Document let else statements

Author: est31

src/statements.md

@@ -5,6 +5,7 @@
 >       `;`\
 >    | [_Item_]\
 >    | [_LetStatement_]\
+>    | [_LetElseStatement_]\
 >    | [_ExpressionStatement_]\
 >    | [_MacroInvocationSemi_]
 
@@ -65,6 +66,25 @@ inference. Any variables introduced by a variable declaration are visible
 from the point of declaration until the end of the enclosing block scope,
 except when they are shadowed by another variable declaration.
 
+
+### `let else` statements
+
+> **<sup>Syntax</sup>**\
+> _LetElseStatement_ :\
+> &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup> `let` [_PatternNoTopAlt_]
+>     ( `:` [_Type_] )<sup>?</sup> `=` [_Expression_] `else` [_BlockExpression_] `;`
+
+A *`let else` statement* introduces a new set of [variables], given by a
+refutable [pattern]. The pattern is followed optionally by a type
+annotation. When no type annotation is given, the compiler will infer the type,
+or signal an error if insufficient type information is available for definite
+inference. It is is then followed by an initializer expression as well as a
+diverging `else` block.
+
+Any variables introduced by a variable declaration are visible
+from the point of declaration until the end of the enclosing block scope,
+except when they are shadowed by another variable declaration.
+
 ## Expression statements
 
 > **<sup>Syntax</sup>**\
@@ -128,10 +148,12 @@ statement are [`cfg`], and [the lint check attributes].
 [`cfg`]: conditional-compilation.md
 [the lint check attributes]: attributes/diagnostics.md#lint-check-attributes
 [pattern]: patterns.md
+[_BlockExpression_]: expressions/block-expr.md
 [_ExpressionStatement_]: #expression-statements
 [_Expression_]: expressions.md
 [_Item_]: items.md
 [_LetStatement_]: #let-statements
+[_LetElseStatement_]: #let-else-statements
 [_MacroInvocationSemi_]: macros.md#macro-invocation
 [_OuterAttribute_]: attributes.md
 [_PatternNoTopAlt_]: patterns.md