patch 9.0.1885: Vim9: no support for abstract methods

Problem:  Vim9: no support for abstract methods
Solution: Add support for defining abstract methods in an abstract class

closes: #13044
closes: #13046

Signed-off-by: Christian Brabandt <[email protected]>
Co-authored-by: Yegappan Lakshmanan <[email protected]>

Author: yegappan

runtime/doc/tags

@@ -5850,6 +5850,7 @@ abandon	editing.txt	/*abandon*
 abbreviations	map.txt	/*abbreviations*
 abel.vim	syntax.txt	/*abel.vim*
 abs()	builtin.txt	/*abs()*
+abstract-method	vim9class.txt	/*abstract-method*
 acos()	builtin.txt	/*acos()*
 active-buffer	windows.txt	/*active-buffer*
 ada#Create_Tags()	ft_ada.txt	/*ada#Create_Tags()*

runtime/doc/vim9class.txt

@@ -358,6 +358,16 @@ class, for which objects can be created.  Example: >
 An abstract class is defined the same way as a normal class, except that it
 does not have any new() method. *E1359*
 
+						*abstract-method*
+An abstract method can be defined in an abstract class by using the "abstract"
+prefix when defining the function: >
+
+	abstract class Shape
+	   abstract def Draw()
+	endclass
+
+A class extending the abstract class must implement all the abstract methods.
+Class methods in an abstract class can also be abstract methods.
 
 ==============================================================================
 

src/errors.h

@@ -3495,6 +3495,12 @@ EXTERN char e_duplicate_member_str[]
 	INIT(= N_("E1369: Duplicate member: %s"));
 EXTERN char e_cannot_define_new_function_as_static[]
 	INIT(= N_("E1370: Cannot define a \"new\" function as static"));
+EXTERN char e_abstract_must_be_followed_by_def_or_static[]
+	INIT(= N_("E1371: Abstract must be followed by \"def\" or \"static\""));
+EXTERN char e_abstract_method_in_concrete_class[]
+	INIT(= N_("E1372: Abstract method \"%s\" cannot be defined in a concrete class"));
+EXTERN char e_abstract_method_str_not_found[]
+	INIT(= N_("E1373: Abstract method \"%s\" is not implemented"));
 EXTERN char e_cannot_mix_positional_and_non_positional_str[]
 	INIT(= N_("E1400: Cannot mix positional and non-positional arguments: %s"));
 EXTERN char e_fmt_arg_nr_unused_str[]

src/structs.h

@@ -1515,6 +1515,7 @@ struct itf2class_S {
 
 #define CLASS_INTERFACE	    1
 #define CLASS_EXTENDED	    2	    // another class extends this one
+#define CLASS_ABSTRACT	    4	    // abstract class
 
 // "class_T": used for v_class of typval of VAR_CLASS
 // Also used for an interface (class_flags has CLASS_INTERFACE).
@@ -1875,6 +1876,7 @@ struct ufunc_S
 
 #define FC_OBJECT   0x4000	// object method
 #define FC_NEW	    0x8000	// constructor
+#define FC_ABSTRACT 0x10000	// abstract method
 
 #define MAX_FUNC_ARGS	20	// maximum number of function arguments
 #define VAR_SHORT_LEN	20	// short variable name length

src/testdir/test_vim9_class.vim

@@ -4473,4 +4473,140 @@ enddef
 "   v9.CheckScriptSuccess(lines)
 " enddef
 
+" Test for abstract methods
+def Test_abstract_method()
+  # Use two abstract methods
+  var lines =<< trim END
+    vim9script
+    abstract class A
+      def M1(): number
+        return 10
+      enddef
+      abstract def M2(): number
+      abstract def M3(): number
+    endclass
+    class B extends A
+      def M2(): number
+        return 20
+      enddef
+      def M3(): number
+        return 30
+      enddef
+    endclass
+    var b = B.new()
+    assert_equal([10, 20, 30], [b.M1(), b.M2(), b.M3()])
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # Don't define an abstract method
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract def Foo()
+    endclass
+    class B extends A
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1373: Abstract method "Foo" is not implemented')
+
+  # Use abstract method in a concrete class
+  lines =<< trim END
+    vim9script
+    class A
+      abstract def Foo()
+    endclass
+    class B extends A
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1372: Abstract method "abstract def Foo()" cannot be defined in a concrete class')
+
+  # Use abstract method in an interface
+  lines =<< trim END
+    vim9script
+    interface A
+      abstract def Foo()
+    endinterface
+    class B implements A
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1372: Abstract method "abstract def Foo()" cannot be defined in a concrete class')
+
+  # Abbreviate the "abstract" keyword
+  lines =<< trim END
+    vim9script
+    class A
+      abs def Foo()
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1065: Command cannot be shortened: abs def Foo()')
+
+  # Use "abstract" with a member variable
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract this.val = 10
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1371: Abstract must be followed by "def" or "static"')
+
+  # Use a static abstract method
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract static def Foo(): number
+    endclass
+    class B extends A
+      static def Foo(): number
+        return 4
+      enddef
+    endclass
+    assert_equal(4, B.Foo())
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # Type mismatch between abstract method and concrete method
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract def Foo(a: string, b: number): list<number>
+    endclass
+    class B extends A
+      def Foo(a: number, b: string): list<string>
+        return []
+      enddef
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1407: Member "Foo": type mismatch, expected func(string, number): list<number> but got func(number, string): list<string>')
+
+  # Use an abstract class to invoke an abstract method
+  # FIXME: This should fail
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract static def Foo()
+    endclass
+    A.Foo()
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # Invoke an abstract method from a def function
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract def Foo(): list<number>
+    endclass
+    class B extends A
+      def Foo(): list<number>
+        return [3, 5]
+      enddef
+    endclass
+    def Bar(c: B)
+      assert_equal([3, 5], c.Foo())
+    enddef
+    var b = B.new()
+    Bar(b)
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/userfunc.c

@@ -5021,6 +5021,7 @@ define_function(
     // Do not define the function when getting the body fails and when
     // skipping.
     if (((class_flags & CF_INTERFACE) == 0
+		&& (class_flags & CF_ABSTRACT_METHOD) == 0
 		&& get_function_body(eap, &newlines, line_arg, lines_to_free)
 								       == FAIL)
 	    || eap->skip)

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1885,
 /**/
     1884,
 /**/

src/vim.h

@@ -2915,5 +2915,6 @@ long elapsed(DWORD start_tick);
 // Flags used by "class_flags" of define_function()
 #define CF_CLASS	1	// inside a class
 #define CF_INTERFACE	2	// inside an interface
+#define CF_ABSTRACT_METHOD	4	// inside an abstract class
 
 #endif // VIM__H