PEP 695: Fix Kotlin/Java details and add Dart

Author: KotlinIsland

pep-0695.rst

@@ -896,7 +896,9 @@ Java
 ----
 
 Java uses angle brackets to declare type parameters and for specialization.
-The "extends" keyword is used to specify an upper bound.
+By default, type parameters are invariant.
+The "extends" keyword is used to specify an upper bound. The "super" keyword
+is used to specify a contravariant bound.
 
 Java uses use-site variance. The compiler places limits on which methods and
 members can be accessed based on the use of a generic type. Variance is
@@ -912,6 +914,8 @@ Java provides no way to specify a default type argument.
 
         // Generic method
         public <S extends Number> void method1(S value) { }
+        // Use site variance
+        public void method1(ClassA<? super Integer> value) { }
     }
     
 
@@ -955,7 +959,7 @@ specialization. The "extends" keyword is used to specify a bound. It can be
 combined with other type operators such as "keyof".
 
 TypeScript uses declaration-site variance. Variance is inferred from
-usage, not specified explicitly. TypeScript 4.7 will introduce the ability
+usage, not specified explicitly. TypeScript 4.7 introduced the ability
 to specify variance using "in" and "out" keywords. This was added to handle
 extremely complex types where inference of variance was expensive.
 
@@ -1036,8 +1040,7 @@ Swift
 Swift uses angle brackets to declare type parameters and for specialization.
 The upper bound of a type parameter is specified using a colon.
 
-Swift uses declaration-site variance, and variance of type parameters is
-inferred from their usage.
+Swift doesn't support generic variance, all type parameters are invariant.
 
 Swift provides no way to specify a default type argument.
 
@@ -1105,7 +1108,9 @@ Kotlin
 ------
 
 Kotlin uses angle brackets to declare type parameters and for specialization.
-The upper bound of a type is specified using a colon.
+By default, type parameters are invariant. The upper bound of a type is
+specified using a colon. Alternatively a "where" clause can specify various
+constraints.
 
 Kotlin supports declaration-site variance where variance of type parameters is
 explicitly declared using "in" and "out" keywords. It also supports use-site
@@ -1116,19 +1121,19 @@ Kotlin provides no way to specify a default type argument.
 ::
 
     // Generic class
-    class ClassA<T> { }
+    class ClassA<T>
 
     // Type parameter with upper bound
-    class ClassB<T: SomeClass1> { }
+    class ClassB<T : SomeClass1>
 
     // Contravariant and covariant type parameters
-    class ClassC<in S, out T> { }
+    class ClassC<in S, out T>
 
     // Generic function
-    fun func1<T>() -> T {}
+    fun <T> func1(): T { }
 
     // Generic type alias
-    typealias<T> = ClassA<T>
+    typealias TypeAliasFoo<T> = ClassA<T>
 
 
 Julia
@@ -1151,6 +1156,37 @@ upper and lower bounds on a type.
     // Alternate form of generic function
     function func2(v::Container{T} where T <: Real)
 
+Dart
+-----
+
+Dart uses angle brackets to declare type parameters and for specialization.
+The upper bound of a type is specified using the "extends" keyword. By default,
+type parameters are covariant.
+
+Dart supports declaration-site variance where variance of type parameters is
+explicitly declared using "in", "out" and "inout" keywords. It does not support
+use-site variance.
+
+Dart provides no way to specify a default type argument.
+
+::
+
+    // Generic class
+    class ClassA<T> { }
+
+    // Type parameter with upper bound
+    class ClassB<T extends SomeClass1> { }
+
+    // Contravariant and covariant type parameters
+    class ClassC<in S, out T> { }
+
+    // Generic function
+    T func1<T>() { }
+
+    // Generic type alias
+    typedef TypeDefFoo<T> = ClassA<T>;
+
+
 
 Summary
 -------
@@ -1162,7 +1198,8 @@ Summary
 | C++        | template | n/a     | n/a    | =        | n/a       | n/a       |
 |            | <>       |         |        |          |           |           |
 +------------+----------+---------+--------+----------+-----------+-----------+
-| Java       | <>       | extends |        |          | use       | inferred  |
+| Java       | <>       | extends |        |          | use       | super,    |
+|            |          |         |        |          |           | extends   |
 +------------+----------+---------+--------+----------+-----------+-----------+
 | C#         | <>       | where   |        |          | decl      | in, out   |
 +------------+----------+---------+--------+----------+-----------+-----------+
@@ -1171,15 +1208,19 @@ Summary
 +------------+----------+---------+--------+----------+-----------+-----------+
 | Scala      | []       | T <: X  | T >: X |          | use, decl | +, -      |
 +------------+----------+---------+--------+----------+-----------+-----------+
-| Swift      | <>       | T: X    |        |          | decl      | inferred  |
+| Swift      | <>       | T: X    |        |          | n/a       | n/a       |
 +------------+----------+---------+--------+----------+-----------+-----------+
 | Rust       | <>       | T: X,   |        | =        | decl      | inferred, |
 |            |          | where   |        |          |           | explicit  |
 +------------+----------+---------+--------+----------+-----------+-----------+
-| Kotlin     | <>       | T: X    |        |          | use, decl | inferred  |
+| Kotlin     | <>       | T: X,   |        |          | use, decl | in, out   |
+|            |          | where   |        |          |           |           |
 +------------+----------+---------+--------+----------+-----------+-----------+
 | Julia      | {}       | T <: X  | X <: T |          | n/a       | n/a       |
 +------------+----------+---------+--------+----------+-----------+-----------+
+| Dart       | <>       | extends |        |          | decl      | in, out,  |
+|            |          |         |        |          |           | inout     |
++------------+----------+---------+--------+----------+-----------+-----------+
 | Python     | []       | T: X    |        |          | decl      | inferred  |
 | (proposed) |          |         |        |          |           |           |
 +------------+----------+---------+--------+----------+-----------+-----------+