Preserve global binding kind during reassignments (#2297)

resources/test/fixtures/pep8_naming/N806.py

@@ -6,7 +6,7 @@ from typing import NewType
 GLOBAL: str = "foo"
 
 
-def f():
+def assign():
     global GLOBAL
     GLOBAL = "bar"
     lower = 0
@@ -18,4 +18,18 @@ def f():
     MyObj2 = namedtuple("MyObj12", ["a", "b"])
 
     T = TypeVar("T")
-    UserId = NewType('UserId', int)
+    UserId = NewType("UserId", int)
+
+
+def aug_assign(rank, world_size):
+    global CURRENT_PORT
+
+    CURRENT_PORT += 1
+    if CURRENT_PORT > MAX_PORT:
+        CURRENT_PORT = START_PORT
+
+
+def loop_assign():
+    global CURRENT_PORT
+    for CURRENT_PORT in range(5):
+        pass

resources/test/fixtures/pylint/global_variable_not_assigned.py

@@ -2,31 +2,37 @@
 # Errors.
 ###
 def f():
-    global x
+    global X
 
 
 def f():
-    global x
+    global X
 
-    print(x)
+    print(X)
 
 
 ###
 # Non-errors.
 ###
 def f():
-    global x
+    global X
 
-    x = 1
+    X = 1
 
 
 def f():
-    global x
+    global X
 
-    (x, y) = (1, 2)
+    (X, y) = (1, 2)
 
 
 def f():
-    global x
+    global X
 
-    del x
+    del X
+
+
+def f():
+    global X
+
+    X += 1

src/checkers/ast.rs

@@ -3859,11 +3859,31 @@ impl<'a> Checker<'a> {
             }
         }
 
-        // Assume the rebound name is used as a global or within a loop.
         let scope = self.current_scope();
         let binding = if let Some(index) = scope.values.get(&name) {
             if matches!(self.bindings[*index].kind, BindingKind::Builtin) {
+                // Avoid overriding builtins.
                 binding
+            } else if matches!(self.bindings[*index].kind, BindingKind::Global) {
+                // If the original binding was a global, and the new binding conflicts within the
+                // current scope, then the new binding is also a global.
+                Binding {
+                    runtime_usage: self.bindings[*index].runtime_usage,
+                    synthetic_usage: self.bindings[*index].synthetic_usage,
+                    typing_usage: self.bindings[*index].typing_usage,
+                    kind: BindingKind::Global,
+                    ..binding
+                }
+            } else if matches!(self.bindings[*index].kind, BindingKind::Nonlocal) {
+                // If the original binding was a nonlocal, and the new binding conflicts within the
+                // current scope, then the new binding is also a nonlocal.
+                Binding {
+                    runtime_usage: self.bindings[*index].runtime_usage,
+                    synthetic_usage: self.bindings[*index].synthetic_usage,
+                    typing_usage: self.bindings[*index].typing_usage,
+                    kind: BindingKind::Nonlocal,
+                    ..binding
+                }
             } else {
                 Binding {
                     runtime_usage: self.bindings[*index].runtime_usage,
@@ -4463,10 +4483,14 @@ impl<'a> Checker<'a> {
                 for (name, index) in &scope.values {
                     let binding = &self.bindings[*index];
                     if matches!(binding.kind, BindingKind::Global) {
-                        diagnostics.push(Diagnostic::new(
-                            violations::GlobalVariableNotAssigned((*name).to_string()),
-                            binding.range,
-                        ));
+                        if let Some(stmt) = &binding.source {
+                            if matches!(stmt.node, StmtKind::Global { .. }) {
+                                diagnostics.push(Diagnostic::new(
+                                    violations::GlobalVariableNotAssigned((*name).to_string()),
+                                    binding.range,
+                                ));
+                            }
+                        }
                     }
                 }
             }

src/rules/pylint/snapshots/ruff__rules__pylint__tests__PLW0602_global_variable_not_assigned.py.snap

@@ -3,7 +3,7 @@ source: src/rules/pylint/mod.rs
 expression: diagnostics
 ---
 - kind:
-    GlobalVariableNotAssigned: x
+    GlobalVariableNotAssigned: X
   location:
     row: 5
     column: 11
@@ -13,7 +13,7 @@ expression: diagnostics
   fix: ~
   parent: ~
 - kind:
-    GlobalVariableNotAssigned: x
+    GlobalVariableNotAssigned: X
   location:
     row: 9
     column: 11