From 9754a60623c5a3a8df0d32600345dd310812bec1 Mon Sep 17 00:00:00 2001 From: Philip Herron Date: Tue, 31 Jan 2023 18:52:33 +0000 Subject: [PATCH] gccrs: Fix higher ranked trait bounds computation of self This updates the higher ranked trait bounds computation to handle ambigious cases. When we have a slice for example: let slice = &a[1..3]; This works by reusing the Index operator overload from libcore, so when the index range of 1..3 is computed, the type system needs to compute what the types of index are; this works by integer inference variables Range<> that need to be unified with the impl Index for Range which computes the real type of usize for the index. This is fine but what happens when we have the Copy and Clone traits bounds which have implementations for all the primitive types i8, i16, i32, i64... which is valid for any integer inference variable so the code prior to this patch would have grabbed the first impl it would have found and used it which is incorrect. When we have integer or float inference variables we need to look for their respective defaults or emit an ambigious type bound error. Signed-off-by: Philip Herron gcc/rust/ChangeLog: * typecheck/rust-hir-trait-reference.h: add const infterface * typecheck/rust-tyty-subst.cc (SubstitutionParamMapping::get_generic_param): make const (SubstitutionRef::monomorphize): fix issue * typecheck/rust-tyty-subst.h: constify interface --- gcc/rust/typecheck/rust-hir-trait-reference.h | 1 + gcc/rust/typecheck/rust-tyty-subst.cc | 107 ++++++++++++++++++++++++-- gcc/rust/typecheck/rust-tyty-subst.h | 2 +- 3 files changed, 102 insertions(+), 8 deletions(-) diff --git a/gcc/rust/typecheck/rust-hir-trait-reference.h b/gcc/rust/typecheck/rust-hir-trait-reference.h index 9b4461b..adb63b4 100644 --- a/gcc/rust/typecheck/rust-hir-trait-reference.h +++ b/gcc/rust/typecheck/rust-hir-trait-reference.h @@ -496,6 +496,7 @@ public: HIR::ImplBlock *get_impl_block () { return impl; } TyTy::BaseType *get_self () { return self; } + const TyTy::BaseType *get_self () const { return self; } TyTy::BaseType * setup_associated_types (const TyTy::BaseType *self, diff --git a/gcc/rust/typecheck/rust-tyty-subst.cc b/gcc/rust/typecheck/rust-tyty-subst.cc index 996bbf2..3dfe958 100644 --- a/gcc/rust/typecheck/rust-tyty-subst.cc +++ b/gcc/rust/typecheck/rust-tyty-subst.cc @@ -65,7 +65,7 @@ SubstitutionParamMapping::get_param_ty () const } const HIR::TypeParam & -SubstitutionParamMapping::get_generic_param () +SubstitutionParamMapping::get_generic_param () const { return generic; } @@ -892,8 +892,7 @@ SubstitutionRef::monomorphize () // setup any associated type mappings for the specified bonds and this // type auto candidates = Resolver::TypeBoundsProbe::Probe (binding); - - Resolver::AssociatedImplTrait *associated_impl_trait = nullptr; + std::vector associated_impl_traits; for (auto &probed_bound : candidates) { const Resolver::TraitReference *bound_trait_ref @@ -914,15 +913,109 @@ SubstitutionRef::monomorphize () = associated->get_self ()->can_eq (binding, false); if (found_trait && found_self) { - associated_impl_trait = associated; - break; + associated_impl_traits.push_back (associated); } } } - if (associated_impl_trait != nullptr) + if (!associated_impl_traits.empty ()) { - associated_impl_trait->setup_associated_types (binding, bound); + // This code is important when you look at slices for example when + // you have a slice such as: + // + // let slice = &array[1..3] + // + // the higher ranked bounds will end up having an Index trait + // implementation for Range so we need this code to resolve + // that we have an integer inference variable that needs to become + // a usize + // + // The other complicated issue is that we might have an intrinsic + // which requires the :Clone or Copy bound but the libcore adds + // implementations for all the integral types so when there are + // multiple candidates we need to resolve to the default + // implementation for that type otherwise its an error for + // ambiguous type bounds + + if (associated_impl_traits.size () == 1) + { + Resolver::AssociatedImplTrait *associate_impl_trait + = associated_impl_traits.at (0); + associate_impl_trait->setup_associated_types (binding, bound); + } + else + { + // if we have a non-general inference variable we need to be + // careful about the selection here + bool is_infer_var + = binding->get_kind () == TyTy::TypeKind::INFER; + bool is_integer_infervar + = is_infer_var + && static_cast (binding) + ->get_infer_kind () + == TyTy::InferType::InferTypeKind::INTEGRAL; + bool is_float_infervar + = is_infer_var + && static_cast (binding) + ->get_infer_kind () + == TyTy::InferType::InferTypeKind::FLOAT; + + Resolver::AssociatedImplTrait *associate_impl_trait = nullptr; + if (is_integer_infervar) + { + TyTy::BaseType *type = nullptr; + bool ok = context->lookup_builtin ("i32", &type); + rust_assert (ok); + + for (auto &impl : associated_impl_traits) + { + bool found = impl->get_self ()->is_equal (*type); + if (found) + { + associate_impl_trait = impl; + break; + } + } + } + else if (is_float_infervar) + { + TyTy::BaseType *type = nullptr; + bool ok = context->lookup_builtin ("f64", &type); + rust_assert (ok); + + for (auto &impl : associated_impl_traits) + { + bool found = impl->get_self ()->is_equal (*type); + if (found) + { + associate_impl_trait = impl; + break; + } + } + } + + if (associate_impl_trait == nullptr) + { + // go for the first one? or error out? + auto &mappings = *Analysis::Mappings::get (); + const auto &type_param = subst.get_generic_param (); + const auto *trait_ref = bound.get (); + + RichLocation r (type_param.get_locus ()); + r.add_range (bound.get_locus ()); + r.add_range ( + mappings.lookup_location (binding->get_ref ())); + + rust_error_at ( + r, "ambiguous type bound for trait %s and type %s", + trait_ref->get_name ().c_str (), + binding->get_name ().c_str ()); + + return false; + } + + associate_impl_trait->setup_associated_types (binding, bound); + } } } } diff --git a/gcc/rust/typecheck/rust-tyty-subst.h b/gcc/rust/typecheck/rust-tyty-subst.h index 039eb36..982861e 100644 --- a/gcc/rust/typecheck/rust-tyty-subst.h +++ b/gcc/rust/typecheck/rust-tyty-subst.h @@ -48,7 +48,7 @@ public: const ParamType *get_param_ty () const; - const HIR::TypeParam &get_generic_param (); + const HIR::TypeParam &get_generic_param () const; // this is used for the backend to override the HirId ref of the param to // what the concrete type is for the rest of the context -- 2.7.4