On type inference errors use the type argument name when possible

```
error[E0282]: type annotations needed in `std::result::Result<i32, E>`
 --> file7.rs:3:13
  |
3 |     let b = Ok(4);
  |         -   ^^ cannot infer type for `E` in `std::result::Result<i32, E>`
  |         |
  |         consider giving `b` a type`
```

10 files changed, 17 insertions, 17 deletions

diff --git a/src/test/ui/issues/issue-12187-1.stderr b/src/test/ui/issues/issue-12187-1.stderr
index 510eeb4b9bb..5f07dbc6673 100644
--- a/src/test/ui/issues/issue-12187-1.stderr
+++ b/src/test/ui/issues/issue-12187-1.stderr
@@ -1,4 +1,4 @@
-error[E0282]: type annotations needed in `&_`
+error[E0282]: type annotations needed in `&T`
   --> $DIR/issue-12187-1.rs:6:10
    |
 LL |     let &v = new();
diff --git a/src/test/ui/issues/issue-12187-2.stderr b/src/test/ui/issues/issue-12187-2.stderr
index 8b12ff5f9d8..5b44278359c 100644
--- a/src/test/ui/issues/issue-12187-2.stderr
+++ b/src/test/ui/issues/issue-12187-2.stderr
@@ -1,4 +1,4 @@
-error[E0282]: type annotations needed in `&_`
+error[E0282]: type annotations needed in `&T`
   --> $DIR/issue-12187-2.rs:6:10
    |
 LL |     let &v = new();
diff --git a/src/test/ui/issues/issue-17551.stderr b/src/test/ui/issues/issue-17551.stderr
index 0d7a31fc60d..95af1e41b58 100644
--- a/src/test/ui/issues/issue-17551.stderr
+++ b/src/test/ui/issues/issue-17551.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `B<_>`
+error[E0282]: type annotations needed in `B<T>`
   --> $DIR/issue-17551.rs:6:15
    |
 LL |     let foo = B(marker::PhantomData);
-   |         ---   ^ cannot infer type for `T` in `B<_>`
+   |         ---   ^ cannot infer type for `T` in `B<T>`
    |         |
    |         consider giving `foo` a type
 
diff --git a/src/test/ui/issues/issue-23046.stderr b/src/test/ui/issues/issue-23046.stderr
index 1363a6f963f..102cfe0085f 100644
--- a/src/test/ui/issues/issue-23046.stderr
+++ b/src/test/ui/issues/issue-23046.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `Expr<'_, _>`
+error[E0282]: type annotations needed in `Expr<'_, VAR>`
   --> $DIR/issue-23046.rs:17:15
    |
 LL |     let ex = |x| {
-   |               ^ consider giving this closure parameter the type `Expr<'_, _>` with the type parameter `VAR` specified
+   |               ^ consider giving this closure parameter the type `Expr<'_, VAR>` with the type parameter `VAR` specified
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-25368.stderr b/src/test/ui/issues/issue-25368.stderr
index 5fc9ab26969..a386fc94628 100644
--- a/src/test/ui/issues/issue-25368.stderr
+++ b/src/test/ui/issues/issue-25368.stderr
@@ -1,11 +1,11 @@
-error[E0282]: type annotations needed in `(std::sync::mpsc::Sender<Foo<_>>, std::sync::mpsc::Receiver<Foo<_>>)`
+error[E0282]: type annotations needed in `(std::sync::mpsc::Sender<Foo<T>>, std::sync::mpsc::Receiver<Foo<T>>)`
   --> $DIR/issue-25368.rs:11:17
    |
 LL |     let (tx, rx) = channel();
    |         -------- consider giving the pattern a type
 ...
 LL |         tx.send(Foo{ foo: PhantomData });
-   |                 ^^^ cannot infer type for `T` in `(std::sync::mpsc::Sender<Foo<_>>, std::sync::mpsc::Receiver<Foo<_>>)`
+   |                 ^^^ cannot infer type for `T` in `(std::sync::mpsc::Sender<Foo<T>>, std::sync::mpsc::Receiver<Foo<T>>)`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/methods/method-ambig-one-trait-unknown-int-type.stderr b/src/test/ui/methods/method-ambig-one-trait-unknown-int-type.stderr
index e8871efc5b2..b9fa36041b1 100644
--- a/src/test/ui/methods/method-ambig-one-trait-unknown-int-type.stderr
+++ b/src/test/ui/methods/method-ambig-one-trait-unknown-int-type.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `std::vec::Vec<_>`
+error[E0282]: type annotations needed in `std::vec::Vec<T>`
   --> $DIR/method-ambig-one-trait-unknown-int-type.rs:24:17
    |
 LL |     let mut x = Vec::new();
-   |         -----   ^^^^^^^^ cannot infer type for `T` in `std::vec::Vec<_>`
+   |         -----   ^^^^^^^^ cannot infer type for `T` in `std::vec::Vec<T>`
    |         |
    |         consider giving `x` a type
 
