Move tuple literals from "Lexical structure" to "Expressions" (#3205)
This commit is contained in:
Rex Jaeschke
Bill Wagner
parent
4df9865acd
commit
5ade4ff123
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@ -2,27 +2,11 @@
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This proposal specifies the changes required to the [C# 6.0 (draft) Language specification](../../spec/introduction.md) to support *Tuples* as a new [value type](../../spec/types.md#value-types).
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## Changes to [Lexical structure](../../spec/lexical-structure.md)
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## Additions to [Expressions](../../spec/expressions.md)
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### Literals
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> Add the following section after [xxx](xxx):
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> The grammar for [Literals](../../spec/lexical-structure.md#literals) is extended to include `tuple_literal`:
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```antlr
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literal
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: boolean_literal
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| integer_literal
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| real_literal
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| character_literal
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| string_literal
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| null_literal
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| tuple_literal // new
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;
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```
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> Add the following section after [The null literal](../../spec/lexical-structure.md#The-null-literal):
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#### Tuple literals
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## Tuple literal expressions
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A tuple literal consists of two or more tuple literal elements, each of which is optionally named.
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@ -40,10 +24,10 @@ A tuple literal is implicitly typed; that is, its type is determined by the cont
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\[Example:
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```csharp
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var t1 = (0, 2); // infer tuple type (int, int) from values
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var t2 = (sum: 0, count: 1); // infer tuple type (int sum, int count) from names and values
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(int, double) t3 = (0, 2); // infer tuple type (int, double) from values; can implicitly convert int to double
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(int, double) t4 = (0.0, 2); // Error: can't implicitly convert double to int
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var t1 = (0, 2); // infer tuple type (int, int) from values
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var t2 = (sum: 0, count: 1); // infer tuple type (int sum, int count) from names and values
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(int, double) t3 = (0, 2); // infer tuple type (int, double) from values; can implicitly convert int to double
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(int, double) t4 = (0.0, 2); // Error: can't implicitly convert double to int
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```
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end example\]
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@ -51,7 +35,7 @@ A tuple literal has a "conversion from expression" to any tuple type of the same
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\[Example:
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```csharp
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(string name, byte age) t = (null, 5); // OK: the expressions null and 5 convert to string and byte, respectively
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(string name, byte age) t = (null, 5); // OK: null and 5 convert to string and byte, respectively
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```
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end example\]
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@ -59,8 +43,8 @@ In cases where a tuple literal is not part of a conversion, the literal's type i
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\[Example:
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```csharp
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var t = ("John", 5); // OK: the natural type is (string, int)
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var t = (null, 5); // Error: null doesn't have a type
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var t = ("John", 5); // OK: the natural type is (string, int)
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var t = (null, 5); // Error: null doesn't have a type
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var t = (name: "John", age: 5); // OK: The natural type is (string name, int age)
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```
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end example\]
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@ -133,7 +117,7 @@ A tuple's type can be declared explicitly. Consider the following declarations:
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The type of `pair2` is `(int, string)` with unknown element names. Similarly, the type of `pair3` is `(int, string)` but this time with the element names `code` and `message`, respectively. For `pair4` and `pair5`, one element is named, the other not.
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In the case of `pair6`, the second element is declared as being unanmed, and any attempt to provide a name in an initializing context shall be ignored. Likewise for any attempt to change an element's name, as in the case of `pair7`.
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In the case of `pair6`, the second element is declared as being unnamed, and any attempt to provide a name in an initializing context shall be ignored. Likewise for any attempt to change an element's name, as in the case of `pair7`.
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A tuple's type can be wholely inferred from the context in which it is used. Consider the following declarations:
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@ -150,8 +134,8 @@ Element names within a tuple type shall be distinct.
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\[Example:
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```csharp
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(int e1, float e1) t = (10, 1.2); // Error: both elements have the same name
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(int e1, (int e1, int e2) e2) t = (10, (20, 30)); // OK: element names in each tuple type are distinct
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(int e1, float e1) t = (10, 1.2); // Error: both elements have the same name
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(int e1, (int e1, int e2) e2) t = (10, (20, 30)); // OK: element names in each tuple type are distinct
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```
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end example\]
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@ -181,17 +165,17 @@ t1.Item2 = 3; // access the second element by its underlying name
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System.ValueTuple<int, int> vt = t1; // identity conversion
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var t2 = (1, 2, 3, 4, 5, 6, 7, 8, 9); // t2 is a System.ValueTuple<T1, T2, T3,..., T7, TRest>
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var t3 = t4.Rest; // t3 is a (int, int); that is, a System.ValueTuple<T1, T2>
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System.Console.WriteLine("Item9 = {0}", t1.Item9); // outputs 9 even though no such name Item9 exists!
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var t2 = (1, 2, 3, 4, 5, 6, 7, 8, 9); // t2 is a System.ValueTuple<T1, T2, T3,..., T7, TRest>
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var t3 = t4.Rest; // t3 is a (int, int); that is, a System.ValueTuple<T1, T2>
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System.Console.WriteLine("Item9 = {0}", t1.Item9); // outputs 9 even though no such name Item9 exists!
