delegation: support mapping of all arguments with Self type

compiler/rustc_ast_lowering/src/delegation/generics.rs

@@ -7,7 +7,7 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{GenericParamDefKind, TyCtxt};
 use rustc_middle::{bug, ty};
 use rustc_span::symbol::kw;
-use rustc_span::{Ident, Span, sym};
+use rustc_span::{ErrorGuaranteed, Ident, Span, sym};
 
 use crate::LoweringContext;
 use crate::delegation::resolution::resolver::DelegationResolver;
@@ -281,7 +281,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         &self,
         delegation: &'a Delegation,
         sig_id: DefId,
-    ) -> GenericsResolution<'a, 'hir> {
+    ) -> Result<GenericsResolution<'a, 'hir>, ErrorGuaranteed> {
         let tcx = self.tcx();
         let delegation_parent_kind = tcx.def_kind(tcx.local_parent(self.owner_id()));
 
@@ -300,9 +300,8 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         let qself_is_none = delegation.qself.is_none();
 
         let parent_args = if let [.., parent_segment, _] = &delegation.path.segments[..] {
-            if let Some(res) = self.get_resolution_id(parent_segment.id)
-                && matches!(tcx.def_kind(res), DefKind::Trait | DefKind::TraitAlias)
-            {
+            let res = self.get_resolution_id(parent_segment.id)?;
+            if matches!(tcx.def_kind(res), DefKind::Trait | DefKind::TraitAlias) {
                 sig_parent_params = &tcx.generics_of(sig_parent).own_params;
                 self.get_user_args(parent_segment)
                     .map(|args| ParentSegmentArgs::Specified(args))
@@ -314,7 +313,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
             ParentSegmentArgs::Invalid
         };
 
-        GenericsResolution {
+        Ok(GenericsResolution {
             parent_args,
             sig_parent_params,
             qself_is_none,
@@ -326,7 +325,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
             child_args: self.get_user_args(
                 delegation.path.segments.last().expect("must be at least one segment"),
             ),
-        }
+        })
     }
 
     fn get_user_args<'a>(&self, segment: &'a PathSegment) -> Option<&'a AngleBracketedArgs> {
@@ -350,14 +349,14 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         &self,
         delegation: &Delegation,
         sig_id: DefId,
-    ) -> GenericsGenerationResults<'hir> {
+    ) -> Result<GenericsGenerationResults<'hir>, ErrorGuaranteed> {
         let res @ GenericsResolution {
             trait_impl,
             generate_self,
             sig_child_params,
             sig_parent_params,
             ..
-        } = self.resolve_generics(delegation, sig_id);
+        } = self.resolve_generics(delegation, sig_id)?;
 
         // If we are in trait impl always generate function whose generics matches
         // those that are defined in trait.
@@ -374,7 +373,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
 
             let child = GenericsGenerationResult::new(child);
 
-            return GenericsGenerationResults { parent, child, self_ty_propagation_kind: None };
+            return Ok(GenericsGenerationResults { parent, child, self_ty_propagation_kind: None });
         }
 
         let tcx = self.tcx();
@@ -421,7 +420,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
             DelegationGenerics::generate_all(sig_child_params, GenericsPosition::Child, trait_impl)
         };
 
-        GenericsGenerationResults {
+        Ok(GenericsGenerationResults {
             parent: GenericsGenerationResult::new(parent_generics),
             child: GenericsGenerationResult::new(child_generics),
             self_ty_propagation_kind: match res.free_to_trait_delegation {
@@ -435,7 +434,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
                 }),
                 false => None,
             },
-        }
+        })
     }
 
     /// Generates generic argument slots for user-specified `args` and

compiler/rustc_ast_lowering/src/delegation/mod.rs

@@ -45,6 +45,7 @@ use hir::def::Res;
 use rustc_abi::ExternAbi;
 use rustc_ast as ast;
 use rustc_ast::*;
+use rustc_hir::def::DefKind;
 use rustc_hir::{self as hir, FnDeclFlags};
 use rustc_middle::ty::Asyncness;
 use rustc_span::def_id::DefId;
@@ -249,20 +250,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let mut unused_target_expr = false;
 
         let block_id = self.lower_body(|this| {
-            let &DelegationResolution {
-                param_info, span, should_generate_block, is_method, ..
-            } = res;
-
+            let &DelegationResolution { param_info, span, is_method, .. } = res;
             let ParamInfo { param_count, .. } = param_info;
+            let arguments_to_map = &res.sig_mapping.arguments_to_map;
 
             let mut parameters: Vec<hir::Param<'_>> = Vec::with_capacity(param_count);
             let mut args: Vec<hir::Expr<'_>> = Vec::with_capacity(param_count);
-            let mut stmts: &[hir::Stmt<'hir>] = &[];
+            let mut stmts = vec![];
 
             // Consider non-specified target expression as generated,
             // as we do not want to emit error when target expression is
             // not specified.
-            unused_target_expr = block.is_some() && (param_count == 0 || !should_generate_block);
+            unused_target_expr =
+                block.is_some() && (param_count == 0 || arguments_to_map.is_empty());
 
             for idx in 0..param_count {
                 let (param, pat_node_id) = this.generate_param(is_method, idx, span);
@@ -271,41 +271,38 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let generate_arg =
                     |this: &mut Self| this.generate_arg(is_method, idx, param.pat.hir_id, span);
 