diff --git a/src/test/ui/type/type-check/cannot_infer_local_or_vec.stderr b/src/test/ui/type/type-check/cannot_infer_local_or_vec.stderr
index 59a8b52a66d..a491d4516cc 100644
--- a/src/test/ui/type/type-check/cannot_infer_local_or_vec.stderr
+++ b/src/test/ui/type/type-check/cannot_infer_local_or_vec.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `std::vec::Vec<_>`
+error[E0282]: type annotations needed in `std::vec::Vec<T>`
   --> $DIR/cannot_infer_local_or_vec.rs:2:13
    |
 LL |     let x = vec![];
-   |         -   ^^^^^^ cannot infer type for `T` in `std::vec::Vec<_>`
+   |         -   ^^^^^^ cannot infer type for `T` in `std::vec::Vec<T>`
    |         |
    |         consider giving `x` a type
    |
diff --git a/src/test/ui/type/type-check/cannot_infer_local_or_vec_in_tuples.stderr b/src/test/ui/type/type-check/cannot_infer_local_or_vec_in_tuples.stderr
index 294b6d93211..1c5b750b9b4 100644
--- a/src/test/ui/type/type-check/cannot_infer_local_or_vec_in_tuples.stderr
+++ b/src/test/ui/type/type-check/cannot_infer_local_or_vec_in_tuples.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `(std::vec::Vec<_>,)`
+error[E0282]: type annotations needed in `(std::vec::Vec<T>,)`
   --> $DIR/cannot_infer_local_or_vec_in_tuples.rs:2:18
    |
 LL |     let (x, ) = (vec![], );
-   |         -----    ^^^^^^ cannot infer type for `T` in `(std::vec::Vec<_>,)`
+   |         -----    ^^^^^^ cannot infer type for `T` in `(std::vec::Vec<T>,)`
    |         |
    |         consider giving the pattern a type
    |
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-failed-recursive-fn-2.stderr b/src/test/ui/unboxed-closures/unboxed-closures-failed-recursive-fn-2.stderr
index 142975144d4..dda453870dc 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-failed-recursive-fn-2.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-failed-recursive-fn-2.stderr
@@ -1,4 +1,4 @@
-error[E0282]: type annotations needed in `std::option::Option<_>`
+error[E0282]: type annotations needed in `std::option::Option<T>`
   --> $DIR/unboxed-closures-failed-recursive-fn-2.rs:16:32
    |
 LL |     let mut closure0 = None;
diff --git a/src/test/ui/vector-no-ann.stderr b/src/test/ui/vector-no-ann.stderr
index 2431927f2ac..a6c805c0c26 100644
--- a/src/test/ui/vector-no-ann.stderr
+++ b/src/test/ui/vector-no-ann.stderr
@@ -1,8 +1,8 @@
-error[E0282]: type annotations needed in `std::vec::Vec<_>`
+error[E0282]: type annotations needed in `std::vec::Vec<T>`
   --> $DIR/vector-no-ann.rs:2:16
    |
 LL |     let _foo = Vec::new();
-   |         ----   ^^^^^^^^ cannot infer type for `T` in `std::vec::Vec<_>`
+   |         ----   ^^^^^^^^ cannot infer type for `T` in `std::vec::Vec<T>`
    |         |
    |         consider giving `_foo` a type