Add layout guarantees for never type !

Author: zachs18

src/glossary.md

@@ -217,6 +217,7 @@ r[glossary.zst]
 A type is zero sized (a ZST) if its size is 0. Such types have at most one possible value. Examples include:
 
 - The [unit type] (see [layout.tuple.unit]).
+- The [never type] `!` (see [types.never.layout]).
 - [Function items] (see [type.fn-item.intro]).
 - The constructors of [tuple-like structs] (see [type.fn-item.intro]).
 - The constructors of [tuple-like enum variants] (see [type.fn-item.intro]).

src/type-layout.md

@@ -41,6 +41,7 @@ The size of most primitives is given in this table.
 | `f32`             | 4                  |
 | `f64`             | 8                  |
 | `char`            | 4                  |
+| [`!`][never-type] | 0                  |
 
 r[layout.primitive.size-minimum]
 `usize` and `isize` have a size big enough to contain every address on the target platform. For example, on a 32 bit target, this is 4 bytes, and on a 64 bit target, this is 8 bytes.
@@ -571,3 +572,4 @@ Because this representation delegates type layout to another type, it cannot be
 [structs]: items/structs.md
 [`transparent`]: #the-transparent-representation
 [`Layout`]: std::alloc::Layout
+[never-type]: types/never.md

src/types/never.md

@@ -55,4 +55,7 @@ Expressions of type `!` can be coerced into any type.
 > [!NOTE]
 > The standard library type [`Infallible`] is a type alias for `!`.
 
+r[type.never.layout]
+The `!` type has a size of 0 and an alignment of 1.
+
 [`Infallible`]: core::convert::Infallible