Rollup merge of #85605 - ptrojahn:closure_struct, r=matthewjasper

Replace Local::new(1) with CAPTURE_STRUCT_LOCAL

compiler/rustc_middle/src/ty/closure.rs

 use crate::hir::place::{
     Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
 };
-use crate::ty;
+use crate::{mir, ty};
 
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_hir as hir;
@@ -12,6 +12,10 @@
 
 use self::BorrowKind::*;
 
+// Captures are represented using fields inside a structure.
+// This represents accessing self in the closure structure
+pub const CAPTURE_STRUCT_LOCAL: mir::Local = mir::Local::from_u32(1);
+
 #[derive(
     Clone,
     Copy,

compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs

@@ -4,10 +4,9 @@
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind};
-use rustc_index::vec::Idx;
 use rustc_middle::mir::{
     self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory,
-    FakeReadCause, Local, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef,
+    FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef,
     ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm,
 };
 use rustc_middle::ty::{self, suggest_constraining_type_param, Ty, TypeFoldable};
@@ -1274,7 +1273,9 @@ fn try_report_cannot_return_reference_to_local(
                         bug!("temporary or return pointer with a name")
                     }
                     LocalKind::Var => "local variable ",
-                    LocalKind::Arg if !self.upvars.is_empty() && local == Local::new(1) => {
+                    LocalKind::Arg
+                        if !self.upvars.is_empty() && local == ty::CAPTURE_STRUCT_LOCAL =>
+                    {
                         "variable captured by `move` "
                     }
                     LocalKind::Arg => "function parameter ",

compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs

 use rustc_hir as hir;
 use rustc_hir::Node;
-use rustc_index::vec::Idx;
 use rustc_middle::hir::map::Map;
 use rustc_middle::mir::{Mutability, Place, PlaceRef, ProjectionElem};
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -115,12 +114,14 @@ pub(crate) fn report_mutability_error(
                 }
             }
             PlaceRef { local: _, projection: [proj_base @ .., ProjectionElem::Deref] } => {
-                if the_place_err.local == Local::new(1)
+                if the_place_err.local == ty::CAPTURE_STRUCT_LOCAL
                     && proj_base.is_empty()
                     && !self.upvars.is_empty()
                 {
                     item_msg = format!("`{}`", access_place_desc.unwrap());
-                    debug_assert!(self.body.local_decls[Local::new(1)].ty.is_region_ptr());
+                    debug_assert!(
+                        self.body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty.is_region_ptr()
+                    );
                     debug_assert!(is_closure_or_generator(
                         Place::ty_from(
                             the_place_err.local,
@@ -478,11 +479,9 @@ pub(crate) fn report_mutability_error(
                 }
             }
 
-            PlaceRef {
-                local,
-                projection: [ProjectionElem::Deref],
-                // FIXME document what is this 1 magic number about
-            } if local == Local::new(1) && !self.upvars.is_empty() => {
+            PlaceRef { local, projection: [ProjectionElem::Deref] }
+                if local == ty::CAPTURE_STRUCT_LOCAL && !self.upvars.is_empty() =>
+            {
                 self.expected_fn_found_fn_mut_call(&mut err, span, act);
             }
 

compiler/rustc_mir_build/src/build/expr/as_place.rs

@@ -209,9 +209,7 @@ fn to_upvars_resolved_place_builder<'a, 'tcx>(
     match from_builder.base {
         PlaceBase::Local(_) => Ok(from_builder),
         PlaceBase::Upvar { var_hir_id, closure_def_id, closure_kind } => {
-            // Captures are represented using fields inside a structure.
-            // This represents accessing self in the closure structure
-            let mut upvar_resolved_place_builder = PlaceBuilder::from(Local::new(1));
+            let mut upvar_resolved_place_builder = PlaceBuilder::from(ty::CAPTURE_STRUCT_LOCAL);
             match closure_kind {
                 ty::ClosureKind::Fn | ty::ClosureKind::FnMut => {
                     upvar_resolved_place_builder = upvar_resolved_place_builder.deref();

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -446,7 +446,7 @@ fn limit_capture_mutability(
                     } => {
                         // Not in a closure
                         debug_assert!(
-                            local == Local::new(1),
+                            local == ty::CAPTURE_STRUCT_LOCAL,
                             "Expected local to be Local(1), found {:?}",
                             local
                         );

compiler/rustc_mir_build/src/build/mod.rs

@@ -953,9 +953,8 @@ fn args_and_body(
         // the given closure and use the necessary information to create upvar
         // debuginfo and to fill `self.upvar_mutbls`.
         if hir_typeck_results.closure_min_captures.get(&fn_def_id).is_some() {
-            let closure_env_arg = Local::new(1);
             let mut closure_env_projs = vec![];
-            let mut closure_ty = self.local_decls[closure_env_arg].ty;
+            let mut closure_ty = self.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty;
             if let ty::Ref(_, ty, _) = closure_ty.kind() {
                 closure_env_projs.push(ProjectionElem::Deref);
                 closure_ty = ty;
@@ -1001,7 +1000,7 @@ fn args_and_body(
                         name,
                         source_info: SourceInfo::outermost(tcx_hir.span(var_id)),
                         value: VarDebugInfoContents::Place(Place {
-                            local: closure_env_arg,
+                            local: ty::CAPTURE_STRUCT_LOCAL,
                             projection: tcx.intern_place_elems(&projs),
                         }),
                     });