Auto merge of #78066 - bugadani:wat, r=jonas-schievink

Clean up small, surprising bits of code

This PR clean up a small number of unrelated, small things I found while browsing the code base.

compiler/rustc_ast/src/util/lev_distance.rs

@@ -54,7 +54,7 @@ where
     T: Iterator<Item = &'a Symbol>,
 {
     let lookup = &lookup.as_str();
-    let max_dist = dist.map_or_else(|| cmp::max(lookup.len(), 3) / 3, |d| d);
+    let max_dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
     let name_vec: Vec<&Symbol> = iter_names.collect();
 
     let (case_insensitive_match, levenshtein_match) = name_vec

compiler/rustc_ast_lowering/src/expr.rs

@@ -1190,7 +1190,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                                          input| {
                             match used_regs.entry(r) {
                                 Entry::Occupied(o) => {
-                                    if !skip {
+                                    if skip {
+                                        return;
+                                    }
                                     skip = true;
 
                                     let idx2 = *o.get();
@@ -1207,14 +1209,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                                         reg2.name()
                                     );
                                     let mut err = sess.struct_span_err(op_sp, &msg);
-                                        err.span_label(
+                                    err.span_label(op_sp, &format!("register `{}`", reg.name()));
-                                            op_sp,
+                                    err.span_label(op_sp2, &format!("register `{}`", reg2.name()));
-                                            &format!("register `{}`", reg.name()),
-                                        );
-                                        err.span_label(
-                                            op_sp2,
-                                            &format!("register `{}`", reg2.name()),
-                                        );
 
                                     match (op, op2) {
                                         (
@@ -1236,7 +1232,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
                                     err.emit();
                                 }
-                                }
                                 Entry::Vacant(v) => {
                                     v.insert(idx);
                                 }

compiler/rustc_lint/src/builtin.rs

@@ -968,7 +968,7 @@ fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &
     while let Some(attr) = attrs.next() {
         if attr.is_doc_comment() {
             sugared_span =
-                Some(sugared_span.map_or_else(|| attr.span, |span| span.with_hi(attr.span.hi())));
+                Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
         }
 
         if attrs.peek().map(|next_attr| next_attr.is_doc_comment()).unwrap_or_default() {

compiler/rustc_middle/src/hir/place.rs

@@ -103,7 +103,7 @@ impl<'tcx> Place<'tcx> {
 
     /// Returns the type of this `Place` after all projections have been applied.
     pub fn ty(&self) -> Ty<'tcx> {
-        self.projections.last().map_or_else(|| self.base_ty, |proj| proj.ty)
+        self.projections.last().map_or(self.base_ty, |proj| proj.ty)
     }
 
     /// Returns the type of this `Place` immediately before `projection_index`th projection

compiler/rustc_mir/src/borrow_check/type_check/input_output.rs

@@ -73,7 +73,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         );
 
         // Equate expected input tys with those in the MIR.
-        for (&normalized_input_ty, argument_index) in normalized_input_tys.iter().zip(0..) {
+        for (argument_index, &normalized_input_ty) in normalized_input_tys.iter().enumerate() {
             // In MIR, argument N is stored in local N+1.
             let local = Local::new(argument_index + 1);
 
@@ -87,8 +87,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
 
         if let Some(user_provided_sig) = user_provided_sig {
-            for (&user_provided_input_ty, argument_index) in
+            for (argument_index, &user_provided_input_ty) in
-                user_provided_sig.inputs().iter().zip(0..)
+                user_provided_sig.inputs().iter().enumerate()
             {
                 // In MIR, closures begin an implicit `self`, so
                 // argument N is stored in local N+2.

compiler/rustc_passes/src/dead.rs

@@ -458,8 +458,8 @@ fn create_and_seed_worklist<'tcx>(
         .map
         .iter()
         .filter_map(
-            |(&id, level)| {
+            |(&id, &level)| {
-                if level >= &privacy::AccessLevel::Reachable { Some(id) } else { None }
+                if level >= privacy::AccessLevel::Reachable { Some(id) } else { None }
             },
         )
         .chain(
@@ -547,7 +547,7 @@ impl DeadVisitor<'tcx> {
         let def_id = self.tcx.hir().local_def_id(id);
         let inherent_impls = self.tcx.inherent_impls(def_id);
         for &impl_did in inherent_impls.iter() {
-            for &item_did in &self.tcx.associated_item_def_ids(impl_did)[..] {
+            for item_did in self.tcx.associated_item_def_ids(impl_did) {
                 if let Some(did) = item_did.as_local() {
                     let item_hir_id = self.tcx.hir().local_def_id_to_hir_id(did);
                     if self.live_symbols.contains(&item_hir_id) {