 ```toml
-[tool.linter]
+[tool.ruff]
 line-length = 88
 exclude = [
     "Lib/lib2to3/tests/data/bom.py",

examples/generate_rules_table.rs

@@ -3,14 +3,19 @@ use ruff::checks::{CheckKind, RejectedCmpop};
 
 fn main() {
     let mut check_kinds: Vec<CheckKind> = vec![
+        CheckKind::AmbiguousVariableName("...".to_string()),
+        CheckKind::AmbiguousClassName("...".to_string()),
+        CheckKind::AmbiguousFunctionName("...".to_string()),
         CheckKind::AssertTuple,
         CheckKind::DefaultExceptNotLast,
         CheckKind::DoNotAssignLambda,
         CheckKind::DuplicateArgumentName,
         CheckKind::FStringMissingPlaceholders,
+        CheckKind::FutureFeatureNotDefined("...".to_string()),
         CheckKind::IOError("...".to_string()),
         CheckKind::IfTuple,
         CheckKind::ImportStarUsage,
+        CheckKind::LateFutureImport,
         CheckKind::LineTooLong,
         CheckKind::ModuleImportNotAtTopOfFile,
         CheckKind::MultiValueRepeatedKeyLiteral,

resources/test/fixtures/E741.py

@@ -0,0 +1,72 @@
+from contextlib import contextmanager
+
+l = 0
+I = 0
+O = 0
+l: int = 0
+
+a, l = 0, 1
+[a, l] = 0, 1
+a, *l = 0, 1, 2
+a = l = 0
+
+o = 0
+i = 0
+
+for l in range(3):
+    pass
+
+
+for a, l in zip(range(3), range(3)):
+    pass
+
+
+def f1():
+    global l
+    l = 0
+
+
+def f2():
+    l = 0
+
+    def f3():
+        nonlocal l
+        l = 1
+
+    f3()
+    return l
+
+
+def f4(l, /, I):
+    return l, I, O
+
+
+def f5(l=0, *, I=1):
+    return l, I
+
+
+def f6(*l, **I):
+    return l, I
+
+
+@contextmanager
+def ctx1():
+    yield 0
+
+
+with ctx1() as l:
+    pass
+
+
+@contextmanager
+def ctx2():
+    yield 0, 1
+
+
+with ctx2() as (a, l):
+    pass
+
+try:
+    pass
+except ValueError as l:
+    pass

resources/test/fixtures/E742.py

@@ -0,0 +1,14 @@
+class l:
+    pass
+
+
+class I:
+    pass
+
+
+class O:
+    pass
+
+
+class X:
+    pass

resources/test/fixtures/E743.py

@@ -0,0 +1,15 @@
+def l():
+    pass
+
+
+def I():
+    pass
+
+
+class X:
+    def O(self):
+        pass
+
+
+def x():
+    pass

resources/test/fixtures/F404.py

@@ -0,0 +1,7 @@
+from __future__ import print_function
+"""Docstring"""
+from __future__ import absolute_import
+
+from collections import namedtuple
+
+from __future__ import print_function

resources/test/fixtures/F407.py

@@ -0,0 +1,2 @@
+from __future__ import print_function
+from __future__ import non_existent_feature

resources/test/fixtures/F841.py

@@ -14,3 +14,11 @@ def f():
     x = 1
     y = 2
     z = x + y
+
+
+def g():
+    foo = (1, 2)
+    (a, b) = (1, 2)
+
+    bar = (1, 2)
+    (c, d) = bar

resources/test/fixtures/pyproject.toml

@@ -9,9 +9,14 @@ select = [
     "E713",
     "E714",
     "E731",
+    "E741",
+    "E742",
+    "E743",
     "E902",
     "F401",
     "F403",
+    "F404",
+    "F407",
     "F541",
     "F601",
     "F602",

src/ast/checks.rs

@@ -93,6 +93,46 @@ pub fn check_do_not_assign_lambda(value: &Expr, location: Location) -> Option<Ch
     }
 }
 
+fn is_ambiguous_name(name: &str) -> bool {
+    name == "l" || name == "I" || name == "O"
+}
+
+/// Check AmbiguousVariableName compliance.
+pub fn check_ambiguous_variable_name(name: &str, location: Location) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousVariableName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check AmbiguousClassName compliance.
+pub fn check_ambiguous_class_name(name: &str, location: Location) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousClassName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check AmbiguousFunctionName compliance.
