Stop being so bail-y in candidate assembly

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -91,14 +91,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             } else if tcx.is_lang_item(def_id, LangItem::Sized) {
                 // Sized is never implementable by end-users, it is
                 // always automatically computed.
-
-                // FIXME: Consider moving this check to the top level as it
-                // may also be useful for predicates other than `Sized`
-                // Error type cannot possibly implement `Sized` (fixes #123154)
-                if let Err(e) = obligation.predicate.skip_binder().self_ty().error_reported() {
-                    return Err(SelectionError::Overflow(e.into()));
-                }
-
                 let sized_conditions = self.sized_conditions(obligation);
                 self.assemble_builtin_bound_candidates(sized_conditions, &mut candidates);
             } else if tcx.is_lang_item(def_id, LangItem::Unsize) {
@@ -230,13 +222,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     ) -> Result<(), SelectionError<'tcx>> {
         debug!(?stack.obligation);
 
-        // An error type will unify with anything. So, avoid
-        // matching an error type with `ParamCandidate`.
-        // This helps us avoid spurious errors like issue #121941.
-        if stack.obligation.predicate.references_error() {
-            return Ok(());
-        }
-
         let bounds = stack
             .obligation
             .param_env
@@ -563,19 +548,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         obligation: &PolyTraitObligation<'tcx>,
         candidates: &mut SelectionCandidateSet<'tcx>,
     ) {
-        // Essentially any user-written impl will match with an error type,
-        // so creating `ImplCandidates` isn't useful. However, we might
-        // end up finding a candidate elsewhere (e.g. a `BuiltinCandidate` for `Sized`)
-        // This helps us avoid overflow: see issue #72839
-        // Since compilation is already guaranteed to fail, this is just
-        // to try to show the 'nicest' possible errors to the user.
-        // We don't check for errors in the `ParamEnv` - in practice,
-        // it seems to cause us to be overly aggressive in deciding
-        // to give up searching for candidates, leading to spurious errors.
-        if obligation.predicate.references_error() {
-            return;
-        }
-
         let drcx = DeepRejectCtxt::relate_rigid_infer(self.tcx());
         let obligation_args = obligation.predicate.skip_binder().trait_ref.args;
         self.tcx().for_each_relevant_impl(

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2487,10 +2487,6 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         let impl_args = self.infcx.fresh_args_for_item(obligation.cause.span, impl_def_id);
 
         let trait_ref = impl_trait_header.trait_ref.instantiate(self.tcx(), impl_args);
-        if trait_ref.references_error() {
-            return Err(());
-        }
-
         debug!(?impl_trait_header);
 
         let Normalized { value: impl_trait_ref, obligations: mut nested_obligations } =

compiler/rustc_ty_utils/src/ty.rs

@@ -6,8 +6,7 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{
-    self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
-    TypeVisitor, Upcast,
+    self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, Upcast,
 };
 use rustc_span::DUMMY_SP;
 use rustc_span::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
@@ -95,9 +94,6 @@ fn adt_sized_constraint<'tcx>(
     let tail_ty = tcx.type_of(tail_def.did).instantiate_identity();
 
     let constraint_ty = sized_constraint_for_ty(tcx, tail_ty)?;
-    if let Err(guar) = constraint_ty.error_reported() {
-        return Some(ty::EarlyBinder::bind(Ty::new_error(tcx, guar)));
-    }
 
     // perf hack: if there is a `constraint_ty: Sized` bound, then we know
     // that the type is sized and do not need to check it on the impl.

