Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/lower/path.rs')
| -rw-r--r-- | crates/hir-ty/src/lower/path.rs | 911 |
1 files changed, 911 insertions, 0 deletions
diff --git a/crates/hir-ty/src/lower/path.rs b/crates/hir-ty/src/lower/path.rs new file mode 100644 index 0000000000..22c5bb9923 --- /dev/null +++ b/crates/hir-ty/src/lower/path.rs @@ -0,0 +1,911 @@ +//! A wrapper around [`TyLoweringContext`] specifically for lowering paths. + +use std::iter; + +use chalk_ir::{cast::Cast, fold::Shift, BoundVar}; +use either::Either; +use hir_def::{ + data::TraitFlags, + expr_store::HygieneId, + generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget}, + path::{GenericArg, GenericArgs, Path, PathSegment, PathSegments}, + resolver::{ResolveValueResult, TypeNs, ValueNs}, + type_ref::{TypeBound, TypeRef}, + GenericDefId, GenericParamId, ItemContainerId, Lookup, TraitId, +}; +use smallvec::SmallVec; +use stdx::never; + +use crate::{ + consteval::unknown_const_as_generic, + error_lifetime, + generics::generics, + lower::{ + generic_arg_to_chalk, named_associated_type_shorthand_candidates, ImplTraitLoweringState, + }, + to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx, + utils::associated_type_by_name_including_super_traits, + AliasEq, AliasTy, GenericArgsProhibitedReason, ImplTraitLoweringMode, Interner, + ParamLoweringMode, PathLoweringDiagnostic, ProjectionTy, QuantifiedWhereClause, Substitution, + TraitRef, Ty, TyBuilder, TyDefId, TyKind, TyLoweringContext, ValueTyDefId, WhereClause, +}; + +type CallbackData<'a> = Either< + super::PathDiagnosticCallbackData, + crate::infer::diagnostics::PathDiagnosticCallbackData<'a>, +>; + +// We cannot use `&mut dyn FnMut()` because of lifetime issues, and we don't want to use `Box<dyn FnMut()>` +// because of the allocation, so we create a lifetime-less callback, tailored for our needs. +pub(crate) struct PathDiagnosticCallback<'a> { + pub(crate) data: CallbackData<'a>, + pub(crate) callback: fn(&CallbackData<'_>, &mut TyLoweringContext<'_>, PathLoweringDiagnostic), +} + +pub(crate) struct PathLoweringContext<'a, 'b> { + ctx: &'a mut TyLoweringContext<'b>, + on_diagnostic: PathDiagnosticCallback<'a>, + path: &'a Path, + segments: PathSegments<'a>, + current_segment_idx: usize, + /// Contains the previous segment if `current_segment_idx == segments.len()` + current_or_prev_segment: PathSegment<'a>, +} + +impl<'a, 'b> PathLoweringContext<'a, 'b> { + #[inline] + pub(crate) fn new( + ctx: &'a mut TyLoweringContext<'b>, + on_diagnostic: PathDiagnosticCallback<'a>, + path: &'a Path, + ) -> Self { + let segments = path.segments(); + let first_segment = segments.first().unwrap_or(PathSegment::MISSING); + Self { + ctx, + on_diagnostic, + path, + segments, + current_segment_idx: 0, + current_or_prev_segment: first_segment, + } + } + + #[inline] + #[cold] + fn on_diagnostic(&mut self, diag: PathLoweringDiagnostic) { + (self.on_diagnostic.callback)(&self.on_diagnostic.data, self.ctx, diag); + } + + #[inline] + pub(crate) fn ty_ctx(&mut self) -> &mut TyLoweringContext<'b> { + self.ctx + } + + #[inline] + fn current_segment_u32(&self) -> u32 { + self.current_segment_idx as u32 + } + + #[inline] + fn skip_resolved_segment(&mut self) { + if !matches!