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 the *array access* variant of *element_access* expressions ([§12.8.12.2](expressions.md#128122-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 access is a variable reference ([§9.5](variables.md#95-variable-references)) to the array element selected by the indices.
+Array elements are accessed using the *array access* variant of *element_access* expressions ([§12.8.12.2](expressions.md#128122-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`, `nint`, `nuint`, `long`, `ulong`, or can be implicitly converted to one or more of these types. The result of an array access is a variable reference ([§9.5](variables.md#95-variable-references)) to the array element selected by the indices.
 
 Array elements of single-dimensional arrays can also be accessed using an array access expression where the sole index, `I₁`, is an expression of type `Index`, `Range`, or can be implicitly converted to one or both of these types. If `I₁` is of type `Index`, or has been implicitly converted to that type, then the result of the array access is a variable reference to the array element selected by the index value. If `I₁` is of type `Range`, or has been implicitly converted to that type, then the result of the element access is a new array formed from a shallow copy of the array elements with indices in the `Range`, maintaining the element order.
 

standard/classes.md

@@ -1555,7 +1555,7 @@ A *constant_declaration* may include a set of *attributes* ([§23](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* ([§12.25](expressions.md#1225-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)).
 
@@ -1789,7 +1789,7 @@ 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

@@ -115,22 +115,28 @@ All identity conversions are symmetric. If an identity conversion exists from `T
 
 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 ([§12.9.8](expressions.md#1298-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.
 
@@ -315,7 +321,7 @@ This implicit conversion seemingly violates the advice in the beginning of [§10
 
 An implicit constant expression conversion permits the following conversions:
 
-- A *constant_expression* ([§12.25](expressions.md#1225-constant-expressions)) of type `int` can be converted to type `sbyte`, `byte`, `short`, `ushort`, `uint`, or `ulong`, provided the value of the *constant_expression* is within the range of the destination type.
+- A *constant_expression* ([§12.25](expressions.md#1225-constant-expressions)) of type `int` can be converted to type `sbyte`, `byte`, `short`, `ushort`, `uint`, `nint`, `nuint`, or `ulong`, provided the value of the *constant_expression* is within the range of the destination type.
 - A *constant_expression* of type `long` can be converted to type `ulong`, provided the value of the *constant_expression* is not negative.
 
 ### 10.2.12 Implicit conversions involving type parameters
@@ -413,18 +419,20 @@ 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 ([§12.9.8](expressions.md#1298-cast-expressions)).
 
@@ -458,8 +466,8 @@ 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.
@@ -748,6 +756,23 @@ 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*