Remove MatchCheckCtxt::create_and_enter.

It has a single call site.

Author: nnethercote

src/librustc_mir_build/hair/pattern/_match.rs

@@ -580,21 +580,11 @@ crate struct MatchCheckCtxt<'a, 'tcx> {
     /// outside it's module and should not be matchable with an empty match
     /// statement.
     crate module: DefId,
-    param_env: ty::ParamEnv<'tcx>,
+    crate param_env: ty::ParamEnv<'tcx>,
     crate pattern_arena: &'a TypedArena<Pat<'tcx>>,
 }
 
 impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
-    crate fn create_and_enter<R>(
-        tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-        pattern_arena: &'a TypedArena<Pat<'tcx>>,
-        module: DefId,
-        f: impl FnOnce(MatchCheckCtxt<'a, 'tcx>) -> R,
-    ) -> R {
-        f(MatchCheckCtxt { tcx, param_env, module, pattern_arena })
-    }
-
     fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
         if self.tcx.features().exhaustive_patterns {
             self.tcx.is_ty_uninhabited_from(self.module, ty, self.param_env)

src/librustc_mir_build/hair/pattern/check_match.rs

@@ -149,13 +149,13 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {
 
     fn check_in_cx(&self, hir_id: HirId, f: impl FnOnce(MatchCheckCtxt<'_, 'tcx>)) {
         let module = self.tcx.parent_module(hir_id);
-        MatchCheckCtxt::create_and_enter(
-            self.tcx,
-            self.param_env,
-            &self.pattern_arena,
-            module.to_def_id(),
-            f,
-        );
+        let cx = MatchCheckCtxt {
+            tcx: self.tcx,
+            param_env: self.param_env,
+            module: module.to_def_id(),
+            pattern_arena: &self.pattern_arena,
+        };
+        f(cx);
     }
 
     fn check_match(