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```
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end example\]
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\[Example:
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```csharp
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var t = (ToString: 0, GetHashCode: 1); // Error: names match underlying member names
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var t1 = (Item1: 0, Item2: 1); // OK
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var t2 = (misc: 0, Item1: 1); // Error: "Item1" used in a wrong position
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var t = (ToString: 0, GetHashCode: 1); // Error: names match underlying member names
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var t1 = (Item1: 0, Item2: 1); // OK
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var t2 = (misc: 0, Item1: 1); // Error: "Item1" used in a wrong position
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```
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end example\]
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@ -210,18 +194,18 @@ public class Base
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}
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public class Derived : Base
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{
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public override void M1((int c, int d) arg){...} // valid override, signatures are equivalent
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public override void M1((int c, int d) arg){...} // valid override, signatures are equivalent
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}
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public class Derived2 : Derived
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{
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public override void M1((int c1, int c) arg){...} // also valid, warning on possible misuse of name 'c'
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public override void M1((int c1, int c) arg){...} // also valid, warning on possible misuse of name 'c'
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}
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public class InvalidOverloading
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{
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public virtual void M1((int c, int d) arg){...}
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public virtual void M1((int x, int y) arg){...} // invalid overload, signatures are eqivalent
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public virtual void M1(ValueTuple<int, int> arg){...} // also invalid
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public virtual void M1((int x, int y) arg){...} // invalid overload, signatures are eqivalent
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public virtual void M1(ValueTuple<int, int> arg){...} // also invalid
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}
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```
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@ -233,8 +217,8 @@ In alignment with the identity conversions, a boxed tuple shall not retain the n
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\[Example:
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```csharp
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object o = (a: 1, b: 2); // boxing conversion
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var t = ((int moo, int boo))o; // unboxing conversion
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object o = (a: 1, b: 2); // boxing conversion
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var t = ((int moo, int boo))o; // unboxing conversion
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```
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end example\]
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@ -253,9 +237,9 @@ Like unassigned variables, discards do not have a value. A discard may only occu
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\[Example:
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```csharp
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M(out _, out var _, out int _); // three out variable discards
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(_, var _, int _) = GetCoordinates(); // deconstruction into discards
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if (x is var _ && y is int _) { ... } // discards in patterns
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M(out _, out var _, out int _); // three out variable discards
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(_, var _, int _) = GetCoordinates(); // deconstruction into discards
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if (x is var _ && y is int _) { ... } // discards in patterns
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```
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end example\]
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@ -317,7 +301,7 @@ A tuple literal is implicitly typed when used in a context specifying a tuple ty
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\[Example:
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```csharp
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(string name, byte age) t = (null, 5); // Ok: the expressions null and 5 convert to string and byte
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(string name, byte age) t = (null, 5); // OK: the expressions null and 5 convert to string and byte
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```
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end example\]
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@ -376,13 +360,13 @@ Element values are copied from the source tuple to the destination(s). Each elem
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int code;
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string message;
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(code, message) = (10, "hello"); // copy both element values to existing variables
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(code, _) = (11, "Go!"); // copy element 1 to code and discard element 2
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(_, _) = (12, "Stop!"); // discard both element values
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(int code2, string message2) = (20, "left"); // copy both element values to newly created variables
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(code, string message3) = (21, "right"); // Error: can't mix existing and new variables
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(code, _) = (30, 2.5, (10, 20)); // Error: can't deconstruct tuple of 3 elements into 2 values
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(code, _, _) = (30, 2.5, (10, 20)); // OK: deconstructing 3 elements into 3 values
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(code, message) = (10, "hello"); // copy both element values to existing variables
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(code, _) = (11, "Go!"); // copy element 1 to code and discard element 2
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(_, _) = (12, "Stop!"); // discard both element values
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(int code2, string message2) = (20, "left"); // copy both element values to newly created variables
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(code, string message3) = (21, "right"); // Error: can't mix existing and new variables
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(code, _) = (30, 2.5, (10, 20)); // Error: can't deconstruct tuple of 3 elements into 2 values
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(code, _, _) = (30, 2.5, (10, 20)); // OK: deconstructing 3 elements into 3 values
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```
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end example\]
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@ -391,13 +375,17 @@ Any object may be deconstructed by providing an accessible `Deconstruct` method,
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```csharp
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class Name
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{
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public void Deconstruct(out string first, out string last) { first = First; last = Last; }
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public void Deconstruct(out string first, out string last) {
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first = First; last = Last;
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}
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...
