Remove old match guard pattern tracking code

This is subsumed by the new changes that count pattern variables as
bound for the whole guard expression.

Author: eholk

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -17,7 +17,6 @@ use rustc_middle::middle::region::{self, Scope, ScopeData, YieldData};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
-use smallvec::SmallVec;
 use tracing::debug;
 
 mod drop_ranges;
@@ -29,13 +28,6 @@ struct InteriorVisitor<'a, 'tcx> {
     expr_count: usize,
     kind: hir::GeneratorKind,
     prev_unresolved_span: Option<Span>,
-    /// Match arm guards have temporary borrows from the pattern bindings.
-    /// In case there is a yield point in a guard with a reference to such bindings,
-    /// such borrows can span across this yield point.
-    /// As such, we need to track these borrows and record them despite of the fact
-    /// that they may succeed the said yield point in the post-order.
-    guard_bindings: SmallVec<[SmallVec<[HirId; 4]>; 1]>,
-    guard_bindings_set: HirIdSet,
     linted_values: HirIdSet,
     drop_ranges: DropRanges,
 }
@@ -48,7 +40,6 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
         scope: Option<region::Scope>,
         expr: Option<&'tcx Expr<'tcx>>,
         source_span: Span,
-        guard_borrowing_from_pattern: bool,
     ) {
         use rustc_span::DUMMY_SP;
 
@@ -89,8 +80,7 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
                             // If it is a borrowing happening in the guard,
                             // it needs to be recorded regardless because they
                             // do live across this yield point.
-                            guard_borrowing_from_pattern
-                                || yield_data.expr_and_pat_count >= self.expr_count
+                            yield_data.expr_and_pat_count >= self.expr_count
                         })
                         .cloned()
                 })
@@ -196,8 +186,6 @@ pub fn resolve_interior<'a, 'tcx>(
         expr_count: 0,
         kind,
         prev_unresolved_span: None,
-        guard_bindings: <_>::default(),
-        guard_bindings_set: <_>::default(),
         linted_values: <_>::default(),
         drop_ranges: drop_ranges::compute_drop_ranges(fcx, def_id, body),
     };
@@ -284,8 +272,41 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         let Arm { guard, pat, body, .. } = arm;
         self.visit_pat(pat);
         if let Some(ref g) = guard {
-            self.guard_bindings.push(<_>::default());
             {
+                // If there is a guard, we need to count all variables bound in the pattern as
+                // borrowed for the entire guard body, regardless of whether they are accessed.
+                // We do this by walking the pattern bindings and recording `&T` for any `x: T`
+                // that is bound.
+
+                struct ArmPatCollector<'a, 'b, 'tcx> {
+                    interior_visitor: &'a mut InteriorVisitor<'b, 'tcx>,
+                    scope: Scope,
+                }
+
+                impl<'a, 'b, 'tcx> Visitor<'tcx> for ArmPatCollector<'a, 'b, 'tcx> {
+                    fn visit_pat(&mut self, pat: &'tcx Pat<'tcx>) {
+                        intravisit::walk_pat(self, pat);
+                        if let PatKind::Binding(_, id, ident, ..) = pat.kind {
+                            let ty =
+                                self.interior_visitor.fcx.typeck_results.borrow().node_type(id);
+                            let tcx = self.interior_visitor.fcx.tcx;
+                            let ty = tcx.mk_ref(
+                                // Use `ReErased` as `resolve_interior` is going to replace all the
+                                // regions anyway.
+                                tcx.mk_region(ty::ReErased),
+                                ty::TypeAndMut { ty, mutbl: hir::Mutability::Not },
+                            );
+                            self.interior_visitor.record(
+                                ty,
+                                id,
+                                Some(self.scope),
+                                None,
+                                ident.span,
+                            );
+                        }
+                    }
+                }
+
                 ArmPatCollector {
                     interior_visitor: self,
                     scope: Scope { id: g.body().hir_id.local_id, data: ScopeData::Node },
@@ -301,12 +322,6 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
                     self.visit_let_expr(l);
                 }
             }
-
-            let mut scope_var_ids =
-                self.guard_bindings.pop().expect("should have pushed at least one earlier");
-            for var_id in scope_var_ids.drain(..) {
-                self.guard_bindings_set.remove(&var_id);
-            }
         }
         self.visit_expr(body);
     }
@@ -319,13 +334,11 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         if let PatKind::Binding(..) = pat.kind {
             let scope = self.region_scope_tree.var_scope(pat.hir_id.local_id).unwrap();
             let ty = self.fcx.typeck_results.borrow().pat_ty(pat);
-            self.record(ty, pat.hir_id, Some(scope), None, pat.span, false);
+            self.record(ty, pat.hir_id, Some(scope), None, pat.span);
         }
     }
 
     fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
-        let mut guard_borrowing_from_pattern = false;
-
         match &expr.kind {
             ExprKind::Call(callee, args) => match &callee.kind {
                 ExprKind::Path(qpath) => {
@@ -352,16 +365,6 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
                 }
                 _ => intravisit::walk_expr(self, expr),
             },
-            ExprKind::Path(qpath) => {
-                intravisit::walk_expr(self, expr);
-                let res = self.fcx.typeck_results.borrow().qpath_res(qpath, expr.hir_id);
-                match res {
-                    Res::Local(id) if self.guard_bindings_set.contains(&id) => {
-                        guard_borrowing_from_pattern = true;
-                    }
-                    _ => {}
-                }
-            }
             _ => intravisit::walk_expr(self, expr),
         }
 
@@ -390,14 +393,7 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         // If there are adjustments, then record the final type --
         // this is the actual value that is being produced.
         if let Some(adjusted_ty) = self.fcx.typeck_results.borrow().expr_ty_adjusted_opt(expr) {
-            self.record(
-                adjusted_ty,
-                expr.hir_id,
-                scope,
-                Some(expr),
-                expr.span,
-                guard_borrowing_from_pattern,
-            );
+            self.record(adjusted_ty, expr.hir_id, scope, Some(expr), expr.span);
         }
 
         // Also record the unadjusted type (which is the only type if
@@ -425,68 +421,13 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         // The type table might not have information for this expression
         // if it is in a malformed scope. (#66387)
         if let Some(ty) = self.fcx.typeck_results.borrow().expr_ty_opt(expr) {
-            if guard_borrowing_from_pattern {
-                // Match guards create references to all the bindings in the pattern that are used
-                // in the guard, e.g. `y if is_even(y) => ...` becomes `is_even(*r_y)` where `r_y`
-                // is a reference to `y`, so we must record a reference to the type of the binding.
-                let tcx = self.fcx.tcx;
-                let ref_ty = tcx.mk_ref(
-                    // Use `ReErased` as `resolve_interior` is going to replace all the regions anyway.
-                    tcx.mk_region(ty::ReErased),
-                    ty::TypeAndMut { ty, mutbl: hir::Mutability::Not },
-                );
-                self.record(
-                    ref_ty,
-                    expr.hir_id,
-                    scope,
-                    Some(expr),
-                    expr.span,
-                    guard_borrowing_from_pattern,
-                );
-            }
-            self.record(
-                ty,
-                expr.hir_id,
-                scope,
-                Some(expr),
-                expr.span,
-                guard_borrowing_from_pattern,
-            );
+            self.record(ty, expr.hir_id, scope, Some(expr), expr.span);
         } else {
             self.fcx.tcx.sess.delay_span_bug(expr.span, "no type for node");
         }
     }
 }
 
-struct ArmPatCollector<'a, 'b, 'tcx> {
-    interior_visitor: &'a mut InteriorVisitor<'b, 'tcx>,
-    scope: Scope,
-}
-
-impl<'a, 'b, 'tcx> Visitor<'tcx> for ArmPatCollector<'a, 'b, 'tcx> {
-    fn visit_pat(&mut self, pat: &'tcx Pat<'tcx>) {
-        intravisit::walk_pat(self, pat);
-        if let PatKind::Binding(_, id, ..) = pat.kind {
-            self.interior_visitor
-                .guard_bindings
-                .last_mut()
-                .expect("should have pushed at least one earlier")
-                .push(id);
-            self.interior_visitor.guard_bindings_set.insert(id);
-
-            let ty = self.interior_visitor.fcx.typeck_results.borrow().node_type(id);
-            let ty = self.interior_visitor.fcx.tcx.mk_ref(
-                // Use `ReErased` as `resolve_interior` is going to replace all the regions anyway.
-                self.interior_visitor.fcx.tcx.mk_region(ty::ReErased),
-                ty::TypeAndMut { ty, mutbl: hir::Mutability::Not },
-            );
-            // FIXME: use the right span
-            let span = rustc_span::DUMMY_SP;
-            self.interior_visitor.record(ty, id, Some(self.scope), None, span, true);
-        }
-    }
-}
-
 #[derive(Default)]
 pub struct SuspendCheckData<'a, 'tcx> {
     expr: Option<&'tcx Expr<'tcx>>,