Keep error types around, even in obligations.

These help silence follow up errors

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -631,13 +631,6 @@ impl<'tcx> InferCtxt<'tcx> {
                 ct_op: |ct| ct,
             });
 
-            if let ty::ClauseKind::Projection(projection) = predicate.kind().skip_binder() {
-                if projection.term.references_error() {
-                    // No point on adding any obligations since there's a type error involved.
-                    obligations.clear();
-                    return;
-                }
-            }
             // Require that the predicate holds for the concrete type.
             debug!(?predicate);
             obligations.push(traits::Obligation::new(

tests/ui/async-await/issues/issue-65159.rs

@@ -5,7 +5,7 @@
 async fn copy() -> Result<()>
 //~^ ERROR enum takes 2 generic arguments
 {
-    Ok(()) //~ ERROR: type annotations needed
+    Ok(())
 }
 
-fn main() { }
+fn main() {}

tests/ui/async-await/issues/issue-65159.stderr

@@ -11,18 +11,6 @@ help: add missing generic argument
 LL | async fn copy() -> Result<(), E>
    |                             +++
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-65159.rs:8:5
-   |
-LL |     Ok(())
-   |     ^^ cannot infer type of the type parameter `E` declared on the enum `Result`
-   |
-help: consider specifying the generic arguments
-   |
-LL |     Ok::<(), E>(())
-   |       +++++++++
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0107, E0282.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0107`.

tests/ui/borrowck/issue-82126-mismatched-subst-and-hir.rs

@@ -17,7 +17,6 @@ async fn buy_lock(coroutine: &Mutex<MarketMultiplier>) -> LockedMarket<'_> {
     //~^ ERROR struct takes 0 lifetime arguments but 1 lifetime argument was supplied
     //~^^ ERROR struct takes 1 generic argument but 0 generic arguments were supplied
     LockedMarket(coroutine.lock().unwrap().buy())
-    //~^ ERROR: cannot return value referencing temporary value
 }
 
 struct LockedMarket<T>(T);

tests/ui/borrowck/issue-82126-mismatched-subst-and-hir.stderr

@@ -7,7 +7,7 @@ LL | async fn buy_lock(coroutine: &Mutex<MarketMultiplier>) -> LockedMarket<'_>
    |                                                           expected 0 lifetime arguments
    |
 note: struct defined here, with 0 lifetime parameters
-  --> $DIR/issue-82126-mismatched-subst-and-hir.rs:23:8
+  --> $DIR/issue-82126-mismatched-subst-and-hir.rs:22:8
    |
 LL | struct LockedMarket<T>(T);
    |        ^^^^^^^^^^^^
@@ -19,7 +19,7 @@ LL | async fn buy_lock(coroutine: &Mutex<MarketMultiplier>) -> LockedMarket<'_>
    |                                                           ^^^^^^^^^^^^ expected 1 generic argument
    |
 note: struct defined here, with 1 generic parameter: `T`
-  --> $DIR/issue-82126-mismatched-subst-and-hir.rs:23:8
+  --> $DIR/issue-82126-mismatched-subst-and-hir.rs:22:8
    |
 LL | struct LockedMarket<T>(T);
    |        ^^^^^^^^^^^^ -
@@ -28,16 +28,6 @@ help: add missing generic argument
 LL | async fn buy_lock(coroutine: &Mutex<MarketMultiplier>) -> LockedMarket<'_, T> {
    |                                                                          +++
 
-error[E0515]: cannot return value referencing temporary value
-  --> $DIR/issue-82126-mismatched-subst-and-hir.rs:19:5
-   |
-LL |     LockedMarket(coroutine.lock().unwrap().buy())
-   |     ^^^^^^^^^^^^^-------------------------^^^^^^^
-   |     |            |
-   |     |            temporary value created here
-   |     returns a value referencing data owned by the current function
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0107, E0515.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0107`.

tests/ui/impl-trait/issue-72911.rs

@@ -15,6 +15,7 @@ fn gather_from_file(dir_entry: &foo::MissingItem) -> impl Iterator<Item = Lint>
 
 fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
     //~^ ERROR: failed to resolve
+    //~| ERROR: `()` is not an iterator
     unimplemented!()
 }
 

tests/ui/impl-trait/issue-72911.stderr

@@ -1,3 +1,11 @@
+error[E0277]: `()` is not an iterator
+  --> $DIR/issue-72911.rs:16:20
+   |
+LL | fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not an iterator
+   |
+   = help: the trait `Iterator` is not implemented for `()`
+
 error[E0433]: failed to resolve: use of undeclared crate or module `foo`
   --> $DIR/issue-72911.rs:11:33
    |
@@ -10,6 +18,7 @@ error[E0433]: failed to resolve: use of undeclared crate or module `foo`
 LL | fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
    |                                         ^^^ use of undeclared crate or module `foo`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0433`.
+Some errors have detailed explanations: E0277, E0433.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/impl-trait/issues/issue-92305.rs

@@ -5,7 +5,6 @@ use std::iter;
 fn f<T>(data: &[T]) -> impl Iterator<Item = Vec> {
     //~^ ERROR: missing generics for struct `Vec` [E0107]
     iter::empty()
-    //~^ ERROR: type annotations needed
 }
 
 fn g<T>(data: &[T], target: T) -> impl Iterator<Item = Vec<T>> {

tests/ui/impl-trait/issues/issue-92305.stderr

@@ -9,18 +9,6 @@ help: add missing generic argument
 LL | fn f<T>(data: &[T]) -> impl Iterator<Item = Vec<T>> {
    |                                                +++
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-92305.rs:7:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0107, E0282.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0107`.