Auto merge of #142830 - cjgillot:lower-incr-2, r=petrochenkov

Make lowering incremental, take 3/N



Rebase of #88186 that was rebased by #127262

No real change in design, so I'm not expecting a perf miracle.

r? @ghost

Author: bors

Cargo.lock

@@ -3640,7 +3640,6 @@ version = "0.0.0"
 dependencies = [
  "rustc_abi",
  "rustc_ast",
- "rustc_ast_pretty",
  "rustc_attr_parsing",
  "rustc_data_structures",
  "rustc_errors",

compiler/rustc_ast/src/ast.rs

@@ -30,6 +30,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::tagged_ptr::Tag;
 use rustc_macros::{Decodable, Encodable, StableHash, Walkable};
 pub use rustc_span::AttrId;
+use rustc_span::def_id::LocalDefId;
 use rustc_span::{
     ByteSymbol, DUMMY_SP, ErrorGuaranteed, Ident, LocalExpnId, Span, Spanned, Symbol, kw, respan,
     sym,
@@ -4362,6 +4363,23 @@ impl TryFrom<ItemKind> for ForeignItemKind {
 
 pub type ForeignItem = Item<ForeignItemKind>;
 
+/// Fragment of the AST according to "HIR owner" semantics.
+///
+/// This is used to map each `LocalDefId` to its content's AST.
+#[derive(Debug)]
+pub enum AstOwner {
+    /// This definition does not correspond to a HIR owner.
+    NonOwner,
+    /// This definition corresponds to a nested `use` tree.
+    /// The `LocalDefId` points to its HIR owner.
+    NestedUseTree(LocalDefId),
+    Crate(Box<Crate>),
+    Item(Box<Item>),
+    TraitItem(Box<AssocItem>),
+    ImplItem(Box<AssocItem>),
+    ForeignItem(Box<ForeignItem>),
+}
+
 // Some nodes are used a lot. Make sure they don't unintentionally get bigger.
 #[cfg(target_pointer_width = "64")]
 mod size_asserts {

compiler/rustc_ast/src/mut_visit.rs

@@ -361,7 +361,10 @@ pub fn walk_flat_map_stmt<T: MutVisitor>(
     stmts
 }
 
-fn walk_flat_map_stmt_kind<T: MutVisitor>(vis: &mut T, kind: StmtKind) -> SmallVec<[StmtKind; 1]> {
+pub fn walk_flat_map_stmt_kind<T: MutVisitor>(
+    vis: &mut T,
+    kind: StmtKind,
+) -> SmallVec<[StmtKind; 1]> {
     match kind {
         StmtKind::Let(mut local) => smallvec![StmtKind::Let({
             vis.visit_local(&mut local);

compiler/rustc_ast_lowering/Cargo.toml

@@ -10,7 +10,6 @@ doctest = false
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }

compiler/rustc_ast_lowering/src/block.rs

@@ -44,17 +44,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     stmts.push(hir::Stmt { hir_id, kind, span });
                 }
                 StmtKind::Item(it) => {
-                    stmts.extend(self.lower_item_ref(it).into_iter().enumerate().map(
-                        |(i, item_id)| {
-                            let hir_id = match i {
-                                0 => self.lower_node_id(s.id),
-                                _ => self.next_id(),
-                            };
-                            let kind = hir::StmtKind::Item(item_id);
-                            let span = self.lower_span(s.span);
-                            hir::Stmt { hir_id, kind, span }
-                        },
-                    ));
+                    let item_id = self.lower_item_ref(it);
+                    let hir_id = self.lower_node_id(s.id);
+                    let kind = hir::StmtKind::Item(item_id);
+                    let span = self.lower_span(s.span);
+                    stmts.push(hir::Stmt { hir_id, kind, span });
                 }
                 StmtKind::Expr(e) => {
                     let e = self.lower_expr(e);

compiler/rustc_ast_lowering/src/delegation.rs

@@ -46,12 +46,12 @@ use rustc_abi::ExternAbi;
 use rustc_ast as ast;
 use rustc_ast::node_id::NodeMap;
 use rustc_ast::*;
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::attrs::{AttributeKind, InlineAttr};
-use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{self as hir, FnDeclFlags};
 use rustc_middle::span_bug;
-use rustc_middle::ty::{Asyncness, PerOwnerResolverData, TyCtxt};
+use rustc_middle::ty::{Asyncness, PerOwnerResolverData};
+use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::symbol::kw;
 use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
 
@@ -62,7 +62,6 @@ use crate::diagnostics::{
 };
 use crate::{
     AllowReturnTypeNotation, ImplTraitContext, ImplTraitPosition, LoweringContext, ParamMode,
-    index_crate,
 };
 
 mod generics;
@@ -121,64 +120,6 @@ static ATTRS_ADDITIONS: &[AttrAdditionInfo] = &[
     },
 ];
 
