Improve parser error recovery for invalid UnaryOp nodes inside unpacking assignments

crates/ruff_python_parser/src/parser/helpers.rs

@@ -17,7 +17,11 @@ pub(super) fn set_expr_ctx(expr: &mut Expr, new_ctx: ExprContext) {
             set_expr_ctx(value, new_ctx);
         }
         Expr::UnaryOp(ast::ExprUnaryOp { operand, .. }) => {
-            set_expr_ctx(operand, new_ctx);
+            // `UnaryOp` is never a valid assignment or deletion target. When the parser
+            // recovers from bad input like `a, not = ...`, the operand isn't genuinely
+            // in target position, so mark it `Invalid` rather than propagating `new_ctx`
+            // and misleading consumers into treating it as a real target sub-expression.
+            set_expr_ctx(operand, ExprContext::Invalid);
         }
         Expr::List(ast::ExprList { elts, ctx, .. })
         | Expr::Tuple(ast::ExprTuple { elts, ctx, .. }) => {

crates/ruff_python_parser/tests/snapshots/invalid_syntax@for_stmt_invalid_target_binary_expr.py.snap

@@ -194,7 +194,7 @@ Module(
                                     node_index: NodeIndex(None),
                                     range: 72..73,
                                     id: Name("x"),
-                                    ctx: Store,
+                                    ctx: Invalid,
                                 },
                             ),
                         },
@@ -239,7 +239,7 @@ Module(
                                     node_index: NodeIndex(None),
                                     range: 92..93,
                                     id: Name("x"),
-                                    ctx: Store,
+                                    ctx: Invalid,
                                 },
                             ),
                         },

crates/ruff_python_parser/tests/snapshots/invalid_syntax@statements__invalid_assignment_targets.py.snap

@@ -233,7 +233,7 @@ Module(
                                         node_index: NodeIndex(None),
                                         range: 341..342,
                                         id: Name("x"),
-                                        ctx: Store,
+                                        ctx: Invalid,
                                     },
                                 ),
                             },

crates/ruff_python_parser/tests/snapshots/invalid_syntax@statements__invalid_augmented_assignment_target.py.snap

@@ -143,7 +143,7 @@ Module(
                                     node_index: NodeIndex(None),
                                     range: 138..139,
                                     id: Name("x"),
-                                    ctx: Store,
+                                    ctx: Invalid,
                                 },
                             ),
                         },

crates/ty_server/tests/e2e/publish_diagnostics.rs

@@ -2,7 +2,7 @@ use std::time::Duration;
 
 use anyhow::Result;
 use lsp_types::{
-    DidOpenTextDocumentParams, FileChangeType, FileEvent, TextDocumentItem, Url,
+    DidOpenTextDocumentParams, FileChangeType, FileEvent, Position, Range, TextDocumentItem, Url,
     notification::{DidOpenTextDocument, PublishDiagnostics},
 };
 use ruff_db::system::SystemPath;
@@ -214,6 +214,106 @@ def foo() -> str:
     Ok(())
 }
 