tests/crashes/130521.rs

@@ -6,7 +6,7 @@ struct Vtable(dyn Cap);
 trait Cap<'a> {}
 
 union Transmute {
-    t: u64,
+    t: u128,
     u: &'static Vtable,
 }
 

tests/ui/const-generics/generic_const_exprs/bad-multiply.rs

@@ -0,0 +1,18 @@
+// regression test for #124350
+
+struct Node<const D: usize> {}
+
+impl<const D: usize> Node<D>
+where
+    SmallVec<{ D * 2 }>:,
+    //~^ ERROR generic parameters may not be used in const operations
+    //~| ERROR constant provided when a type was expected
+{
+    fn new() -> Self {
+        Node::new()
+    }
+}
+
+struct SmallVec<T1>(T1);
+
+fn main() {}

tests/ui/const-generics/generic_const_exprs/bad-multiply.stderr

@@ -0,0 +1,18 @@
+error: generic parameters may not be used in const operations
+  --> $DIR/bad-multiply.rs:7:16
+   |
+LL |     SmallVec<{ D * 2 }>:,
+   |                ^ cannot perform const operation using `D`
+   |
+   = help: const parameters may only be used as standalone arguments, i.e. `D`
+   = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
+
+error[E0747]: constant provided when a type was expected
+  --> $DIR/bad-multiply.rs:7:14
+   |
+LL |     SmallVec<{ D * 2 }>:,
+   |              ^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0747`.

tests/ui/const-generics/kind_mismatch.rs

@@ -20,5 +20,4 @@ pub fn remove_key<K, S: SubsetExcept<K>>() -> S {
 
 fn main() {
     let map: KeyHolder<0> = remove_key::<_, _>();
-    //~^ ERROR: the trait bound `KeyHolder<0>: SubsetExcept<_>` is not satisfied
 }

tests/ui/const-generics/kind_mismatch.stderr

@@ -14,26 +14,6 @@ LL | impl<K> ContainsKey<K> for KeyHolder<K> {}
    |      |
    |      help: consider changing this type parameter to a const parameter: `const K: u8`
 
-error[E0277]: the trait bound `KeyHolder<0>: SubsetExcept<_>` is not satisfied
-  --> $DIR/kind_mismatch.rs:22:45
-   |
-LL |     let map: KeyHolder<0> = remove_key::<_, _>();
-   |                                             ^ the trait `ContainsKey<0>` is not implemented for `KeyHolder<0>`
-   |
-note: required for `KeyHolder<0>` to implement `SubsetExcept<_>`
-  --> $DIR/kind_mismatch.rs:15:28
-   |
-LL | impl<P, T: ContainsKey<0>> SubsetExcept<P> for T {}
-   |            --------------  ^^^^^^^^^^^^^^^     ^
-   |            |
-   |            unsatisfied trait bound introduced here
-note: required by a bound in `remove_key`
-  --> $DIR/kind_mismatch.rs:17:25
-   |
-LL | pub fn remove_key<K, S: SubsetExcept<K>>() -> S {
-   |                         ^^^^^^^^^^^^^^^ required by this bound in `remove_key`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0277, E0747.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0747`.

tests/ui/generic-associated-types/issue-71176.rs

@@ -16,6 +16,8 @@ struct Holder<B> {
 
 fn main() {
     Holder {
-        inner: Box::new(()), //~ ERROR: the trait `Provider` cannot be made into an object
+        inner: Box::new(()),
+        //~^ ERROR: the trait `Provider` cannot be made into an object
+        //~| ERROR: the trait `Provider` cannot be made into an object
     };
 }

tests/ui/generic-associated-types/issue-71176.stderr

@@ -80,7 +80,24 @@ LL |     type A<'a>;
    = help: consider moving `A` to another trait
    = help: only type `()` implements the trait, consider using it directly instead
 
-error: aborting due to 5 previous errors
+error[E0038]: the trait `Provider` cannot be made into an object
+  --> $DIR/issue-71176.rs:19:16
+   |
+LL |         inner: Box::new(()),
+   |                ^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |
+note: for a trait to be "dyn-compatible" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/issue-71176.rs:2:10
+   |
+LL | trait Provider {
+   |       -------- this trait cannot be made into an object...
+LL |     type A<'a>;
+   |          ^ ...because it contains the generic associated type `A`
+   = help: consider moving `A` to another trait
+   = help: only type `()` implements the trait, consider using it directly instead
+   = note: required for the cast from `Box<()>` to `Box<(dyn Provider<A<'_> = _> + 'static), {type error}>`
+
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0038, E0107.
 For more information about an error, try `rustc --explain E0038`.

