Reduce follow-up errors that are not helpful

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -58,7 +58,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) -> VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>> {
         opaque_ty_decls
             .into_iter()
-            .filter_map(|(opaque_type_key, (concrete_type, decl_span, origin))| {
+            .map(|(opaque_type_key, (concrete_type, decl_span, origin))| {
                 let substs = opaque_type_key.substs;
                 // FIXME: why are the spans in decl_span often DUMMY_SP?
                 let span = decl_span.substitute_dummy(span);
@@ -112,8 +112,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     span,
                 );
 
-                check_opaque_type_parameter_valid(infcx.tcx, opaque_type_key, origin, span)
+                (
-                    .then_some((opaque_type_key, remapped_type))
+                    opaque_type_key,
+                    if check_opaque_type_parameter_valid(infcx.tcx, opaque_type_key, origin, span) {
+                        remapped_type
+                    } else {
+                        infcx.tcx.ty_error()
+                    },
+                )
             })
             .collect()
     }

src/test/ui/generic-associated-types/issue-88595.rs

@@ -18,7 +18,6 @@ struct C;
 impl<'a> A<'a> for C {
     type B<'b> = impl Clone;
     //~^ ERROR: lifetime bound not satisfied
-    //~| ERROR: unconstrained opaque type
 
     fn a(&'a self) -> Self::B<'a> {} //~ ERROR: non-defining opaque type use in defining scope
 }

src/test/ui/generic-associated-types/issue-88595.stderr

@@ -16,7 +16,7 @@ LL |     type B<'b> = impl Clone;
    |            ^^
 
 error: non-defining opaque type use in defining scope
-  --> $DIR/issue-88595.rs:23:35
+  --> $DIR/issue-88595.rs:22:35
    |
 LL |     fn a(&'a self) -> Self::B<'a> {}
    |                                   ^^
@@ -29,14 +29,6 @@ LL | impl<'a> A<'a> for C {
 LL |     type B<'b> = impl Clone;
    |            ^^
 
-error: unconstrained opaque type
+error: aborting due to 2 previous errors
-  --> $DIR/issue-88595.rs:19:18
-   |
-LL |     type B<'b> = impl Clone;
-   |                  ^^^^^^^^^^
-   |
-   = note: `B` must be used in combination with a concrete type within the same module
-
-error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0478`.

src/test/ui/type-alias-impl-trait/bound_reduction2.rs

@@ -7,7 +7,6 @@ trait TraitWithAssoc {
 }
 
 type Foo<V> = impl Trait<V>;
-//~^ ERROR unconstrained opaque type
 
 trait Trait<U> {}
 

src/test/ui/type-alias-impl-trait/bound_reduction2.stderr

@@ -1,5 +1,5 @@
 error: non-defining opaque type use in defining scope
-  --> $DIR/bound_reduction2.rs:17:5
+  --> $DIR/bound_reduction2.rs:16:5
    |
 LL |     ()
    |     ^^
@@ -10,13 +10,5 @@ note: used non-generic type `<T as TraitWithAssoc>::Assoc` for generic parameter
 LL | type Foo<V> = impl Trait<V>;
    |          ^
 
-error: unconstrained opaque type
+error: aborting due to previous error
-  --> $DIR/bound_reduction2.rs:9:15
-   |
-LL | type Foo<V> = impl Trait<V>;
-   |               ^^^^^^^^^^^^^
-   |
-   = note: `Foo` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors
 

src/test/ui/type-alias-impl-trait/bounds-are-checked.rs

@@ -4,7 +4,6 @@
 #![feature(type_alias_impl_trait)]
 
 type X<'a> = impl Into<&'static str> + From<&'a str>;
-//~^ ERROR unconstrained opaque type
 
 fn f<'a: 'static>(t: &'a str) -> X<'a> {
     //~^ WARNING unnecessary lifetime parameter

src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr

@@ -1,5 +1,5 @@
 warning: unnecessary lifetime parameter `'a`
-  --> $DIR/bounds-are-checked.rs:9:6
+  --> $DIR/bounds-are-checked.rs:8:6
    |
 LL | fn f<'a: 'static>(t: &'a str) -> X<'a> {
    |      ^^^^^^^^^^^
@@ -7,7 +7,7 @@ LL | fn f<'a: 'static>(t: &'a str) -> X<'a> {
    = help: you can use the `'static` lifetime directly, in place of `'a`
 
 error: non-defining opaque type use in defining scope
-  --> $DIR/bounds-are-checked.rs:11:5
+  --> $DIR/bounds-are-checked.rs:10:5
    |
 LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
    |        -- cannot use static lifetime; use a bound lifetime instead or remove the lifetime parameter from the opaque type
@@ -15,13 +15,5 @@ LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
 LL |     t
    |     ^
 
