Add support for native-sized integers

standard/arrays.md

@@ -112,7 +112,7 @@ Elements of arrays created by *array_creation_expression*s are always initialize
 
 ## 17.4 Array element access
 
-Array elements are accessed using *element_access* expressions ([§12.8.11.2](expressions.md#128112-array-access)) of the form `A[I₁, I₂, ..., Iₓ]`, where `A` is an expression of an array type and each `Iₑ` is an expression of type `int`, `uint`, `long`, `ulong`, or can be implicitly converted to one or more of these types. The result of an array element access is a variable, namely the array element selected by the indices.
+Array elements are accessed using *element_access* expressions ([§12.8.11.2](expressions.md#128112-array-access)) of the form `A[I₁, I₂, ..., Iₓ]`, where `A` is an expression of an array type and each `Iₑ` is an expression of type `int`, `uint`, `long`, `nint`, `nuint`, `ulong`, or can be implicitly converted to one or more of these types. The result of an array element access is a variable, namely the array element selected by the indices.
 
 The elements of an array can be enumerated using a `foreach` statement ([§13.9.5](statements.md#1395-the-foreach-statement)).
 

standard/classes.md

@@ -1404,7 +1404,7 @@ A *constant_declaration* may include a set of *attributes* ([§22](attributes.md
 
 The *type* of a *constant_declaration* specifies the type of the members introduced by the declaration. The type is followed by a list of *constant_declarator*s ([§13.6.3](statements.md#1363-local-constant-declarations)), each of which introduces a new member. A *constant_declarator* consists of an *identifier* that names the member, followed by an “`=`” token, followed by a *constant_expression* ([§12.23](expressions.md#1223-constant-expressions)) that gives the value of the member.
 
-The *type* specified in a constant declaration shall be `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, `float`, `double`, `decimal`, `bool`, `string`, an *enum_type*, or a *reference_type*. Each *constant_expression* shall yield a value of the target type or of a type that can be converted to the target type by an implicit conversion ([§10.2](conversions.md#102-implicit-conversions)).
+The *type* specified in a constant declaration shall be `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, `float`, `double`, `decimal`, `bool`, `string`, an *enum_type*, or a *reference_type*. Each *constant_expression* shall yield a value of the target type or of a type that can be converted to the target type by an implicit conversion ([§10.2](conversions.md#102-implicit-conversions)).
 
 The *type* of a constant shall be at least as accessible as the constant itself ([§7.5.5](basic-concepts.md#755-accessibility-constraints)).
 
@@ -1638,7 +1638,7 @@ These restrictions ensure that all threads will observe volatile writes performe
 
 - A *reference_type*.
 - A *type_parameter* that is known to be a reference type ([§15.2.5](classes.md#1525-type-parameter-constraints)).
-- The type `byte`, `sbyte`, `short`, `ushort`, `int`, `uint`, `char`, `float`, `bool`, `System.IntPtr`, or `System.UIntPtr`.
+- The type `byte`, `sbyte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `char`, `float`, `bool`, `System.IntPtr`, or `System.UIntPtr`.
 - An *enum_type* having an *enum_base* type of `byte`, `sbyte`, `short`, `ushort`, `int`, or `uint`.
 
 > *Example*: The example

standard/conversions.md

@@ -87,22 +87,28 @@ In some cases there is an identity conversion between types that are not exactly
 
 In most cases, an identity conversion has no effect at runtime. However, since floating point operations may be performed at higher precision than prescribed by their type ([§8.3.7](types.md#837-floating-point-types)), assignment of their results may result in a loss of precision, and explicit casts are guaranteed to reduce precision to what is prescribed by the type ([§12.9.7](expressions.md#1297-cast-expressions)).
 