+pub fn check_ambiguous_function_name(name: &str, location: Location) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousFunctionName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
 /// Check UselessObjectInheritance compliance.
 pub fn check_useless_object_inheritance(
     stmt: &Stmt,

src/ast/operations.rs

@@ -66,6 +66,58 @@ pub fn extract_all_names(stmt: &Stmt, scope: &Scope) -> Vec<String> {
     names
 }
 
+/// Check if a node is parent of a conditional branch.
+pub fn on_conditional_branch(parent_stack: &[usize], parents: &[&Stmt]) -> bool {
+    for index in parent_stack.iter().rev() {
+        let parent = parents[*index];
+        if matches!(parent.node, StmtKind::If { .. })
+            || matches!(parent.node, StmtKind::While { .. })
+        {
+            return true;
+        }
+        if let StmtKind::Expr { value } = &parent.node {
+            if matches!(value.node, ExprKind::IfExp { .. }) {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+/// Check if a node is in a nested block.
+pub fn in_nested_block(parent_stack: &[usize], parents: &[&Stmt]) -> bool {
+    for index in parent_stack.iter().rev() {
+        let parent = parents[*index];
+        if matches!(parent.node, StmtKind::Try { .. })
+            || matches!(parent.node, StmtKind::If { .. })
+            || matches!(parent.node, StmtKind::With { .. })
+        {
+            return true;
+        }
+    }
+
+    false
+}
+
+/// Check if a node represents an unpacking assignment.
+pub fn is_unpacking_assignment(stmt: &Stmt) -> bool {
+    if let StmtKind::Assign { targets, value, .. } = &stmt.node {
+        for child in targets {
+            match &child.node {
+                ExprKind::Set { .. } | ExprKind::List { .. } | ExprKind::Tuple { .. } => {}
+                _ => return false,
+            }
+        }
+        match &value.node {
+            ExprKind::Set { .. } | ExprKind::List { .. } | ExprKind::Tuple { .. } => return false,
+            _ => {}
+        }
+        return true;
+    }
+    false
+}
+
 /// Struct used to efficiently slice source code at (row, column) Locations.
 pub struct SourceCodeLocator<'a> {
     content: &'a str,

src/ast/types.rs

@@ -35,8 +35,10 @@ impl Scope {
 
 #[derive(Clone, Debug)]
 pub enum BindingKind {
+    Annotation,
     Argument,
     Assignment,
+    Binding,
     Builtin,
     ClassDefinition,
     Definition,

src/check_ast.rs

@@ -1,3 +1,4 @@
+use std::ops::Deref;
 use std::path::Path;
 
 use rustpython_parser::ast::{
@@ -10,10 +11,11 @@ use crate::ast::operations::{extract_all_names, SourceCodeLocator};
 use crate::ast::relocate::relocate_expr;
 use crate::ast::types::{Binding, BindingKind, Scope, ScopeKind};
 use crate::ast::visitor::{walk_excepthandler, Visitor};
-use crate::ast::{checks, visitor};
+use crate::ast::{checks, operations, visitor};
 use crate::autofix::fixer;
 use crate::checks::{Check, CheckCode, CheckKind};
 use crate::python::builtins::{BUILTINS, MAGIC_GLOBALS};
+use crate::python::future::ALL_FEATURE_NAMES;
 use crate::python::typing;
 use crate::settings::Settings;
 
@@ -37,12 +39,14 @@ struct Checker<'a> {
     deferred_annotations: Vec<(Location, &'a str)>,
     deferred_functions: Vec<(&'a Stmt, Vec<usize>, Vec<usize>)>,
     deferred_lambdas: Vec<(&'a Expr, Vec<usize>, Vec<usize>)>,
+    deferred_assignments: Vec<usize>,
     // Derivative state.
     in_f_string: bool,
     in_annotation: bool,
     in_literal: bool,
     seen_non_import: bool,
     seen_docstring: bool,
+    futures_allowed: bool,
 }
 
 impl<'a> Checker<'a> {
@@ -66,11 +70,13 @@ impl<'a> Checker<'a> {
             deferred_annotations: vec![],
             deferred_functions: vec![],
             deferred_lambdas: vec![],
+            deferred_assignments: vec![],
             in_f_string: false,
             in_annotation: false,
             in_literal: false,
             seen_non_import: false,
             seen_docstring: false,
+            futures_allowed: true,
         }
     }
 }
@@ -98,6 +104,66 @@ where
     fn visit_stmt(&mut self, stmt: &'b Stmt) {
         self.push_parent(stmt);
 
+        // Track whether we've seen docstrings, non-imports, etc.
