Rollup merge of rust-lang#94006 - pierwill:upvar-field, r=nikomatsakis

Use a `Field` in `ConstraintCategory::ClosureUpvar`

As part of rust-lang#90317, we do not want `HirId` to implement `Ord`, `PartialOrd`. This line of code has made that difficult

https://github.com/rust-lang/rust/blob/1b27144afc77031ba9c05d86c06c64485589775a/compiler/rustc_borrowck/src/region_infer/mod.rs#L2184

since it sorts a [`ConstraintCategory::ClosureUpvar(HirId)`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.ConstraintCategory.html#variant.ClosureUpvar).

This PR makes that variant take a [`Field`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/struct.Field.html) instead.

r? `@nikomatsakis`

Author: matthiaskrgr

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -5,6 +5,7 @@ use rustc_infer::infer::{
     error_reporting::nice_region_error::NiceRegionError,
     error_reporting::unexpected_hidden_region_diagnostic, NllRegionVariableOrigin,
 };
+use rustc_middle::hir::place::PlaceBase;
 use rustc_middle::mir::{ConstraintCategory, ReturnConstraint};
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
 use rustc_middle::ty::{self, RegionVid, Ty};
@@ -421,17 +422,26 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
         diag.span_label(*span, message);
 
-        // FIXME(project-rfc-2229#48): This should store a captured_place not a hir id
-        if let ReturnConstraint::ClosureUpvar(upvar) = kind {
+        if let ReturnConstraint::ClosureUpvar(upvar_field) = kind {
             let def_id = match self.regioncx.universal_regions().defining_ty {
                 DefiningTy::Closure(def_id, _) => def_id,
                 ty => bug!("unexpected DefiningTy {:?}", ty),
             };
 
-            let upvar_def_span = self.infcx.tcx.hir().span(upvar);
-            let upvar_span = self.infcx.tcx.upvars_mentioned(def_id).unwrap()[&upvar].span;
-            diag.span_label(upvar_def_span, "variable defined here");
-            diag.span_label(upvar_span, "variable captured here");
+            let captured_place = &self.upvars[upvar_field.index()].place;
+            let defined_hir = match captured_place.place.base {
+                PlaceBase::Local(hirid) => Some(hirid),
+                PlaceBase::Upvar(upvar) => Some(upvar.var_path.hir_id),
+                _ => None,
+            };
+
+            if defined_hir.is_some() {
+                let upvars_map = self.infcx.tcx.upvars_mentioned(def_id).unwrap();
+                let upvar_def_span = self.infcx.tcx.hir().span(defined_hir.unwrap());
+                let upvar_span = upvars_map.get(&defined_hir.unwrap()).unwrap().span;
+                diag.span_label(upvar_def_span, "variable defined here");
+                diag.span_label(upvar_span, "variable captured here");
+            }
         }
 
         if let Some(fr_span) = self.give_region_a_name(*outlived_fr).unwrap().span() {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2530,9 +2530,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             body,
         );
         let category = if let Some(field) = field {
-            let var_hir_id = self.borrowck_context.upvars[field.index()].place.get_root_variable();
-            // FIXME(project-rfc-2229#8): Use Place for better diagnostics
-            ConstraintCategory::ClosureUpvar(var_hir_id)
+            ConstraintCategory::ClosureUpvar(field)
         } else {
             ConstraintCategory::Boring
         };

compiler/rustc_middle/src/mir/query.rs

@@ -341,7 +341,7 @@ pub enum ConstraintCategory {
     /// like `Foo { field: my_val }`)
     Usage,
     OpaqueType,
-    ClosureUpvar(hir::HirId),
+    ClosureUpvar(Field),
 
     /// A constraint from a user-written predicate
     /// with the provided span, written on the item
@@ -363,7 +363,7 @@ pub enum ConstraintCategory {
 #[derive(TyEncodable, TyDecodable, HashStable)]
 pub enum ReturnConstraint {
     Normal,
-    ClosureUpvar(hir::HirId),
+    ClosureUpvar(Field),
 }
 
 /// The subject of a `ClosureOutlivesRequirement` -- that is, the thing