-                let arg = if let Some(block) = block
-                    && idx == 0
-                    && should_generate_block
-                {
-                    let mut self_resolver = SelfResolver {
-                        ctxt: this,
-                        path_id: delegation.id,
-                        self_param_id: pat_node_id,
-                    };
-                    self_resolver.visit_block(block);
-                    // Target expr needs to lower `self` path.
-                    this.ident_and_label_to_local_id.insert(pat_node_id, param.pat.hir_id.local_id);
-
-                    // Lower with `HirId::INVALID` as we will use only expr and stmts.
-                    // FIXME(fn_delegation): Alternatives for target expression lowering:
-                    // https://github.com/rust-lang/rfcs/pull/3530#issuecomment-2197170600.
-                    let block = this.lower_block_noalloc(HirId::INVALID, block, false);
-
-                    stmts = block.stmts;
-
-                    // The behavior of the delegation's target expression differs from the
-                    // behavior of the usual block, where if there is no final expression
-                    // the `()` is returned. In case of the similar situation in delegation
-                    // (no final expression) we propagate first argument instead of replacing
-                    // it with `()`.
-                    if let Some(&expr) = block.expr { expr } else { generate_arg(this) }
-                } else {
-                    generate_arg(this)
-                };
+                let arg = block
+                    .filter(|_| arguments_to_map.contains(&idx))
+                    .and_then(|block| {
+                        let block = this.lower_block_maybe_more_than_once(
+                            block,
+                            pat_node_id,
+                            param.pat.hir_id.local_id,
+                            delegation.id,
+                        );
+
+                        stmts.push(block.stmts);
+
+                        // The behavior of the delegation's target expression differs from the
+                        // behavior of the usual block, where if there is no final expression
+                        // the `()` is returned. In case of the similar situation in delegation
+                        // (no final expression) we propagate first argument instead of replacing
+                        // it with `()`.
+                        block.expr.copied()
+                    })
+                    .unwrap_or_else(|| generate_arg(this));
 
                 args.push(arg);
             }
 
-            let (final_expr, hir_id) =
-                this.finalize_body_lowering(delegation, stmts, args, res, generics, span);
+            let (final_expr, hir_id) = this.finalize_body_lowering(
+                delegation,
+                this.arena.alloc_from_iter(stmts.into_iter().flatten().copied()),
+                args,
+                res,
+                generics,
+                span,
+            );
 
             call_expr_id = hir_id;
 
@@ -317,6 +314,48 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (block_id, call_expr_id, unused_target_expr)
     }
 
+    fn lower_block_maybe_more_than_once(
+        &mut self,
+        block: &Block,
+        pat_node_id: NodeId,
+        param_local_id: hir::ItemLocalId,
+        delegation_id: NodeId,
+    ) -> hir::Block<'hir> {
+        let mut self_resolver = SelfResolver {
+            ctxt: self,
+            path_id: delegation_id,
+            self_param_id: pat_node_id,
+            overwrites: vec![],
+        };
+
+        self_resolver.visit_block(block);
+
+        let overwrites = self_resolver.overwrites;
+
+        // Target expr needs to lower `self` path.
+        self.ident_and_label_to_local_id.insert(pat_node_id, param_local_id);
+
+        let block = cfg_select! {
+            debug_assertions => {
+                crate::re_lowering::ReloweringChecker::allow_relowering(self, |this| {
+                    this.lower_block_noalloc(HirId::INVALID, block, false)
+                })
+            },
+            _ => self.lower_block_noalloc(HirId::INVALID, block, false)
+        };
+
+        // Remove node ids for which we overwrote resolution to generated param
+        // before block lowering as block can be relowered. We need to do it because
+        // check in `SelfResolver` uses `get_partial_res` to decide whether to overwrite
+        // resolution, and if it is already overwritten from previous block lowering this
+        // check will not pass.
+        for id in overwrites {
+            self.partial_res_overrides.remove(&id);
+        }
+
+        block
+    }
+
     fn finalize_body_lowering(
         &mut self,
         delegation: &Delegation,
@@ -392,8 +431,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let args = self.arena.alloc_from_iter(args);
         let call = self.mk_expr(hir::ExprKind::Call(callee_path, args), span);
 
-        let expr = if let Some((parent, of_trait)) = res.output_self_mapping {
-            let res = Res::SelfTyAlias { alias_to: parent.to_def_id(), is_trait_impl: of_trait };
+        let expr = if res.sig_mapping.map_return {
+            let res = Res::SelfTyAlias {
+                alias_to: res.parent.to_def_id(),
+                is_trait_impl: self.tcx.def_kind(res.parent) == DefKind::Impl { of_trait: true },
+            };
+
             let ident = Ident::new(kw::SelfUpper, span);
             let path = self.create_resolved_path(res, ident, span);
 
@@ -538,6 +581,7 @@ struct SelfResolver<'a, 'b, 'hir> {
     ctxt: &'a mut LoweringContext<'b, 'hir>,
     path_id: NodeId,
     self_param_id: NodeId,
+    overwrites: Vec<NodeId>,
 }
 
 impl SelfResolver<'_, '_, '_> {
@@ -546,6 +590,7 @@ impl SelfResolver<'_, '_, '_> {
             && let Some(Res::Local(sig_id)) = res.full_res()
             && sig_id == self.path_id
         {
+            self.overwrites.push(id);
             self.ctxt.partial_res_overrides.insert(id, self.self_param_id);
         }
     }