Impl Traits lowering minor refactors

compiler/rustc_ast_lowering/src/item.rs

@@ -19,7 +19,6 @@ use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Span;
 use rustc_target::spec::abi;
 use smallvec::{smallvec, SmallVec};
-use tracing::debug;
 
 use std::iter;
 
@@ -117,6 +116,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
         self.owners[def_id]
     }
 
+    #[instrument(level = "debug", skip(self, c))]
     fn lower_crate(&mut self, c: &Crate) {
         debug_assert_eq!(self.resolver.local_def_id(CRATE_NODE_ID), CRATE_DEF_ID);
 
@@ -127,6 +127,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
         })
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn lower_item(&mut self, item: &Item) {
         self.with_lctx(item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item)))
     }
@@ -485,6 +486,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (ty, self.lower_const_body(span, body))
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn lower_use_tree(
         &mut self,
         tree: &UseTree,
@@ -494,8 +496,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         ident: &mut Ident,
         attrs: Option<&'hir [Attribute]>,
     ) -> hir::ItemKind<'hir> {
-        debug!("lower_use_tree(tree={:?})", tree);
-
         let path = &tree.prefix;
         let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
 
@@ -1298,6 +1298,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     /// Return the pair of the lowered `generics` as `hir::Generics` and the evaluation of `f` with
     /// the carried impl trait definitions and bounds.
+    #[instrument(level = "debug", skip(self, f))]
     fn lower_generics<T>(
         &mut self,
         generics: &Generics,

compiler/rustc_ast_lowering/src/lib.rs

@@ -37,6 +37,9 @@
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 
+#[macro_use]
+extern crate tracing;
+
 use rustc_ast::visit;
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust;
@@ -63,7 +66,6 @@ use rustc_span::{Span, DUMMY_SP};
 
 use smallvec::SmallVec;
 use std::collections::hash_map::Entry;
-use tracing::{debug, trace};
 
 macro_rules! arena_vec {
     ($this:expr; $($x:expr),*) => (
@@ -439,7 +441,7 @@ pub fn lower_crate<'a, 'hir>(
     arena.alloc(krate)
 }
 
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, PartialEq, Debug)]
 enum ParamMode {
     /// Any path in a type context.
     Explicit,
@@ -455,6 +457,7 @@ enum ParenthesizedGenericArgs {
 }
 
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    #[instrument(level = "debug", skip(self, f))]
     fn with_hir_id_owner(
         &mut self,
         owner: NodeId,
@@ -599,12 +602,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.lower_node_id(node_id)
     }
 
