// Check that trait predicates are WF when params are substituted by their defaults.
// We don't want to overly constrain the predicates that may be written but we
// want to catch obviously wrong cases such as `struct Foo<T: Copy = String>`
- // or cases that may cause backwards incompatibility such as a library going from
- // `pub struct Foo<T>` to `pub struct Foo<T, U = i32>` where U: Trait<T>`
- // which may break existing uses of Foo<T>.
- // Therefore the check we do is: If if all params appearing in the LHS of the predicate
- // have defaults then we verify that it is WF with all defaults substituted simultaneously.
+ // or cases where defaults don't work together such as:
+ // `struct Foo<T = i32, U = u8> where T: into<U>`
+ // Therefore we check if a predicate in which all type params are defaulted
+ // is WF with those defaults simultaneously substituted.
// For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
//
- // First, we build the defaulted substitution.
+ // First we build the defaulted substitution.
let mut defaulted_params = Vec::new();
let substs = ty::subst::Substs::for_item(fcx.tcx, def_id, |def, _| {
// All regions are identity.
fcx.tcx.type_of(def.def_id)
}
});
- // In `trait Trait: Super`, checking `Self: Trait` or `Self: Super` is problematic.
- // We avoid those by skipping any predicates in trait declarations that contain `Self`,
- // which is excessive so we end up checking less than we could.
- for pred in predicates.predicates.iter()
- .filter_map(ty::Predicate::as_poly_trait_predicate)
- .filter(|p| !(is_trait && p.has_self_ty())) {
- let is_defaulted_param = |ty: ty::Ty| match ty.sty {
- ty::TyParam(p) => defaulted_params.contains(&p.idx),
- _ => false
- };
- // If there is a non-defaulted param in the LHS, don't check the substituted predicate.
- // `skip_binder()` is ok, we're only inspecting the type params.
- if !pred.skip_binder().self_ty().walk().all(is_defaulted_param) {
+ let defaulted_params = &defaulted_params;
+ // Now we build the substituted predicates.
+ for &pred in predicates.predicates.iter() {
+ struct HasNonDefaulted<'a> { defaulted_params: &'a Vec<u32> }
+ impl<'tcx, 'a> ty::fold::TypeVisitor<'tcx> for HasNonDefaulted<'a> {
+ fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+ match t.sty {
+ ty::TyParam(p) => !self.defaulted_params.contains(&p.idx),
+ _ => t.super_visit_with(self)
+ }
+ }
+ }
+ // If there is a non-defaulted param in the predicate, don't check it.
+ if pred.visit_with(&mut HasNonDefaulted { defaulted_params }) {
continue;
}
let substituted_pred = pred.subst(fcx.tcx, substs);
- // `skip_binder()` is ok, we're only inspecting for `has_self_ty()`.
- let substituted_lhs = substituted_pred.skip_binder().self_ty();
// In trait defs, don't check `Self: Sized` when `Self` is the default.
- let pred_is_sized = Some(pred.def_id()) == fcx.tcx.lang_items().sized_trait();
- if is_trait && substituted_lhs.has_self_ty() && pred_is_sized {
- continue;
+ if let ty::Predicate::Trait(trait_pred) = substituted_pred {
+ // `skip_binder()` is ok, we're only inspecting for `has_self_ty()`.
+ let lhs_is_self = trait_pred.skip_binder().self_ty().has_self_ty();
+ let pred_sized = Some(trait_pred.def_id()) == fcx.tcx.lang_items().sized_trait();
+ if is_trait && lhs_is_self && pred_sized {
+ continue;
+ }
}
- let pred = ty::Predicate::Trait(pred.subst(fcx.tcx, substs));
- // Avoid duplicates.
- if !predicates.predicates.contains(&pred) {
- substituted_predicates.push(pred);
+ // Avoid duplication of predicates that contain no parameters, for example.
+ if !predicates.predicates.contains(&substituted_pred) {
+ substituted_predicates.push(substituted_pred);
}
}
trait Trait<T> {}
struct Foo<U, V=i32>(U, V) where U: Trait<V>;
-trait Trait2 {}
+trait Marker {}
struct TwoParams<T, U>(T, U);
-impl Trait2 for TwoParams<i32, i32> {}
+impl Marker for TwoParams<i32, i32> {}
// Check that defaults are substituted simultaneously.
-struct IndividuallyBogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait2;
+struct IndividuallyBogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Marker;
// Clauses with non-defaulted params are not checked.
-struct NonDefaultedInClause<T, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Trait2;
+struct NonDefaultedInClause<T, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Marker;
+struct DefaultedLhs<U, V=i32>(U, V) where V: Trait<U>;
+
fn main() {}
trait Base<T = String>: Super<T> { }
//~^ error: the trait bound `T: std::marker::Copy` is not satisfied [E0277]
-trait Trait<T> {}
-struct DefaultedLhs<U, V=i32>(U, V) where V: Trait<U>;
-//~^ error: the trait bound `i32: Trait<U>` is not satisfied [E0277]
+trait ProjectionPred<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
+//~^ error: the trait bound `i32: std::ops::Add<u8>` is not satisfied [E0277]
+
+// Defaults must work together.
+struct TwoParams<T = u32, U = i32>(T, U) where T: Bar<U>;
+//~^ the trait bound `u32: Bar<i32>` is not satisfied [E0277]
+trait Bar<V> {}
+impl Bar<String> for u32 { }
+impl Bar<i32> for String { }
-// FIXME: Deal with projection predicates
-// trait ProjectionPred<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
-// ~^ error: the trait bound `i32: std::ops::Add<u8>` is not satisfied [E0277]
fn main() { }
36 | trait Super<T: Copy> { }
| ^^^^^^^^^^^^^^^^^^^^
-error[E0277]: the trait bound `i32: Trait<U>` is not satisfied
- --> $DIR/type-check-defaults.rs:41:1
+error[E0277]: the trait bound `i32: std::ops::Add<u8>` is not satisfied
+ --> $DIR/type-check-defaults.rs:40:1
|
-41 | struct DefaultedLhs<U, V=i32>(U, V) where V: Trait<U>;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait<U>` is not implemented for `i32`
+40 | trait ProjectionPred<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `i32 + u8`
|
-note: required by `Trait`
- --> $DIR/type-check-defaults.rs:40:1
+ = help: the trait `std::ops::Add<u8>` is not implemented for `i32`
+ = note: required by `std::ops::Add`
+
+error[E0277]: the trait bound `u32: Bar<i32>` is not satisfied
+ --> $DIR/type-check-defaults.rs:44:1
+ |
+44 | struct TwoParams<T = u32, U = i32>(T, U) where T: Bar<U>;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bar<i32>` is not implemented for `u32`
+ |
+ = help: the following implementations were found:
+ <u32 as Bar<std::string::String>>
+note: required by `Bar`
+ --> $DIR/type-check-defaults.rs:46:1
|
-40 | trait Trait<T> {}
- | ^^^^^^^^^^^^^^
+46 | trait Bar<V> {}
+ | ^^^^^^^^^^^^
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
projects / rust.git / commitdiff