Create bindings for MatchAs patterns (#3098)

crates/ruff/resources/test/fixtures/pyflakes/F821_9.py

@@ -0,0 +1,26 @@
+"""Test: match statements."""
+from dataclasses import dataclass
+
+
+@dataclass
+class Car:
+    make: str
+    model: str
+
+
+def f():
+    match Car("Toyota", "Corolla"):
+        case Car("Toyota", model):
+            print(model)
+        case Car(make, "Corolla"):
+            print(make)
+
+
+def f(provided: int) -> int:
+    match provided:
+        case True:
+            return captured  # F821
+        case [captured, *_]:
+            return captured
+        case captured:
+            return captured

crates/ruff/resources/test/fixtures/pyflakes/F841_0.py

@@ -119,3 +119,5 @@ def f(x: int):
             print("A")
         case [Bar.A, *_]:
             print("A")
+        case y:
+            pass

crates/ruff/src/checkers/ast.rs

@@ -10,7 +10,8 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use rustpython_common::cformat::{CFormatError, CFormatErrorType};
 use rustpython_parser::ast::{
     Arg, Arguments, Comprehension, Constant, Excepthandler, ExcepthandlerKind, Expr, ExprContext,
-    ExprKind, KeywordData, Located, Location, Operator, Stmt, StmtKind, Suite,
+    ExprKind, KeywordData, Located, Location, Operator, Pattern, PatternKind, Stmt, StmtKind,
+    Suite,
 };
 use rustpython_parser::parser;
 use smallvec::smallvec;
@@ -28,7 +29,7 @@ use crate::ast::types::{
     RefEquality, Scope, ScopeKind,
 };
 use crate::ast::typing::{match_annotated_subscript, Callable, SubscriptKind};
-use crate::ast::visitor::{walk_excepthandler, Visitor};
+use crate::ast::visitor::{walk_excepthandler, walk_pattern, Visitor};
 use crate::ast::{branch_detection, cast, helpers, operations, typing, visitor};
 use crate::docstrings::definition::{Definition, DefinitionKind, Docstring, Documentable};
 use crate::registry::{Diagnostic, Rule};
@@ -3840,6 +3841,28 @@ where
         }
     }
 
+    fn visit_pattern(&mut self, pattern: &'b Pattern) {
+        if let PatternKind::MatchAs {
+            name: Some(name), ..
+        } = &pattern.node
+        {
+            self.add_binding(
+                name,
+                Binding {
+                    kind: BindingKind::Assignment,
+                    runtime_usage: None,
+                    synthetic_usage: None,
+                    typing_usage: None,
+                    range: Range::from_located(pattern),
+                    source: Some(self.current_stmt().clone()),
+                    context: self.execution_context(),
+                },
+            );
+        }
+
+        walk_pattern(self, pattern);
+    }
+
     fn visit_format_spec(&mut self, format_spec: &'b Expr) {
         match &format_spec.node {
             ExprKind::JoinedStr { values } => {

crates/ruff/src/rules/pyflakes/mod.rs

@@ -101,6 +101,7 @@ mod tests {
     #[test_case(Rule::UndefinedName, Path::new("F821_6.py"); "F821_6")]
     #[test_case(Rule::UndefinedName, Path::new("F821_7.py"); "F821_7")]
     #[test_case(Rule::UndefinedName, Path::new("F821_8.pyi"); "F821_8")]
+    #[test_case(Rule::UndefinedName, Path::new("F821_9.py"); "F821_9")]
     #[test_case(Rule::UndefinedExport, Path::new("F822_0.py"); "F822_0")]
     #[test_case(Rule::UndefinedExport, Path::new("F822_1.py"); "F822_1")]
     #[test_case(Rule::UndefinedExport, Path::new("F822_2.py"); "F822_2")]

crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__F821_F821_9.py.snap

@@ -0,0 +1,16 @@
+---
+source: crates/ruff/src/rules/pyflakes/mod.rs
+expression: diagnostics
+---
+- kind:
+    UndefinedName:
+      name: captured
+  location:
+    row: 22
+    column: 19
+  end_location:
+    row: 22
+    column: 27
+  fix: ~
+  parent: ~
+

crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__F841_F841_0.py.snap

@@ -186,4 +186,15 @@ expression: diagnostics
       row: 115
       column: 10
   parent: ~
+- kind:
+    UnusedVariable:
+      name: y
+  location:
+    row: 122
+    column: 13
+  end_location:
+    row: 122
+    column: 14
+  fix: ~
+  parent: ~
 

crates/ruff/src/rules/pyflakes/snapshots/ruff__rules__pyflakes__tests__f841_dummy_variable_rgx.snap

@@ -222,4 +222,15 @@ expression: diagnostics
       row: 115
       column: 10
   parent: ~
+- kind:
+    UnusedVariable:
+      name: y
+  location:
+    row: 122
+    column: 13
+  end_location:
+    row: 122
+    column: 14
+  fix: ~
+  parent: ~