Avoid panic when typename is provided as a keyword argument (#6955)

## Summary

The `typename` argument to `NamedTuple` and `TypedDict` is a required
positional argument. We assumed as much, but panicked if it was provided
as a keyword argument or otherwise omitted. This PR handles the case
gracefully.

Closes https://github.com/astral-sh/ruff/issues/6953.

crates/ruff/resources/test/fixtures/pyupgrade/UP014.py

@@ -22,3 +22,4 @@ MyType = typing.NamedTuple("MyType", a=int, b=tuple[str, ...])
 # unfixable
 MyType = typing.NamedTuple("MyType", [("a", int)], [("b", str)])
 MyType = typing.NamedTuple("MyType", [("a", int)], b=str)
+MyType = typing.NamedTuple(typename="MyType", a=int, b=str)

crates/ruff/src/rules/pyupgrade/rules/convert_named_tuple_functional_to_class.rs

@@ -72,8 +72,7 @@ fn match_named_tuple_assign<'a>(
     value: &'a Expr,
     semantic: &SemanticModel,
 ) -> Option<(&'a str, &'a [Expr], &'a [Keyword], &'a Expr)> {
-    let target = targets.get(0)?;
-    let Expr::Name(ast::ExprName { id: typename, .. }) = target else {
+    let [Expr::Name(ast::ExprName { id: typename, .. })] = targets else {
         return None;
     };
     let Expr::Call(ast::ExprCall {
@@ -209,13 +208,13 @@ pub(crate) fn convert_named_tuple_functional_to_class(
         return;
     };
 
-    let properties = match (&args[1..], keywords) {
+    let properties = match (args, keywords) {
         // Ex) NamedTuple("MyType")
-        ([], []) => vec![Stmt::Pass(ast::StmtPass {
+        ([_typename], []) => vec![Stmt::Pass(ast::StmtPass {
             range: TextRange::default(),
         })],
         // Ex) NamedTuple("MyType", [("a", int), ("b", str)])
-        ([fields], []) => {
+        ([_typename, fields], []) => {
             if let Ok(properties) = create_properties_from_fields_arg(fields) {
                 properties
             } else {
@@ -224,7 +223,7 @@ pub(crate) fn convert_named_tuple_functional_to_class(
             }
         }
         // Ex) NamedTuple("MyType", a=int, b=str)
-        ([], keywords) => {
+        ([_typename], keywords) => {
             if let Ok(properties) = create_properties_from_keywords(keywords) {
                 properties
             } else {

crates/ruff/src/rules/pyupgrade/rules/convert_typed_dict_functional_to_class.rs

@@ -71,8 +71,7 @@ fn match_typed_dict_assign<'a>(
     value: &'a Expr,
     semantic: &SemanticModel,
 ) -> Option<(&'a str, &'a Arguments, &'a Expr)> {
-    let target = targets.get(0)?;
-    let Expr::Name(ast::ExprName { id: class_name, .. }) = target else {
+    let [Expr::Name(ast::ExprName { id: class_name, .. })] = targets else {
         return None;
     };
     let Expr::Call(ast::ExprCall {
@@ -210,28 +209,34 @@ fn match_properties_and_total(arguments: &Arguments) -> Result<(Vec<Stmt>, Optio
     // ```
     // MyType = TypedDict('MyType', {'a': int, 'b': str}, a=int, b=str)
     // ```
-    if let Some(dict) = arguments.args.get(1) {
-        let total = arguments.find_keyword("total");
-        match dict {
-            Expr::Dict(ast::ExprDict {
-                keys,
-                values,
-                range: _,
-            }) => Ok((properties_from_dict_literal(keys, values)?, total)),
-            Expr::Call(ast::ExprCall {
-                func,
-                arguments: Arguments { keywords, .. },
-                ..
-            }) => Ok((properties_from_dict_call(func, keywords)?, total)),
-            _ => bail!("Expected `arg` to be `Expr::Dict` or `Expr::Call`"),
+    match (arguments.args.as_slice(), arguments.keywords.as_slice()) {
+        // Ex) `TypedDict("MyType", {"a": int, "b": str})`
+        ([_typename, fields], [..]) => {
+            let total = arguments.find_keyword("total");
+            match fields {
+                Expr::Dict(ast::ExprDict {
+                    keys,
+                    values,
+                    range: _,
+                }) => Ok((properties_from_dict_literal(keys, values)?, total)),
+                Expr::Call(ast::ExprCall {
+                    func,
+                    arguments: Arguments { keywords, .. },
+                    range: _,
+                }) => Ok((properties_from_dict_call(func, keywords)?, total)),
+                _ => bail!("Expected `arg` to be `Expr::Dict` or `Expr::Call`"),
+            }
         }
-    } else if !arguments.keywords.is_empty() {
-        Ok((properties_from_keywords(&arguments.keywords)?, None))
-    } else {
-        let node = Stmt::Pass(ast::StmtPass {
-            range: TextRange::default(),
-        });
-        Ok((vec![node], None))
+        // Ex) `TypedDict("MyType")`
+        ([_typename], []) => {
+            let node = Stmt::Pass(ast::StmtPass {
+                range: TextRange::default(),
+            });
+            Ok((vec![node], None))
+        }
+        // Ex) `TypedDict("MyType", a=int, b=str)`
+        ([_typename], fields) => Ok((properties_from_keywords(fields)?, None)),
+        _ => bail!("Expected `args` to have exactly one or two elements"),
     }
 }