+        match &stmt.node {
+            StmtKind::ImportFrom { module, .. } => {
+                // Allow __future__ imports until we see a non-__future__ import.
+                if self.futures_allowed {
+                    if let Some(module) = module {
+                        if module != "__future__" {
+                            self.futures_allowed = false;
+                        }
+                    }
+                }
+            }
+            StmtKind::Import { .. } => {
+                self.futures_allowed = false;
+            }
+            StmtKind::Expr { value } => {
+                if self.seen_docstring
+                    && !self.seen_non_import
+                    && !operations::in_nested_block(&self.parent_stack, &self.parents)
+                {
+                    self.seen_non_import = true;
+                }
+
+                if !self.seen_docstring
+                    && !operations::in_nested_block(&self.parent_stack, &self.parents)
+                    && matches!(
+                        &value.node,
+                        ExprKind::Constant {
+                            value: Constant::Str(_),
+                            ..
+                        },
+                    )
+                {
+                    self.seen_docstring = true;
+                }
+
+                // Allow docstrings to interrupt __future__ imports.
+                if self.futures_allowed
+                    && !matches!(
+                        &value.node,
+                        ExprKind::Constant {
+                            value: Constant::Str(_),
+                            ..
+                        },
+                    )
+                {
+                    self.futures_allowed = false;
+                }
+            }
+            _ => {
+                self.futures_allowed = false;
+
+                if !self.seen_non_import
+                    && !operations::in_nested_block(&self.parent_stack, &self.parents)
+                {
+                    self.seen_non_import = true;
+                }
+            }
+        }
+
         // Pre-visit.
         match &stmt.node {
             StmtKind::Global { names } | StmtKind::Nonlocal { names } => {
@@ -121,6 +187,12 @@ where
                         }
                     }
                 }
+
+                if self.settings.select.contains(&CheckCode::E741) {
+                    self.checks.extend(names.iter().filter_map(|name| {
+                        checks::check_ambiguous_variable_name(name, stmt.location)
+                    }));
+                }
             }
             StmtKind::FunctionDef {
                 name,
@@ -136,6 +208,12 @@ where
                 args,
                 ..
             } => {
+                if self.settings.select.contains(&CheckCode::E743) {
+                    if let Some(check) = checks::check_ambiguous_function_name(name, stmt.location)
+                    {
+                        self.checks.push(check);
+                    }
+                }
                 for expr in decorator_list {
                     self.visit_expr(expr);
                 }
@@ -224,6 +302,12 @@ where
                     }
                 }
 
+                if self.settings.select.contains(&CheckCode::E742) {
+                    if let Some(check) = checks::check_ambiguous_class_name(name, stmt.location) {
+                        self.checks.push(check);
+                    }
+                }
+
                 for expr in bases {
                     self.visit_expr(expr)
                 }
@@ -320,6 +404,21 @@ where
                                 location: stmt.location,
                             },
                         );
+
+                        if self.settings.select.contains(&CheckCode::F407)
+                            && !ALL_FEATURE_NAMES.contains(&alias.node.name.deref())
+                        {
+                            self.checks.push(Check::new(
+                                CheckKind::FutureFeatureNotDefined(alias.node.name.to_string()),
+                                stmt.location,
+                            ));
+                        }
+
+                        if self.settings.select.contains(&CheckCode::F404) && !self.futures_allowed
+                        {
+                            self.checks
+                                .push(Check::new(CheckKind::LateFutureImport, stmt.location));
+                        }
                     } else if alias.node.name == "*" {
                         self.add_binding(
                             name,
@@ -357,7 +456,6 @@ where
                 }
             }
             StmtKind::AugAssign { target, .. } => {
-                self.seen_non_import = true;
                 self.handle_node_load(target);
             }
             StmtKind::If { test, .. } => {
@@ -368,7 +466,6 @@ where
                 }
             }
             StmtKind::Assert { test, .. } => {
-                self.seen_non_import = true;
                 if self.settings.select.contains(CheckKind::AssertTuple.code()) {
                     if let Some(check) = checks::check_assert_tuple(test, stmt.location) {
                         self.checks.push(check);
@@ -382,21 +479,7 @@ where
                     }
                 }
             }
-            StmtKind::Expr { value } => {
-                if !self.seen_docstring {
-                    if let ExprKind::Constant {
-                        value: Constant::Str(_),
-                        ..
