Add if let to the reference

This commit is contained in:
Jakub Wieczorek 2014-09-29 22:40:26 +02:00
parent 13e00e4a3d
commit e53f4a6b94

View file

@ -3231,7 +3231,7 @@ for i in range(0u, 256) {
if_expr : "if" no_struct_literal_expr '{' block '}'
else_tail ? ;
else_tail : "else" [ if_expr
else_tail : "else" [ if_expr | if_let_expr
| '{' block '}' ] ;
```
@ -3436,6 +3436,19 @@ let message = match maybe_digit {
};
```
### If let expressions
```{.ebnf .gram}
if_let_expr : "if" "let" pat '=' expr '{' block '}'
else_tail ? ;
else_tail : "else" [ if_expr | if_let_expr | '{' block '}' ] ;
```
An `if let` expression is semantically identical to an `if` expression but in place
of a condition expression it expects a refutable let statement. If the value of the
expression on the right hand side of the let statement matches the pattern, the corresponding
block will execute, otherwise flow proceeds to the first `else` block that follows.
### Return expressions
```{.ebnf .gram}