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Add docs for "!" Never type (rfc 1216) #35286

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Sep 29, 2016
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Add docs for "!" Never type (rfc 1216) #35286

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5 changes: 4 additions & 1 deletion src/doc/book/syntax-index.md
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Expand Up @@ -61,7 +61,6 @@
* `-` (`- expr`): arithmetic negation. Overloadable (`Neg`).
* `-=` (`var -= expr`): arithmetic subtraction & assignment. Overloadable (`SubAssign`).
* `->` (`fn(…) -> type`, `|…| -> type`): function and closure return type. See [Functions], [Closures].
* `-> !` (`fn(…) -> !`, `|…| -> !`): diverging function or closure. See [Diverging Functions].
* `.` (`expr.ident`): member access. See [Structs], [Method Syntax].
* `..` (`..`, `expr..`, `..expr`, `expr..expr`): right-exclusive range literal.
* `..` (`..expr`): struct literal update syntax. See [Structs (Update syntax)].
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* `/*!…*/`: inner block doc comment. See [Comments].
* `/**…*/`: outer block doc comment. See [Comments].

<!-- Special types -->

* `!`: always empty Never type. See [Diverging Functions].

<!-- Various things involving parens and tuples -->

* `()`: empty tuple (*a.k.a.* unit), both literal and type.
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7 changes: 7 additions & 0 deletions src/doc/grammar.md
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Expand Up @@ -764,6 +764,13 @@ bound-list := bound | bound '+' bound-list
bound := path | lifetime
```

### Never type
An empty type
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Better, though I feel like we could say a lot more here. :) For example, "A type representing the result of a function which never returns -- for example because it panics or goes into an infinite loop."


```antlr
never_type : "!" ;
```

### Object types

**FIXME:** grammar?
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