+    #[instrument(level = "trace", skip(self))]
     fn lower_res(&mut self, res: Res<NodeId>) -> Res {
         let res: Result<Res, ()> = res.apply_id(|id| {
             let owner = self.current_hir_id_owner;
             let local_id = self.node_id_to_local_id.get(&id).copied().ok_or(())?;
             Ok(hir::HirId { owner, local_id })
         });
+        trace!(?res);
+
         // We may fail to find a HirId when the Res points to a Local from an enclosing HIR owner.
         // This can happen when trying to lower the return type `x` in erroneous code like
         //   async fn foo(x: u8) -> x {}
@@ -851,6 +857,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// ```
     ///
     /// returns a `hir::TypeBinding` representing `Item`.
+    #[instrument(level = "debug", skip(self))]
     fn lower_assoc_ty_constraint(
         &mut self,
         constraint: &AssocConstraint,
@@ -1011,6 +1018,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         err.emit();
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn lower_generic_arg(
         &mut self,
         arg: &ast::GenericArg,
@@ -1081,6 +1089,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext) -> &'hir hir::Ty<'hir> {
         self.arena.alloc(self.lower_ty_direct(t, itctx))
     }
@@ -1212,41 +1221,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         )
                     }
                     ImplTraitContext::Universal => {
-                        // Add a definition for the in-band `Param`.
-                        let def_id = self.resolver.local_def_id(def_node_id);
-
-                        let hir_bounds =
-                            self.lower_param_bounds(bounds, ImplTraitContext::Universal);
-                        // Set the name to `impl Bound1 + Bound2`.
+                        let span = t.span;
                         let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
-                        let param = hir::GenericParam {
-                            hir_id: self.lower_node_id(def_node_id),
-                            name: ParamName::Plain(self.lower_ident(ident)),
-                            pure_wrt_drop: false,
-                            span: self.lower_span(span),
-                            kind: hir::GenericParamKind::Type { default: None, synthetic: true },
-                            colon_span: None,
-                        };
+                        let (param, bounds, path) =
+                            self.lower_generic_and_bounds(def_node_id, span, ident, bounds);
                         self.impl_trait_defs.push(param);
-
-                        if let Some(preds) = self.lower_generic_bound_predicate(
-                            ident,
-                            def_node_id,
-                            &GenericParamKind::Type { default: None },
-                            hir_bounds,
-                            hir::PredicateOrigin::ImplTrait,
-                        ) {
-                            self.impl_trait_bounds.push(preds)
+                        if let Some(bounds) = bounds {
+                            self.impl_trait_bounds.push(bounds);
                         }
-
-                        hir::TyKind::Path(hir::QPath::Resolved(
-                            None,
-                            self.arena.alloc(hir::Path {
-                                span: self.lower_span(span),
-                                res: Res::Def(DefKind::TyParam, def_id.to_def_id()),
-                                segments: arena_vec![self; hir::PathSegment::from_ident(self.lower_ident(ident))],
-                            }),
-                        ))
+                        path
                     }
                     ImplTraitContext::Disallowed(position) => {
                         let mut err = struct_span_err!(
@@ -1737,6 +1720,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         )
     }
 
+    #[instrument(level = "trace", skip(self))]
     fn lower_param_bound(
         &mut self,
         tpb: &GenericBound,
@@ -1862,8 +1846,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc_from_iter(self.lower_generic_params_mut(params))
     }
 
+    #[instrument(level = "trace", skip(self))]
     fn lower_generic_param(&mut self, param: &GenericParam) -> hir::GenericParam<'hir> {
-        let (name, kind) = match param.kind {
+        let (name, kind) = self.lower_generic_param_kind(param);
+
+        let hir_id = self.lower_node_id(param.id);
+        self.lower_attrs(hir_id, &param.attrs);
+        hir::GenericParam {
+            hir_id,
+            name,
+            span: self.lower_span(param.span()),
+            pure_wrt_drop: self.sess.contains_name(&param.attrs, sym::may_dangle),
+            kind,
+            colon_span: param.colon_span.map(|s| self.lower_span(s)),
+        }
+    }
+
+    fn lower_generic_param_kind(
+        &mut self,
+        param: &GenericParam,
+    ) -> (hir::ParamName, hir::GenericParamKind<'hir>) {
+        match param.kind {
             GenericParamKind::Lifetime => {
                 // AST resolution emitted an error on those parameters, so we lower them using
                 // `ParamName::Error`.
@@ -1897,17 +1900,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     hir::GenericParamKind::Const { ty, default },
                 )
             }
-        };
-
-        let hir_id = self.lower_node_id(param.id);
-        self.lower_attrs(hir_id, &param.attrs);
-        hir::GenericParam {
-            hir_id,
-            name,
-            span: self.lower_span(param.span()),
-            pure_wrt_drop: self.sess.contains_name(&param.attrs, sym::may_dangle),
-            kind,
-            colon_span: param.colon_span.map(|s| self.lower_span(s)),
         }
     }
 
@@ -1954,6 +1946,47 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx))
     }
 
