return ty::Error when equating ty::Error

This helps iron out a difference between Sub and Equate

compiler/rustc_infer/src/infer/relate/equate.rs

@@ -89,6 +89,11 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
                 self.fields.instantiate(a, ty::Invariant, b_id, self.a_is_expected)?;
             }
 
+            (&ty::Error(e), _) | (_, &ty::Error(e)) => {
+                infcx.set_tainted_by_errors(e);
+                return Ok(Ty::new_error(self.tcx(), e));
+            }
+
             (
                 &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, .. }),
                 &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }),

tests/ui/generic-associated-types/issue-79636-1.rs

@@ -15,7 +15,6 @@ where
     //~^ ERROR: missing generics for associated type `Monad::Wrapped`
 {
     outer.bind(|inner| inner)
-    //~^ ERROR type annotations needed
 }
 
 fn main() {

tests/ui/generic-associated-types/issue-79636-1.stderr

@@ -30,19 +30,8 @@ help: function arguments must have a statically known size, borrowed types alway
 LL |     fn bind<B, F>(&self, f: F) -> Self::Wrapped<B> {
    |                   +
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-79636-1.rs:17:17
-   |
-LL |     outer.bind(|inner| inner)
-   |                 ^^^^^
-   |
-help: consider giving this closure parameter an explicit type
-   |
-LL |     outer.bind(|inner: /* Type */| inner)
-   |                      ++++++++++++
-
 error[E0277]: the trait bound `Option<Option<bool>>: Monad` is not satisfied
-  --> $DIR/issue-79636-1.rs:22:21
+  --> $DIR/issue-79636-1.rs:21:21
    |
 LL |     assert_eq!(join(Some(Some(true))), Some(true));
    |                ---- ^^^^^^^^^^^^^^^^ the trait `Monad` is not implemented for `Option<Option<bool>>`
@@ -63,7 +52,7 @@ LL | where
 LL |     MOuter: Monad<Unwrapped = MInner>,
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `join`
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0107, E0277, E0282.
+Some errors have detailed explanations: E0107, E0277.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/impl-trait/where-allowed.rs

@@ -59,7 +59,6 @@ fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
 fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
 //~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 //~| ERROR nested `impl Trait` is not allowed
-//~| ERROR: type annotations needed
 
 // Allowed
 fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }