Reduce follow-up errors that are not helpful

Author: oli-obk

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
-  --> $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
+error: aborting due to 2 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
-  --> $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
+error: aborting due to previous error
 

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

@@ -1,27 +1,19 @@
 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> {
    |      ^^^^^^^^^^^
    |
    = 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
 ...
 LL |     t
    |     ^
 
-error: unconstrained opaque type
-  --> $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
+error: aborting due to previous error; 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
-  --> $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
+error: aborting due to previous error
 

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