+    fn lower_generic_and_bounds(
+        &mut self,
+        node_id: NodeId,
+        span: Span,
+        ident: Ident,
+        bounds: &[GenericBound],
+    ) -> (hir::GenericParam<'hir>, Option<hir::WherePredicate<'hir>>, hir::TyKind<'hir>) {
+        // Add a definition for the in-band `Param`.
+        let def_id = self.resolver.local_def_id(node_id);
+
+        let hir_bounds = self.lower_param_bounds(bounds, ImplTraitContext::Universal);
+        // Set the name to `impl Bound1 + Bound2`.
+        let param = hir::GenericParam {
+            hir_id: self.lower_node_id(node_id),
+            name: ParamName::Plain(self.lower_ident(ident)),
+            pure_wrt_drop: false,
+            span: self.lower_span(span),
+            kind: hir::GenericParamKind::Type { default: None, synthetic: true },
+            colon_span: None,
+        };
+
+        let preds = self.lower_generic_bound_predicate(
+            ident,
+            node_id,
+            &GenericParamKind::Type { default: None },
+            hir_bounds,
+            hir::PredicateOrigin::ImplTrait,
+        );
+
+        let ty = hir::TyKind::Path(hir::QPath::Resolved(
+            None,
+            self.arena.alloc(hir::Path {
+                span: self.lower_span(span),
+                res: Res::Def(DefKind::TyParam, def_id.to_def_id()),
+                segments: arena_vec![self; hir::PathSegment::from_ident(self.lower_ident(ident))],
+            }),
+        ));
+
+        (param, preds, ty)
+    }
+
     /// Lowers a block directly to an expression, presuming that it
     /// has no attributes and is not targeted by a `break`.
     fn lower_block_expr(&mut self, b: &Block) -> hir::Expr<'hir> {

compiler/rustc_ast_lowering/src/path.rs

@@ -15,6 +15,7 @@ use smallvec::smallvec;
 use tracing::debug;
 
 impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    #[instrument(level = "trace", skip(self))]
     pub(crate) fn lower_qpath(
         &mut self,
         id: NodeId,
@@ -23,7 +24,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         param_mode: ParamMode,
         itctx: ImplTraitContext,
     ) -> hir::QPath<'hir> {
-        debug!("lower_qpath(id: {:?}, qself: {:?}, p: {:?})", id, qself, p);
         let qself_position = qself.as_ref().map(|q| q.position);
         let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
 

compiler/rustc_typeck/src/astconv/mod.rs

@@ -23,7 +23,7 @@ use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{walk_generics, Visitor as _};
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{GenericArg, GenericArgs};
+use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
 use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::ty::subst::{self, GenericArgKind, InternalSubsts, Subst, SubstsRef};
 use rustc_middle::ty::GenericParamDefKind;
@@ -2628,16 +2628,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let def_id = item_id.def_id.to_def_id();
 
                 match opaque_ty.kind {
-                    hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => self
-                        .impl_trait_ty_to_ty(
-                            def_id,
-                            lifetimes,
-                            matches!(
-                                origin,
-                                hir::OpaqueTyOrigin::FnReturn(..)
-                                    | hir::OpaqueTyOrigin::AsyncFn(..)
-                            ),
-                        ),
+                    hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
+                        self.impl_trait_ty_to_ty(def_id, lifetimes, origin)
+                    }
                     ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
                 }
             }
@@ -2706,7 +2699,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         &self,
         def_id: DefId,
         lifetimes: &[hir::GenericArg<'_>],
-        replace_parent_lifetimes: bool,
+        origin: OpaqueTyOrigin,
     ) -> Ty<'tcx> {
         debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
         let tcx = self.tcx();
@@ -2736,7 +2729,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     // For `impl Trait` in the types of statics, constants,
                     // locals and type aliases. These capture all parent
                     // lifetimes, so they can use their identity subst.
-                    GenericParamDefKind::Lifetime if replace_parent_lifetimes => {
+                    GenericParamDefKind::Lifetime
+                        if matches!(
+                            origin,
+                            hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..)
+                        ) =>
+                    {
                         tcx.lifetimes.re_static.into()
                     }
                     _ => tcx.mk_param_from_def(param),