This is the most conservative possible and should be always correct.
fn check_trait(&mut self, item: &hir::Item) {
let trait_def_id = self.tcx.hir.local_def_id(item.id);
self.for_item(item).with_fcx(|fcx, _| {
- self.check_trait_where_clauses(fcx, item.span, trait_def_id);
+ self.check_where_clauses(fcx, item.span, trait_def_id);
vec![]
});
}
fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
span: Span,
def_id: DefId) {
- self.inner_check_where_clauses(fcx, span, def_id, false)
- }
-
- fn check_trait_where_clauses<'fcx, 'tcx>(&mut self,
- fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
- span: Span,
- def_id: DefId) {
- self.inner_check_where_clauses(fcx, span, def_id, true)
- }
-
- /// Checks where clauses and inline bounds that are declared on def_id.
- fn inner_check_where_clauses<'fcx, 'tcx>(&mut self,
- fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
- span: Span,
- def_id: DefId,
- is_trait: bool)
- {
use ty::subst::Subst;
use rustc::ty::TypeFoldable;
}
// 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 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.
+ // We don't want to overly constrain the predicates that may be written but we want to
+ // catch cases where a default my never be applied such as `struct Foo<T: Copy = String>`.
+ // Therefore we check if a predicate which contains a single type param
+ // with a concrete default is WF with that default substituted.
// For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
//
// First we build the defaulted substitution.
// All regions are identity.
fcx.tcx.mk_region(ty::ReEarlyBound(def.to_early_bound_region_data()))
}, |def, _| {
- if !is_our_default(def) {
- // We don't want to use non-defaulted params in a substitution, mark as err.
- fcx.tcx.types.err
- } else {
- // Substitute with default.
- fcx.tcx.type_of(def.def_id)
+ // If the param has a default,
+ if is_our_default(def) {
+ let default_ty = fcx.tcx.type_of(def.def_id);
+ // and it's not a dependent default
+ if !default_ty.needs_subst() {
+ // then substitute with the default.
+ return default_ty;
+ }
}
+ // Mark unwanted params as err.
+ fcx.tcx.types.err
});
// Now we build the substituted predicates.
for &pred in predicates.predicates.iter() {
+ struct CountParams { params: FxHashSet<u32> }
+ impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams {
+ fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+ match t.sty {
+ ty::TyParam(p) => {
+ self.params.insert(p.idx);
+ t.super_visit_with(self)
+ }
+ _ => t.super_visit_with(self)
+ }
+ }
+ }
+ let mut param_count = CountParams { params: FxHashSet() };
+ pred.visit_with(&mut param_count);
let substituted_pred = pred.subst(fcx.tcx, substs);
- // If there is a non-defaulted param in the predicate, don't check it.
- if substituted_pred.references_error() {
+ // Don't check non-defaulted params, dependent defaults or preds with multiple params.
+ if substituted_pred.references_error() || param_count.params.len() > 1 {
continue;
}
- // In trait defs, don't check `Self: Sized` when `Self` is the default.
- 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;
- }
- }
// Avoid duplication of predicates that contain no parameters, for example.
if !predicates.predicates.contains(&substituted_pred) {
substituted_predicates.push(substituted_pred);
trait Marker {}
struct TwoParams<T, U>(T, U);
impl Marker for TwoParams<i32, i32> {}
-// Check that defaults are substituted simultaneously.
+
+// Clauses with more than 1 param are not checked.
struct IndividuallyBogus<T = i32, U = i32>(TwoParams<T, U>) where TwoParams<T, U>: Marker;
+struct BogusTogether<T = u32, U = i32>(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>: Marker;
struct DefaultedLhs<U, V=i32>(U, V) where V: Trait<U>;
-// Dependent defaults.
-struct Dependent<T: Copy, U = T>(T, U) where U: Copy;
+// Dependent defaults are not checked.
+struct Dependent<T, U = T>(T, U) where U: Copy;
+trait SelfBound<T: Copy=Self> {}
fn main() {}
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 Super<T: Copy> { }
trait Base<T = String>: Super<T> { }
//~^ error: the trait bound `T: std::marker::Copy` 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 { }
-
-// Dependent defaults.
-struct Dependent<T, U = T>(T, U) where U: Copy;
-//~^ the trait bound `T: std::marker::Copy` is not satisfied [E0277]
+//~^ error: cannot add `u8` to `i32` [E0277]
fn main() { }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0277]: the trait bound `A: std::iter::Iterator` is not satisfied
- --> $DIR/type-check-defaults.rs:21:1
+ --> $DIR/type-check-defaults.rs:21:32
|
21 | struct WellFormedProjection<A, T=<A as Iterator>::Item>(A, T);
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `A` is not an iterator; maybe try calling `.iter()` or a similar method
+ | ^ `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
+ = note: required by `std::iter::Iterator`
error[E0277]: the trait bound `std::string::String: std::marker::Copy` is not satisfied
--> $DIR/type-check-defaults.rs:24:1
|
= note: required by `std::marker::Copy`
-error[E0277]: the trait bound `Self: std::marker::Copy` is not satisfied
- --> $DIR/type-check-defaults.rs:33:1
- |
-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 `T: std::marker::Copy` is not satisfied
- --> $DIR/type-check-defaults.rs:37:1
+ --> $DIR/type-check-defaults.rs:34:1
|
-37 | trait Base<T = String>: Super<T> { }
+34 | trait Base<T = String>: Super<T> { }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
|
= help: consider adding a `where T: std::marker::Copy` bound
note: required by `Super`
- --> $DIR/type-check-defaults.rs:36:1
+ --> $DIR/type-check-defaults.rs:33:1
|
-36 | trait Super<T: Copy> { }
+33 | trait Super<T: Copy> { }
| ^^^^^^^^^^^^^^^^^^^^
-error[E0277]: the trait bound `i32: std::ops::Add<u8>` is not satisfied
- --> $DIR/type-check-defaults.rs:40:1
+error[E0277]: cannot add `u8` to `i32`
+ --> $DIR/type-check-defaults.rs:37:1
|
-40 | trait ProjectionPred<T:Iterator = IntoIter<i32>> where T::Item : Add<u8> {}
+37 | trait ProjectionPred<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 `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
- |
-46 | trait Bar<V> {}
- | ^^^^^^^^^^^^
-
-error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
- --> $DIR/type-check-defaults.rs:51:1
- |
-51 | struct Dependent<T, U = T>(T, U) where U: Copy;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
- |
- = help: consider adding a `where T: std::marker::Copy` bound
- = note: required by `std::marker::Copy`
-
-error: aborting due to 11 previous errors
+error: aborting due to 8 previous errors
projects / rust.git / commitdiff