Remove Upvar duplication

This cuts out an extra allocation and copying over from the already
cached closure capture information.

Author: Mark-Simulacrum

Diff for: compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -217,9 +217,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         projection: place.projection.split_at(index + 1).0,
                     }) {
                         let var_index = field.index();
-                        buf = self.upvars[var_index].place.to_string(self.infcx.tcx);
+                        buf = self.upvars[var_index].to_string(self.infcx.tcx);
                         ok = Ok(());
-                        if !self.upvars[var_index].by_ref {
+                        if !self.upvars[var_index].is_by_ref() {
                             buf.insert(0, '*');
                         }
                     } else {
@@ -250,7 +250,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         local,
                         projection: place.projection.split_at(index + 1).0,
                     }) {
-                        buf = self.upvars[field.index()].place.to_string(self.infcx.tcx);
+                        buf = self.upvars[field.index()].to_string(self.infcx.tcx);
                         ok = Ok(());
                     } else {
                         let field_name = self.describe_field(

Diff for: compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -363,8 +363,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     format!("captured variable in an `{closure_kind}` closure");
 
                 let upvar = &self.upvars[upvar_field.unwrap().index()];
-                let upvar_hir_id = upvar.place.get_root_variable();
-                let upvar_name = upvar.place.to_string(self.infcx.tcx);
+                let upvar_hir_id = upvar.get_root_variable();
+                let upvar_name = upvar.to_string(self.infcx.tcx);
                 let upvar_span = self.infcx.tcx.hir().span(upvar_hir_id);
 
                 let place_name = self.describe_any_place(move_place.as_ref());

Diff for: compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -66,7 +66,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 ));
 
                 let imm_borrow_derefed = self.upvars[upvar_index.index()]
-                    .place
                     .place
                     .deref_tys()
                     .any(|ty| matches!(ty.kind(), ty::Ref(.., hir::Mutability::Not)));
@@ -85,7 +84,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     if self.is_upvar_field_projection(access_place.as_ref()).is_some() {
                         reason = ", as it is not declared as mutable".to_string();
                     } else {
-                        let name = self.upvars[upvar_index.index()].place.to_string(self.infcx.tcx);
+                        let name = self.upvars[upvar_index.index()].to_string(self.infcx.tcx);
                         reason = format!(", as `{name}` is not declared as mutable");
                     }
                 }
@@ -388,7 +387,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     Place::ty_from(local, proj_base, self.body, self.infcx.tcx).ty
                 ));
 
-                let captured_place = &self.upvars[upvar_index.index()].place;
+                let captured_place = self.upvars[upvar_index.index()];
 
                 err.span_label(span, format!("cannot {act}"));
 

Diff for: compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -605,7 +605,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             };
 
             let captured_place = &self.upvars[upvar_field.index()].place;
-            let defined_hir = match captured_place.place.base {
+            let defined_hir = match captured_place.base {
                 PlaceBase::Local(hirid) => Some(hirid),
                 PlaceBase::Upvar(upvar) => Some(upvar.var_path.hir_id),
                 _ => None,

Diff for: compiler/rustc_borrowck/src/diagnostics/var_name.rs

@@ -2,10 +2,9 @@
 #![deny(rustc::diagnostic_outside_of_impl)]
 
 use crate::region_infer::RegionInferenceContext;
-use crate::Upvar;
 use rustc_index::IndexSlice;
 use rustc_middle::mir::{Body, Local};
-use rustc_middle::ty::{RegionVid, TyCtxt};
+use rustc_middle::ty::{self, RegionVid, TyCtxt};
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 
@@ -15,7 +14,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
         local_names: &IndexSlice<Local, Option<Symbol>>,
-        upvars: &[Upvar<'tcx>],
+        upvars: &[&ty::CapturedPlace<'tcx>],
         fr: RegionVid,
     ) -> Option<(Option<Symbol>, Span)> {
         debug!("get_var_name_and_span_for_region(fr={fr:?})");
@@ -66,10 +65,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn get_upvar_name_and_span_for_region(
         &self,
         tcx: TyCtxt<'tcx>,
-        upvars: &[Upvar<'tcx>],
+        upvars: &[&ty::CapturedPlace<'tcx>],
         upvar_index: usize,
     ) -> (Symbol, Span) {
-        let upvar_hir_id = upvars[upvar_index].place.get_root_variable();
+        let upvar_hir_id = upvars[upvar_index].get_root_variable();
         debug!("get_upvar_name_and_span_for_region: upvar_hir_id={upvar_hir_id:?}");
 
         let upvar_name = tcx.hir().name(upvar_hir_id);