-                    } = &value.node
-                    {
-                        self.seen_docstring = true;
-                    }
-                } else {
-                    self.seen_non_import = true;
-                }
-            }
             StmtKind::Assign { value, .. } => {
-                self.seen_non_import = true;
                 if self.settings.select.contains(&CheckCode::E731) {
                     if let Some(check) = checks::check_do_not_assign_lambda(value, stmt.location) {
                         self.checks.push(check);
@@ -404,7 +487,6 @@ where
                 }
             }
             StmtKind::AnnAssign { value, .. } => {
-                self.seen_non_import = true;
                 if self.settings.select.contains(&CheckCode::E731) {
                     if let Some(value) = value {
                         if let Some(check) =
@@ -415,9 +497,7 @@ where
                     }
                 }
             }
-            StmtKind::Delete { .. } => {
-                self.seen_non_import = true;
-            }
+            StmtKind::Delete { .. } => {}
             _ => {}
         }
 
@@ -473,7 +553,7 @@ where
                     self.in_literal = true;
                 }
             }
-            ExprKind::Tuple { elts, ctx } => {
+            ExprKind::Tuple { elts, ctx } | ExprKind::List { elts, ctx } => {
                 if matches!(ctx, ExprContext::Store) {
                     let check_too_many_expressions =
                         self.settings.select.contains(&CheckCode::F621);
@@ -489,12 +569,19 @@ where
                     }
                 }
             }
-            ExprKind::Name { ctx, .. } => match ctx {
+            ExprKind::Name { id, ctx } => match ctx {
                 ExprContext::Load => self.handle_node_load(expr),
                 ExprContext::Store => {
+                    if self.settings.select.contains(&CheckCode::E741) {
+                        if let Some(check) =
+                            checks::check_ambiguous_variable_name(id, expr.location)
+                        {
+                            self.checks.push(check);
+                        }
+                    }
                     let parent =
                         self.parents[*(self.parent_stack.last().expect("No parent found."))];
-                    self.handle_node_store(expr, Some(parent));
+                    self.handle_node_store(expr, parent);
                 }
                 ExprContext::Del => self.handle_node_delete(expr),
             },
@@ -728,6 +815,13 @@ where
         match &excepthandler.node {
             ExcepthandlerKind::ExceptHandler { name, .. } => match name {
                 Some(name) => {
+                    if self.settings.select.contains(&CheckCode::E741) {
+                        if let Some(check) =
+                            checks::check_ambiguous_variable_name(name, excepthandler.location)
+                        {
+                            self.checks.push(check);
+                        }
+                    }
                     let scope =
                         &self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
                     if scope.values.contains_key(name) {
@@ -741,7 +835,7 @@ where
                                     ctx: ExprContext::Store,
                                 },
                             ),
-                            Some(parent),
+                            parent,
                         );
                         self.parents.push(parent);
                     }
@@ -759,7 +853,7 @@ where
                                 ctx: ExprContext::Store,
                             },
                         ),
-                        Some(parent),
+                        parent,
                     );
                     self.parents.push(parent);
 
@@ -820,6 +914,13 @@ where
                 location: arg.location,
             },
         );
+
+        if self.settings.select.contains(&CheckCode::E741) {
+            if let Some(check) = checks::check_ambiguous_variable_name(&arg.node.arg, arg.location)
+            {
+                self.checks.push(check);
+            }
+        }
     }
 }
 
@@ -922,7 +1023,7 @@ impl<'a> Checker<'a> {
         }
     }
 
-    fn handle_node_store(&mut self, expr: &Expr, parent: Option<&Stmt>) {
+    fn handle_node_store(&mut self, expr: &Expr, parent: &Stmt) {
         if let ExprKind::Name { id, .. } = &expr.node {
             let current =
                 &self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
@@ -952,40 +1053,69 @@ impl<'a> Checker<'a> {
                 }
             }
 
-            // TODO(charlie): Handle alternate binding types (like `Annotation`).
-            if id == "__all__"
-                && matches!(current.kind, ScopeKind::Module)
-                && parent
-                    .map(|stmt| {
-                        matches!(stmt.node, StmtKind::Assign { .. })
-                            || matches!(stmt.node, StmtKind::AugAssign { .. })
-                            || matches!(stmt.node, StmtKind::AnnAssign { .. })
-                    })
-                    .unwrap_or_default()
+            if matches!(parent.node, StmtKind::AnnAssign { value: None, .. }) {
+                self.add_binding(
+                    id.to_string(),
+                    Binding {
+                        kind: BindingKind::Annotation,
+                        used: None,
+                        location: expr.location,
+                    },
+                );
+                return;
+            }
+
+            // TODO(charlie): Include comprehensions here.
