change the .vv sample with a more lightweight one, update the .out fi…

…le for it

vlib/v/checker/tests/struct_implements_interface_more_than_once_err.out

@@ -1,7 +1,14 @@
-vlib/v/checker/tests/struct_implements_interface_more_than_once_err.vv:4:35: error: struct type Walker cannot implement interface `v.ast.walker.Visitor more than once`
-    2 | import v.ast { Node }
-    3 | 
-    4 | struct Walker implements Visitor, Visitor, Visitor {
-      |                                   ~~~~~~~
-    5 |     aaa string
-    6 | }
+vlib/v/checker/tests/struct_implements_interface_more_than_once_err.vv:3:31: error: struct type Abc cannot implement interface `io.Writer more than once`
+    1 | import io { Writer }
+    2 | 
+    3 | struct Abc implements Writer, Writer, Writer {
+      |                               ~~~~~~
+    4 |     aaa string
+    5 | }
+vlib/v/checker/tests/struct_implements_interface_more_than_once_err.vv:12:31: error: struct type Def cannot implement interface `io.Writer more than once`
+   10 | 
+   11 | // vfmt off
+   12 | struct Def implements Writer, io.Writer {
+      |                               ~~
+   13 |     aaa string
+   14 | }

vlib/v/checker/tests/struct_implements_interface_more_than_once_err.vv

@@ -1,10 +1,19 @@
-import v.ast.walker { Visitor }
-import v.ast { Node }
+import io { Writer }
 
-struct Walker implements Visitor, Visitor, Visitor {
+struct Abc implements Writer, Writer, Writer {
 	aaa string
 }
 
-fn (mut n Walker) visit(node &Node) ! {
-	panic('not implemented')
+fn (a Abc) write(buf []u8) !int {
+	return 42
+}
+
+// vfmt off
+struct Def implements Writer, io.Writer {
+	aaa string
+}
+// vfmt on
+
+fn (a Def) write(buf []u8) !int {
+	return 42
 }