Auto merge of #83842 - LeSeulArtichaut:thir-vec, r=nikomatsakis

Store THIR in `IndexVec`s instead of an `Arena`

This is a necessary step to store the THIR in a query: #85273. See [relevant discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/278509-project-thir-unsafeck/topic/THIR-dependent.20queries.20design).

r? `@ghost` cc `@cjgillot` `@nikomatsakis`

compiler/rustc_driver/src/pretty.rs

@@ -8,14 +8,12 @@ use rustc_hir_pretty as pprust_hir;
 use rustc_middle::hir::map as hir_map;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_mir::util::{write_mir_graphviz, write_mir_pretty};
-use rustc_mir_build::thir;
 use rustc_session::config::{Input, PpAstTreeMode, PpHirMode, PpMode, PpSourceMode};
 use rustc_session::Session;
 use rustc_span::symbol::Ident;
 use rustc_span::FileName;
 
 use std::cell::Cell;
-use std::fmt::Write;
 use std::path::Path;
 
 pub use self::PpMode::*;
@@ -490,18 +488,8 @@ fn print_with_analysis(
         }
 
         ThirTree => {
-            let mut out = String::new();
-            abort_on_err(rustc_typeck::check_crate(tcx), tcx.sess);
-            debug!("pretty printing THIR tree");
-            for did in tcx.body_owners() {
-                let hir = tcx.hir();
-                let body = hir.body(hir.body_owned_by(hir.local_def_id_to_hir_id(did)));
-                let arena = thir::Arena::default();
-                let thir =
-                    thir::build_thir(tcx, ty::WithOptConstParam::unknown(did), &arena, &body.value);
-                let _ = writeln!(out, "{:?}:\n{:#?}\n", did, thir);
-            }
-            out
+            // FIXME(rust-lang/project-thir-unsafeck#8)
+            todo!()
         }
 
         _ => unreachable!(),

compiler/rustc_mir_build/src/build/block.rs

@@ -12,18 +12,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         destination: Place<'tcx>,
         block: BasicBlock,
-        ast_block: &Block<'_, 'tcx>,
+        ast_block: &Block,
         source_info: SourceInfo,
     ) -> BlockAnd<()> {
         let Block {
             region_scope,
             opt_destruction_scope,
             span,
-            stmts,
+            ref stmts,
             expr,
             targeted_by_break,
             safety_mode,
         } = *ast_block;
+        let expr = expr.map(|expr| &self.thir[expr]);
         self.in_opt_scope(opt_destruction_scope.map(|de| (de, source_info)), move |this| {
             this.in_scope((region_scope, source_info), LintLevel::Inherited, move |this| {
                 if targeted_by_break {
@@ -32,13 +33,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             destination,
                             block,
                             span,
-                            stmts,
+                            &stmts,
                             expr,
                             safety_mode,
                         ))
                     })
                 } else {
-                    this.ast_block_stmts(destination, block, span, stmts, expr, safety_mode)
+                    this.ast_block_stmts(destination, block, span, &stmts, expr, safety_mode)
                 }
             })
         })
@@ -49,8 +50,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         destination: Place<'tcx>,
         mut block: BasicBlock,
         span: Span,
-        stmts: &[Stmt<'_, 'tcx>],
-        expr: Option<&Expr<'_, 'tcx>>,
+        stmts: &[StmtId],
+        expr: Option<&Expr<'tcx>>,
         safety_mode: BlockSafety,
     ) -> BlockAnd<()> {
         let this = self;
@@ -78,23 +79,30 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         this.update_source_scope_for_safety_mode(span, safety_mode);
 