+            if matches!(parent.node, StmtKind::For { .. })
+                || matches!(parent.node, StmtKind::AsyncFor { .. })
+                || operations::is_unpacking_assignment(parent)
             {
                 self.add_binding(
                     id.to_string(),
                     Binding {
-                        kind: BindingKind::Export(extract_all_names(parent.unwrap(), current)),
+                        kind: BindingKind::Binding,
                         used: None,
                         location: expr.location,
                     },
                 );
-            } else {
+                return;
+            }
+
+            if id == "__all__"
+                && matches!(current.kind, ScopeKind::Module)
+                && (matches!(parent.node, StmtKind::Assign { .. })
+                    || matches!(parent.node, StmtKind::AugAssign { .. })
+                    || matches!(parent.node, StmtKind::AnnAssign { .. }))
+            {
                 self.add_binding(
                     id.to_string(),
                     Binding {
-                        kind: BindingKind::Assignment,
+                        kind: BindingKind::Export(extract_all_names(parent, current)),
                         used: None,
                         location: expr.location,
                     },
                 );
+                return;
             }
+
+            self.add_binding(
+                id.to_string(),
+                Binding {
+                    kind: BindingKind::Assignment,
+                    used: None,
+                    location: expr.location,
+                },
+            );
         }
     }
 
     fn handle_node_delete(&mut self, expr: &Expr) {
         if let ExprKind::Name { id, .. } = &expr.node {
+            // Check if we're on a conditional branch.
+            if operations::on_conditional_branch(&self.parent_stack, &self.parents) {
+                return;
+            }
+
             let scope =
                 &mut self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
             if scope.values.remove(id).is_none() && self.settings.select.contains(&CheckCode::F821)
@@ -1033,11 +1163,8 @@ impl<'a> Checker<'a> {
                 _ => {}
             }
 
-            if self.settings.select.contains(&CheckCode::F841) {
-                let scope =
-                    &self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
-                self.checks.extend(checks::check_unused_variables(scope));
-            }
+            self.deferred_assignments
+                .push(*self.scope_stack.last().expect("No current scope found."));
 
             self.pop_scope();
         }
@@ -1056,16 +1183,23 @@ impl<'a> Checker<'a> {
                 self.visit_expr(body);
             }
 
-            if self.settings.select.contains(&CheckCode::F841) {
-                let scope =
-                    &self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
-                self.checks.extend(checks::check_unused_variables(scope));
-            }
+            self.deferred_assignments
+                .push(*self.scope_stack.last().expect("No current scope found."));
 
             self.pop_scope();
         }
     }
 
+    fn check_deferred_assignments(&mut self) {
+        while !self.deferred_assignments.is_empty() {
+            let index = self.deferred_assignments.pop().unwrap();
+            if self.settings.select.contains(&CheckCode::F841) {
+                self.checks
+                    .extend(checks::check_unused_variables(&self.scopes[index]));
+            }
+        }
+    }
+
     fn check_dead_scopes(&mut self) {
         if !self.settings.select.contains(&CheckCode::F822)
             && !self.settings.select.contains(&CheckCode::F401)
@@ -1143,6 +1277,7 @@ pub fn check_ast(
     // Check any deferred statements.
     checker.check_deferred_functions();
     checker.check_deferred_lambdas();
+    checker.check_deferred_assignments();
     let mut allocator = vec![];
     checker.check_deferred_annotations(path, &mut allocator);
 

src/checks.rs

@@ -15,9 +15,14 @@ pub enum CheckCode {
     E713,
     E714,
     E731,
+    E741,
+    E742,
+    E743,
     E902,
     F401,
     F403,
+    F404,
+    F407,
     F541,
     F601,
     F602,
@@ -50,9 +55,14 @@ impl FromStr for CheckCode {
             "E713" => Ok(CheckCode::E713),
             "E714" => Ok(CheckCode::E714),
             "E731" => Ok(CheckCode::E731),
+            "E741" => Ok(CheckCode::E741),
+            "E742" => Ok(CheckCode::E742),
+            "E743" => Ok(CheckCode::E743),
             "E902" => Ok(CheckCode::E902),
             "F401" => Ok(CheckCode::F401),
             "F403" => Ok(CheckCode::F403),
+            "F404" => Ok(CheckCode::F404),
+            "F407" => Ok(CheckCode::F407),
             "F541" => Ok(CheckCode::F541),
             "F601" => Ok(CheckCode::F601),
             "F602" => Ok(CheckCode::F602),
@@ -86,9 +96,14 @@ impl CheckCode {
             CheckCode::E713 => "E713",
             CheckCode::E714 => "E714",
             CheckCode::E731 => "E731",
+            CheckCode::E741 => "E741",