(self.path, Path::LangItem(..)) { + // In lang items, the resolved "segment" is not one of the segments. Perhaps we should've put it + // point at -1, but I don't feel this is clearer. + self.current_segment_idx += 1; + } + self.update_current_segment(); + } + + #[inline] + fn update_current_segment(&mut self) { + self.current_or_prev_segment = + self.segments.get(self.current_segment_idx).unwrap_or(self.current_or_prev_segment); + } + + #[inline] + pub(crate) fn ignore_last_segment(&mut self) { + self.segments = self.segments.strip_last(); + } + + #[inline] + pub(crate) fn set_current_segment(&mut self, segment: usize) { + self.current_segment_idx = segment; + self.current_or_prev_segment = self + .segments + .get(segment) + .expect("invalid segment passed to PathLoweringContext::set_current_segment()"); + } + + pub(crate) fn lower_ty_relative_path( + &mut self, + ty: Ty, + // We need the original resolution to lower `Self::AssocTy` correctly + res: Option<TypeNs>, + ) -> (Ty, Option<TypeNs>) { + match self.segments.len() - self.current_segment_idx { + 0 => (ty, res), + 1 => { + // resolve unselected assoc types + (self.select_associated_type(res), None) + } + _ => { + // FIXME report error (ambiguous associated type) + (TyKind::Error.intern(Interner), None) + } + } + } + + fn prohibit_parenthesized_generic_args(&mut self) -> bool { + if let Some(generic_args) = self.current_or_prev_segment.args_and_bindings { + if generic_args.desugared_from_fn { + let segment = self.current_segment_u32(); + self.on_diagnostic( + PathLoweringDiagnostic::ParenthesizedGenericArgsWithoutFnTrait { segment }, + ); + return true; + } + } + false + } + + // When calling this, the current segment is the resolved segment (we don't advance it yet). + pub(crate) fn lower_partly_resolved_path( + &mut self, + resolution: TypeNs, + infer_args: bool, + ) -> (Ty, Option<TypeNs>) { + let remaining_segments = self.segments.skip(self.current_segment_idx + 1); + + let ty = match resolution { + TypeNs::TraitId(trait_) => { + let ty = match remaining_segments.len() { + 1 => { + let trait_ref = self.lower_trait_ref_from_resolved_path( + trait_, + TyKind::Error.intern(Interner), + ); + + self.skip_resolved_segment(); + let segment = self.current_or_prev_segment; + let found = + self.ctx.db.trait_data(trait_).associated_type_by_name(segment.name); + + match found { + Some(associated_ty) => { + // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent + // generic params. It's inefficient to splice the `Substitution`s, so we may want + // that method to optionally take parent `Substitution` as we already know them at + // this point (`trait_ref.substitution`). + let substitution = self.substs_from_path_segment( + associated_ty.into(), + false, + None, + ); + let len_self = + generics(self.ctx.db.upcast(), associated_ty.into()).len_self(); + let substitution = Substitution::from_iter( + Interner, + substitution + .iter(Interner) + .take(len_self) + .chain(trait_ref.substitution.iter(Interner)), + ); + TyKind::Alias(AliasTy::Projection(ProjectionTy { + associated_ty_id: to_assoc_type_id(associated_ty), + substitution, + })) + .intern(Interner) + } + None => { + // FIXME: report error (associated type not found) + TyKind::Error.intern(Interner) + } + } + } + 0 => { + // Trait object type without dyn; this should be handled in upstream. See + // `lower_path()`. + stdx::never!("unexpected fully resolved trait path"); + TyKind::Error.intern(Interner) + } + _ => { + // FIXME report error (ambiguous associated type) + TyKind::Error.intern(Interner) + } + }; + return (ty, None); + } + TypeNs::TraitAliasId(_) => { + // FIXME(trait_alias): Implement trait alias. + return (TyKind::Error.intern(Interner), None); + } + TypeNs::GenericParam(param_id) => match self.ctx.type_param_mode { + ParamLoweringMode::Placeholder => { + TyKind::Placeholder(to_placeholder_idx(self.ctx.db, param_id.into())) + } + ParamLoweringMode::Variable => { + let idx = match self + .ctx + .generics() + .expect("generics in scope") + .type_or_const_param_idx(param_id.into()) + { + None => { + never!