Point to the value instead of the TAIT declaration for obligation failures

Author: oli-obk

compiler/rustc_trait_selection/src/opaque_types.rs

@@ -965,10 +965,10 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
             debug!("instantiate_opaque_types: returning concrete ty {:?}", opaque_defn.concrete_ty);
             return opaque_defn.concrete_ty;
         }
-        let span = tcx.def_span(def_id);
-        debug!("fold_opaque_ty {:?} {:?}", self.value_span, span);
-        let ty_var = infcx
-            .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
+        let ty_var = infcx.next_ty_var(TypeVariableOrigin {
+            kind: TypeVariableOriginKind::TypeInference,
+            span: self.value_span,
+        });
 
         // Make sure that we are in fact defining the *entire* type
         // (e.g., `type Foo<T: Bound> = impl Bar;` needs to be
@@ -993,16 +993,12 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
         }
 
         debug!("instantiate_opaque_types: ty_var={:?}", ty_var);
-        self.compute_opaque_type_obligations(opaque_type_key, span);
+        self.compute_opaque_type_obligations(opaque_type_key);
 
         ty_var
     }
 
-    fn compute_opaque_type_obligations(
-        &mut self,
-        opaque_type_key: OpaqueTypeKey<'tcx>,
-        span: Span,
-    ) {
+    fn compute_opaque_type_obligations(&mut self, opaque_type_key: OpaqueTypeKey<'tcx>) {
         let infcx = self.infcx;
         let tcx = infcx.tcx;
         let OpaqueTypeKey { def_id, substs } = opaque_type_key;
@@ -1014,7 +1010,7 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
 
         let param_env = tcx.param_env(def_id);
         let InferOk { value: bounds, obligations } = infcx.partially_normalize_associated_types_in(
-            ObligationCause::misc(span, self.body_id),
+            ObligationCause::misc(self.value_span, self.body_id),
             param_env,
             bounds,
         );
@@ -1038,7 +1034,8 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
             // This also instantiates nested instances of `impl Trait`.
             let predicate = self.instantiate_opaque_types_in_map(predicate);
 
-            let cause = traits::ObligationCause::new(span, self.body_id, traits::OpaqueType);
+            let cause =
+                traits::ObligationCause::new(self.value_span, self.body_id, traits::OpaqueType);
 
             // Require that the predicate holds for the concrete type.
             debug!("instantiate_opaque_types: predicate={:?}", predicate);

src/test/ui/associated-type-bounds/assoc-type-eq-with-dyn-atb-fail.rs

@@ -28,9 +28,9 @@ impl Bar for AssocNoCopy {
 
 impl Thing for AssocNoCopy {
     type Out = Box<dyn Bar<Assoc: Copy>>;
-    //~^ ERROR the trait bound `String: Copy` is not satisfied
 
     fn func() -> Self::Out {
+        //~^ ERROR the trait bound `String: Copy` is not satisfied
         Box::new(AssocNoCopy)
     }
 }

src/test/ui/associated-type-bounds/assoc-type-eq-with-dyn-atb-fail.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `String: Copy` is not satisfied
-  --> $DIR/assoc-type-eq-with-dyn-atb-fail.rs:30:28
+  --> $DIR/assoc-type-eq-with-dyn-atb-fail.rs:32:18
    |
-LL |     type Out = Box<dyn Bar<Assoc: Copy>>;
-   |                            ^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
+LL |     fn func() -> Self::Out {
+   |                  ^^^^^^^^^ the trait `Copy` is not implemented for `String`
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/issue-55872-1.rs

@@ -8,12 +8,12 @@ pub trait Bar {
 
 impl<S: Default> Bar for S {
     type E = impl Copy;
-    //~^ ERROR the trait bound `S: Copy` is not satisfied in `(S, T)` [E0277]
-    //~^^ ERROR the trait bound `T: Copy` is not satisfied in `(S, T)` [E0277]
 
     fn foo<T: Default>() -> Self::E {
         //~^ ERROR type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
         //~| ERROR impl has stricter requirements than trait
+        //~| ERROR the trait bound `S: Copy` is not satisfied in `(S, T)` [E0277]
+        //~| ERROR the trait bound `T: Copy` is not satisfied in `(S, T)` [E0277]
         (S::default(), T::default())
     }
 }