+#[test]
+fn on_did_change_invalid_tuple_assignment_target_does_not_panic() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+something, somethingelse = (1, 2)
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(workspace_root, None)?
+        .with_file(foo, foo_content)?
+        .enable_pull_diagnostics(false)
+        .build()
+        .wait_until_workspaces_are_initialized();
+
+    server.open_text_document(foo, foo_content, 1);
+    let _ = server.await_notification::<PublishDiagnostics>();
+
+    server.change_text_document(
+        foo,
+        vec![lsp_types::TextDocumentContentChangeEvent {
+            range: Some(Range::new(Position::new(0, 11), Position::new(0, 24))),
+            range_length: None,
+            text: "not".to_string(),
+        }],
+        2,
+    );
+
+    let diagnostics = server.await_notification::<PublishDiagnostics>();
+
+    assert_eq!(diagnostics.version, Some(2));
+
+    insta::assert_debug_snapshot!(diagnostics);
+
+    Ok(())
+}
+
+#[test]
+fn on_did_change_nested_invalid_tuple_assignment_target_does_not_panic() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+something, somethingelse = (1, 2)
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(workspace_root, None)?
+        .with_file(foo, foo_content)?
+        .enable_pull_diagnostics(false)
+        .build()
+        .wait_until_workspaces_are_initialized();
+
+    server.open_text_document(foo, foo_content, 1);
+    let _ = server.await_notification::<PublishDiagnostics>();
+
+    server.change_text_document(
+        foo,
+        vec![lsp_types::TextDocumentContentChangeEvent {
+            range: Some(Range::new(Position::new(0, 11), Position::new(0, 24))),
+            range_length: None,
+            text: "not x".to_string(),
+        }],
+        2,
+    );
+
+    let diagnostics = server.await_notification::<PublishDiagnostics>();
+
+    assert_eq!(diagnostics.version, Some(2));
+
+    insta::assert_debug_snapshot!(diagnostics);
+
+    Ok(())
+}
+
+#[test]
+fn completions_do_not_panic_on_invalid_not_target() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+something, not x = (1, 2)
+something
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(workspace_root, None)?
+        .with_file(foo, foo_content)?
+        .enable_pull_diagnostics(false)
+        .build()
+        .wait_until_workspaces_are_initialized();
+
+    server.open_text_document(foo, foo_content, 1);
+    let _ = server.await_notification::<PublishDiagnostics>();
+
+    // Ask for completions — forces `all_reachable_members` which calls
+    // `binding_type` on every live binding in scope.
+    let _ = server.completion_request(&server.file_uri(foo), Position::new(1, 9));
+
+    Ok(())
+}
+
 #[test]
 fn on_did_change_diagnostics_off() -> Result<()> {
     let workspace_root = SystemPath::new("src");

crates/ty_server/tests/e2e/snapshots/e2e__publish_diagnostics__on_did_change_invalid_tuple_assignment_target_does_not_panic.snap

@@ -0,0 +1,78 @@
+---
+source: crates/ty_server/tests/e2e/publish_diagnostics.rs
+expression: diagnostics
+---
+PublishDiagnosticsParams {
+    uri: Url {
+        scheme: "file",
+        cannot_be_a_base: false,
+        username: "",
+        password: None,
+        host: None,
+        port: None,
+        path: "<temp_dir>/src/foo.py",
+        query: None,
+        fragment: None,
+    },
+    diagnostics: [
+        Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 0,
+                    character: 11,
+                },
+                end: Position {
+                    line: 0,
+                    character: 14,
+                },
+            },
+            severity: Some(
+                Error,
+            ),
+            code: Some(
+                String(
+                    "invalid-syntax",
+                ),
+            ),
+            code_description: None,
+            source: Some(
+                "ty",
+            ),
+            message: "Invalid assignment target",
+            related_information: None,
+            tags: None,
+            data: None,
+        },
+        Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 0,
+                    character: 15,
+                },
+                end: Position {
+                    line: 0,
+                    character: 16,
+                },
+            },
+            severity: Some(
+                Error,
+            ),
+            code: Some(
+                String(
+                    "invalid-syntax",
+                ),
+            ),
+            code_description: None,
+            source: Some(
+                "ty",
+            ),
+            message: "Expected an expression",
+            related_information: None,
+            tags: None,
+            data: None,
+        },
+    ],
+    version: Some(
+        2,
+    ),
+}

crates/ty_server/tests/e2e/snapshots/e2e__publish_diagnostics__on_did_change_nested_invalid_tuple_assignment_target_does_not_panic.snap

@@ -0,0 +1,50 @@
+---
+source: crates/ty_server/tests/e2e/publish_diagnostics.rs
+expression: diagnostics
+---
+PublishDiagnosticsParams {
+    uri: Url {
+        scheme: "file",
+        cannot_be_a_base: false,
+        username: "",
+        password: None,
+        host: None,
+        port: None,
+        path: "<temp_dir>/src/foo.py",
+        query: None,
+        fragment: None,
+    },
+    diagnostics: [
+        Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 0,
+                    character: 11,
+                },
+                end: Position {
+                    line: 0,
+                    character: 16,
+                },
+            },
+            severity: Some(
+                Error,
+            ),
+            code: Some(
+                String(
+                    "invalid-syntax",
+                ),
+            ),
+            code_description: None,
+            source: Some(
+                "ty",
+            ),
+            message: "Invalid assignment target",
+            related_information: None,
+            tags: None,
+            data: None,
+        },
+    ],
+    version: Some(
+        2,
+    ),
+}