Diff for: compiler/rustc_borrowck/src/lib.rs

@@ -35,7 +35,7 @@ use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::DefiningAnchor;
-use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
+use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt};
 use rustc_session::lint::builtin::UNUSED_MUT;
 use rustc_span::{Span, Symbol};
 use rustc_target::abi::FieldIdx;
@@ -100,15 +100,6 @@ use renumber::RegionCtxt;
 
 fluent_messages! { "../messages.ftl" }
 
-// FIXME(eddyb) perhaps move this somewhere more centrally.
-#[derive(Debug)]
-struct Upvar<'tcx> {
-    place: CapturedPlace<'tcx>,
-
-    /// If true, the capture is behind a reference.
-    by_ref: bool,
-}
-
 /// Associate some local constants with the `'tcx` lifetime
 struct TyCtxtConsts<'tcx>(TyCtxt<'tcx>);
 impl<'tcx> TyCtxtConsts<'tcx> {
@@ -193,18 +184,6 @@ fn do_mir_borrowck<'tcx>(
         infcx.set_tainted_by_errors(e);
         errors.set_tainted_by_errors(e);
     }
-    let upvars: Vec<_> = tcx
-        .closure_captures(def)
-        .iter()
-        .map(|&captured_place| {
-            let capture = captured_place.info.capture_kind;
-            let by_ref = match capture {
-                ty::UpvarCapture::ByValue => false,
-                ty::UpvarCapture::ByRef(..) => true,
-            };
-            Upvar { place: captured_place.clone(), by_ref }
-        })
-        .collect();
 
     // Replace all regions with fresh inference variables. This
     // requires first making our own copy of the MIR. This copy will
@@ -254,7 +233,7 @@ fn do_mir_borrowck<'tcx>(
         &mut flow_inits,
         &mdpe.move_data,
         &borrow_set,
-        &upvars,
+        tcx.closure_captures(def),
         consumer_options,
     );
 
@@ -324,7 +303,7 @@ fn do_mir_borrowck<'tcx>(
             used_mut: Default::default(),
             used_mut_upvars: SmallVec::new(),
             borrow_set: Rc::clone(&borrow_set),
-            upvars: Vec::new(),
+            upvars: &[],
             local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
             region_names: RefCell::default(),
             next_region_name: RefCell::new(1),
@@ -365,7 +344,7 @@ fn do_mir_borrowck<'tcx>(
         used_mut: Default::default(),
         used_mut_upvars: SmallVec::new(),
         borrow_set: Rc::clone(&borrow_set),
-        upvars,
+        upvars: tcx.closure_captures(def),
         local_names,
         region_names: RefCell::default(),
         next_region_name: RefCell::new(1),
@@ -584,7 +563,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     borrow_set: Rc<BorrowSet<'tcx>>,
 
     /// Information about upvars not necessarily preserved in types or MIR
-    upvars: Vec<Upvar<'tcx>>,
+    upvars: &'tcx [&'tcx ty::CapturedPlace<'tcx>],
 
     /// Names of local (user) variables (extracted from `var_debug_info`).
     local_names: IndexVec<Local, Option<Symbol>>,
@@ -2294,7 +2273,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                     // unique path to the `&mut`
                                     hir::Mutability::Mut => {
                                         let mode = match self.is_upvar_field_projection(place) {
-                                            Some(field) if self.upvars[field.index()].by_ref => {
+                                            Some(field)
+                                                if self.upvars[field.index()].is_by_ref() =>
+                                            {
                                                 is_local_mutation_allowed
                                             }
                                             _ => LocalMutationIsAllowed::Yes,
@@ -2342,7 +2323,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                  place={:?}, place_base={:?}",
                                 upvar, is_local_mutation_allowed, place, place_base
                             );
-                            match (upvar.place.mutability, is_local_mutation_allowed) {
+                            match (upvar.mutability, is_local_mutation_allowed) {
                                 (
                                     Mutability::Not,
                                     LocalMutationIsAllowed::No