         let source_info = this.source_info(span);
-        for Stmt { kind, opt_destruction_scope } in stmts {
+        for stmt in stmts {
+            let Stmt { ref kind, opt_destruction_scope } = this.thir[*stmt];
             match kind {
-                &StmtKind::Expr { scope, expr } => {
+                StmtKind::Expr { scope, expr } => {
                     this.block_context.push(BlockFrame::Statement { ignores_expr_result: true });
                     unpack!(
                         block = this.in_opt_scope(
                             opt_destruction_scope.map(|de| (de, source_info)),
                             |this| {
-                                let si = (scope, source_info);
+                                let si = (*scope, source_info);
                                 this.in_scope(si, LintLevel::Inherited, |this| {
-                                    this.stmt_expr(block, expr, Some(scope))
+                                    this.stmt_expr(block, &this.thir[*expr], Some(*scope))
                                 })
                             }
                         )
                     );
                 }
-                StmtKind::Let { remainder_scope, init_scope, pattern, initializer, lint_level } => {
+                StmtKind::Let {
+                    remainder_scope,
+                    init_scope,
+                    ref pattern,
+                    initializer,
+                    lint_level,
+                } => {
                     let ignores_expr_result = matches!(*pattern.kind, PatKind::Wild);
                     this.block_context.push(BlockFrame::Statement { ignores_expr_result });
 
@@ -110,6 +118,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                     // Evaluate the initializer, if present.
                     if let Some(init) = initializer {
+                        let init = &this.thir[*init];
                         let initializer_span = init.span;
 
                         unpack!(
@@ -145,7 +154,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                         debug!("ast_block_stmts: pattern={:?}", pattern);
                         this.visit_primary_bindings(
-                            &pattern,
+                            pattern,
                             UserTypeProjections::none(),
                             &mut |this, _, _, _, node, span, _, _| {
                                 this.storage_live_binding(block, node, span, OutsideGuard, true);

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

@@ -8,11 +8,13 @@ use rustc_middle::ty::CanonicalUserTypeAnnotation;
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, yielding a compile-time constant. Assumes that
     /// `expr` is a valid compile-time constant!
-    crate fn as_constant(&mut self, expr: &Expr<'_, 'tcx>) -> Constant<'tcx> {
+    crate fn as_constant(&mut self, expr: &Expr<'tcx>) -> Constant<'tcx> {
         let this = self;
         let Expr { ty, temp_lifetime: _, span, ref kind } = *expr;
         match *kind {
-            ExprKind::Scope { region_scope: _, lint_level: _, value } => this.as_constant(value),
+            ExprKind::Scope { region_scope: _, lint_level: _, value } => {
+                this.as_constant(&this.thir[value])
+            }
             ExprKind::Literal { literal, user_ty, const_id: _ } => {
                 let user_ty = user_ty.map(|user_ty| {
                     this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {

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

@@ -17,7 +17,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     crate fn as_local_operand(
         &mut self,
         block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Operand<'tcx>> {
         let local_scope = self.local_scope();
         self.as_operand(block, Some(local_scope), expr)
@@ -74,7 +74,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     crate fn as_local_call_operand(
         &mut self,
         block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Operand<'tcx>> {
         let local_scope = self.local_scope();
         self.as_call_operand(block, Some(local_scope), expr)
@@ -93,16 +93,17 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         mut block: BasicBlock,
         scope: Option<region::Scope>,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Operand<'tcx>> {
         debug!("as_operand(block={:?}, expr={:?})", block, expr);
         let this = self;
 
         if let ExprKind::Scope { region_scope, lint_level, value } = expr.kind {
             let source_info = this.source_info(expr.span);
             let region_scope = (region_scope, source_info);
-            return this
-                .in_scope(region_scope, lint_level, |this| this.as_operand(block, scope, value));
+            return this.in_scope(region_scope, lint_level, |this| {
+                this.as_operand(block, scope, &this.thir[value])
+            });
         }
 
         let category = Category::of(&expr.kind).unwrap();
@@ -123,7 +124,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         mut block: BasicBlock,
         scope: Option<region::Scope>,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Operand<'tcx>> {
         debug!("as_call_operand(block={:?}, expr={:?})", block, expr);
         let this = self;
@@ -132,7 +133,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             let source_info = this.source_info(expr.span);
             let region_scope = (region_scope, source_info);
             return this.in_scope(region_scope, lint_level, |this| {
-                this.as_call_operand(block, scope, value)
+                this.as_call_operand(block, scope, &this.thir[value])
             });
         }
 
@@ -151,7 +152,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // type, and that value is coming from the deref of a box.
                 if let ExprKind::Deref { arg } = expr.kind {
                     // Generate let tmp0 = arg0
-                    let operand = unpack!(block = this.as_temp(block, scope, arg, Mutability::Mut));
+                    let operand = unpack!(
+                        block = this.as_temp(block, scope, &this.thir[arg], Mutability::Mut)
+                    );
 
