Rollup merge of rust-lang#118884 - matthiaskrgr:auszweimacheins, r=Nadrieril

NFC: simplify merging of two vecs

Author: matthiaskrgr

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -979,7 +979,8 @@ impl ConstructorSet {
             && !(pcx.is_top_level && matches!(self, Self::NoConstructors))
         {
             // Treat all missing constructors as nonempty.
-            missing.extend(missing_empty.drain(..));
+            // This clears `missing_empty`.
+            missing.append(&mut missing_empty);
         }
 
         SplitConstructorSet { present, missing, missing_empty }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -2178,7 +2178,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 let (span, text) = match path.segments.first() {
                     Some(seg) if let Some(name) = seg.ident.as_str().strip_prefix("let") => {
                         // a special case for #117894
-                        let name = name.strip_prefix("_").unwrap_or(name);
+                        let name = name.strip_prefix('_').unwrap_or(name);
                         (ident_span, format!("let {name}"))
                     }
                     _ => (ident_span.shrink_to_lo(), "let ".to_string()),