Don't emit errors containing type error as another (more useful) er…

…ror must have been emitted already

compiler/rustc_typeck/src/collect/type_of.rs

@@ -540,7 +540,10 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
                 }
 
                 if let Some((prev_span, prev_ty)) = self.found {
-                    if *concrete_type != prev_ty {
+                    if *concrete_type != prev_ty
+                        && !concrete_type.references_error()
+                        && !prev_ty.references_error()
+                    {
                         debug!("find_opaque_ty_constraints: span={:?}", span);
                         // Found different concrete types for the opaque type.
                         let mut err = self.tcx.sess.struct_span_err(

src/test/ui/generator/layout-error.min_tait.stderr

@@ -22,19 +22,7 @@ LL |     static POOL: Task<F> = Task::new();
    = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information
    = help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable
 
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/layout-error.rs:31:24
-   |
-LL |     Task::spawn(&POOL, || cb());
-   |                        ^^^^^^^ expected `[type error]`, got `impl Future`
-   |
-note: previous use here
-  --> $DIR/layout-error.rs:30:5
-   |
-LL |     static POOL: Task<F> = Task::new();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0425, E0658.
 For more information about an error, try `rustc --explain E0425`.

src/test/ui/generator/layout-error.rs

@@ -29,5 +29,4 @@ fn main() {
     // Check that statics are inhabited computes they layout.
     static POOL: Task<F> = Task::new(); //[min_tait]~ ERROR not permitted here
     Task::spawn(&POOL, || cb()); //[min_tait]~ ERROR type alias impl trait is not permitted here
-    //[min_tait]~^ ERROR concrete type differs from previous
 }

src/test/ui/generator/metadata-sufficient-for-layout.full_tait.stderr

@@ -16,7 +16,7 @@ LL | #![cfg_attr(full_tait, feature(type_alias_impl_trait, impl_trait_in_binding
    = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information
 
 error: fatal error triggered by #[rustc_error]
-  --> $DIR/metadata-sufficient-for-layout.rs:29:1
+  --> $DIR/metadata-sufficient-for-layout.rs:28:1
    |
 LL | fn main() {}
    | ^^^^^^^^^

src/test/ui/generator/metadata-sufficient-for-layout.min_tait.stderr

@@ -7,18 +7,6 @@ LL | static A: Option<F> = None;
    = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information
    = help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable
 
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/metadata-sufficient-for-layout.rs:25:1
-   |
-LL | fn f() -> F { metadata_sufficient_for_layout::g() }
-   | ^^^^^^^^^^^ expected `[type error]`, got `impl Generator`
-   |
-note: previous use here
-  --> $DIR/metadata-sufficient-for-layout.rs:22:1
-   |
-LL | static A: Option<F> = None;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/generator/metadata-sufficient-for-layout.rs

@@ -23,7 +23,6 @@ static A: Option<F> = None;
 //[min_tait]~^ ERROR not permitted here
 
 fn f() -> F { metadata_sufficient_for_layout::g() }
-//[min_tait]~^ ERROR concrete type differs
 
 #[rustc_error]
 fn main() {} //[full_tait]~ ERROR

src/test/ui/type-alias-impl-trait/issue-52843-closure-constrain.min_tait.stderr

@@ -7,18 +7,6 @@ LL |     let null = || -> Opaque { 0 };
    = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/issue-52843-closure-constrain.rs:13:16
-   |
-LL |     let null = || -> Opaque { 0 };
-   |                ^^^^^^^^^^^^^^^^^^ expected `String`, got `[type error]`
-   |
-note: previous use here
-  --> $DIR/issue-52843-closure-constrain.rs:12:5
-   |
-LL |     fn _unused() -> Opaque { String::new() }
-   |     ^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/type-alias-impl-trait/issue-52843-closure-constrain.rs

@@ -11,6 +11,6 @@ fn main() {
     type Opaque = impl Debug;
     fn _unused() -> Opaque { String::new() }
     let null = || -> Opaque { 0 }; //[min_tait]~ ERROR: not permitted here
-    //~^ ERROR: concrete type differs from previous defining opaque type use
+    //[full_tait]~^ ERROR: concrete type differs from previous defining opaque type use
     println!("{:?}", null());
 }

src/test/ui/type-alias-impl-trait/issue-60407.min_tait.stderr

@@ -7,18 +7,6 @@ LL | static mut TEST: Option<Debuggable> = None;
    = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information
    = help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable
 
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/issue-60407.rs:16:1
-   |
-LL | fn foo() -> Debuggable {
-   | ^^^^^^^^^^^^^^^^^^^^^^ expected `[type error]`, got `u32`
-   |
-note: previous use here
-  --> $DIR/issue-60407.rs:9:1
-   |
-LL | static mut TEST: Option<Debuggable> = None;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/type-alias-impl-trait/issue-60407.rs

@@ -13,6 +13,6 @@ fn main() { //[full_tait]~ ERROR
     unsafe { TEST = Some(foo()) }
 }
 
-fn foo() -> Debuggable { //[min_tait]~ ERROR concrete type differs
+fn foo() -> Debuggable {
     0u32
 }

src/test/ui/type-alias-impl-trait/multiple-def-uses-in-one-fn3.rs

@@ -13,7 +13,6 @@ fn f<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<B, A>)
 }
 
 fn g<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<A, B>) {
-    //~^ ERROR concrete type differs from previous defining opaque type use
     (a, b) //~ ERROR mismatched types
 }
 

src/test/ui/type-alias-impl-trait/multiple-def-uses-in-one-fn3.stderr

@@ -23,13 +23,12 @@ LL | fn f<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<B
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0308]: mismatched types
-  --> $DIR/multiple-def-uses-in-one-fn3.rs:17:9
+  --> $DIR/multiple-def-uses-in-one-fn3.rs:16:9
    |
 LL | fn g<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<A, B>) {
    |      -                    - found type parameter
    |      |
    |      expected type parameter
-LL |
 LL |     (a, b)
    |         ^ expected type parameter `A`, found type parameter `B`
    |
@@ -38,18 +37,6 @@ LL |     (a, b)
    = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
    = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
 
-error: concrete type differs from previous defining opaque type use
-  --> $DIR/multiple-def-uses-in-one-fn3.rs:15:1
-   |
-LL | fn g<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<A, B>) {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `[type error]`, got `A`
-   |
-note: previous use here
-  --> $DIR/multiple-def-uses-in-one-fn3.rs:9:1
-   |
-LL | fn f<A: ToString + Clone, B: ToString + Clone>(a: A, b: B) -> (X<A, B>, X<B, A>) {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.