try comment

compiler/rustc_infer/src/infer/mod.rs

@@ -1013,7 +1013,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let r_b = self.shallow_resolve(predicate.skip_binder().b);
         match (r_a.kind(), r_b.kind()) {
             (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
-                self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
+                //self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
                 return None;
             }
             _ => {}

src/test/ui/const-generics/occurs-check/unused-substs-5.stderr

@@ -1,10 +1,8 @@
 error[E0308]: mismatched types
-  --> $DIR/unused-substs-5.rs:15:9
+  --> $DIR/unused-substs-5.rs:15:19
    |
 LL |     x = q::<_, N>(x);
-   |         ^^^^^^^^^^^^- help: try using a conversion method: `.to_vec()`
-   |         |
-   |         cyclic type of infinite size
+   |                   ^ cyclic type of infinite size
 
 error: aborting due to previous error
 

src/test/ui/inference/cannot-infer-closure-circular.stderr

@@ -1,8 +1,13 @@
-error[E0282]: type annotations needed for `Result<(), E>`
-  --> $DIR/cannot-infer-closure-circular.rs:7:14
+error[E0282]: type annotations needed for the closure `fn(Result<(), _>) -> Result<(), _>`
+  --> $DIR/cannot-infer-closure-circular.rs:10:9
    |
-LL |     let x = |r| {
-   |              ^ consider giving this closure parameter the explicit type `Result<(), E>`, where the type parameter `E` is specified
+LL |         Ok(v)
+   |         ^^ cannot infer type for type parameter `E` declared on the enum `Result`
+   |
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let x = |r| -> Result<(), _> {
+   |                 ++++++++++++++++
 
 error: aborting due to previous error
 

src/test/ui/inference/issue-71732.stderr

@@ -2,9 +2,7 @@ error[E0283]: type annotations needed
   --> $DIR/issue-71732.rs:18:10
    |
 LL |         .get(&"key".into())
-   |          ^^^  ------------ this method call resolves to `T`
-   |          |
-   |          cannot infer type for type parameter `Q` declared on the associated function `get`
+   |          ^^^ cannot infer type for type parameter `Q` declared on the associated function `get`
    |
    = note: cannot satisfy `String: Borrow<_>`
 

src/test/ui/inference/issue-72616.stderr

@@ -2,9 +2,7 @@ error[E0283]: type annotations needed
   --> $DIR/issue-72616.rs:20:30
    |
 LL |         if String::from("a") == "a".try_into().unwrap() {}
-   |                              ^^ -------------- this method call resolves to `Result<T, <Self as TryInto<T>>::Error>`
-   |                              |
-   |                              cannot infer type
+   |                              ^^ cannot infer type
    |
    = note: cannot satisfy `String: PartialEq<_>`
 

src/test/ui/issues/issue-51116.stderr

@@ -2,7 +2,7 @@ error[E0282]: type annotations needed
   --> $DIR/issue-51116.rs:6:13
    |
 LL |         for tile in row {
-   |                     --- the element type for this iterator is not specified
+   |             ---- consider giving `tile` a type
 LL |
 LL |             *tile = 0;
    |             ^^^^^ cannot infer type

src/test/ui/issues/issue-59494.stderr

@@ -1,16 +1,9 @@
-error[E0277]: expected a `Fn<(_,)>` closure, found `impl Fn<(((_, _), _),)>`
-  --> $DIR/issue-59494.rs:21:22
+error[E0308]: mismatched types
+  --> $DIR/issue-59494.rs:20:40
    |
-LL |     let t8 = t8n(t7, t7p(f, g));
-   |                      ^^^^^^^^^ expected an `Fn<(_,)>` closure, found `impl Fn<(((_, _), _),)>`
-   |
-   = help: the trait `Fn<(_,)>` is not implemented for `impl Fn<(((_, _), _),)>`
-note: required by a bound in `t8n`
-  --> $DIR/issue-59494.rs:5:45
-   |
-LL | fn t8n<A, B, C>(f: impl Fn(A) -> B, g: impl Fn(A) -> C) -> impl Fn(A) -> (B, C)
-   |                                             ^^^^^^^^^^ required by this bound in `t8n`
+LL |     let t7 = |env| |a| |b| t7p(f, g)(((env, a), b));
+   |                                        ^^^ cyclic type of infinite size
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/occurs-check-2.stderr