("no matching generics"); + return (TyKind::Error.intern(Interner), None); + } + Some(idx) => idx, + }; + + TyKind::BoundVar(BoundVar::new(self.ctx.in_binders, idx)) + } + } + .intern(Interner), + TypeNs::SelfType(impl_id) => { + let generics = self.ctx.generics().expect("impl should have generic param scope"); + + match self.ctx.type_param_mode { + ParamLoweringMode::Placeholder => { + // `def` can be either impl itself or item within, and we need impl itself + // now. + let generics = generics.parent_or_self(); + let subst = generics.placeholder_subst(self.ctx.db); + self.ctx.db.impl_self_ty(impl_id).substitute(Interner, &subst) + } + ParamLoweringMode::Variable => { + let starting_from = match generics.def() { + GenericDefId::ImplId(_) => 0, + // `def` is an item within impl. We need to substitute `BoundVar`s but + // remember that they are for parent (i.e. impl) generic params so they + // come after our own params. + _ => generics.len_self(), + }; + TyBuilder::impl_self_ty(self.ctx.db, impl_id) + .fill_with_bound_vars(self.ctx.in_binders, starting_from) + .build() + } + } + } + TypeNs::AdtSelfType(adt) => { + let generics = generics(self.ctx.db.upcast(), adt.into()); + let substs = match self.ctx.type_param_mode { + ParamLoweringMode::Placeholder => generics.placeholder_subst(self.ctx.db), + ParamLoweringMode::Variable => { + generics.bound_vars_subst(self.ctx.db, self.ctx.in_binders) + } + }; + self.ctx.db.ty(adt.into()).substitute(Interner, &substs) + } + + TypeNs::AdtId(it) => self.lower_path_inner(it.into(), infer_args), + TypeNs::BuiltinType(it) => self.lower_path_inner(it.into(), infer_args), + TypeNs::TypeAliasId(it) => self.lower_path_inner(it.into(), infer_args), + // FIXME: report error + TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(Interner), None), + }; + + self.skip_resolved_segment(); + self.lower_ty_relative_path(ty, Some(resolution)) + } + + fn handle_type_ns_resolution(&mut self, resolution: &TypeNs) { + let mut prohibit_generics_on_resolved = |reason| { + if self.current_or_prev_segment.args_and_bindings.is_some() { + let segment = self.current_segment_u32(); + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment, + reason, + }); + } + }; + + match resolution { + TypeNs::SelfType(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::SelfTy) + } + TypeNs::GenericParam(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::TyParam) + } + TypeNs::AdtSelfType(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::SelfTy) + } + TypeNs::BuiltinType(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::PrimitiveTy) + } + TypeNs::AdtId(_) + | TypeNs::EnumVariantId(_) + | TypeNs::TypeAliasId(_) + | TypeNs::TraitId(_) + | TypeNs::TraitAliasId(_) => {} + } + } + + pub(crate) fn resolve_path_in_type_ns_fully(&mut self) -> Option<TypeNs> { + let (res, unresolved) = self.resolve_path_in_type_ns()?; + if unresolved.is_some() { + return None; + } + Some(res) + } + + pub(crate) fn resolve_path_in_type_ns(&mut self) -> Option<(TypeNs, Option<usize>)> { + let (resolution, remaining_index, _, prefix_info) = self + .ctx + .resolver + .resolve_path_in_type_ns_with_prefix_info(self.ctx.db.upcast(), self.path)?; + + let segments = self.segments; + if segments.is_empty() || matches!(self.path, Path::LangItem(..)) { + // `segments.is_empty()` can occur with `self`. + return Some((resolution, remaining_index)); + } + + let (module_segments, resolved_segment_idx, enum_segment) = match remaining_index { + None if prefix_info.enum_variant => { + (segments.strip_last_two(), segments.len() - 1, Some(segments.len() - 2)) + } + None => (segments.strip_last(), segments.len() - 1, None), + Some(i) => (segments.take(i - 1), i - 1, None), + }; + + self.current_segment_idx = resolved_segment_idx; + self.current_or_prev_segment = + segments.get(resolved_segment_idx).expect("should have resolved segment"); + + if matches!