+            CheckCode::E742 => "E742",
+            CheckCode::E743 => "E743",
             CheckCode::E902 => "E902",
             CheckCode::F401 => "F401",
             CheckCode::F403 => "F403",
+            CheckCode::F404 => "F404",
+            CheckCode::F407 => "F407",
             CheckCode::F541 => "F541",
             CheckCode::F601 => "F601",
             CheckCode::F602 => "F602",
@@ -120,9 +135,14 @@ impl CheckCode {
             CheckCode::E713 => &LintSource::AST,
             CheckCode::E714 => &LintSource::AST,
             CheckCode::E731 => &LintSource::AST,
+            CheckCode::E741 => &LintSource::AST,
+            CheckCode::E742 => &LintSource::AST,
+            CheckCode::E743 => &LintSource::AST,
             CheckCode::E902 => &LintSource::FileSystem,
             CheckCode::F401 => &LintSource::AST,
             CheckCode::F403 => &LintSource::AST,
+            CheckCode::F404 => &LintSource::AST,
+            CheckCode::F407 => &LintSource::AST,
             CheckCode::F541 => &LintSource::AST,
             CheckCode::F601 => &LintSource::AST,
             CheckCode::F602 => &LintSource::AST,
@@ -161,13 +181,18 @@ pub enum RejectedCmpop {
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub enum CheckKind {
     AssertTuple,
+    AmbiguousVariableName(String),
+    AmbiguousClassName(String),
+    AmbiguousFunctionName(String),
     DefaultExceptNotLast,
     DoNotAssignLambda,
     DuplicateArgumentName,
     FStringMissingPlaceholders,
+    FutureFeatureNotDefined(String),
     IOError(String),
     IfTuple,
     ImportStarUsage,
+    LateFutureImport,
     LineTooLong,
     ModuleImportNotAtTopOfFile,
     MultiValueRepeatedKeyLiteral,
@@ -195,12 +220,17 @@ impl CheckKind {
     pub fn name(&self) -> &'static str {
         match self {
             CheckKind::AssertTuple => "AssertTuple",
+            CheckKind::AmbiguousVariableName(_) => "AmbiguousVariableName",
+            CheckKind::AmbiguousClassName(_) => "AmbiguousClassName",
+            CheckKind::AmbiguousFunctionName(_) => "AmbiguousFunctionName",
             CheckKind::DefaultExceptNotLast => "DefaultExceptNotLast",
             CheckKind::DuplicateArgumentName => "DuplicateArgumentName",
             CheckKind::FStringMissingPlaceholders => "FStringMissingPlaceholders",
+            CheckKind::FutureFeatureNotDefined(_) => "FutureFeatureNotDefined",
             CheckKind::IOError(_) => "IOError",
             CheckKind::IfTuple => "IfTuple",
             CheckKind::ImportStarUsage => "ImportStarUsage",
+            CheckKind::LateFutureImport => "LateFutureImport",
             CheckKind::LineTooLong => "LineTooLong",
             CheckKind::DoNotAssignLambda => "DoNotAssignLambda",
             CheckKind::ModuleImportNotAtTopOfFile => "ModuleImportNotAtTopOfFile",
@@ -234,11 +264,16 @@ impl CheckKind {
             CheckKind::DefaultExceptNotLast => &CheckCode::F707,
             CheckKind::DuplicateArgumentName => &CheckCode::F831,
             CheckKind::FStringMissingPlaceholders => &CheckCode::F541,
+            CheckKind::FutureFeatureNotDefined(_) => &CheckCode::F407,
             CheckKind::IOError(_) => &CheckCode::E902,
             CheckKind::IfTuple => &CheckCode::F634,
             CheckKind::ImportStarUsage => &CheckCode::F403,
+            CheckKind::LateFutureImport => &CheckCode::F404,
             CheckKind::LineTooLong => &CheckCode::E501,
             CheckKind::DoNotAssignLambda => &CheckCode::E731,
+            CheckKind::AmbiguousVariableName(_) => &CheckCode::E741,
+            CheckKind::AmbiguousClassName(_) => &CheckCode::E742,
+            CheckKind::AmbiguousFunctionName(_) => &CheckCode::E743,
             CheckKind::ModuleImportNotAtTopOfFile => &CheckCode::E402,
             CheckKind::MultiValueRepeatedKeyLiteral => &CheckCode::F601,
             CheckKind::MultiValueRepeatedKeyVariable(_) => &CheckCode::F602,
@@ -276,15 +311,30 @@ impl CheckKind {
             CheckKind::FStringMissingPlaceholders => {
                 "f-string without any placeholders".to_string()
             }
+            CheckKind::FutureFeatureNotDefined(name) => {
+                format!("future feature '{name}' is not defined")
+            }
             CheckKind::IOError(name) => {
                 format!("No such file or directory: `{name}`")
             }
             CheckKind::IfTuple => "If test is a tuple, which is always `True`".to_string(),
             CheckKind::ImportStarUsage => "Unable to detect undefined names".to_string(),
+            CheckKind::LateFutureImport => {
+                "from __future__ imports must occur at the beginning of the file".to_string()
+            }
             CheckKind::LineTooLong => "Line too long".to_string(),
             CheckKind::DoNotAssignLambda => {
                 "Do not assign a lambda expression, use a def".to_string()
             }
+            CheckKind::AmbiguousClassName(name) => {
+                format!("ambiguous class name '{}'", name)
+            }
+            CheckKind::AmbiguousFunctionName(name) => {
+                format!("ambiguous function name '{}'", name)
