Update error code docs even more

Author: rylev

compiler/rustc_error_codes/src/error_codes/E0782.md

@@ -4,7 +4,7 @@ Erroneous code example:
 
 ```edition2021,compile_fail,E782
 trait Foo {}
-fn test(arg: Box<Foo>) {}
+fn test(arg: Box<Foo>) {} // error!
 ```
 
 Trait objects are a way to call methods on types that are not known until
@@ -20,7 +20,7 @@ To fix this issue, add `dyn` before the trait name.
 
 ```
 trait Foo {}
-fn test(arg: Box<dyn Foo>) {}
+fn test(arg: Box<dyn Foo>) {} // ok!
 ```
 
 This used to be allowed before edition 2021, but is now an error.

compiler/rustc_error_codes/src/error_codes/E0783.md

@@ -3,11 +3,9 @@ The range pattern `...` is no longer allowed.
 Erroneous code example:
 
 ```edition2021,compile_fail,E782
-fn main() {
-    match 2u8 {
-        0...9 => println!("Got a number less than 10"),
-        _ => println!("Got a number 10 or more")
-    }
+match 2u8 {
+    0...9 => println!("Got a number less than 10"), // error!
+    _ => println!("Got a number 10 or more"),
 }
 ```
 
@@ -17,10 +15,8 @@ ranges which are now signified using `..=`.
 To make this code compile replace the `...` with `..=`.
 
 ```
-fn main() {
-    match 2u8 {
-        0..=9 => println!("Got a number less than 10"),
-        _ => println!("Got a number 10 or more")
-    }
+match 2u8 {
+    0..=9 => println!("Got a number less than 10"), // ok!
+    _ => println!("Got a number 10 or more"),
 }
 ```