-error: unconstrained opaque type
+error: aborting due to previous error; 1 warning emitted
-  --> $DIR/bounds-are-checked.rs:6:14
-   |
-LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `X` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors; 1 warning emitted
 

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

@@ -3,7 +3,7 @@
 fn main() {}
 
 type Two<'a, 'b> = impl std::fmt::Debug;
-//~^ ERROR unconstrained opaque type
+
 
 fn one<'a>(t: &'a ()) -> Two<'a, 'a> {
     t

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

@@ -10,13 +10,5 @@ note: lifetime used multiple times
 LL | type Two<'a, 'b> = impl std::fmt::Debug;
    |          ^^  ^^
 
-error: unconstrained opaque type
+error: aborting due to previous error
-  --> $DIR/generic_duplicate_lifetime_param.rs:5:20
-   |
-LL | type Two<'a, 'b> = impl std::fmt::Debug;
-   |                    ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `Two` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors
 

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

@@ -6,11 +6,11 @@ fn main() {}
 
 // test that unused generic parameters are ok
 type TwoTys<T, U> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 type TwoLifetimes<'a, 'b> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 type TwoConsts<const X: usize, const Y: usize> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 
 fn one_ty<T: Debug>(t: T) -> TwoTys<T, T> {
     t

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

@@ -10,14 +10,6 @@ note: type used multiple times
 LL | type TwoTys<T, U> = impl Debug;
    |             ^  ^
 
-error: unconstrained opaque type
-  --> $DIR/generic_duplicate_param_use.rs:8:21
-   |
-LL | type TwoTys<T, U> = impl Debug;
-   |                     ^^^^^^^^^^
-   |
-   = note: `TwoTys` must be used in combination with a concrete type within the same module
-
 error: non-defining opaque type use in defining scope
   --> $DIR/generic_duplicate_param_use.rs:21:5
    |
@@ -30,14 +22,6 @@ note: lifetime used multiple times
 LL | type TwoLifetimes<'a, 'b> = impl Debug;
    |                   ^^  ^^
 
-error: unconstrained opaque type
-  --> $DIR/generic_duplicate_param_use.rs:10:29
-   |
-LL | type TwoLifetimes<'a, 'b> = impl Debug;
-   |                             ^^^^^^^^^^
-   |
-   = note: `TwoLifetimes` must be used in combination with a concrete type within the same module
-
 error: non-defining opaque type use in defining scope
   --> $DIR/generic_duplicate_param_use.rs:26:5
    |
@@ -50,13 +34,5 @@ note: constant used multiple times
 LL | type TwoConsts<const X: usize, const Y: usize> = impl Debug;
    |                      ^               ^
 
-error: unconstrained opaque type
+error: aborting due to 3 previous errors
-  --> $DIR/generic_duplicate_param_use.rs:12:50
-   |
-LL | type TwoConsts<const X: usize, const Y: usize> = impl Debug;
-   |                                                  ^^^^^^^^^^
-   |
-   = note: `TwoConsts` must be used in combination with a concrete type within the same module
-
-error: aborting due to 6 previous errors
 

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.rs

@@ -8,11 +8,6 @@ fn main() {}
 type Two<T, U> = impl Debug;
 //~^ ERROR `T` doesn't implement `Debug`
 
-fn one<T: Debug>(t: T) -> Two<T, T> {
-    t
-    //~^ ERROR non-defining opaque type use in defining scope
-}
-
 fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
     t
 }

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use2.stderr

@@ -1,15 +1,3 @@
-error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use2.rs:12:5
-   |
-LL |     t
-   |     ^
-   |
-note: type used multiple times
-  --> $DIR/generic_duplicate_param_use2.rs:8:10
-   |
-LL | type Two<T, U> = impl Debug;
-   |          ^  ^
-
 error[E0277]: `T` doesn't implement `Debug`
   --> $DIR/generic_duplicate_param_use2.rs:8:18
    |
@@ -21,6 +9,6 @@ help: consider restricting type parameter `T`
 LL | type Two<T: std::fmt::Debug, U> = impl Debug;
    |           +++++++++++++++++
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.rs

@@ -8,11 +8,6 @@ fn main() {}
 type Two<T, U> = impl Debug;
 //~^ ERROR `T` doesn't implement `Debug`
 