-pub(crate) fn delegations_resolutions(
-    tcx: TyCtxt<'_>,
-    _: (),
-) -> FxIndexMap<LocalDefId, Result<DefId, ErrorGuaranteed>> {
-    let krate = tcx.hir_crate(());
-
-    let (resolver, ast_crate) = &*krate.delayed_resolver.borrow();
-
-    // FIXME!!!(fn_delegation): make ast index lifetime same as resolver,
-    // as it is too bad to reindex whole crate on each delegation lowering.
-    let ast_index = index_crate(resolver, ast_crate);
-
-    let mut result = FxIndexMap::<LocalDefId, Result<DefId, ErrorGuaranteed>>::default();
-
-    for &def_id in &krate.delayed_ids {
-        let delegation = ast_index[def_id].delegation().expect("processing delegations");
-        let span = delegation.last_segment_span();
-
-        if let Some(info) = tcx.resolutions(()).delegation_infos.get(&def_id) {
-            let res = info.resolution_id.map(|id| check_for_cycles(tcx, id, span).map(|_| id));
-            result.insert(def_id, res.flatten());
-        } else {
-            tcx.dcx().span_delayed_bug(
-                span,
-                format!("delegation resolution record was not found for {def_id:?}"),
-            );
-        }
-    }
-
-    result
-}
-
-fn check_for_cycles(tcx: TyCtxt<'_>, mut def_id: DefId, span: Span) -> Result<(), ErrorGuaranteed> {
-    let mut visited: FxHashSet<DefId> = Default::default();
-
-    loop {
-        visited.insert(def_id);
-
-        // If def_id is in local crate and it corresponds to another delegation
-        // it means that we refer to another delegation as a callee, so in order to obtain
-        // a signature DefId we obtain NodeId of the callee delegation and try to get signature from it.
-        if let Some(local_id) = def_id.as_local()
-            && let Some(info) = tcx.resolutions(()).delegation_infos.get(&local_id)
-            && let Ok(id) = info.resolution_id
-        {
-            def_id = id;
-            if visited.contains(&def_id) {
-                return Err(match visited.len() {
-                    1 => tcx.dcx().emit_err(UnresolvedDelegationCallee { span }),
-                    _ => tcx.dcx().emit_err(CycleInDelegationSignatureResolution { span }),
-                });
-            }
-        } else {
-            return Ok(());
-        }
-    }
-}
-
 impl<'hir> LoweringContext<'_, 'hir> {
     fn is_method(&self, def_id: DefId, span: Span) -> bool {
         match self.tcx.def_kind(def_id) {
@@ -188,18 +129,53 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
+    fn check_for_cycles(&self, mut def_id: DefId, span: Span) -> Result<(), ErrorGuaranteed> {
+        let mut visited: FxHashSet<DefId> = Default::default();
+
+        loop {
+            visited.insert(def_id);
+
+            // If def_id is in local crate and it corresponds to another delegation
+            // it means that we refer to another delegation as a callee, so in order to obtain
+            // a signature DefId we obtain NodeId of the callee delegation and try to get signature from it.
+            if let Some(local_id) = def_id.as_local()
+                && let Some(info) = self.tcx.resolutions(()).delegation_infos.get(&local_id)
+                && let Ok(id) = info.resolution_id
+            {
+                def_id = id;
+                if visited.contains(&def_id) {
+                    return Err(match visited.len() {
+                        1 => self.dcx().emit_err(UnresolvedDelegationCallee { span }),
+                        _ => self.dcx().emit_err(CycleInDelegationSignatureResolution { span }),
+                    });
+                }
+            } else {
+                return Ok(());
+            }
+        }
+    }
+
     pub(crate) fn lower_delegation(
         &mut self,
         delegation: &Delegation,
         item_id: NodeId,
     ) -> DelegationResults<'hir> {
         let span = self.lower_span(delegation.last_segment_span());
 
-        let sig_id = self.tcx.delegations_resolutions(()).get(&self.owner.def_id).copied();
+        let Some(info) = self.tcx.resolutions(()).delegation_infos.get(&self.owner.def_id) else {
+            self.dcx().span_delayed_bug(
+                span,
+                format!("delegation resolution record was not found for {:?}", self.owner.def_id),
+            );
+
+            return self.generate_delegation_error(span, delegation);
+        };
+
+        let sig_id = info.resolution_id.and_then(|id| self.check_for_cycles(id, span).map(|_| id));
 
         // Delegation can be missing from the `delegations_resolutions` table
         // in illegal places such as function bodies in extern blocks (see #151356).
-        let Some(Ok(sig_id)) = sig_id else {
+        let Ok(sig_id) = sig_id else {
             self.dcx().span_delayed_bug(
                 span,
                 format!("LoweringContext: the delegation {:?} is unresolved", item_id),

compiler/rustc_ast_lowering/src/expr.rs

@@ -4,7 +4,6 @@ use std::sync::Arc;
 
 use rustc_ast::node_id::NodeMap;
 use rustc_ast::*;
-use rustc_ast_pretty::pprust::expr_to_string;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::msg;
 use rustc_hir as hir;
@@ -557,13 +556,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let mut invalid_expr_error = |tcx: TyCtxt<'_>, span| {
             // Avoid emitting the error multiple times.
             if error.is_none() {
+                let sm = tcx.sess.source_map();
                 let mut const_args = vec![];
                 let mut other_args = vec![];
                 for (idx, arg) in args.iter().enumerate() {
-                    if legacy_args_idx.contains(&idx) {
-                        const_args.push(format!("{{ {} }}", expr_to_string(arg)));
-                    } else {
-                        other_args.push(expr_to_string(arg));
+                    if let Ok(arg) = sm.span_to_snippet(arg.span) {
+                        if legacy_args_idx.contains(&idx) {
+                            const_args.push(format!("{{ {} }}", arg));
+                        } else {
+                            other_args.push(arg);
+                        }
                     }
                 }
                 let suggestion = UseConstGenericArg {