                     // Return the operand *tmp0 to be used as the call argument
                     let place = Place {

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

@@ -381,7 +381,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     crate fn as_place(
         &mut self,
         mut block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Place<'tcx>> {
         let place_builder = unpack!(block = self.as_place_builder(block, expr));
         block.and(place_builder.into_place(self.tcx, self.typeck_results))
@@ -392,7 +392,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     crate fn as_place_builder(
         &mut self,
         block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<PlaceBuilder<'tcx>> {
         self.expr_as_place(block, expr, Mutability::Mut, None)
     }
@@ -405,7 +405,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     crate fn as_read_only_place(
         &mut self,
         mut block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<Place<'tcx>> {
         let place_builder = unpack!(block = self.as_read_only_place_builder(block, expr));
         block.and(place_builder.into_place(self.tcx, self.typeck_results))
@@ -420,15 +420,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn as_read_only_place_builder(
         &mut self,
         block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
     ) -> BlockAnd<PlaceBuilder<'tcx>> {
         self.expr_as_place(block, expr, Mutability::Not, None)
     }
 
     fn expr_as_place(
         &mut self,
         mut block: BasicBlock,
-        expr: &Expr<'_, 'tcx>,
+        expr: &Expr<'tcx>,
         mutability: Mutability,
         fake_borrow_temps: Option<&mut Vec<Local>>,
     ) -> BlockAnd<PlaceBuilder<'tcx>> {
@@ -440,23 +440,27 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         match expr.kind {
             ExprKind::Scope { region_scope, lint_level, value } => {
                 this.in_scope((region_scope, source_info), lint_level, |this| {
-                    this.expr_as_place(block, value, mutability, fake_borrow_temps)
+                    this.expr_as_place(block, &this.thir[value], mutability, fake_borrow_temps)
                 })
             }
             ExprKind::Field { lhs, name } => {
-                let place_builder =
-                    unpack!(block = this.expr_as_place(block, lhs, mutability, fake_borrow_temps,));
+                let place_builder = unpack!(
+                    block =
+                        this.expr_as_place(block, &this.thir[lhs], mutability, fake_borrow_temps,)
+                );
                 block.and(place_builder.field(name, expr.ty))
             }
             ExprKind::Deref { arg } => {
-                let place_builder =
-                    unpack!(block = this.expr_as_place(block, arg, mutability, fake_borrow_temps,));
+                let place_builder = unpack!(
+                    block =
+                        this.expr_as_place(block, &this.thir[arg], mutability, fake_borrow_temps,)
+                );
                 block.and(place_builder.deref())
             }
             ExprKind::Index { lhs, index } => this.lower_index_expression(
                 block,
-                lhs,
-                index,
+                &this.thir[lhs],
+                &this.thir[index],
                 mutability,
                 fake_borrow_temps,
                 expr.temp_lifetime,
@@ -481,7 +485,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
             ExprKind::PlaceTypeAscription { source, user_ty } => {
                 let place_builder = unpack!(
-                    block = this.expr_as_place(block, source, mutability, fake_borrow_temps,)
+                    block = this.expr_as_place(
+                        block,
+                        &this.thir[source],
+                        mutability,
+                        fake_borrow_temps,
+                    )
                 );
                 if let Some(user_ty) = user_ty {
                     let annotation_index =
@@ -509,6 +518,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 block.and(place_builder)
             }
             ExprKind::ValueTypeAscription { source, user_ty } => {
+                let source = &this.thir[source];
                 let temp =
                     unpack!(block = this.as_temp(block, source.temp_lifetime, source, mutability));
                 if let Some(user_ty) = user_ty {
@@ -613,8 +623,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn lower_index_expression(
         &mut self,
         mut block: BasicBlock,
-        base: &Expr<'_, 'tcx>,
-        index: &Expr<'_, 'tcx>,
+        base: &Expr<'tcx>,
+        index: &Expr<'tcx>,
         mutability: Mutability,
         fake_borrow_temps: Option<&mut Vec<Local>>,
         temp_lifetime: Option<region::Scope>,