misc cleanups

compiler/rustc_attr/src/builtin.rs

@@ -619,11 +619,11 @@ pub fn eval_condition(
                 // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true`
                 // and `true`, and we want to keep the former working without feature gate
                 gate_cfg(
-                    &((
+                    &(
                         if *b { kw::True } else { kw::False },
                         sym::cfg_boolean_literals,
                         |features: &Features| features.cfg_boolean_literals(),
-                    )),
+                    ),
                     cfg.span(),
                     sess,
                     features,

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -959,13 +959,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         None
                     }
                 }
-                hir::ExprKind::MethodCall(_, _, args, span) => {
-                    if let Some(def_id) = typeck_results.type_dependent_def_id(*hir_id) {
-                        Some((def_id, *span, *args))
-                    } else {
-                        None
-                    }
-                }
+                hir::ExprKind::MethodCall(_, _, args, span) => typeck_results
+                    .type_dependent_def_id(*hir_id)
+                    .map(|def_id| (def_id, *span, *args)),
                 _ => None,
             }
         };

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -537,7 +537,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && binding_id != self.binding_id
                 {
                     if self.check_and_add_sugg_binding(LetStmt {
-                        ty_hir_id_opt: if let Some(ty) = ty { Some(ty.hir_id) } else { None },
+                        ty_hir_id_opt: ty.map(|ty| ty.hir_id),
                         binding_id,
                         span: pat.span,
                         init_hir_id: init.hir_id,

compiler/rustc_infer/src/infer/type_variable.rs

@@ -187,10 +187,7 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         value_count: usize,
     ) -> (Range<TyVid>, Vec<TypeVariableOrigin>) {
         let range = TyVid::from_usize(value_count)..TyVid::from_usize(self.num_vars());
-        (
-            range.start..range.end,
-            (range.start..range.end).map(|index| self.var_origin(index)).collect(),
-        )
+        (range.clone(), range.map(|index| self.var_origin(index)).collect())
     }
 
     /// Returns indices of all variables that are not yet

compiler/rustc_middle/src/mir/pretty.rs

@@ -277,9 +277,9 @@ pub fn create_dump_file<'tcx>(
             )
         })?;
     }
-    Ok(fs::File::create_buffered(&file_path).map_err(|e| {
+    fs::File::create_buffered(&file_path).map_err(|e| {
         io::Error::new(e.kind(), format!("IO error creating MIR dump file: {file_path:?}; {e}"))
-    })?)
+    })
 }
 
 ///////////////////////////////////////////////////////////////////////////

compiler/rustc_mir_transform/src/coverage/mappings.rs

@@ -363,7 +363,7 @@ fn calc_test_vectors_index(conditions: &mut Vec<MCDCBranch>) -> usize {
             let ConditionInfo { condition_id, true_next_id, false_next_id } = branch.condition_info;
             [true_next_id, false_next_id]
                 .into_iter()
-                .filter_map(std::convert::identity)
+                .flatten()
                 .for_each(|next_id| indegree_stats[next_id] += 1);
             (condition_id, branch)
         })

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -87,7 +87,7 @@ fn remove_unwanted_expansion_spans(covspans: &mut Vec<SpanFromMir>) {
     covspans.retain(|covspan| {
         match covspan.expn_kind {
             // Retain only the first await-related or macro-expanded covspan with this span.
-            Some(ExpnKind::Desugaring(kind)) if kind == DesugaringKind::Await => {
+            Some(ExpnKind::Desugaring(DesugaringKind::Await)) => {
                 deduplicated_spans.insert(covspan.span)
             }
             Some(ExpnKind::Macro(MacroKind::Bang, _)) => deduplicated_spans.insert(covspan.span),