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}
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// or
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static class Extensions
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{
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public static void Deconstruct(this Name name, out string first, out string last) { first = name.First; last = name.Last; }
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public static void Deconstruct(this Name name, out string first, out string last) {
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first = name.First; last = name.Last;
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}
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}
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```
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```csharp
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namespace System
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{
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2)>, IEquatable<(T1, T2)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2> : IStructuralComparable,
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IStructuralEquatable, IComparable, IComparable<(T1, T2)>, IEquatable<(T1, T2)>, ITuple
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{
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[NullableAttribute(1)]
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public T1 Item1;
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@ -489,7 +478,9 @@ namespace System
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namespace System
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{
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3)>, IEquatable<(T1, T2, T3)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3>
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: IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3)>,
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IEquatable<(T1, T2, T3)>, ITuple
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{
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[NullableAttribute(1)]
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public T1 Item1;
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@ -513,7 +504,9 @@ namespace System
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{
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[NullableAttribute(0)]
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[NullableContextAttribute(1)]
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3, [NullableAttribute(2)] T4> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4)>, IEquatable<(T1, T2, T3, T4)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3,
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[NullableAttribute(2)] T4> : IStructuralComparable, IStructuralEquatable, IComparable,
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IComparable<(T1, T2, T3, T4)>, IEquatable<(T1, T2, T3, T4)>, ITuple
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{
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public T1 Item1;
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public T2 Item2;
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@ -533,7 +526,9 @@ namespace System
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{
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[NullableAttribute(0)]
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[NullableContextAttribute(1)]
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3, [NullableAttribute(2)] T4, [NullableAttribute(2)] T5> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4, T5)>, IEquatable<(T1, T2, T3, T4, T5)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3,
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[NullableAttribute(2)] T4, [NullableAttribute(2)] T5> : IStructuralComparable, IStructuralEquatable,
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IComparable, IComparable<(T1, T2, T3, T4, T5)>, IEquatable<(T1, T2, T3, T4, T5)>, ITuple
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{
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public T1 Item1;
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public T2 Item2;
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@ -554,7 +549,10 @@ namespace System
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{
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[NullableAttribute(0)]
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[NullableContextAttribute(1)]
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3, [NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4, T5, T6)>, IEquatable<(T1, T2, T3, T4, T5, T6)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3,
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[NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6> : IStructuralComparable,
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IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4, T5, T6)>,
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IEquatable<(T1, T2, T3, T4, T5, T6)>, ITuple
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{
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public T1 Item1;
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public T2 Item2;
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@ -576,7 +574,10 @@ namespace System
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{
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[NullableAttribute(0)]
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[NullableContextAttribute(1)]
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3, [NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6, [NullableAttribute(2)] T7> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4, T5, T6, T7)>, IEquatable<(T1, T2, T3, T4, T5, T6, T7)>, ITuple
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3,
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[NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6, [NullableAttribute(2)] T7>
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: IStructuralComparable, IStructuralEquatable, IComparable, IComparable<(T1, T2, T3, T4, T5, T6, T7)>,
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IEquatable<(T1, T2, T3, T4, T5, T6, T7)>, ITuple
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{
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public T1 Item1;
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public T2 Item2;
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@ -586,10 +587,12 @@ namespace System
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public T6 Item6;
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public T7 Item7;
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public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7);
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public int CompareTo([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1 })] (T1, T2, T3, T4, T5, T6, T7) other);
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public int CompareTo([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1 })]
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(T1, T2, T3, T4, T5, T6, T7) other);
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[NullableContextAttribute(2)]
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public override bool Equals(object? obj);
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public bool Equals([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1 })] (T1, T2, T3, T4, T5, T6, T7) other);
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public bool Equals([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1 })]
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(T1, T2, T3, T4, T5, T6, T7) other);
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public override int GetHashCode();
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public override string ToString();
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}
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@ -599,7 +602,11 @@ namespace System
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{
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[NullableAttribute(0)]
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[NullableContextAttribute(1)]
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3, [NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6, [NullableAttribute(2)] T7, [NullableAttribute(0)] TRest> : IStructuralComparable, IStructuralEquatable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, ITuple where TRest : struct
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public struct ValueTuple<[NullableAttribute(2)] T1, [NullableAttribute(2)] T2, [NullableAttribute(2)] T3,
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[NullableAttribute(2)] T4, [NullableAttribute(2)] T5, [NullableAttribute(2)] T6, [NullableAttribute(2)] T7,
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[NullableAttribute(0)] TRest> : IStructuralComparable, IStructuralEquatable, IComparable,
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IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>,
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IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, ITuple where TRest : struct
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{
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public T1 Item1;
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public T2 Item2;
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@ -610,11 +617,14 @@ namespace System
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public T7 Item7;
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[NullableAttribute(0)]
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public TRest Rest;
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public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, [NullableAttribute(0)] TRest rest);
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public int CompareTo([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1, 0 })] ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other);
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public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7,
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[NullableAttribute(0)] TRest rest);
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public int CompareTo([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1, 0 })]
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ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other);
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[NullableContextAttribute(2)]
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public override bool Equals(object? obj);
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public bool Equals([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1, 0 })] ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other);
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public bool Equals([NullableAttribute(new[] { 0, 1, 1, 1, 1, 1, 1, 1, 0 })]
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ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other);
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public override int GetHashCode();
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public override string ToString();
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}
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