patch 9.0.1760: vim9 class problem with new() constructor

Problem:  vim9 class problem with new() constructor
Solution: Don't allow a return type for the new() class constructor.

closes: #12863
closes: #12040

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/errors.h

@@ -3478,6 +3478,8 @@ EXTERN char e_incomplete_type[]
 #endif
 EXTERN char e_warning_pointer_block_corrupted[]
 	INIT(= N_("E1364: Warning: Pointer block corrupted"));
+EXTERN char e_cannot_use_a_return_type_with_new[]
+	INIT(= N_("E1365: Cannot use a return type with the \"new\" function"));
 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[]
@@ -3495,4 +3497,4 @@ EXTERN char e_member_str_type_mismatch_expected_str_but_got_str[]
 EXTERN char e_method_str_type_mismatch_expected_str_but_got_str[]
 	INIT(= N_("E1407: Member \"%s\": type mismatch, expected %s but got %s"));
 
-// E1365 - E1399 unused
+// E1366 - E1399 unused

src/testdir/test_vim9_class.vim

@@ -1577,6 +1577,16 @@ def Test_class_implements_interface()
   END
   v9.CheckScriptFailure(lines, 'E1349:')
 
+  # implements should be followed by a white space
+  lines =<< trim END
+    vim9script
+    interface A
+    endinterface
+    class B implements A;
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1315:')
+
   lines =<< trim END
       vim9script
 
@@ -2515,4 +2525,104 @@ def Test_stack_expansion_with_methods()
   END
   v9.CheckScriptSuccess(lines)
 enddef
+
+" Test the return type of the new() constructor
+def Test_new_return_type()
+  # new() uses the default return type and there is no return statement
+  var lines =<< trim END
+    vim9script
+
+    class C
+      this._bufnr: number
+
+      def new(this._bufnr)
+        if !bufexists(this._bufnr)
+          this._bufnr = -1
+        endif
+      enddef
+    endclass
+
+    var c = C.new(12345)
+    assert_equal('object<C>', typename(c))
+
+    var v1: C
+    v1 = C.new(12345)
+    assert_equal('object<C>', typename(v1))
+
+    def F()
+      var v2: C
+      v2 = C.new(12345)
+      assert_equal('object<C>', typename(v2))
+    enddef
+    F()
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # new() uses the default return type and an empty 'return' statement
+  lines =<< trim END
+    vim9script
+
+    class C
+      this._bufnr: number
+
+      def new(this._bufnr)
+        if !bufexists(this._bufnr)
+          this._bufnr = -1
+          return
+        endif
+      enddef
+    endclass
+
+    var c = C.new(12345)
+    assert_equal('object<C>', typename(c))
+
+    var v1: C
+    v1 = C.new(12345)
+    assert_equal('object<C>', typename(v1))
+
+    def F()
+      var v2: C
+      v2 = C.new(12345)
+      assert_equal('object<C>', typename(v2))
+    enddef
+    F()
+  END
+  v9.CheckScriptSuccess(lines)
+
+  # new() uses "any" return type and returns "this"
+  lines =<< trim END
+    vim9script
+
+    class C
+      this._bufnr: number
+
+      def new(this._bufnr): any
+        if !bufexists(this._bufnr)
+          this._bufnr = -1
+          return this
+        endif
+      enddef
+    endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1365:')
+
+  # new() uses 'Dict' return type and returns a Dict
+  lines =<< trim END
+    vim9script
+
+    class C
+      this._state: dict<any>
+
+      def new(): dict<any>
+        this._state = {}
+        return this._state
+      enddef
+    endclass
+
+    var c = C.new()
+    assert_equal('object<C>', typename(c))
+  END
+  v9.CheckScriptFailure(lines, 'E1365:')
+enddef
+
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1760,
 /**/
     1759,
 /**/

src/vim9class.c

@@ -687,7 +687,7 @@ add_class_members(class_T *cl, exarg_T *eap)
 }
 
 /*
- * Add a default constructor to the class "cl".
+ * Add a default constructor method (new()) to the class "cl".
  */
     static void
 add_default_constructor(
@@ -1150,6 +1150,18 @@ early_ret:
 		    func_clear_free(uf, FALSE);
 		    break;
 		}
+		if (is_new)
+		{
+		    // A return type should not be specified for the new()
+		    // constructor method.
+		    if (uf->uf_ret_type->tt_type != VAR_VOID)
+		    {
+			emsg(_(e_cannot_use_a_return_type_with_new));
+			success = FALSE;
+			func_clear_free(uf, FALSE);
+			break;
+		    }
+		}
 		garray_T *fgap = has_static || is_new
 					       ? &classfunctions : &objmethods;
 		// Check the name isn't used already.
@@ -1303,15 +1315,22 @@ early_ret:
 	if (is_class && cl->class_class_member_count > 0)
 	    add_class_members(cl, eap);
 
-	int have_new = FALSE;
+	int	have_new = FALSE;
+	ufunc_T	*class_func = NULL;
 	for (int i = 0; i < classfunctions.ga_len; ++i)
-	    if (STRCMP(((ufunc_T **)classfunctions.ga_data)[i]->uf_name,
-								   "new") == 0)
+	{
+	    class_func = ((ufunc_T **)classfunctions.ga_data)[i];
+	    if (STRCMP(class_func->uf_name, "new") == 0)
 	    {
 		have_new = TRUE;
 		break;
 	    }
-	if (is_class && !is_abstract && !have_new)
+	}
+
+	if (have_new)
+	    // The return type of new() is an object of class "cl"
+	    class_func->uf_ret_type->tt_class = cl;
+	else if (is_class && !is_abstract && !have_new)
 	    // No new() method was defined, add the default constructor.
 	    add_default_constructor(cl, &classfunctions, &type_list);
 

src/vim9cmds.c

@@ -2617,8 +2617,16 @@ compile_return(char_u *arg, int check_return_type, int legacy, cctx_T *cctx)
 	    return NULL;
 	}
 
-	// No argument, return zero.
-	generate_PUSHNR(cctx, 0);
+	if (cctx->ctx_ufunc->uf_flags & FC_NEW)
+	{
+	    // For a class new() constructor, return an object of the class.
+	    generate_instr(cctx, ISN_RETURN_OBJECT);
+	    cctx->ctx_ufunc->uf_ret_type =
+		&cctx->ctx_ufunc->uf_class->class_object_type;
+	}
+	else
+	    // No argument, return zero.
+	    generate_PUSHNR(cctx, 0);
     }
 
     // may need ENDLOOP when inside a :for or :while loop