-fn one<T: Debug>(t: T) -> Two<T, T> {
-    t
-    //~^ ERROR non-defining opaque type use in defining scope
-}
-
 fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
     t
 }

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use3.stderr

@@ -1,23 +1,11 @@
-error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use3.rs:12:5
-   |
-LL |     t
-   |     ^
-   |
-note: type used multiple times
-  --> $DIR/generic_duplicate_param_use3.rs:8:10
-   |
-LL | type Two<T, U> = impl Debug;
-   |          ^  ^
-
 error: concrete type differs from previous defining opaque type use
-  --> $DIR/generic_duplicate_param_use3.rs:20:1
+  --> $DIR/generic_duplicate_param_use3.rs:15:1
    |
 LL | fn three<T, U: Debug>(_: T, u: U) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `T`, got `U`
    |
 note: previous use here
-  --> $DIR/generic_duplicate_param_use3.rs:16:1
+  --> $DIR/generic_duplicate_param_use3.rs:11:1
    |
 LL | fn two<T: Debug, U>(t: T, _: U) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -33,6 +21,6 @@ help: consider restricting type parameter `T`
 LL | type Two<T: std::fmt::Debug, U> = impl Debug;
    |           +++++++++++++++++
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use4.rs

@@ -8,11 +8,6 @@ fn main() {}
 type Two<T, U> = impl Debug;
 //~^ ERROR `U` doesn't implement `Debug`
 
-fn one<T: Debug>(t: T) -> Two<T, T> {
-    t
-    //~^ ERROR non-defining opaque type use in defining scope
-}
-
 fn three<T, U: Debug>(_: T, u: U) -> Two<T, U> {
     u
 }

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use4.stderr

@@ -1,15 +1,3 @@
-error: non-defining opaque type use in defining scope
-  --> $DIR/generic_duplicate_param_use4.rs:12:5
-   |
-LL |     t
-   |     ^
-   |
-note: type used multiple times
-  --> $DIR/generic_duplicate_param_use4.rs:8:10
-   |
-LL | type Two<T, U> = impl Debug;
-   |          ^  ^
-
 error[E0277]: `U` doesn't implement `Debug`
   --> $DIR/generic_duplicate_param_use4.rs:8:18
    |
@@ -21,6 +9,6 @@ help: consider restricting type parameter `U`
 LL | type Two<T, U: std::fmt::Debug> = impl Debug;
    |              +++++++++++++++++
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0277`.

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

@@ -5,11 +5,11 @@ use std::fmt::Debug;
 fn main() {}
 
 type OneTy<T> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 type OneLifetime<'a> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 type OneConst<const X: usize> = impl Debug;
-//~^ ERROR unconstrained opaque type
+
 
 // Not defining uses, because they doesn't define *all* possible generics.
 

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

@@ -10,14 +10,6 @@ note: used non-generic type `u32` for generic parameter
 LL | type OneTy<T> = impl Debug;
    |            ^
 
-error: unconstrained opaque type
-  --> $DIR/generic_nondefining_use.rs:7:17
-   |
-LL | type OneTy<T> = impl Debug;
-   |                 ^^^^^^^^^^
-   |
-   = note: `OneTy` must be used in combination with a concrete type within the same module
-
 error: non-defining opaque type use in defining scope
   --> $DIR/generic_nondefining_use.rs:22:5
    |
@@ -27,14 +19,6 @@ LL | type OneLifetime<'a> = impl Debug;
 LL |     6u32
    |     ^^^^
 
-error: unconstrained opaque type
-  --> $DIR/generic_nondefining_use.rs:9:24
-   |
-LL | type OneLifetime<'a> = impl Debug;
-   |                        ^^^^^^^^^^
-   |
-   = note: `OneLifetime` must be used in combination with a concrete type within the same module
-
 error: non-defining opaque type use in defining scope
   --> $DIR/generic_nondefining_use.rs:27:5
    |
@@ -47,13 +31,5 @@ note: used non-generic constant `123_usize` for generic parameter
 LL | type OneConst<const X: usize> = impl Debug;
    |                     ^
 
