Auto merge of #87449 - matthiaskrgr:clippyy_v2, r=nagisa

more clippy::complexity fixes

(also a couple of clippy::perf fixes)

compiler/rustc_typeck/src/check/method/prelude2021.rs

@@ -357,7 +357,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
                 (expr_text, true)
             } else {
-                (format!("(..)"), false)
+                ("(..)".to_string(), false)
             };
 
         let adjusted_text = if let Some(probe::AutorefOrPtrAdjustment::ToConstPtr) =

compiler/rustc_typeck/src/check/mod.rs

@@ -791,7 +791,7 @@ fn fn_sig_suggestion<'tcx>(
             })
         })
         .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
-        .filter_map(|arg| arg)
+        .flatten()
         .collect::<Vec<String>>()
         .join(", ");
     let output = sig.output();