Check generators for well formedness

Author: oli-obk

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -295,6 +295,7 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
     /// This is called much less often than `needs_process_obligation`, so we
     /// never inline it.
     #[inline(never)]
+    #[instrument(level = "debug", skip(self, pending_obligation))]
     fn process_obligation(
         &mut self,
         pending_obligation: &mut PendingPredicateObligation<'tcx>,
@@ -303,7 +304,7 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
 
         let obligation = &mut pending_obligation.obligation;
 
-        debug!(?obligation, "process_obligation pre-resolve");
+        debug!(?obligation, "pre-resolve");
 
         if obligation.predicate.has_infer_types_or_consts() {
             obligation.predicate =
@@ -312,8 +313,6 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
 
         let obligation = &pending_obligation.obligation;
 
-        debug!(?obligation, ?obligation.cause, "process_obligation");
-
         let infcx = self.selcx.infcx();
 
         if obligation.predicate.has_projections() {

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -559,14 +559,16 @@ impl<'tcx> WfPredicates<'tcx> {
                     }
                 }
 
-                ty::Generator(..) => {
+                ty::Generator(did, substs, ..) => {
                     // Walk ALL the types in the generator: this will
                     // include the upvar types as well as the yield
                     // type. Note that this is mildly distinct from
                     // the closure case, where we have to be careful
                     // about the signature of the closure. We don't
                     // have the problem of implied bounds here since
                     // generators don't take arguments.
+                    let obligations = self.nominal_obligations(did, substs);
+                    self.out.extend(obligations);
                 }
 
                 ty::Closure(did, substs) => {
@@ -618,11 +620,9 @@ impl<'tcx> WfPredicates<'tcx> {
                 }
 
                 ty::Opaque(did, substs) => {
-                    // all of the requirements on type parameters
-                    // should've been checked by the instantiation
-                    // of whatever returned this exact `impl Trait`.
-
-                    // for named opaque `impl Trait` types we still need to check them
+                    // All of the requirements on type parameters
+                    // have already been checked for `impl Trait` in
+                    // return position. We do need to check type-alias-impl-trait though.
                     if ty::is_impl_trait_defn(self.tcx, did).is_none() {
                         let obligations = self.nominal_obligations(did, substs);
                         self.out.extend(obligations);
@@ -684,6 +684,7 @@ impl<'tcx> WfPredicates<'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip(self))]
     fn nominal_obligations(
         &mut self,
         def_id: DefId,
@@ -698,6 +699,7 @@ impl<'tcx> WfPredicates<'tcx> {
         }
 
         let predicates = predicates.instantiate(self.tcx, substs);
+        trace!("{:#?}", predicates);
         debug_assert_eq!(predicates.predicates.len(), origins.len());
 
         iter::zip(iter::zip(predicates.predicates, predicates.spans), origins.into_iter().rev())

src/test/ui/generic-associated-types/issue-88287.rs

@@ -1,4 +1,3 @@
-// check-pass
 // edition:2018
 
 #![feature(generic_associated_types)]
@@ -34,6 +33,7 @@ where
 
     fn search<'c>(&'c self, _client: &'c ()) -> Self::Future<'c, Self, Criteria> {
         async move { todo!() }
+        //~^ ERROR: the size for values of type `A` cannot be known at compilation time
     }
 }
 

src/test/ui/generic-associated-types/issue-88287.stderr

@@ -0,0 +1,27 @@
+error[E0277]: the size for values of type `A` cannot be known at compilation time
+  --> $DIR/issue-88287.rs:35:9
+   |
+LL | type SearchFutureTy<'f, A, B: 'f>
+   |                         - this type parameter needs to be `std::marker::Sized`
+...
+LL |         async move { todo!() }
+   |         ^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+note: required by a bound in `<T as SearchableResourceExt<Criteria>>`
+  --> $DIR/issue-88287.rs:25:6
+   |
+LL | impl<T, Criteria> SearchableResourceExt<Criteria> for T
+   |      ^ required by this bound in `<T as SearchableResourceExt<Criteria>>`
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL -     A: SearchableResource<B> + ?Sized + 'f,
+LL +     A: SearchableResource<B> + 'f,
+   |
+help: consider relaxing the implicit `Sized` restriction
+   |
+LL |     T: SearchableResource<Criteria> + ?Sized,
+   |                                     ++++++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/lifetimes/issue-76168-hr-outlives-2.rs

@@ -0,0 +1,22 @@
+// edition:2018
+// check-pass
+
+trait Trait<Input> {
+    type Output;
+}
+
+async fn walk<F>(filter: F)
+where
+    for<'a> F: Trait<&'a u32> + 'a,
+    for<'a> <F as Trait<&'a u32>>::Output: 'a,
+{
+}
+
+async fn walk2<F: 'static>(filter: F)
+where
+    for<'a> F: Trait<&'a u32> + 'a,
+    for<'a> <F as Trait<&'a u32>>::Output: 'a,
+{
+}
+
+fn main() {}

src/test/ui/type-alias-impl-trait/future.rs

@@ -0,0 +1,22 @@
+#![feature(type_alias_impl_trait)]
+
+// edition:2021
+// compile-flags: --crate-type=lib
+
+use std::future::Future;
+
+trait Bar {
+    fn bar(&self);
+}
+
+type FooFuture<B> = impl Future<Output = ()>;
+
+fn foo<B: Bar>(bar: B) -> FooFuture<B> {
+    async move { bar.bar() }
+    //~^ ERROR: the trait bound `B: Bar` is not satisfied
+}
+
+pub fn mainish(ctx: &mut std::task::Context) {
+    let boom: FooFuture<u32> = unsafe { core::mem::zeroed() };
+    Box::pin(boom).as_mut().poll(ctx);
+}

src/test/ui/type-alias-impl-trait/future.stderr

@@ -0,0 +1,19 @@
+error[E0277]: the trait bound `B: Bar` is not satisfied
+  --> $DIR/future.rs:15:5
+   |
+LL |     async move { bar.bar() }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `B`
+   |
+note: required by a bound in `foo`
+  --> $DIR/future.rs:14:11
+   |
+LL | fn foo<B: Bar>(bar: B) -> FooFuture<B> {
+   |           ^^^ required by this bound in `foo`
+help: consider restricting type parameter `B`
+   |
+LL | type FooFuture<B: Bar> = impl Future<Output = ()>;
+   |                 +++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.