+There is an identity conversion between `nint` and `System.IntPtr`, and between `nuint` and `System.UIntPtr`.
+
+For the compound types array, nullable type, constructed type, and tuple, there is an identity conversion between native integers ([§8.3.6]( types.md#836-integral-types)) and their underlying types.
+
 ### 10.2.3 Implicit numeric conversions
 
 The implicit numeric conversions are:
 
-- From `sbyte` to `short`, `int`, `long`, `float`, `double`, or `decimal`.
-- From `byte` to `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `float`, `double`, or `decimal`.
-- From `short` to `int`, `long`, `float`, `double`, or `decimal`.
-- From `ushort` to `int`, `uint`, `long`, `ulong`, `float`, `double`, or `decimal`.
-- From `int` to `long`, `float`, `double`, or `decimal`.
-- From `uint` to `long`, `ulong`, `float`, `double`, or `decimal`.
+- From `sbyte` to `short`, `int`, `nint`, `long`, `float`, `double`, or `decimal`.
+- From `byte` to `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `float`, `double`, or `decimal`.
+- From `short` to `int`, `nint`, `long`, `float`, `double`, or `decimal`.
+- From `ushort` to `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `float`, `double`, or `decimal`.
+- From `int` to `nint`, `long`, `float`, `double`, or `decimal`.
+- From `uint` to `long`, `nuint`, `ulong`, `float`, `double`, or `decimal`.
+- From `nint` to `long`, `float`, `double`, or `decimal`.
+- From `nuint` to `ulong`, `float`, `double`, or `decimal`.
 - From `long` to `float`, `double`, or `decimal`.
 - From `ulong` to `float`, `double`, or `decimal`.
-- From `char` to `ushort`, `int`, `uint`, `long`, `ulong`, `float`, `double`, or `decimal`.
+- From `char` to `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `float`, `double`, or `decimal`.
 - From `float` to `double`.
 
-Conversions from `int`, `uint`, `long` or `ulong` to `float` and from `long` or `ulong` to `double` may cause a loss of precision, but will never cause a loss of magnitude. The other implicit numeric conversions never lose any information.
+Conversions from `int`, `uint`, `nint`, `nuint`, `long` or `ulong` to `float` and from `nint`, `nuint`, `long` or `ulong` to `double` may cause a loss of precision, but will never cause a loss of magnitude. The other implicit numeric conversions never lose any information.
 
 There are no predefined implicit conversions to the `char` type, so values of the other integral types do not automatically convert to the `char` type.
 
@@ -382,18 +388,20 @@ The explicit conversions that are not implicit conversions are conversions that
 
 The explicit numeric conversions are the conversions from a *numeric_type* to another *numeric_type* for which an implicit numeric conversion ([§10.2.3](conversions.md#1023-implicit-numeric-conversions)) does not already exist:
 
-- From `sbyte` to `byte`, `ushort`, `uint`, `ulong`, or `char`.
+- From `sbyte` to `byte`, `ushort`, `uint`, `ulong`, `nuint`, or `char`.
 - From `byte` to `sbyte` or `char`.
-- From `short` to `sbyte`, `byte`, `ushort`, `uint`, `ulong`, or `char`.
+- From `short` to `sbyte`, `byte`, `ushort`, `uint`, `nuint`, `ulong`, or `char`.
 - From `ushort` to `sbyte`, `byte`, `short`, or `char`.
-- From `int` to `sbyte`, `byte`, `short`, `ushort`, `uint`, `ulong`, or `char`.
-- From `uint` to `sbyte`, `byte`, `short`, `ushort`, `int`, or `char`.
-- From `long` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `ulong`, or `char`.
-- From `ulong` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, or `char`.
+- From `int` to `sbyte`, `byte`, `short`, `ushort`, `uint`, `nuint`, `ulong`, or `char`.
+- From `uint` to `sbyte`, `byte`, `short`, `ushort`, `int`, `nint`, or `char`.
+- From `nint` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nuint`, `long`, `ulong`, or `char`.
+- From `nuint` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, or `char`.
+- From `long` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `ulong`, or `char`.
+- From `ulong` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, or `char`.
 - From `char` to `sbyte`, `byte`, or `short`.
-- From `float` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, or `decimal`.
-- From `double` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, `float`, or `decimal`.
-- From `decimal` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, `float`, or `double`.
+- From `float` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, or `decimal`.
+- From `double` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, `float`, or `decimal`.
+- From `decimal` to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, `float`, or `double`.
 
 Because the explicit conversions include all implicit and explicit numeric conversions, it is always possible to convert from any *numeric_type* to any other *numeric_type* using a cast expression ([§12.9.7](expressions.md#1297-cast-expressions)).
 
