Rollup of 9 pull requests

.mailmap

@@ -350,6 +350,7 @@ John Van Enk <vanenkj@gmail.com>
 Jon Gjengset <jon@thesquareplanet.com> <jongje@amazon.com>
 Jonas Tepe <jonasprogrammer@gmail.com>
 Jonathan Bailey <jbailey@mozilla.com> <jbailey@jbailey-20809.local>
+Jonathan Brouwer <jonathantbrouwer@gmail.com> <jonathan.brouwer@technolution.nl>
 Jonathan Chan Kwan Yin <sofe2038@gmail.com>
 Jonathan L <Xmasreturns@users.noreply.github.com>
 Jonathan S <gereeter@gmail.com> Jonathan S <gereeter+code@gmail.com>

compiler/rustc_ast/src/ast.rs

@@ -294,6 +294,14 @@ impl GenericArg {
             GenericArg::Const(ct) => ct.value.span,
         }
     }
+
+    pub fn is_maybe_parenthesised_infer(&self) -> bool {
+        match self {
+            GenericArg::Lifetime(lt) => lt.ident.name == kw::UnderscoreLifetime,
+            GenericArg::Type(ty) => ty.is_maybe_parenthesised_infer(),
+            GenericArg::Const(_) => false,
+        }
+    }
 }
 
 /// A path like `Foo<'a, T>`.

compiler/rustc_ast_lowering/src/delegation/generics.rs

@@ -1,3 +1,5 @@
+use std::assert_matches;
+
 use hir::HirId;
 use hir::def::{DefKind, Res};
 use rustc_ast::*;
@@ -11,7 +13,10 @@ use rustc_span::{ErrorGuaranteed, Ident, Span, sym};
 
 use crate::LoweringContext;
 use crate::delegation::resolution::resolver::DelegationResolver;
-use crate::diagnostics::DelegationInfersMismatch;
+use crate::diagnostics::{
+    DelegationInfersMismatch, DelegationToInherentImplMustContainParentGenerics,
+    DelegationToInherentImplParentContainsInfer,
+};
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub(super) enum GenericsPosition {
@@ -25,6 +30,7 @@ pub(super) enum GenericArgSlot<T> {
     Generate(T, Option<usize> /* Infer arg index from AST */),
 }
 
+#[derive(Debug)]
 pub(super) struct DelegationGenerics<T> {
     data: T,
     pos: GenericsPosition,
@@ -57,11 +63,13 @@ impl<'hir> DelegationGenerics<TyGenerics<'hir>> {
 /// meaning we did not propagate them and thus we do not need to generate generic params
 /// (i.e., method call scenarios), in such a case this approach helps
 /// a lot as if `into_hir_generics` will not be called then uplifting will not happen.
+#[derive(Debug)]
 pub(super) enum HirOrTyGenerics<'hir> {
     Ty(DelegationGenerics<TyGenerics<'hir>>),
     Hir(DelegationGenerics<&'hir hir::Generics<'hir>>),
 }
 
+#[derive(Debug)]
 pub(super) struct GenericsGenerationResult<'hir> {
     pub(super) generics: HirOrTyGenerics<'hir>,
     pub(super) args_segment_id: HirId,
@@ -80,6 +88,7 @@ pub(super) struct GenericsGenerationResults<'hir> {
     pub(super) self_ty_propagation_kind: Option<hir::DelegationSelfTyPropagationKind>,
 }
 
+#[derive(Debug)]
 pub(super) struct DelegationGenericArgsIterator<'hir> {
     index: usize = Default::default(),
     params: &'hir [hir::GenericParam<'hir>],
@@ -145,6 +154,7 @@ impl<'hir> DelegationGenericArgsIterator<'hir> {
         ctx: &mut LoweringContext<'_, 'hir>,
     ) -> Vec<hir::GenericArg<'hir>> {
         let mut args = vec![];
+
         while let Some(arg) = self.next(ctx, |ctx| ctx.next_id()) {
             args.push(arg);
         }
@@ -238,6 +248,7 @@ impl<'hir> GenericsGenerationResult<'hir> {
     }
 }
 
