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Go back to checking only the LHS of trait predicates.

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This commit is contained in:
leonardo.yvens 2017-12-23 11:29:01 -02:00
parent d9c336afb7
commit 3b4a06272e
4 changed files with 57 additions and 23 deletions
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19
src/librustc_typeck/check/wfcheck.rs
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@ -387,7 +387,7 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
let d = param_def.def_id;
fcx.register_wf_obligation(fcx.tcx.type_of(d), fcx.tcx.def_span(d), self.code.clone());
// Check the clauses are well-formed when the param is substituted by it's default.
// In trait definitions, predicates as `Self: Trait` and `Self: Super` are problematic.
// In trait definitions, the predicate `Self: Trait` is problematic.
// Therefore we skip such predicates. This means we check less than we could.
for pred in predicates.predicates.iter().filter(|p| !(is_trait && p.has_self_ty())) {
let mut skip = true;
@ -418,9 +418,20 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
}
}
});
if !skip {
substituted_predicates.push(pred.subst(fcx.tcx, substs));
}
if skip { continue; }
substituted_predicates.push(match pred {
// In trait predicates, substitute defaults only for the LHS.
ty::Predicate::Trait(trait_pred) => {
let t_pred = trait_pred.skip_binder();
let self_ty = t_pred.self_ty().subst(fcx.tcx, substs);
let mut trait_substs = t_pred.trait_ref.substs.to_vec();
trait_substs[0] = self_ty.into();
let trait_ref = ty::TraitRef::new(t_pred.def_id(),
fcx.tcx.intern_substs(&trait_substs));
ty::Predicate::Trait(ty::Binder(trait_ref).to_poly_trait_predicate())
}
_ => pred.subst(fcx.tcx, substs)
});
}
}

14
src/test/run-pass/defaults-well-formedness.rs Normal file
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@ -0,0 +1,14 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
trait Trait<T> {}
struct Foo<U, V=i32>(U, V) where U: Trait<V>;
fn main() {}

11
src/test/ui/type-check-defaults.rs
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@ -7,7 +7,6 @@
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: --error-format=human
use std::iter::FromIterator;
use std::vec::IntoIter;
@ -15,24 +14,34 @@ use std::ops::Add;
struct Foo<T, U: FromIterator<T>>(T, U);
struct WellFormed<Z = Foo<i32, i32>>(Z);
//~^ error: the trait bound `i32: std::iter::FromIterator<i32>` is not satisfied [E0277]
struct WellFormedNoBounds<Z:?Sized = Foo<i32, i32>>(Z);
//~^ error: the trait bound `i32: std::iter::FromIterator<i32>` is not satisfied [E0277]
struct WellFormedProjection<A, T=<A as Iterator>::Item>(A, T);
//~^ error: the trait bound `A: std::iter::Iterator` is not satisfied [E0277]
struct Bounds<T:Copy=String>(T);
//~^ error: the trait bound `std::string::String: std::marker::Copy` is not satisfied [E0277]
struct WhereClause<T=String>(T) where T: Copy;
//~^ error: the trait bound `std::string::String: std::marker::Copy` is not satisfied [E0277]
trait TraitBound<T:Copy=String> {}
//~^ error: the trait bound `std::string::String: std::marker::Copy` is not satisfied [E0277]
trait SelfBound<T:Copy=Self> {}
//~^ error: the trait bound `Self: std::marker::Copy` is not satisfied [E0277]
trait FooTrait<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
//~^ error: the trait bound `i32: std::ops::Add<u8>` is not satisfied [E0277]
trait Trait {}
struct TwoParams<T, U>(T, U);
impl Trait for TwoParams<i32, i32> {}
// Check that each default is substituted individually in the clauses.
struct Bogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait;
//~^ error: the trait bound `TwoParams<i32, U>: Trait` is not satisfied [E0277]
//~^^ error: the trait bound `TwoParams<T, i32>: Trait` is not satisfied [E0277]
fn main() { }

