Rollup merge of #23590 - FuGangqiang:attr, r=alexcrichton

Author: Manishearth

src/doc/reference.md

@@ -1982,7 +1982,7 @@ the namespace hierarchy as it normally would.
 ## Attributes
 
 ```{.ebnf .gram}
-attribute : "#!" ? '[' meta_item ']' ;
+attribute : '#' '!' ? '[' meta_item ']' ;
 meta_item : ident [ '=' literal
                   | '(' meta_seq ')' ] ? ;
 meta_seq : meta_item [ ',' meta_seq ] ? ;
@@ -3158,7 +3158,7 @@ ten_times(|j| println!("hello, {}", j));
 ### While loops
 
 ```{.ebnf .gram}
-while_expr : "while" no_struct_literal_expr '{' block '}' ;
+while_expr : [ lifetime ':' ] "while" no_struct_literal_expr '{' block '}' ;
 ```
 
 A `while` loop begins by evaluating the boolean loop conditional expression.
@@ -3223,7 +3223,7 @@ A `continue` expression is only permitted in the body of a loop.
 ### For expressions
 
 ```{.ebnf .gram}
-for_expr : "for" pat "in" no_struct_literal_expr '{' block '}' ;
+for_expr : [ lifetime ':' ] "for" pat "in" no_struct_literal_expr '{' block '}' ;
 ```
 
 A `for` expression is a syntactic construct for looping over elements provided