patch 9.0.2170: Vim9: no support for const/final class/objects vars
Problem: Vim9: no support for const/final class/objects vars
Solution: Support final and const object and class variables
closes: #13655
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/vim9class.txt b/runtime/doc/vim9class.txt
index 97813f0..4dc67bd 100644
--- a/runtime/doc/vim9class.txt
+++ b/runtime/doc/vim9class.txt
@@ -364,6 +364,78 @@
corresponding class member will be used. The type of the class member in a
child class can be different from that in the super class.
+ *object-final-variable* *E1409*
+The |:final| keyword can be used to make a class or object variable a
+constant. Examples: >
+
+ class A
+ final v1 = [1, 2] # final object variable
+ public final v2 = {x: 1} # final object variable
+ static final v3 = 'abc' # final class variable
+ public static final v4 = 0z10 # final class variable
+ endclass
+<
+A final variable can be changed only from a constructor function. Example: >
+
+ class A
+ final v1: list<number>
+ def new()
+ this.v1 = [1, 2]
+ enddef
+ endclass
+ var a = A.new()
+ echo a.v1
+<
+Note that the value of a final variable can be changed. Example: >
+
+ class A
+ public final v1 = [1, 2]
+ endclass
+ var a = A.new()
+ a.v1[0] = 6 # OK
+ a.v1->add(3) # OK
+ a.v1 = [3, 4] # Error
+<
+ *E1408*
+Final variables are not supported in an interface. A class or object method
+cannot be final.
+
+ *object-const-variable*
+The |:const| keyword can be used to make a class or object variable and the
+value a constant. Examples: >
+
+ class A
+ const v1 = [1, 2] # const object variable
+ public const v2 = {x: 1} # const object variable
+ static const v3 = 'abc' # const class variable
+ public static const v4 = 0z10 # const class variable
+ endclass
+<
+A const variable can be changed only from a constructor function. Example: >
+
+ class A
+ const v1: list<number>
+ def new()
+ this.v1 = [1, 2]
+ enddef
+ endclass
+ var a = A.new()
+ echo a.v1
+<
+A const variable and its value cannot be changed. Example: >
+
+ class A
+ public const v1 = [1, 2]
+ endclass
+ var a = A.new()
+ a.v1[0] = 6 # Error
+ a.v1->add(3) # Error
+ a.v1 = [3, 4] # Error
+<
+ *E1410*
+Const variables are not supported in an interface. A class or object method
+cannot be a const.
+
==============================================================================
4. Using an abstract class *Vim9-abstract-class*
@@ -982,8 +1054,6 @@
reuses the general function declaration syntax for methods. So, for the sake
of consistency, we require "var" in these declarations.
-This also allows for a natural use of "final" and "const" in the future.
-
Using "ClassName.new()" to construct an object ~