+            }
+            CheckKind::AmbiguousVariableName(name) => {
+                format!("ambiguous variable name '{}'", name)
+            }
             CheckKind::ModuleImportNotAtTopOfFile => {
                 "Module level import not at top of file".to_string()
             }
@@ -358,22 +408,27 @@ impl CheckKind {
     /// Whether the check kind is (potentially) fixable.
     pub fn fixable(&self) -> bool {
         match self {
+            CheckKind::AmbiguousClassName(_) => true,
+            CheckKind::AmbiguousFunctionName(_) => true,
+            CheckKind::AmbiguousVariableName(_) => false,
             CheckKind::AssertTuple => false,
             CheckKind::DefaultExceptNotLast => false,
+            CheckKind::DoNotAssignLambda => false,
             CheckKind::DuplicateArgumentName => false,
             CheckKind::FStringMissingPlaceholders => false,
+            CheckKind::FutureFeatureNotDefined(_) => false,
             CheckKind::IOError(_) => false,
             CheckKind::IfTuple => false,
             CheckKind::ImportStarUsage => false,
-            CheckKind::DoNotAssignLambda => false,
+            CheckKind::LateFutureImport => false,
             CheckKind::LineTooLong => false,
             CheckKind::ModuleImportNotAtTopOfFile => false,
             CheckKind::MultiValueRepeatedKeyLiteral => false,
             CheckKind::MultiValueRepeatedKeyVariable(_) => false,
             CheckKind::NoAssertEquals => true,
+            CheckKind::NoneComparison(_) => false,
             CheckKind::NotInTest => false,
             CheckKind::NotIsTest => false,
-            CheckKind::NoneComparison(_) => false,
             CheckKind::RaiseNotImplemented => false,
             CheckKind::ReturnOutsideFunction => false,
             CheckKind::TooManyExpressionsInStarredAssignment => false,

src/linter.rs

@@ -298,6 +298,225 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn e741() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/E741.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::E741]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(3, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("I".to_string()),
+                location: Location::new(4, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("O".to_string()),
+                location: Location::new(5, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(6, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(8, 4),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(9, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(10, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(11, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(16, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(20, 8),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(25, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(26, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(30, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(33, 9),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(34, 9),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(40, 8),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("I".to_string()),
+                location: Location::new(40, 14),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(44, 8),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("I".to_string()),
+                location: Location::new(44, 16),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(48, 9),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("I".to_string()),
+                location: Location::new(48, 14),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(57, 16),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(66, 20),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousVariableName("l".to_string()),
+                location: Location::new(71, 1),
+                fix: None,
+            },
+        ];
+
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn e742() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/E742.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::E742]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![
+            Check {
+                kind: CheckKind::AmbiguousClassName("l".to_string()),
+                location: Location::new(1, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousClassName("I".to_string()),
+                location: Location::new(5, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousClassName("O".to_string()),
+                location: Location::new(9, 1),
+                fix: None,
+            },
+        ];
+
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn e743() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/E743.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::E743]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![
+            Check {
+                kind: CheckKind::AmbiguousFunctionName("l".to_string()),
+                location: Location::new(1, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousFunctionName("I".to_string()),
