Suggest giving return type to closures on E0282

src/test/ui/error-codes/E0282.stderr

@@ -2,10 +2,7 @@ error[E0282]: type annotations needed
   --> $DIR/E0282.rs:2:9
    |
 LL |     let x = "hello".chars().rev().collect();
-   |         ^
-   |         |
-   |         cannot infer type
-   |         consider giving `x` a type
+   |         ^ consider giving `x` a type
 
 error: aborting due to previous error
 

src/test/ui/for/for-loop-unconstrained-element-type.stderr

@@ -2,10 +2,7 @@ error[E0282]: type annotations needed
   --> $DIR/for-loop-unconstrained-element-type.rs:8:14
    |
 LL |     for i in Vec::new() { }
-   |              ^^^^^^^^^^
-   |              |
-   |              cannot infer type
-   |              the element type for this iterator is not specified
+   |              ^^^^^^^^^^ the element type for this iterator is not specified
 
 error: aborting due to previous error
 

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

@@ -1,10 +1,12 @@
-error[E0282]: type annotations needed for the closure
+error[E0282]: type annotations needed for the closure `fn((), ()) -> std::result::Result<(), _>`
   --> $DIR/cannot-infer-closure.rs:3:9
    |
-LL |     let x = |a: (), b: ()| {
-   |         - consider giving `x` a boxed closure type like `Box<dyn Fn((), ()) -> std::result::Result<(), _>>`
 LL |         Err(a)?;
    |         ^^^^^^^ cannot infer type
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let x = |a: (), b: ()| -> std::result::Result<(), _> {
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-18159.stderr

@@ -2,10 +2,7 @@ error[E0282]: type annotations needed
   --> $DIR/issue-18159.rs:2:9
    |
 LL |     let x;
-   |         ^
-   |         |
-   |         cannot infer type
-   |         consider giving `x` a type
+   |         ^ consider giving `x` a type
 
 error: aborting due to previous error
 

src/test/ui/match/match-unresolved-one-arm.stderr

@@ -2,10 +2,7 @@ error[E0282]: type annotations needed
   --> $DIR/match-unresolved-one-arm.rs:4:9
    |
 LL |     let x = match () {
-   |         ^
-   |         |
-   |         cannot infer type
-   |         consider giving `x` a type
+   |         ^ consider giving `x` a type
 
 error: aborting due to previous error
 

src/test/ui/suggestions/suggest-closure-return-type-1.rs

@@ -0,0 +1,3 @@
+fn main() {
+    let _v = || -> _ { [] }; //~ ERROR type annotations needed for the closure
+}

src/test/ui/suggestions/suggest-closure-return-type-1.stderr

@@ -0,0 +1,13 @@
+error[E0282]: type annotations needed for the closure `fn() -> [_; 0]`
+  --> $DIR/suggest-closure-return-type-1.rs:2:24
+   |
+LL |     let _v = || -> _ { [] };
+   |                        ^^ cannot infer type
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let _v = || -> [_; 0] { [] };
+   |                    ^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.

src/test/ui/suggestions/suggest-closure-return-type-2.rs

@@ -0,0 +1,3 @@
+fn main() {
+    let _v = || { [] }; //~ ERROR type annotations needed for the closure
+}

src/test/ui/suggestions/suggest-closure-return-type-2.stderr

@@ -0,0 +1,13 @@
+error[E0282]: type annotations needed for the closure `fn() -> [_; 0]`
+  --> $DIR/suggest-closure-return-type-2.rs:2:19
+   |
+LL |     let _v = || { [] };
+   |                   ^^ cannot infer type
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let _v = || -> [_; 0] { [] };
+   |                 ^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.

src/test/ui/suggestions/suggest-closure-return-type-3.rs

@@ -0,0 +1,3 @@
+fn main() {
+    let _v = || []; //~ ERROR type annotations needed for the closure
+}

src/test/ui/suggestions/suggest-closure-return-type-3.stderr

@@ -0,0 +1,13 @@
+error[E0282]: type annotations needed for the closure `fn() -> [_; 0]`
+  --> $DIR/suggest-closure-return-type-3.rs:2:17
+   |
+LL |     let _v = || [];
+   |                 ^^ cannot infer type
+help: give this closure an explicit return type without `_` placeholders
+   |
+LL |     let _v = || -> [_; 0] { [] };
+   |                 ^^^^^^^^^^^    ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.