36
src/test/ui/type-check-defaults.stderr
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@ -1,7 +1,7 @@
error[E0277]: the trait bound `i32: std::iter::FromIterator<i32>` is not satisfied
--> $DIR/type-check-defaults.rs:17:19
--> $DIR/type-check-defaults.rs:16:19
|
17 | struct WellFormed<Z = Foo<i32, i32>>(Z);
16 | struct WellFormed<Z = Foo<i32, i32>>(Z);
| ^ a collection of type `i32` cannot be built from an iterator over elements of type `i32`
|
= help: the trait `std::iter::FromIterator<i32>` is not implemented for `i32`
@ -17,69 +17,69 @@ error[E0277]: the trait bound `i32: std::iter::FromIterator<i32>` is not satisfi
= note: required by `Foo`
error[E0277]: the trait bound `A: std::iter::Iterator` is not satisfied
--> $DIR/type-check-defaults.rs:20:1
--> $DIR/type-check-defaults.rs:21:1
|
20 | struct WellFormedProjection<A, T=<A as Iterator>::Item>(A, T);
21 | struct WellFormedProjection<A, T=<A as Iterator>::Item>(A, T);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `A` is not an iterator; maybe try calling `.iter()` or a similar method
|
= help: the trait `std::iter::Iterator` is not implemented for `A`
= help: consider adding a `where A: std::iter::Iterator` bound
error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
--> $DIR/type-check-defaults.rs:22:1
--> $DIR/type-check-defaults.rs:24:1
|
22 | struct Bounds<T:Copy=String>(T);
24 | struct Bounds<T:Copy=String>(T);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
|
= note: required by `std::marker::Copy`
error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
--> $DIR/type-check-defaults.rs:24:1
--> $DIR/type-check-defaults.rs:27:1
|
24 | struct WhereClause<T=String>(T) where T: Copy;
27 | struct WhereClause<T=String>(T) where T: Copy;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
|
= note: required by `std::marker::Copy`
error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
--> $DIR/type-check-defaults.rs:26:1
--> $DIR/type-check-defaults.rs:30:1
|
26 | trait TraitBound<T:Copy=String> {}
30 | trait TraitBound<T:Copy=String> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
|
= note: required by `std::marker::Copy`
error[E0277]: the trait bound `Self: std::marker::Copy` is not satisfied
--> $DIR/type-check-defaults.rs:28:1
--> $DIR/type-check-defaults.rs:33:1
|
28 | trait SelfBound<T:Copy=Self> {}
33 | trait SelfBound<T:Copy=Self> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `Self`
|
= help: consider adding a `where Self: std::marker::Copy` bound
= note: required by `std::marker::Copy`
error[E0277]: the trait bound `i32: std::ops::Add<u8>` is not satisfied
--> $DIR/type-check-defaults.rs:30:1
--> $DIR/type-check-defaults.rs:36:1
|
30 | trait FooTrait<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
36 | trait FooTrait<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `i32 + u8`
|
= help: the trait `std::ops::Add<u8>` is not implemented for `i32`
= note: required by `std::ops::Add`
error[E0277]: the trait bound `TwoParams<i32, U>: Trait` is not satisfied
--> $DIR/type-check-defaults.rs:36:1
--> $DIR/type-check-defaults.rs:43:1
|
36 | struct Bogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait;
43 | struct Bogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `TwoParams<i32, U>`
|
= help: consider adding a `where TwoParams<i32, U>: Trait` bound
= note: required by `Trait`
error[E0277]: the trait bound `TwoParams<T, i32>: Trait` is not satisfied
--> $DIR/type-check-defaults.rs:36:1
--> $DIR/type-check-defaults.rs:43:1
|
36 | struct Bogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait;
43 | struct Bogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `TwoParams<T, i32>`
|
= help: consider adding a `where TwoParams<T, i32>: Trait` bound