-error: unconstrained opaque type
+error: aborting due to 3 previous errors
-  --> $DIR/generic_nondefining_use.rs:11:33
-   |
-LL | type OneConst<const X: usize> = impl Debug;
-   |                                 ^^^^^^^^^^
-   |
-   = note: `OneConst` must be used in combination with a concrete type within the same module
-
-error: aborting due to 6 previous errors
 

src/test/ui/type-alias-impl-trait/issue-60564.rs

@@ -6,7 +6,6 @@ trait IterBits {
 }
 
 type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
-//~^ ERROR unconstrained opaque type
 
 impl<T: Copy, E> IterBits for T
 where

src/test/ui/type-alias-impl-trait/issue-60564.stderr

@@ -1,5 +1,5 @@
 error: non-defining opaque type use in defining scope
-  --> $DIR/issue-60564.rs:21:9
+  --> $DIR/issue-60564.rs:20:9
    |
 LL |         (0u8..n).rev().map(move |shift| ((self >> T::from(shift)) & T::from(1)).try_into().unwrap())
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -10,13 +10,5 @@ note: used non-generic type `u8` for generic parameter
 LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
    |                         ^
 
-error: unconstrained opaque type
+error: aborting due to previous error
-  --> $DIR/issue-60564.rs:8:30
-   |
-LL | type IterBitsIter<T, E, I> = impl std::iter::Iterator<Item = I>;
-   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `IterBitsIter` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors
 

src/test/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.rs

@@ -5,7 +5,7 @@
 #![feature(type_alias_impl_trait)]
 trait Trait<T> {}
 type Alias<'a, U> = impl Trait<U>;
-//~^ ERROR unconstrained opaque type
+
 fn f<'a>() -> Alias<'a, ()> {}
 //~^ ERROR non-defining opaque type use in defining scope
 

src/test/ui/type-alias-impl-trait/issue-68368-non-defining-use-2.stderr

@@ -10,13 +10,5 @@ note: used non-generic type `()` for generic parameter
 LL | type Alias<'a, U> = impl Trait<U>;
    |                ^
 
-error: unconstrained opaque type
+error: aborting due to previous error
-  --> $DIR/issue-68368-non-defining-use-2.rs:7:21
-   |
-LL | type Alias<'a, U> = impl Trait<U>;
-   |                     ^^^^^^^^^^^^^
-   |
-   = note: `Alias` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors
 

src/test/ui/type-alias-impl-trait/issue-68368-non-defining-use.rs

@@ -5,7 +5,7 @@
 #![feature(type_alias_impl_trait)]
 trait Trait<T> {}
 type Alias<'a, U> = impl Trait<U>;
-//~^ ERROR unconstrained opaque type
+
 fn f<'a>() -> Alias<'a, ()> {}
 //~^ ERROR non-defining opaque type use in defining scope
 

src/test/ui/type-alias-impl-trait/issue-68368-non-defining-use.stderr

@@ -10,13 +10,5 @@ note: used non-generic type `()` for generic parameter
 LL | type Alias<'a, U> = impl Trait<U>;
    |                ^
 
-error: unconstrained opaque type
+error: aborting due to previous error
-  --> $DIR/issue-68368-non-defining-use.rs:7:21
-   |
-LL | type Alias<'a, U> = impl Trait<U>;
-   |                     ^^^^^^^^^^^^^
-   |
-   = note: `Alias` must be used in combination with a concrete type within the same module
-
-error: aborting due to 2 previous errors
 

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

@@ -7,11 +7,6 @@ fn main() {}
 type Two<T, U> = impl Debug;
 //~^ ERROR `T` doesn't implement `Debug`
 
-fn two<T: Debug>(t: T) -> Two<T, u32> {
-    (t, 4i8)
-    //~^ ERROR non-defining opaque type use in defining scope
-}
-
 fn three<T: Debug, U>(t: T) -> Two<T, U> {
     (t, 5i8)
 }

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

@@ -1,23 +1,11 @@
-error: non-defining opaque type use in defining scope
-  --> $DIR/not_a_defining_use.rs:11:5
-   |
-LL |     (t, 4i8)
-   |     ^^^^^^^^
-   |
-note: used non-generic type `u32` for generic parameter
-  --> $DIR/not_a_defining_use.rs:7:13
-   |
-LL | type Two<T, U> = impl Debug;
-   |             ^
-
 error: concrete type differs from previous defining opaque type use
-  --> $DIR/not_a_defining_use.rs:29:1
+  --> $DIR/not_a_defining_use.rs:24:1
    |
 LL | fn four<T: Debug, U: Bar>(t: T) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `(T, i8)`, got `(T, <U as Bar>::Blub)`
    |
 note: previous use here
-  --> $DIR/not_a_defining_use.rs:15:1
+  --> $DIR/not_a_defining_use.rs:10:1
    |
 LL | fn three<T: Debug, U>(t: T) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -34,6 +22,6 @@ help: consider restricting type parameter `T`
 LL | type Two<T: std::fmt::Debug, U> = impl Debug;
    |           +++++++++++++++++
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.