Diff for: compiler/rustc_borrowck/src/nll.rs

@@ -37,7 +37,7 @@ use crate::{
     renumber,
     type_check::{self, MirTypeckRegionConstraints, MirTypeckResults},
     universal_regions::UniversalRegions,
-    BorrowckInferCtxt, Upvar,
+    BorrowckInferCtxt,
 };
 
 pub type PoloniusOutput = Output<RustcFacts>;
@@ -166,7 +166,7 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
     flow_inits: &mut ResultsCursor<'cx, 'tcx, MaybeInitializedPlaces<'cx, 'tcx>>,
     move_data: &MoveData<'tcx>,
     borrow_set: &BorrowSet<'tcx>,
-    upvars: &[Upvar<'tcx>],
+    upvars: &[&ty::CapturedPlace<'tcx>],
     consumer_options: Option<ConsumerOptions>,
 ) -> NllOutput<'tcx> {
     let is_polonius_legacy_enabled = infcx.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled();

Diff for: compiler/rustc_borrowck/src/path_utils.rs

@@ -4,7 +4,6 @@ use crate::borrow_set::{BorrowData, BorrowSet, TwoPhaseActivation};
 use crate::places_conflict;
 use crate::AccessDepth;
 use crate::BorrowIndex;
-use crate::Upvar;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_middle::mir::BorrowKind;
 use rustc_middle::mir::{BasicBlock, Body, Location, Place, PlaceRef, ProjectionElem};
@@ -150,7 +149,7 @@ pub(super) fn borrow_of_local_data(place: Place<'_>) -> bool {
 /// of a closure type.
 pub(crate) fn is_upvar_field_projection<'tcx>(
     tcx: TyCtxt<'tcx>,
-    upvars: &[Upvar<'tcx>],
+    upvars: &[&rustc_middle::ty::CapturedPlace<'tcx>],
     place_ref: PlaceRef<'tcx>,
     body: &Body<'tcx>,
 ) -> Option<FieldIdx> {
@@ -166,7 +165,7 @@ pub(crate) fn is_upvar_field_projection<'tcx>(
         Some((place_base, ProjectionElem::Field(field, _ty))) => {
             let base_ty = place_base.ty(body, tcx).ty;
             if (base_ty.is_closure() || base_ty.is_coroutine())
-                && (!by_ref || upvars[field.index()].by_ref)
+                && (!by_ref || upvars[field.index()].is_by_ref())
             {
                 Some(field)
             } else {

Diff for: compiler/rustc_borrowck/src/type_check/mod.rs

@@ -68,7 +68,7 @@ use crate::{
     region_infer::TypeTest,
     type_check::free_region_relations::{CreateResult, UniversalRegionRelations},
     universal_regions::{DefiningTy, UniversalRegions},
-    BorrowckInferCtxt, Upvar,
+    BorrowckInferCtxt,
 };
 
 macro_rules! span_mirbug {
@@ -138,7 +138,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
     flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
     move_data: &MoveData<'tcx>,
     elements: &Rc<RegionValueElements>,
-    upvars: &[Upvar<'tcx>],
+    upvars: &[&ty::CapturedPlace<'tcx>],
     use_polonius: bool,
 ) -> MirTypeckResults<'tcx> {
     let implicit_region_bound = ty::Region::new_var(infcx.tcx, universal_regions.fr_fn_body);
@@ -857,7 +857,7 @@ struct BorrowCheckContext<'a, 'tcx> {
     all_facts: &'a mut Option<AllFacts>,
     borrow_set: &'a BorrowSet<'tcx>,
     pub(crate) constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
-    upvars: &'a [Upvar<'tcx>],
+    upvars: &'a [&'a ty::CapturedPlace<'tcx>],
 
     /// The set of loans that are live at a given point in the CFG, filled in by `liveness::trace`,
     /// when using `-Zpolonius=next`.

Diff for: compiler/rustc_middle/src/ty/closure.rs

@@ -247,6 +247,13 @@ impl<'tcx> CapturedPlace<'tcx> {
                 .span
         }
     }
+
+    pub fn is_by_ref(&self) -> bool {
+        match self.info.capture_kind {
+            ty::UpvarCapture::ByValue => false,
+            ty::UpvarCapture::ByRef(..) => true,
+        }
+    }
 }
 
 #[derive(Copy, Clone, Debug, HashStable)]