Change Search::infcx to tcx.

Because the `infcx` isn't needed. This removes one lifetime from
`Search`.

Author: nnethercote

compiler/rustc_trait_selection/src/traits/structural_match.rs

@@ -60,7 +60,7 @@ pub fn search_for_structural_match_violation<'tcx>(
 ) -> Option<NonStructuralMatchTy<'tcx>> {
     // FIXME: we should instead pass in an `infcx` from the outside.
     tcx.infer_ctxt().enter(|infcx| {
-        ty.visit_with(&mut Search { infcx, span, seen: FxHashSet::default() }).break_value()
+        ty.visit_with(&mut Search { tcx: infcx.tcx, span, seen: FxHashSet::default() }).break_value()
     })
 }
 
@@ -114,27 +114,23 @@ fn type_marked_structural<'tcx>(
 /// This implements the traversal over the structure of a given type to try to
 /// find instances of ADTs (specifically structs or enums) that do not implement
 /// the structural-match traits (`StructuralPartialEq` and `StructuralEq`).
-struct Search<'a, 'tcx> {
+struct Search<'tcx> {
     span: Span,
 
-    infcx: InferCtxt<'a, 'tcx>,
+    tcx: TyCtxt<'tcx>,
 
     /// Tracks ADTs previously encountered during search, so that
     /// we will not recur on them again.
     seen: FxHashSet<hir::def_id::DefId>,
 }
 
-impl<'a, 'tcx> Search<'a, 'tcx> {
-    fn tcx(&self) -> TyCtxt<'tcx> {
-        self.infcx.tcx
-    }
-
+impl<'tcx> Search<'tcx> {
     fn type_marked_structural(&self, adt_ty: Ty<'tcx>) -> bool {
-        adt_ty.is_structural_eq_shallow(self.tcx())
+        adt_ty.is_structural_eq_shallow(self.tcx)
     }
 }
 
-impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
+impl<'tcx> TypeVisitor<'tcx> for Search<'tcx> {
     type BreakTy = NonStructuralMatchTy<'tcx>;
 
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
@@ -193,7 +189,7 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
                 return ControlFlow::CONTINUE;
             }
             ty::Array(_, n)
-                if { n.try_eval_usize(self.tcx(), ty::ParamEnv::reveal_all()) == Some(0) } =>
+                if { n.try_eval_usize(self.tcx, ty::ParamEnv::reveal_all()) == Some(0) } =>
             {
                 // rust-lang/rust#62336: ignore type of contents
                 // for empty array.
@@ -214,7 +210,7 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
                 bug!("unexpected type during structural-match checking: {:?}", ty);
             }
             ty::Error(_) => {
-                self.tcx().sess.delay_span_bug(self.span, "ty::Error in structural-match check");
+                self.tcx.sess.delay_span_bug(self.span, "ty::Error in structural-match check");
                 // We still want to check other types after encountering an error,
                 // as this may still emit relevant errors.
                 return ControlFlow::CONTINUE;
@@ -244,9 +240,9 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
 
         // even though we skip super_visit_with, we must recur on
         // fields of ADT.
-        let tcx = self.tcx();
+        let tcx = self.tcx;
         adt_def.all_fields().map(|field| field.ty(tcx, substs)).try_for_each(|field_ty| {
-            let ty = self.tcx().normalize_erasing_regions(ty::ParamEnv::empty(), field_ty);
+            let ty = self.tcx.normalize_erasing_regions(ty::ParamEnv::empty(), field_ty);
             debug!("structural-match ADT: field_ty={:?}, ty={:?}", field_ty, ty);
             ty.visit_with(self)
         })