src/test/ui/impl-trait/issue-55872-1.stderr

@@ -1,5 +1,5 @@
 error[E0276]: impl has stricter requirements than trait
-  --> $DIR/issue-55872-1.rs:14:5
+  --> $DIR/issue-55872-1.rs:12:5
    |
 LL |     fn foo<T>() -> Self::E;
    |     ----------------------- definition of `foo` from trait
@@ -8,10 +8,10 @@ LL |     fn foo<T: Default>() -> Self::E {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl has extra requirement `T: Default`
 
 error[E0277]: the trait bound `S: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:10:14
+  --> $DIR/issue-55872-1.rs:12:29
    |
-LL |     type E = impl Copy;
-   |              ^^^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `S`
+LL |     fn foo<T: Default>() -> Self::E {
+   |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `S`
    |
    = note: required because it appears within the type `(S, T)`
 help: consider further restricting this bound
@@ -20,10 +20,10 @@ LL | impl<S: Default + std::marker::Copy> Bar for S {
    |                 ^^^^^^^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `T: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:10:14
+  --> $DIR/issue-55872-1.rs:12:29
    |
-LL |     type E = impl Copy;
-   |              ^^^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `T`
+LL |     fn foo<T: Default>() -> Self::E {
+   |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `T`
    |
    = note: required because it appears within the type `(S, T)`
 help: consider further restricting this bound
@@ -32,12 +32,14 @@ LL |     fn foo<T: Default + std::marker::Copy>() -> Self::E {
    |                       ^^^^^^^^^^^^^^^^^^^
 
 error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
-  --> $DIR/issue-55872-1.rs:14:37
+  --> $DIR/issue-55872-1.rs:12:37
    |
 LL |       fn foo<T: Default>() -> Self::E {
    |  _____________________________________^
 LL | |
 LL | |
+LL | |
+LL | |
 LL | |         (S::default(), T::default())
 LL | |     }
    | |_____^

src/test/ui/impl-trait/issue-55872-2.rs

@@ -11,9 +11,9 @@ pub trait Bar {
 
 impl<S> Bar for S {
     type E = impl std::marker::Copy;
-    //~^ ERROR the trait bound `impl Future: Copy` is not satisfied [E0277]
     fn foo<T>() -> Self::E {
         //~^ ERROR type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
+        //~| ERROR the trait bound `impl Future: Copy` is not satisfied [E0277]
         async {}
     }
 }

src/test/ui/impl-trait/issue-55872-2.stderr

@@ -1,15 +1,16 @@
 error[E0277]: the trait bound `impl Future: Copy` is not satisfied
-  --> $DIR/issue-55872-2.rs:13:14
+  --> $DIR/issue-55872-2.rs:14:20
    |
-LL |     type E = impl std::marker::Copy;
-   |              ^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `impl Future`
+LL |     fn foo<T>() -> Self::E {
+   |                    ^^^^^^^ the trait `Copy` is not implemented for `impl Future`
 
 error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
-  --> $DIR/issue-55872-2.rs:15:28
+  --> $DIR/issue-55872-2.rs:14:28
    |
 LL |       fn foo<T>() -> Self::E {
    |  ____________________________^
 LL | |
+LL | |
 LL | |         async {}
 LL | |     }
    | |_____^

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

@@ -7,9 +7,9 @@ fn main() {
 }
 
 type WrongGeneric<T> = impl 'static;
-//~^ ERROR the parameter type `T` may not live long enough
-//~| ERROR: at least one trait must be specified
+//~^ ERROR: at least one trait must be specified
 
 fn wrong_generic<T>(t: T) -> WrongGeneric<T> {
+    //~^ ERROR the parameter type `T` may not live long enough
     t
 }

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

@@ -19,13 +19,12 @@ LL | type WrongGeneric<T> = impl 'static;
            found opaque type `impl Sized`
 
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/generic_type_does_not_live_long_enough.rs:9:24
+  --> $DIR/generic_type_does_not_live_long_enough.rs:12:30
    |
-LL | type WrongGeneric<T> = impl 'static;
-   |                        ^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
-...
 LL | fn wrong_generic<T>(t: T) -> WrongGeneric<T> {
-   |                  - help: consider adding an explicit lifetime bound...: `T: 'static`
+   |                  -           ^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
+   |                  |
+   |                  help: consider adding an explicit lifetime bound...: `T: 'static`
 
 error: aborting due to 3 previous errors
 

src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.rs

@@ -15,9 +15,9 @@ struct X;
 
 impl Foo for X {
     type Bar = impl Baz<Self, Self>;
-    //~^ ERROR implementation of `FnOnce` is not general enough
 
     fn bar(&self) -> Self::Bar {
+        //~^ ERROR implementation of `FnOnce` is not general enough
         |x| x
     }
 }