+#[derive(Debug)]
 enum ParentSegmentArgs<'a> {
     /// Parent segment is valid and generic args are specified:
     /// `reuse Trait::<'static, ()>::foo;`.
@@ -273,7 +284,7 @@ struct GenericsResolution<'a, 'tcx> {
     /// `reuse <_ as Trait>::foo;`.
     qself_is_infer: bool,
     /// Whether we should generate `Self` generic param.
-    generate_self: bool,
+    generate_free_to_trait_self: bool,
 }
 
 impl<'hir> DelegationResolver<'_, 'hir> {
@@ -288,8 +299,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         let delegation_in_free_ctx =
             !matches!(delegation_parent_kind, DefKind::Trait | DefKind::Impl { .. });
 
-        let sig_parent = tcx.parent(sig_id);
-        let sig_in_trait = matches!(tcx.def_kind(sig_parent), DefKind::Trait);
+        let sig_in_trait = matches!(tcx.def_kind(tcx.parent(sig_id)), DefKind::Trait);
         let free_to_trait_delegation = delegation_in_free_ctx && sig_in_trait;
 
         let mut sig_parent_params: &[ty::GenericParamDef] = &[];
@@ -301,8 +311,13 @@ impl<'hir> DelegationResolver<'_, 'hir> {
 
         let parent_args = if let [.., parent_segment, _] = &delegation.path.segments[..] {
             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;
+            if !matches!(tcx.def_kind(res), DefKind::Mod) {
+                assert_matches!(
+                    tcx.def_kind(res),
+                    DefKind::Trait | DefKind::Struct | DefKind::Enum
+                );
+
+                sig_parent_params = &tcx.generics_of(res).own_params;
                 self.get_user_args(parent_segment)
                     .map(|args| ParentSegmentArgs::Specified(args))
                     .unwrap_or(ParentSegmentArgs::NotSpecified)
@@ -319,7 +334,8 @@ impl<'hir> DelegationResolver<'_, 'hir> {
             qself_is_none,
             qself_is_infer,
             free_to_trait_delegation,
-            generate_self: free_to_trait_delegation && (qself_is_none || qself_is_infer),
+            generate_free_to_trait_self: free_to_trait_delegation
+                && (qself_is_none || qself_is_infer),
             trait_impl: matches!(delegation_parent_kind, DefKind::Impl { of_trait: true }),
             sig_child_params: &tcx.generics_of(sig_id).own_params,
             child_args: self.get_user_args(
@@ -349,10 +365,11 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         &self,
         delegation: &Delegation,
         sig_id: DefId,
+        span: Span,
     ) -> Result<GenericsGenerationResults<'hir>, ErrorGuaranteed> {
         let res @ GenericsResolution {
             trait_impl,
-            generate_self,
+            generate_free_to_trait_self,
             sig_child_params,
             sig_parent_params,
             ..
@@ -376,20 +393,27 @@ impl<'hir> DelegationResolver<'_, 'hir> {
             return Ok(GenericsGenerationResults { parent, child, self_ty_propagation_kind: None });
         }
 
+        self.check_delegation_to_inherent_impl(&res.parent_args, sig_id, span)?;
+
         let tcx = self.tcx();
+
+        // If parent is inherent impl then there is no `Self` param to skip, so add additional check.
+        let skip_self =
+            !generate_free_to_trait_self && tcx.def_kind(tcx.parent(sig_id)) == DefKind::Trait;
+
         let parent_generics = match res.parent_args {
             ParentSegmentArgs::Specified(args) => DelegationGenerics {
                 data: Self::create_slots_from_args(
                     tcx,
                     args,
-                    &sig_parent_params[usize::from(!generate_self)..],
-                    generate_self,
+                    &sig_parent_params[usize::from(skip_self)..],
+                    generate_free_to_trait_self,
                 ),
                 pos: GenericsPosition::Parent,
                 trait_impl,
             },
             ParentSegmentArgs::NotSpecified => DelegationGenerics::generate_all(
-                &sig_parent_params[usize::from(!generate_self)..],
+                &sig_parent_params[usize::from(skip_self)..],
                 GenericsPosition::Parent,
                 trait_impl,
             ),
@@ -437,6 +461,46 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         })
     }
 
