---

yaml
---
r: 135251
b: refs/heads/snap-stage3
c: e53f4a6
h: refs/heads/master
i:
  135249: f84c765
  135247: 6d73149
v: v3

Author: Jakub Wieczorek

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: 74090504219e4e37c1a6d9fdd8600f44b51c7b04
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
-refs/heads/snap-stage3: 13e00e4a3d18802ca6407e59935be9f2c33ec061
+refs/heads/snap-stage3: e53f4a6b94623076a912df0c770c591d710c5de0
 refs/heads/try: 14378ea357c06c23607ca61ade44f60a7a64a1c7
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b

branches/snap-stage3/src/doc/reference.md

@@ -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}