@@ -427,8 +435,8 @@ The explicit numeric conversions possibly lose information or possibly cause exc
 
 The explicit enumeration conversions are:
 
-- From `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, `float`, `double`, or `decimal` to any *enum_type*.
-- From any *enum_type* to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `long`, `ulong`, `char`, `float`, `double`, or `decimal`.
+- From `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, `float`, `double`, or `decimal` to any *enum_type*.
+- From any *enum_type* to `sbyte`, `byte`, `short`, `ushort`, `int`, `uint`, `nint`, `nuint`, `long`, `ulong`, `char`, `float`, `double`, or `decimal`.
 - From any *enum_type* to any other *enum_type*.
 
 An explicit enumeration conversion between two types is processed by treating any participating *enum_type* as the underlying type of that *enum_type*, and then performing an implicit or explicit numeric conversion between the resulting types.
@@ -758,6 +766,23 @@ Evaluation of a nullable conversion based on an underlying conversion from `S`
 - If the nullable conversion is from `S` to `T?`, the conversion is evaluated as the underlying conversion from `S` to `T` followed by a wrapping from `T` to `T?`.
 - If the nullable conversion is from `S?` to `T`, the conversion is evaluated as an unwrapping from `S?` to `S` followed by the underlying conversion from `S` to `T`.
 
+Conversion from `A` to `Nullable<B>` is:
+
+- an implicit nullable conversion if there is an identity conversion or implicit conversion from `A` to `B`;
+- an explicit nullable conversion if there is an explicit conversion from `A` to `B`;
+- otherwise, invalid.
+
+Conversion from `Nullable<A>` to `B` is:
+
+- an explicit nullable conversion if there is an identity conversion or implicit or explicit numeric conversion from `A` to `B`;
+- otherwise, invalid.
+
+Conversion from `Nullable<A>` to `Nullable<B>` is:
+
+- an identity conversion if there is an identity conversion from `A` to `B`;
+- an explicit nullable conversion if there is an implicit or explicit numeric conversion from `A` to `B`;
+- otherwise, invalid.
+
 ### 10.6.2 Lifted conversions
 
 Given a user-defined conversion operator that converts from a non-nullable value type `S` to a non-nullable value type `T`, a ***lifted conversion operator*** exists that converts from `S?` to `T?`. This lifted conversion operator performs an unwrapping from `S?` to `S` followed by the user-defined conversion from `S` to `T` followed by a wrapping from `T` to `T?`, except that a null valued `S?` converts directly to a null valued `T?`. A lifted conversion operator has the same implicit or explicit classification as its underlying user-defined conversion operator.

standard/enums.md

@@ -44,7 +44,7 @@ enum_body
     ;
 ```
 
-Each enum type has a corresponding integral type called the ***underlying type*** of the enum type. This underlying type shall be able to represent all the enumerator values defined in the enumeration. If the *enum_base* is present, it explicitly declares the underlying type. The underlying type shall be one of the *integral types* ([§8.3.6](types.md#836-integral-types)) other than `char`. The underlying type may be specified either by an `integral_type` ([§8.3.5](types.md#835-simple-types)), or an `integral_type_name`. The `integral_type_name` is resolved in the same way as `type_name` ([§7.8.1](basic-concepts.md#781-general)), including taking any using directives ([§14.5](namespaces.md#145-using-directives)) into account.
+Each enum type has a corresponding integral type called the ***underlying type*** of the enum type. This underlying type shall be able to represent all the enumerator values defined in the enumeration. If the *enum_base* is present, it explicitly declares the underlying type. The underlying type shall be one of the *integral types* ([§8.3.6](types.md#836-integral-types)) other than `nint`, `nuint`, and `char`. The underlying type may be specified either by an `integral_type` ([§8.3.5](types.md#835-simple-types)), or an `integral_type_name`. The `integral_type_name` is resolved in the same way as `type_name` ([§7.8.1](basic-concepts.md#781-general)), including taking any using directives ([§14.5](namespaces.md#145-using-directives)) into account.
 
 > *Note*: The `char` type cannot be used as an underlying type, either by keyword or via an `integral_type_name`. *end note*