Make `ast_to_token_tree` infallible

It could never return `None`, so reflect that in the return type

1 files changed, 1 insertions, 1 deletions

diff --git a/crates/mbe/src/tests/rule.rs b/crates/mbe/src/tests/rule.rs
index bf48112b3..5c61a98fd 100644
--- a/crates/mbe/src/tests/rule.rs
+++ b/crates/mbe/src/tests/rule.rs
@@ -44,6 +44,6 @@ fn parse_macro_arm(arm_definition: &str) -> Result<crate::MacroRules, ParseError
     let macro_definition =
         source_file.syntax().descendants().find_map(ast::MacroRules::cast).unwrap();
 
-    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap()).unwrap();
+    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap());
     crate::MacroRules::parse(&definition_tt)
 }