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Fix inference of indexing argument (partly) #5211

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Jul 3, 2020
Merged

Fix inference of indexing argument (partly) #5211

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20 changes: 12 additions & 8 deletions crates/ra_hir_ty/src/infer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@ use hir_def::{
path::{path, Path},
resolver::{HasResolver, Resolver, TypeNs},
type_ref::{Mutability, TypeRef},
AdtId, AssocItemId, DefWithBodyId, EnumVariantId, FieldId, FunctionId, TraitId, TypeAliasId,
VariantId,
AdtId, AssocItemId, DefWithBodyId, EnumVariantId, FieldId, FunctionId, Lookup, TraitId,
TypeAliasId, VariantId,
};
use hir_expand::{diagnostics::DiagnosticSink, name::name};
use ra_arena::map::ArenaMap;
Expand Down Expand Up @@ -376,17 +376,21 @@ impl<'a> InferenceContext<'a> {
) -> Ty {
match assoc_ty {
Some(res_assoc_ty) => {
let trait_ = match res_assoc_ty.lookup(self.db.upcast()).container {
hir_def::AssocContainerId::TraitId(trait_) => trait_,
_ => panic!("resolve_associated_type called with non-associated type"),
};
let ty = self.table.new_type_var();
let builder = Substs::build_for_def(self.db, res_assoc_ty)
let substs = Substs::build_for_def(self.db, res_assoc_ty)
.push(inner_ty)
.fill(params.iter().cloned());
.fill(params.iter().cloned())
.build();
let trait_ref = TraitRef { trait_, substs: substs.clone() };
let projection = ProjectionPredicate {
ty: ty.clone(),
projection_ty: ProjectionTy {
associated_ty: res_assoc_ty,
parameters: builder.build(),
},
projection_ty: ProjectionTy { associated_ty: res_assoc_ty, parameters: substs },
};
self.obligations.push(Obligation::Trait(trait_ref));
self.obligations.push(Obligation::Projection(projection));
self.resolve_ty_as_possible(ty)
}
Expand Down
36 changes: 36 additions & 0 deletions crates/ra_hir_ty/src/tests/traits.rs
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Expand Up @@ -540,6 +540,42 @@ mod ops {
);
}

#[test]
fn infer_ops_index_int() {
check_types(
r#"
//- /main.rs crate:main deps:std
struct Bar;
struct Foo;

impl std::ops::Index<u32> for Bar {
type Output = Foo;
}

struct Range;
impl std::ops::Index<Range> for Bar {
type Output = Bar;
}

fn test() {
let a = Bar;
let b = a[1];
b;
//^ Foo
}

//- /std.rs crate:std
#[prelude_import] use ops::*;
mod ops {
#[lang = "index"]
pub trait Index<Idx> {
type Output;
}
}
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@matklad matklad Jul 3, 2020 •
edited

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at some point we need to figure a better way to specify such preludes...

I guess, we can do //- core, and have that auto-magically insert everything, but I wonder if it makes sense to keep stuff more granular?

LGTM!

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I do kind of like having it explicit what types/traits are actually needed by the test. Also, keeping it small helps when debugging tests.

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Yeah, that's true. But we might do something granular, but still with only one trait Index written down

//- include(std::core::Index, std::result::Result)

but that won't you see at a glance what's going on...

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That might be nice. Maybe there should just be std/core "snippets" that the tests can include.

"#,
);
}

#[test]
fn infer_ops_index_autoderef() {
check_types(
Expand Down