Extend test to trigger on 2015, 2018 and 2021 editions

tests/ui/lexer/lex-bad-str-literal-as-char-3.fixed

@@ -1,4 +0,0 @@
-//@ run-rustfix
-fn main() {
-    println!("hello world"); //~ ERROR unterminated character literal
-}

tests/ui/lexer/lex-bad-str-literal-as-char-3.rs

@@ -1,4 +1,8 @@
-//@ run-rustfix
+//@ revisions: rust2015 rust2018 rust2021
+//@[rust2018] edition:2018
+//@[rust2021] edition:2021
 fn main() {
-    println!('hello world'); //~ ERROR unterminated character literal
+    println!('hello world');
+    //[rust2015,rust2018,rust2021]~^ ERROR unterminated character literal
+    //[rust2021]~^^ ERROR prefix `world` is unknown
 }

tests/ui/lexer/lex-bad-str-literal-as-char-3.rust2015.stderr

@@ -1,8 +1,8 @@
 error[E0762]: unterminated character literal
-  --> $DIR/lex-bad-str-literal-as-char-3.rs:3:26
+  --> $DIR/lex-bad-str-literal-as-char-3.rs:5:26
    |
 LL |     println!('hello world');
-   |                          ^^^^
+   |                          ^^^
    |
 help: if you meant to write a string literal, use double quotes
    |

tests/ui/lexer/lex-bad-str-literal-as-char-3.rust2018.stderr

@@ -0,0 +1,14 @@
+error[E0762]: unterminated character literal
+  --> $DIR/lex-bad-str-literal-as-char-3.rs:5:26
+   |
+LL |     println!('hello world');
+   |                          ^^^
+   |
+help: if you meant to write a string literal, use double quotes
+   |
+LL |     println!("hello world");
+   |              ~           ~
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0762`.

tests/ui/lexer/lex-bad-str-literal-as-char-3.rust2021.stderr

@@ -0,0 +1,26 @@
+error: prefix `world` is unknown
+  --> $DIR/lex-bad-str-literal-as-char-3.rs:5:21
+   |
+LL |     println!('hello world');
+   |                     ^^^^^ unknown prefix
+   |
+   = note: prefixed identifiers and literals are reserved since Rust 2021
+help: if you meant to write a string literal, use double quotes
+   |
+LL |     println!("hello world");
+   |              ~           ~
+
+error[E0762]: unterminated character literal
+  --> $DIR/lex-bad-str-literal-as-char-3.rs:5:26
+   |
+LL |     println!('hello world');
+   |                          ^^^
+   |
+help: if you meant to write a string literal, use double quotes
+   |
+LL |     println!("hello world");
+   |              ~           ~
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0762`.