make struct-variant matches less future-proof, and other clippy fixes

Author: RalfJung

src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs

@@ -865,7 +865,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let this = self.eval_context_mut();
         let new_perm = NewPermission::from_ref_ty(val.layout.ty, kind, this);
         let cause = match kind {
-            RetagKind::TwoPhase { .. } => RetagCause::TwoPhase,
+            RetagKind::TwoPhase => RetagCause::TwoPhase,
             RetagKind::FnEntry => unreachable!(),
             RetagKind::Raw | RetagKind::Default => RetagCause::Normal,
         };
@@ -880,7 +880,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let this = self.eval_context_mut();
         let retag_fields = this.machine.borrow_tracker.as_mut().unwrap().get_mut().retag_fields;
         let retag_cause = match kind {
-            RetagKind::TwoPhase { .. } => unreachable!(), // can only happen in `retag_ptr_value`
+            RetagKind::TwoPhase => unreachable!(), // can only happen in `retag_ptr_value`
             RetagKind::FnEntry => RetagCause::FnEntry,
             RetagKind::Default | RetagKind::Raw => RetagCause::Normal,
         };

src/tools/miri/src/eval.rs

@@ -558,15 +558,15 @@ where
 
                 match chars.next() {
                     Some('"') => {
-                        cmd.extend(iter::repeat('\\').take(nslashes * 2 + 1));
+                        cmd.extend(iter::repeat_n('\\', nslashes * 2 + 1));
                         cmd.push('"');
                     }
                     Some(c) => {
-                        cmd.extend(iter::repeat('\\').take(nslashes));
+                        cmd.extend(iter::repeat_n('\\', nslashes));
                         cmd.push(c);
                     }
                     None => {
-                        cmd.extend(iter::repeat('\\').take(nslashes * 2));
+                        cmd.extend(iter::repeat_n('\\', nslashes * 2));
                         break;
                     }
                 }

src/tools/miri/src/lib.rs

@@ -36,6 +36,9 @@
     clippy::needless_question_mark,
     clippy::needless_lifetimes,
     clippy::too_long_first_doc_paragraph,
+    // Temporarily disabled as fixing it would cause conflicts
+    clippy::manual_repeat_n,
+    // We don't use translatable diagnostics
     rustc::diagnostic_outside_of_impl,
     // We are not implementing queries here so it's fine
     rustc::potential_query_instability,