Fix clippy::needless_borrow in the compiler

`x clippy compiler -Aclippy::all -Wclippy::needless_borrow --fix`.

Then I had to remove a few unnecessary parens and muts that were exposed
now.

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -60,9 +60,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
             let ConstCx { tcx, body, .. } = *ccx;
 
             FlowSensitiveAnalysis::new(NeedsDrop, ccx)
-                .into_engine(tcx, &body)
+                .into_engine(tcx, body)
                 .iterate_to_fixpoint()
-                .into_results_cursor(&body)
+                .into_results_cursor(body)
         });
 
         needs_drop.seek_before_primary_effect(location);
@@ -122,9 +122,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
             let ConstCx { tcx, body, .. } = *ccx;
 
             FlowSensitiveAnalysis::new(HasMutInterior, ccx)
-                .into_engine(tcx, &body)
+                .into_engine(tcx, body)
                 .iterate_to_fixpoint()
-                .into_results_cursor(&body)
+                .into_results_cursor(body)
         });
 
         has_mut_interior.seek_before_primary_effect(location);
@@ -170,9 +170,9 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
 
             hir::ConstContext::Const { .. } | hir::ConstContext::Static(_) => {
                 let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx)
-                    .into_engine(ccx.tcx, &ccx.body)
+                    .into_engine(ccx.tcx, ccx.body)
                     .iterate_to_fixpoint()
-                    .into_results_cursor(&ccx.body);
+                    .into_results_cursor(ccx.body);
 
                 cursor.seek_after_primary_effect(return_loc);
                 cursor.get().contains(RETURN_PLACE)
@@ -225,7 +225,7 @@ impl<'mir, 'tcx> Deref for Checker<'mir, 'tcx> {
     type Target = ConstCx<'mir, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 
@@ -272,7 +272,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         }
 
         if !tcx.has_attr(def_id, sym::rustc_do_not_const_check) {
-            self.visit_body(&body);
+            self.visit_body(body);
         }
 
         // If we got through const-checking without emitting any "primary" errors, emit any
@@ -503,7 +503,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Fake, place)
             | Rvalue::AddressOf(Mutability::Not, place) => {
                 let borrowed_place_has_mut_interior = qualifs::in_place::<HasMutInterior, _>(
-                    &self.ccx,
+                    self.ccx,
                     &mut |local| self.qualifs.has_mut_interior(self.ccx, local, location),
                     place.as_ref(),
                 );

compiler/rustc_const_eval/src/transform/check_consts/mod.rs

@@ -83,7 +83,7 @@ pub fn rustc_allow_const_fn_unstable(
     feature_gate: Symbol,
 ) -> bool {
     let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(def_id));
-    attr::rustc_allow_const_fn_unstable(&tcx.sess, attrs).any(|name| name == feature_gate)
+    attr::rustc_allow_const_fn_unstable(tcx.sess, attrs).any(|name| name == feature_gate)
 }
 
 /// Returns `true` if the given `const fn` is "const-stable".

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -129,7 +129,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                             tcx,
                             generics,
                             err,
-                            &param_ty.name.as_str(),
+                            param_ty.name.as_str(),
                             &constraint,
                             None,
                             None,

compiler/rustc_const_eval/src/transform/check_consts/post_drop_elaboration.rs

@@ -54,7 +54,7 @@ impl<'mir, 'tcx> std::ops::Deref for CheckLiveDrops<'mir, 'tcx> {
     type Target = ConstCx<'mir, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 

compiler/rustc_const_eval/src/transform/promote_consts.rs

@@ -188,7 +188,7 @@ impl<'a, 'tcx> std::ops::Deref for Validator<'a, 'tcx> {
     type Target = ConstCx<'a, 'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &self.ccx
+        self.ccx
     }
 }
 
@@ -229,7 +229,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 let statement = &self.body[loc.block].statements[loc.statement_index];
                 match &statement.kind {
                     StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>(
-                        &self.ccx,
+                        self.ccx,
                         &mut |l| self.qualif_local::<Q>(l),
                         rhs,
                     ),
@@ -246,7 +246,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 match &terminator.kind {
                     TerminatorKind::Call { .. } => {
                         let return_ty = self.body.local_decls[local].ty;
-                        Q::in_any_value_of_ty(&self.ccx, return_ty)
+                        Q::in_any_value_of_ty(self.ccx, return_ty)
                     }
                     kind => {
                         span_bug!(terminator.source_info.span, "{:?} not promotable", kind);