Move E0562 to librustc from librustc_typeck

With the check for impl trait moving from type checking to HIR lowering
the error needs to move too.

Author: chrisvittal

src/librustc/diagnostics.rs

@@ -1770,6 +1770,46 @@ If you want to get command-line arguments, use `std::env::args`. To exit with a
 specified exit code, use `std::process::exit`.
 "##,
 
+E0562: r##"
+Abstract return types (written `impl Trait` for some trait `Trait`) are only
+allowed as function return types.
+
+Erroneous code example:
+
+```compile_fail,E0562
+#![feature(conservative_impl_trait)]
+
+fn main() {
+    let count_to_ten: impl Iterator<Item=usize> = 0..10;
+    // error: `impl Trait` not allowed outside of function and inherent method
+    //        return types
+    for i in count_to_ten {
+        println!("{}", i);
+    }
+}
+```
+
+Make sure `impl Trait` only appears in return-type position.
+
+```
+#![feature(conservative_impl_trait)]
+
+fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
+    0..n
+}
+
+fn main() {
+    for i in count_to_n(10) {  // ok!
+        println!("{}", i);
+    }
+}
+```
+
+See [RFC 1522] for more details.
+
+[RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
+"##,
+
 E0591: r##"
 Per [RFC 401][rfc401], if you have a function declaration `foo`:
 

src/librustc_typeck/diagnostics.rs

@@ -3818,46 +3818,6 @@ let s = Simba { mother: 1, father: 0 }; // ok!
 ```
 "##,
 
-E0562: r##"
-Abstract return types (written `impl Trait` for some trait `Trait`) are only
-allowed as function return types.
-
-Erroneous code example:
-
-```compile_fail,E0562
-#![feature(conservative_impl_trait)]
-
-fn main() {
-    let count_to_ten: impl Iterator<Item=usize> = 0..10;
-    // error: `impl Trait` not allowed outside of function and inherent method
-    //        return types
-    for i in count_to_ten {
-        println!("{}", i);
-    }
-}
-```
-
-Make sure `impl Trait` only appears in return-type position.
-
-```
-#![feature(conservative_impl_trait)]
-
-fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
-    0..n
-}
-
-fn main() {
-    for i in count_to_n(10) {  // ok!
-        println!("{}", i);
-    }
-}
-```
-
-See [RFC 1522] for more details.
-
-[RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
-"##,
-
 E0569: r##"
 If an impl has a generic parameter with the `#[may_dangle]` attribute, then
 that impl must be declared as an `unsafe impl.