Join implicit concatenated strings when they fit on a line (#13663)

crates/ruff_formatter/src/builders.rs

@@ -1454,7 +1454,7 @@ impl<Context> std::fmt::Debug for Group<'_, Context> {
 /// layout doesn't exceed the line width too, in which case it falls back to the flat layout.
 ///
 /// This IR is identical to the following [`best_fitting`] layout but is implemented as custom IR for
-/// best performance.
+/// better performance.
 ///
 /// ```rust
 /// # use ruff_formatter::prelude::*;

crates/ruff_formatter/src/format_extensions.rs

@@ -139,7 +139,7 @@ where
     /// # Ok(())
     /// # }
     /// ```
-    pub fn inspect(&mut self, f: &mut Formatter<Context>) -> FormatResult<&[FormatElement]> {
+    pub fn inspect(&self, f: &mut Formatter<Context>) -> FormatResult<&[FormatElement]> {
         let result = self.memory.get_or_init(|| f.intern(&self.inner));
 
         match result.as_ref() {