@@ -1,13 +1,8 @@
 error[E0308]: mismatched types
-  --> $DIR/occurs-check-2.rs:7:9
+  --> $DIR/occurs-check-2.rs:6:9
    |
-LL |     f = box g;
-   |         ^^^^^ cyclic type of infinite size
-   |
-help: try using a conversion method
-   |
-LL |     f = (box g).to_string();
-   |         +     +++++++++++++
+LL |     g = f;
+   |         ^ cyclic type of infinite size
 
 error: aborting due to previous error
 

src/test/ui/occurs-check-3.stderr

@@ -1,8 +1,8 @@
 error[E0308]: mismatched types
-  --> $DIR/occurs-check-3.rs:4:24
+  --> $DIR/occurs-check-3.rs:4:32
    |
 LL | fn main() { let c; c = Clam::A(c); match c { Clam::A::<isize>(_) => { } } }
-   |                        ^^^^^^^^^^ cyclic type of infinite size
+   |                                ^ cyclic type of infinite size
 
 error: aborting due to previous error
 

src/test/ui/pattern/pat-tuple-bad-type.stderr

@@ -1,9 +1,6 @@
 error[E0282]: type annotations needed
   --> $DIR/pat-tuple-bad-type.rs:5:9
    |
-LL |     let x;
-   |         - consider giving `x` a type
-...
 LL |         (..) => {}
    |         ^^^^ cannot infer type
    |

src/test/ui/question-mark-type-infer.stderr

@@ -1,14 +1,10 @@
 error[E0284]: type annotations needed
-  --> $DIR/question-mark-type-infer.rs:12:21
+  --> $DIR/question-mark-type-infer.rs:12:5
    |
 LL |     l.iter().map(f).collect()?
-   |                     ^^^^^^^ cannot infer type
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type
    |
    = note: cannot satisfy `<_ as Try>::Residual == _`
-help: consider specifying the type argument in the method call
-   |
-LL |     l.iter().map(f).collect::<B>()?
-   |                            +++++
 
 error: aborting due to previous error
 

src/test/ui/span/issue-42234-unknown-receiver-type.full.stderr

@@ -1,10 +1,11 @@
-error[E0282]: type annotations needed for `Option<_>`
+error[E0282]: type annotations needed
   --> $DIR/issue-42234-unknown-receiver-type.rs:10:7
    |
-LL |     let x: Option<_> = None;
-   |         - consider giving `x` the explicit type `Option<_>`, where the type parameter `T` is specified
 LL |     x.unwrap().method_that_could_exist_on_some_type();
-   |       ^^^^^^ cannot infer type for type parameter `T`
+   |     --^^^^^^--
+   |     | |
+   |     | cannot infer type for type parameter `T`
+   |     this method call resolves to `T`
    |
    = note: type must be known at this point
 

src/test/ui/span/issue-42234-unknown-receiver-type.generic_arg.stderr

@@ -1,10 +1,11 @@
-error[E0282]: type annotations needed for `Option<_>`
+error[E0282]: type annotations needed
   --> $DIR/issue-42234-unknown-receiver-type.rs:10:7
    |
-LL |     let x: Option<_> = None;
-   |         - consider giving `x` the explicit type `Option<_>`, where the type parameter `T` is specified
 LL |     x.unwrap().method_that_could_exist_on_some_type();
-   |       ^^^^^^ cannot infer type for type parameter `T`
+   |     --^^^^^^--
+   |     | |
+   |     | cannot infer type for type parameter `T`
+   |     this method call resolves to `T`
    |
    = note: type must be known at this point
 

src/test/ui/traits/issue-77982.stderr

@@ -2,19 +2,15 @@ error[E0283]: type annotations needed
   --> $DIR/issue-77982.rs:8:10
    |
 LL |     opts.get(opt.as_ref());
-   |          ^^^ ------------ this method call resolves to `&T`
-   |          |
-   |          cannot infer type for type parameter `Q` declared on the associated function `get`
+   |          ^^^ cannot infer type for type parameter `Q` declared on the associated function `get`
    |
    = note: cannot satisfy `String: Borrow<_>`
 
 error[E0283]: type annotations needed
   --> $DIR/issue-77982.rs:12:44
    |
 LL |     let ips: Vec<_> = (0..100_000).map(|_| u32::from(0u32.into())).collect();
-   |                                            ^^^^^^^^^ ----------- this method call resolves to `T`
-   |                                            |
-   |                                            cannot infer type for type parameter `T` declared on the trait `From`
+   |                                            ^^^^^^^^^ cannot infer type for type parameter `T` declared on the trait `From`
    |
    = note: cannot satisfy `u32: From<_>`
 note: required by `from`

src/test/ui/type-inference/sort_by_key.stderr

@@ -3,11 +3,6 @@ error[E0282]: type annotations needed
    |
 LL |     lst.sort_by_key(|&(v, _)| v.iter().sum());
    |         ^^^^^^^^^^^ cannot infer type for type parameter `K` declared on the associated function `sort_by_key`
-   |
-help: consider specifying the type argument in the method call
-   |
-LL |     lst.sort_by_key(|&(v, _)| v.iter().sum::<S>());
-   |                                           +++++
 
 error: aborting due to previous error