+                location: Location::new(5, 1),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::AmbiguousFunctionName("O".to_string()),
+                location: Location::new(10, 5),
+                fix: None,
+            },
+        ];
+
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn f401() -> Result<()> {
         let mut actual = check_path(
@@ -366,6 +585,57 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn f404() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/F404.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::F404]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![Check {
+            kind: CheckKind::LateFutureImport,
+            location: Location::new(7, 1),
+            fix: None,
+        }];
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn f407() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/F407.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::F407]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![Check {
+            kind: CheckKind::FutureFeatureNotDefined("non_existent_feature".to_string()),
+            location: Location::new(2, 1),
+            fix: None,
+        }];
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn f541() -> Result<()> {
         let mut actual = check_path(
@@ -814,6 +1084,21 @@ mod tests {
                 location: Location::new(16, 5),
                 fix: None,
             },
+            Check {
+                kind: CheckKind::UnusedVariable("foo".to_string()),
+                location: Location::new(20, 5),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::UnusedVariable("a".to_string()),
+                location: Location::new(21, 6),
+                fix: None,
+            },
+            Check {
+                kind: CheckKind::UnusedVariable("b".to_string()),
+                location: Location::new(21, 9),
+                fix: None,
+            },
         ];
         assert_eq!(actual.len(), expected.len());
         for i in 0..actual.len() {

src/main.rs

@@ -6,6 +6,7 @@ use std::time::Instant;
 use anyhow::Result;
 use clap::{Parser, ValueHint};
 use colored::Colorize;
+use glob::Pattern;
 use log::{debug, error};
 use notify::{raw_watcher, RecursiveMode, Watcher};
 use rayon::prelude::*;
@@ -47,12 +48,15 @@ struct Cli {
     /// Disable cache reads.
     #[clap(short, long, action)]
     no_cache: bool,
-    /// Comma-separated list of error codes to enable.
+    /// List of error codes to enable.
     #[clap(long, multiple = true)]
     select: Vec<CheckCode>,
-    /// Comma-separated list of error codes to ignore.
+    /// List of error codes to ignore.
     #[clap(long, multiple = true)]
     ignore: Vec<CheckCode>,
+    /// List of file and/or directory patterns to exclude from checks.
+    #[clap(long, multiple = true)]
+    exclude: Vec<Pattern>,
 }
 
 #[cfg(feature = "update-informer")]
@@ -188,6 +192,9 @@ fn inner_main() -> Result<ExitCode> {
     if !cli.ignore.is_empty() {
         settings.ignore(&cli.ignore);
     }
+    if !cli.exclude.is_empty() {
+        settings.exclude(cli.exclude);
+    }
 
     if cli.watch {
         if cli.fix {

src/message.rs

@@ -20,7 +20,7 @@ impl Ord for Message {
         (&self.filename, self.location.row(), self.location.column()).cmp(&(
             &other.filename,
             other.location.row(),
-            self.location.column(),
+            other.location.column(),
         ))
     }
 }

src/pyproject.rs

@@ -266,9 +266,14 @@ other-attribute = 1
                     CheckCode::E713,
                     CheckCode::E714,
                     CheckCode::E731,
+                    CheckCode::E741,
+                    CheckCode::E742,
+                    CheckCode::E743,
                     CheckCode::E902,
                     CheckCode::F401,
                     CheckCode::F403,
+                    CheckCode::F404,
+                    CheckCode::F407,
                     CheckCode::F541,
                     CheckCode::F601,
                     CheckCode::F602,

src/python.rs

@@ -1,2 +1,3 @@
 pub mod builtins;
+pub mod future;
 pub mod typing;

src/python/future.rs

@@ -0,0 +1,13 @@
+/// A copy of `__future__.all_feature_names`.
+pub const ALL_FEATURE_NAMES: &[&str] = &[
+    "nested_scopes",
+    "generators",
+    "division",
+    "absolute_import",
+    "with_statement",
+    "print_function",
+    "unicode_literals",
+    "barry_as_FLUFL",
+    "generator_stop",
+    "annotations",
+];

src/settings.rs

@@ -51,9 +51,13 @@ impl Settings {
                     CheckCode::E713,
                     CheckCode::E714,
                     CheckCode::E731,
+                    CheckCode::E741,
+                    CheckCode::E742,
+                    CheckCode::E743,
                     CheckCode::E902,
                     CheckCode::F401,
                     CheckCode::F403,
+                    CheckCode::F407,
                     CheckCode::F541,
                     CheckCode::F601,
                     CheckCode::F602,
@@ -94,4 +98,8 @@ impl Settings {
             self.select.remove(code);
         }
     }
+
+    pub fn exclude(&mut self, exclude: Vec<Pattern>) {
+        self.exclude = exclude;
+    }
 }