(self.path, Path::BarePath(..)) { + // Bare paths cannot have generics, so skip them as an optimization. + return Some((resolution, remaining_index)); + } + + for (i, mod_segment) in module_segments.iter().enumerate() { + if mod_segment.args_and_bindings.is_some() { + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment: i as u32, + reason: GenericArgsProhibitedReason::Module, + }); + } + } + + if let Some(enum_segment) = enum_segment { + if segments.get(enum_segment).is_some_and(|it| it.args_and_bindings.is_some()) + && segments.get(enum_segment + 1).is_some_and(|it| it.args_and_bindings.is_some()) + { + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment: (enum_segment + 1) as u32, + reason: GenericArgsProhibitedReason::EnumVariant, + }); + } + } + + self.handle_type_ns_resolution(&resolution); + + Some((resolution, remaining_index)) + } + + pub(crate) fn resolve_path_in_value_ns( + &mut self, + hygiene_id: HygieneId, + ) -> Option<ResolveValueResult> { + let (res, prefix_info) = self.ctx.resolver.resolve_path_in_value_ns_with_prefix_info( + self.ctx.db.upcast(), + self.path, + hygiene_id, + )?; + + let segments = self.segments; + if segments.is_empty() || matches!(self.path, Path::LangItem(..)) { + // `segments.is_empty()` can occur with `self`. + return Some(res); + } + + let (mod_segments, enum_segment, resolved_segment_idx) = match res { + ResolveValueResult::Partial(_, unresolved_segment, _) => { + (segments.take(unresolved_segment - 1), None, unresolved_segment - 1) + } + ResolveValueResult::ValueNs(ValueNs::EnumVariantId(_), _) + if prefix_info.enum_variant => + { + (segments.strip_last_two(), segments.len().checked_sub(2), segments.len() - 1) + } + ResolveValueResult::ValueNs(..) => (segments.strip_last(), None, segments.len() - 1), + }; + + self.current_segment_idx = resolved_segment_idx; + self.current_or_prev_segment = + segments.get(resolved_segment_idx).expect("should have resolved segment"); + + for (i, mod_segment) in mod_segments.iter().enumerate() { + if mod_segment.args_and_bindings.is_some() { + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment: i as u32, + reason: GenericArgsProhibitedReason::Module, + }); + } + } + + if let Some(enum_segment) = enum_segment { + if segments.get(enum_segment).is_some_and(|it| it.args_and_bindings.is_some()) + && segments.get(enum_segment + 1).is_some_and(|it| it.args_and_bindings.is_some()) + { + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment: (enum_segment + 1) as u32, + reason: GenericArgsProhibitedReason::EnumVariant, + }); + } + } + + match &res { + ResolveValueResult::ValueNs(resolution, _) => { + let resolved_segment_idx = self.current_segment_u32(); + let resolved_segment = self.current_or_prev_segment; + + let mut prohibit_generics_on_resolved = |reason| { + if resolved_segment.args_and_bindings.is_some() { + self.on_diagnostic(PathLoweringDiagnostic::GenericArgsProhibited { + segment: resolved_segment_idx, + reason, + }); + } + }; + + match resolution { + ValueNs::ImplSelf(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::SelfTy) + } + // FIXME: rustc generates E0107 (incorrect number of generic arguments) and not + // E0109 (generic arguments provided for a type that doesn't accept them) for + // consts and statics, presumably as a defense against future in which consts + // and statics can be generic, or just because it was easier for rustc implementors. + // That means we'll show the wrong error code. Because of us it's easier to do it + // this way :) + ValueNs::GenericParam(_) | ValueNs::ConstId(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::Const) + } + ValueNs::StaticId(_) => { + prohibit_generics_on_resolved(GenericArgsProhibitedReason::Static) + } + ValueNs::FunctionId(_) | ValueNs::StructId(_) | ValueNs::EnumVariantId(_) => {} + ValueNs::LocalBinding(_) => {} + } + } + ResolveValueResult::Partial(resolution, _, _) => { + self.handle_type_ns_resolution(resolution); + } + }; + Some(res) + } + + fn select_associated_type(&mut self, res: Option<TypeNs>) -> Ty { + let Some((generics, res)) = self.ctx.generics().zip(res) else { + return TyKind::Error.intern(Interner); + }; + let segment = self.current_or_prev_segment; + let ty = named_associated_type_shorthand_candidates( + self.ctx.db, + generics.def(), + res, + Some(segment.name.clone()), + move |name, t, associated_ty| { + let generics = self.ctx.generics().unwrap(); + + if name != segment.name { + return None; + } + + let parent_subst = t.substitution.clone(); + let parent_subst = match self.ctx.type_param_mode { + ParamLoweringMode::Placeholder => { + // if we're lowering to placeholders, we have to put them in now. + let s = generics.placeholder_subst(self.ctx.db); + s.apply(parent_subst, Interner) + } + ParamLoweringMode::Variable => { + // We need to shift in the bound vars, since + // `named_associated_type_shorthand_candidates` does not do that. + parent_subst.shifted_in_from(Interner, self.ctx.in_binders) + } + }; + + // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent + // generic params. It's inefficient to splice the `Substitution`s, so we may want + // that method to optionally take parent `Substitution` as we already know them at + // this point (`t.substitution`). + let substs = self.substs_from_path_segment(associated_ty.into(), false, None); + + let len_self = + crate::generics::generics(self.ctx.db.upcast(), associated_ty.into()) + .len_self(); + + let substs = Substitution::from_iter( + Interner, + substs.iter(Interner).take(len_self).chain(parent_subst.iter(Interner)), + ); + + Some( + TyKind::Alias(AliasTy::Projection(ProjectionTy { + associated_ty_id: to_assoc_type_id(associated_ty), + substitution: substs, + })) + .intern(Interner), + ) + }, + ); + + ty.unwrap_or_else(|| TyKind::Error.intern(Interner)) + } + + fn lower_path_inner(&mut self, typeable: TyDefId, infer_args: bool) -> Ty { + let generic_def = match typeable { + TyDefId::BuiltinType(builtin) => return TyBuilder::builtin(builtin), + TyDefId::AdtId(it) => it.into(), + TyDefId::TypeAliasId(it) => it.into(), + }; + let substs = self.substs_from_path_segment(generic_def, infer_args, None); + self.ctx.db.ty(typeable).substitute(Interner, &substs) + } + + /// Collect generic arguments from a path into a `Substs`. See also + /// `create_substs_for_ast_path` and `def_to_ty` in rustc. + pub(crate) fn substs_from_path( + &mut self, + // Note that we don't call `db.value_type(resolved)` here, + // `ValueTyDefId` is just a convenient way to pass generics and + // special-case enum variants + resolved: ValueTyDefId, + infer_args: bool, + ) -> Substitution { + let prev_current_segment_idx = self.current_segment_idx; + let prev_current_segment = self.current_or_prev_segment; + + let generic_def = match resolved { + ValueTyDefId::FunctionId(it) => it.into(), + ValueTyDefId::StructId(it) => it.into(), + ValueTyDefId::UnionId(it) => it.into(), + ValueTyDefId::ConstId(it) => it.into(), + ValueTyDefId::StaticId(_) => return Substitution::empty(Interner), + ValueTyDefId::EnumVariantId(var) => { + // the generic args for an enum variant may be either specified + // on the segment referring to the enum, or on the segment + // referring to the variant. So `Option::<T>::None` and + // `Option::None::<T>` are both allowed (though the former is + // FIXME: This isn't strictly correct, enum variants may be used not through the enum + // (via `use Enum::Variant`). The resolver returns whether they were, but we don't have its result + // available here. The worst that can happen is that we will show some confusing diagnostics to the user, + // if generics exist on the module and they don't match with the variant. + // preferred). See also `def_ids_for_path_segments` in rustc. + // + // `wrapping_sub(1)` will return a number which `get` will return None for if current_segment_idx<2. + // This simplifies the code a bit. + let penultimate_idx = self.current_segment_idx.wrapping_sub(1); + let penultimate = self.segments.get(penultimate_idx); + if let Some(penultimate) = penultimate { + if self.current_or_prev_segment.args_and_bindings.is_none() + && penultimate.args_and_bindings.is_some() + { + self.current_segment_idx = penultimate_idx; + self.current_or_prev_segment = penultimate; + } + } + var.lookup(self.ctx.db.upcast()).parent.into() + } + }; + let result = self.substs_from_path_segment(generic_def, infer_args, None); + self.current_segment_idx = prev_current_segment_idx; + self.current_or_prev_segment = prev_current_segment; + result + } + + pub(crate) fn substs_from_path_segment( + &mut self, + def: GenericDefId, + infer_args: bool, + explicit_self_ty: Option<Ty>, + ) -> Substitution { + let prohibit_parens = match def { + GenericDefId::TraitId(trait_) => { + let trait_data = self.ctx.db.trait_data(trait_); + !trait_data.flags.contains(TraitFlags::RUSTC_PAREN_SUGAR) + } + _ => true, + }; + if prohibit_parens && self.prohibit_parenthesized_generic_args() { + return TyBuilder::unknown_subst(self.ctx.db, def); + } + + self.substs_from_args_and_bindings( + self.current_or_prev_segment.args_and_bindings, + def, + infer_args, + explicit_self_ty, + ) + } + + pub(super) fn substs_from_args_and_bindings( + &mut self, + args_and_bindings: Option<&GenericArgs>, + def: GenericDefId, + infer_args: bool, + explicit_self_ty: Option<Ty>, + ) -> Substitution { + // Order is + // - Optional Self parameter + // - Lifetime parameters + // - Type or Const parameters + // - Parent parameters + let def_generics = generics(self.ctx.db.upcast(), def); + let ( + parent_params, + self_param, + type_params, + const_params, + impl_trait_params, + lifetime_params, + ) = def_generics.provenance_split(); + let item_len = + self_param as usize + type_params + const_params + impl_trait_params + lifetime_params; + let total_len = parent_params + item_len; + + let mut substs = Vec::new(); + + // we need to iterate the lifetime and type/const params separately as our order of them + // differs from the supplied syntax + + let ty_error = || TyKind::Error.intern(Interner).cast(Interner); + let mut def_toc_iter = def_generics.iter_self_type_or_consts_id(); + let fill_self_param = || { + if self_param { + let self_ty = explicit_self_ty.map(|x| x.cast(Interner)).unwrap_or_else(ty_error); + + if let Some(id) = def_toc_iter.next() { + assert!(matches!(id, GenericParamId::TypeParamId(_))); + substs.push(self_ty); + } + } + }; + let mut had_explicit_args = false; + + if let Some(&GenericArgs { ref args, has_self_type, .. }) = args_and_bindings { + // Fill in the self param first + if has_self_type && self_param { + had_explicit_args = true; + if let Some(id) = def_toc_iter.next() { + assert!(matches!