tests/ui/layout/ice-type-error-in-tail-124031.rs

@@ -1,3 +1,5 @@
+//@ normalize-stderr-test: "\d+ bits" -> "$$BITS bits"
+
 // Regression test for issue #124031
 // Checks that we don't ICE when the tail
 // of an ADT has a type error
@@ -16,5 +18,6 @@ struct Other {
 fn main() {
     unsafe {
         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+        //~^ ERROR cannot transmute between types of different sizes
     }
 }

tests/ui/layout/ice-type-error-in-tail-124031.stderr

@@ -1,12 +1,22 @@
 error[E0046]: not all trait items implemented, missing: `RefTarget`
-  --> $DIR/ice-type-error-in-tail-124031.rs:9:1
+  --> $DIR/ice-type-error-in-tail-124031.rs:11:1
    |
 LL |     type RefTarget;
    |     -------------- `RefTarget` from trait
 ...
 LL | impl Trait for () {}
    | ^^^^^^^^^^^^^^^^^ missing `RefTarget` in implementation
 
-error: aborting due to 1 previous error
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> $DIR/ice-type-error-in-tail-124031.rs:20:9
+   |
+LL |         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `Option<()>` ($BITS bits)
+   = note: target type: `Option<&Other>` ($BITS bits)
+
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0046`.
+Some errors have detailed explanations: E0046, E0512.
+For more information about an error, try `rustc --explain E0046`.

tests/ui/lazy-type-alias/bad-lazy-type-alias.rs

@@ -0,0 +1,18 @@
+// regression test for #127351
+
+#![feature(lazy_type_alias)]
+//~^ WARN the feature `lazy_type_alias` is incomplete
+
+type ExplicitTypeOutlives<T> = T;
+
+pub struct Warns {
+    _significant_drop: ExplicitTypeOutlives,
+    //~^ ERROR missing generics for type alias `ExplicitTypeOutlives`
+    field: String,
+}
+
+pub fn test(w: Warns) {
+    let _ = || drop(w.field);
+}
+
+fn main() {}

tests/ui/lazy-type-alias/bad-lazy-type-alias.stderr

@@ -0,0 +1,28 @@
+warning: the feature `lazy_type_alias` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/bad-lazy-type-alias.rs:3:12
+   |
+LL | #![feature(lazy_type_alias)]
+   |            ^^^^^^^^^^^^^^^
+   |
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0107]: missing generics for type alias `ExplicitTypeOutlives`
+  --> $DIR/bad-lazy-type-alias.rs:9:24
+   |
+LL |     _significant_drop: ExplicitTypeOutlives,
+   |                        ^^^^^^^^^^^^^^^^^^^^ expected 1 generic argument
+   |
+note: type alias defined here, with 1 generic parameter: `T`
+  --> $DIR/bad-lazy-type-alias.rs:6:6
+   |
+LL | type ExplicitTypeOutlives<T> = T;
+   |      ^^^^^^^^^^^^^^^^^^^^ -
+help: add missing generic argument
+   |
+LL |     _significant_drop: ExplicitTypeOutlives<T>,
+   |                                            +++
+
+error: aborting due to 1 previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0107`.

tests/ui/nll/user-annotations/region-error-ice-109072.rs

@@ -11,5 +11,4 @@ impl Lt<'missing> for () { //~ ERROR undeclared lifetime
 
 fn main() {
     let _: <() as Lt<'_>>::T = &();
-    //~^ ERROR the trait bound `(): Lt<'_>` is not satisfied
 }