+    fn check_delegation_to_inherent_impl(
+        &self,
+        parent_args: &ParentSegmentArgs<'_>,
+        sig_id: DefId,
+        span: Span,
+    ) -> Result<(), ErrorGuaranteed> {
+        let tcx = self.tcx();
+
+        if !(tcx.def_kind(sig_id) == DefKind::AssocFn
+            && matches!(tcx.def_kind(tcx.parent(sig_id)), DefKind::Impl { of_trait: false }))
+        {
+            return Ok(());
+        }
+
+        let ty::Adt(def, _) = tcx.type_of(tcx.parent(sig_id)).skip_binder().kind() else {
+            unreachable!("parent of inherent function can be only struct or enum")
+        };
+
+        match parent_args {
+            ParentSegmentArgs::Invalid => unreachable!(),
+            ParentSegmentArgs::Specified(args) => args
+                .args
+                .iter()
+                .all(|arg| {
+                    let AngleBracketedArg::Arg(arg) = arg else { return false };
+                    !arg.is_maybe_parenthesised_infer()
+                })
+                .ok_or_else(|| {
+                    self.tcx().dcx().emit_err(DelegationToInherentImplParentContainsInfer { span })
+                }),
+            ParentSegmentArgs::NotSpecified => match tcx.generics_of(def.did()).own_params.len() {
+                0 => Ok(()),
+                _ => Err(self
+                    .tcx()
+                    .dcx()
+                    .emit_err(DelegationToInherentImplMustContainParentGenerics { span })),
+            },
+        }
+    }
+
     /// Generates generic argument slots for user-specified `args` and
     /// generic `params` of the signature function. This function checks whether
     /// there are infers (`kw::UnderscoreLifetime` or `kw::Underscore`) in
@@ -459,12 +523,7 @@ impl<'hir> DelegationResolver<'_, 'hir> {
         let params = &params[usize::from(add_first_self)..];
         for (idx, (arg, param)) in args.args.iter().zip(params).enumerate() {
             let AngleBracketedArg::Arg(arg) = arg else { continue };
-
-            let is_infer = match arg {
-                GenericArg::Lifetime(lt) => lt.ident.name == kw::UnderscoreLifetime,
-                GenericArg::Type(ty) => ty.is_maybe_parenthesised_infer(),
-                GenericArg::Const(_) => false,
-            };
+            let is_infer = arg.is_maybe_parenthesised_infer();
 
             // If `'_` is used instead of `_` (or vice versa) we emit a meaningful
             // error instead of processing this infer or leaving it as is for signature

compiler/rustc_ast_lowering/src/delegation/mod.rs

@@ -47,7 +47,7 @@ use rustc_ast as ast;
 use rustc_ast::*;
 use rustc_hir::attrs::lang_items::LangItem;
 use rustc_hir::def::DefKind;
-use rustc_hir::{self as hir, FnDeclFlags};
+use rustc_hir::{self as hir, FnDeclFlags, QPath};
 use rustc_middle::ty::Asyncness;
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::kw;
@@ -62,7 +62,7 @@ use crate::{
 
 mod attributes;
 mod generics;
-mod resolution;
+pub(crate) mod resolution;
 
 pub(crate) struct DelegationResults<'hir> {
     pub body_id: hir::BodyId,
@@ -416,7 +416,37 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
                 hir::QPath::Resolved(ty, self.arena.alloc(new_path))
             }
-            hir::QPath::TypeRelative(..) => unreachable!("until inherent methods are supported"),
+            hir::QPath::TypeRelative(mut ty, segment) => {
+                let mut segment = self.process_segment(span, segment, &mut generics.child);
+                segment.res = Res::Def(self.tcx.def_kind(res.call_path_res), res.call_path_res);
+
+                let ty_hir_id = ty.hir_id;
+
+                // Propagating child generics if needed.
+                ty = if let hir::TyKind::Path(QPath::Resolved(ty, path)) = ty.kind {
+                    let mut new_path = path.clone();
+
+                    new_path.segments = self.arena.alloc_from_iter(
+                        new_path.segments.iter().enumerate().map(|(idx, segment)| {
+                            if idx + 1 == new_path.segments.len() {
+                                self.process_segment(span, segment, &mut generics.parent)
+                            } else {
+                                segment.clone()
+                            }
+                        }),
+                    );
+
+                    self.arena.alloc(hir::Ty {
+                        hir_id: ty_hir_id,
+                        span,
+                        kind: hir::TyKind::Path(QPath::Resolved(ty, self.arena.alloc(new_path))),
+                    })
+                } else {
+                    ty
+                };
+
+                hir::QPath::TypeRelative(ty, self.arena.alloc(segment))
+            }
         };
 
         if let Some(hir::DelegationSelfTyPropagationKind::SelfTy(id)) =
@@ -491,6 +521,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         result.generics.into_hir_generics(self, span);
 
         let mut segment = segment.clone();
+
         let mut args_iter = result.generics.create_args_iterator();
 
         let new_args = segment