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Merge pull request #54 from scalexm/cologic
Auto traits
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| use ir::*; | ||
| use solve::infer::InferenceTable; | ||
| use cast::Cast; | ||
|
|
||
| impl Program { | ||
| pub(super) fn add_default_impls(&mut self) { | ||
| // For each auto trait `MyAutoTrait` and for each struct/type `MyStruct` | ||
| for auto_trait in self.trait_data.values().filter(|t| t.binders.value.auto) { | ||
| for struct_datum in self.struct_data.values() { | ||
|
|
||
| // `MyStruct: MyAutoTrait` | ||
| let trait_ref = TraitRef { | ||
| trait_id: auto_trait.binders.value.trait_ref.trait_id, | ||
| parameters: vec![ | ||
| ParameterKind::Ty(Ty::Apply(struct_datum.binders.value.self_ty.clone())) | ||
| ] | ||
| }; | ||
|
|
||
| // If a positive or negative impl is already provided for a type family | ||
| // which includes `MyStruct`, we do not generate a default impl. | ||
| if self.impl_provided_for(trait_ref.clone(), struct_datum) { | ||
| continue; | ||
| } | ||
|
|
||
| self.default_impl_data.push(DefaultImplDatum { | ||
| binders: Binders { | ||
| binders: struct_datum.binders.binders.clone(), | ||
| value: DefaultImplDatumBound { | ||
| trait_ref, | ||
| accessible_tys: struct_datum.binders.value.fields.clone(), | ||
| } | ||
| } | ||
| }); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn impl_provided_for(&self, trait_ref: TraitRef, struct_datum: &StructDatum) -> bool { | ||
| let goal: DomainGoal = trait_ref.cast(); | ||
|
|
||
| let env = Environment::new(); | ||
| let mut infer = InferenceTable::new(); | ||
|
|
||
| let goal = infer.instantiate_in(env.universe, struct_datum.binders.binders.clone(), &goal); | ||
|
|
||
| for impl_datum in self.impl_data.values() { | ||
| // We retrieve the trait ref given by the positive impl (even if the actual impl is negative) | ||
| let impl_goal: DomainGoal = impl_datum.binders.value.trait_ref.trait_ref().clone().cast(); | ||
|
|
||
| let impl_goal = infer.instantiate_in(env.universe, impl_datum.binders.binders.clone(), &impl_goal); | ||
|
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| // We check whether the impl `MyStruct: (!)MyAutoTrait` unifies with an existing impl. | ||
| // Examples: | ||
| // | ||
| // ``` | ||
| // struct MyStruct; | ||
| // impl<T> Send for T where T: Foo { } | ||
| // ``` | ||
| // `MyStruct: Send` unifies with `T: Send` so no default impl is generated for `MyStruct`. | ||
| // | ||
| // ``` | ||
| // struct MyStruct; | ||
| // impl<T> Send for Vec<T> where T: Foo { } | ||
| // ``` | ||
| // `Vec<i32>: Send` unifies with `Vec<T>: Send` so no default impl is generated for `Vec<i32>`. | ||
| // But a default impl is generated for `MyStruct`. | ||
| // | ||
| // ``` | ||
| // struct MyStruct; | ||
| // impl<T> !Send for T where T: Foo { } | ||
| // ``` | ||
| // `MyStruct: !Send` unifies with `T: !Send` so no default impl is generated for `MyStruct`. | ||
| if infer.unify(&Environment::new(), &goal, &impl_goal).is_ok() { | ||
| return true; | ||
| } | ||
| } | ||
|
|
||
| false | ||
| } | ||
| } |
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