(id, GenericParamId::TypeParamId(_))); + had_explicit_args = true; + if let GenericArg::Type(ty) = &args[0] { + substs.push(self.ctx.lower_ty(*ty).cast(Interner)); + } + } + } else { + fill_self_param() + }; + + // Then fill in the supplied lifetime args, or error lifetimes if there are too few + // (default lifetimes aren't a thing) + for arg in args + .iter() + .filter_map(|arg| match arg { + GenericArg::Lifetime(arg) => Some(self.ctx.lower_lifetime(arg)), + _ => None, + }) + .chain(iter::repeat(error_lifetime())) + .take(lifetime_params) + { + substs.push(arg.cast(Interner)); + } + + let skip = if has_self_type { 1 } else { 0 }; + // Fill in supplied type and const args + // Note if non-lifetime args are provided, it should be all of them, but we can't rely on that + for (arg, id) in args + .iter() + .filter(|arg| !matches!(arg, GenericArg::Lifetime(_))) + .skip(skip) + .take(type_params + const_params) + .zip(def_toc_iter) + { + had_explicit_args = true; + let arg = generic_arg_to_chalk( + self.ctx.db, + id, + arg, + self.ctx, + self.ctx.types_map, + |ctx, type_ref| ctx.lower_ty(type_ref), + |ctx, const_ref, ty| ctx.lower_const(const_ref, ty), + |ctx, lifetime_ref| ctx.lower_lifetime(lifetime_ref), + ); + substs.push(arg); + } + } else { + fill_self_param(); + } + + let param_to_err = |id| match id { + GenericParamId::ConstParamId(x) => { + unknown_const_as_generic(self.ctx.db.const_param_ty(x)) + } + GenericParamId::TypeParamId(_) => ty_error(), + GenericParamId::LifetimeParamId(_) => error_lifetime().cast(Interner), + }; + // handle defaults. In expression or pattern path segments without + // explicitly specified type arguments, missing type arguments are inferred + // (i.e. defaults aren't used). + // Generic parameters for associated types are not supposed to have defaults, so we just + // ignore them. + let is_assoc_ty = || match def { + GenericDefId::TypeAliasId(id) => { + matches!(id.lookup(self.ctx.db.upcast()).container, ItemContainerId::TraitId(_)) + } + _ => false, + }; + let fill_defaults = (!infer_args || had_explicit_args) && !is_assoc_ty(); + if fill_defaults { + let defaults = &*self.ctx.db.generic_defaults(def); + let (item, _parent) = defaults.split_at(item_len); + let parent_from = item_len - substs.len(); + + let mut rem = + def_generics.iter_id().skip(substs.len()).map(param_to_err).collect::<Vec<_>>(); + // Fill in defaults for type/const params + for (idx, default_ty) in item[substs.len()..].iter().enumerate() { + // each default can depend on the previous parameters + let substs_so_far = Substitution::from_iter( + Interner, + substs.iter().cloned().chain(rem[idx..].iter().cloned()), + ); + substs.push(default_ty.clone().substitute(Interner, &substs_so_far)); + } + // Fill in remaining parent params + substs.extend(rem.drain(parent_from..)); + } else { + // Fill in remaining def params and parent params + substs.extend(def_generics.iter_id().skip(substs.len()).map(param_to_err)); + } + + assert_eq!(substs.len(), total_len, "expected {} substs, got {}", total_len, substs.len()); + Substitution::from_iter(Interner, substs) + } + + pub(crate) fn lower_trait_ref_from_resolved_path( + &mut self, + resolved: TraitId, + explicit_self_ty: Ty, + ) -> TraitRef { + let substs = self.trait_ref_substs_from_path(resolved, explicit_self_ty); + TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs } + } + + fn trait_ref_substs_from_path( + &mut self, + resolved: TraitId, + explicit_self_ty: Ty, + ) -> Substitution { + self.substs_from_path_segment(resolved.into(), false, Some(explicit_self_ty)) + } + + pub(super) fn assoc_type_bindings_from_type_bound<'c>( + mut self, + bound: &'c TypeBound, + trait_ref: TraitRef, + ) -> Option<impl Iterator<Item = QuantifiedWhereClause> + use<'a, 'b, 'c>> { + self.current_or_prev_segment.args_and_bindings.map(|args_and_bindings| { + args_and_bindings.bindings.iter().flat_map(move |binding| { + let found = associated_type_by_name_including_super_traits( + self.ctx.db, + trait_ref.clone(), + &binding.name, + ); + let (super_trait_ref, associated_ty) = match found { + None => return SmallVec::new(), + Some(t) => t, + }; + // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent + // generic params. It's inefficient to splice the `Substitution`s, so we may want + // that method to optionally take parent `Substitution` as we already know them at + // this point (`super_trait_ref.substitution`). + let substitution = self.substs_from_args_and_bindings( + binding.args.as_ref(), + associated_ty.into(), + false, // this is not relevant + Some(super_trait_ref.self_type_parameter(Interner)), + ); + let self_params = generics(self.ctx.db.upcast(), associated_ty.into()).len_self(); + let substitution = Substitution::from_iter( + Interner, + substitution + .iter(Interner) + .take(self_params) + .chain(super_trait_ref.substitution.iter(Interner)), + ); + let projection_ty = ProjectionTy { + associated_ty_id: to_assoc_type_id(associated_ty), + substitution, + }; + let mut predicates: SmallVec<[_; 1]> = SmallVec::with_capacity( + binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(), + ); + if let Some(type_ref) = binding.type_ref { + match (&self.ctx.types_map[type_ref], self.ctx.impl_trait_mode.mode) { + (TypeRef::ImplTrait(_), ImplTraitLoweringMode::Disallowed) => (), + (_, ImplTraitLoweringMode::Disallowed | ImplTraitLoweringMode::Opaque) => { + let ty = self.ctx.lower_ty(type_ref); + let alias_eq = + AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty }; + predicates + .push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq))); + } + (_, ImplTraitLoweringMode::Param | ImplTraitLoweringMode::Variable) => { + // Find the generic index for the target of our `bound` + let target_param_idx = + self.ctx.resolver.where_predicates_in_scope().find_map(|(p, _)| { + match p { + WherePredicate::TypeBound { + target: WherePredicateTypeTarget::TypeOrConstParam(idx), + bound: b, + } if b == bound => Some(idx), + _ => None, + } + }); + let ty = if let Some(target_param_idx) = target_param_idx { + let mut counter = 0; + let generics = self.ctx.generics().expect("generics in scope"); + for (idx, data) in generics.iter_self_type_or_consts() { + // Count the number of `impl Trait` things that appear before + // the target of our `bound`. + // Our counter within `impl_trait_mode` should be that number + // to properly lower each types within `type_ref` + if data.type_param().is_some_and(|p| { + p.provenance == TypeParamProvenance::ArgumentImplTrait + }) { + counter += 1; + } + if idx == *target_param_idx { + break; + } + } + let mut ext = TyLoweringContext::new_maybe_unowned( + self.ctx.db, + self.ctx.resolver, + self.ctx.types_map, + self.ctx.types_source_map, + self.ctx.owner, + ) + .with_type_param_mode(self.ctx.type_param_mode); + match self.ctx.impl_trait_mode.mode { + ImplTraitLoweringMode::Param => { + ext.impl_trait_mode = + ImplTraitLoweringState::param(counter); + } + ImplTraitLoweringMode::Variable => { + ext.impl_trait_mode = + ImplTraitLoweringState::variable(counter); + } + _ => unreachable!(), + } + let ty = ext.lower_ty(type_ref); + self.ctx.diagnostics.extend(ext.diagnostics); + ty + } else { + self.ctx.lower_ty(type_ref) + }; + + let alias_eq = + AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty }; + predicates + .push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq))); + } + } + } + for bound in binding.bounds.iter() { + predicates.extend(self.ctx.lower_type_bound( + bound, + TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(Interner), + false, + )); + } + predicates + }) + }) + } +} |