gen: fix interface pointers

vlib/v/gen/cgen.v

@@ -3660,6 +3660,14 @@ _Interface I_${cctype}_to_Interface_${interface_name}(${cctype}* x) {
 		._object = (void*) (x),
 		._interface_idx = ${interface_index_name}
 	};
+}
+
+_Interface* I_${cctype}_to_Interface_${interface_name}_ptr(${cctype}* x) {
+	/* TODO Remove memdup */
+	return (_Interface*) memdup(&(_Interface) {
+		._object = (void*) (x),
+		._interface_idx = ${interface_index_name}
+	}, sizeof(_Interface));
 }')
 			methods_struct.writeln('\t{')
 			st_sym := g.table.get_type_symbol(st)
@@ -3766,7 +3774,11 @@ fn (mut g Gen) array_init(it ast.ArrayInit) {
 fn (g &Gen) interface_call(typ, interface_type table.Type) {
 	interface_styp := g.cc_type(interface_type)
 	styp := g.cc_type(typ)
-	g.write('/* $interface_styp */ I_${styp}_to_Interface_${interface_styp}(')
+	mut cast_fn_name := 'I_${styp}_to_Interface_${interface_styp}'
+	if interface_type.is_ptr() {
+		cast_fn_name += '_ptr'
+	}
+	g.write('${cast_fn_name}(')
 	if !typ.is_ptr() {
 		g.write('&')
 	}

vlib/v/gen/fn.v

@@ -298,9 +298,10 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 		// Speaker_name_table[s._interface_idx].speak(s._object)
 		g.write('${c_name(receiver_type_name)}_name_table[')
 		g.expr(node.left)
-		g.write('._interface_idx].${node.name}(')
+		dot := if node.left_type.is_ptr() { '->' } else { '.' }
+		g.write('${dot}_interface_idx].${node.name}(')
 		g.expr(node.left)
-		g.write('._object')
+		g.write('${dot}_object')
 		if node.args.len > 0 {
 			g.write(', ')
 			g.call_args(node.args, node.expected_arg_types)
@@ -554,11 +555,14 @@ fn (mut g Gen) call_args(args []ast.CallArg, expected_types []table.Type) {
 				// styp := g.typ(arg.typ) // g.table.get_type_symbol(arg.typ)
 				if exp_sym.kind == .interface_ {
 					g.interface_call(arg.typ, expected_types[i])
-					// g.write('/*Z*/I_${styp}_to_${exp_styp}(')
 					is_interface = true
 				}
 			}
+			if is_interface {
+				g.expr(arg.expr)
+			} else {
 				g.ref_or_deref_arg(arg, expected_types[i])
+			}
 		} else {
 			g.expr(arg.expr)
 		}

vlib/v/tests/interface_test.v

@@ -3,6 +3,7 @@ struct Dog {
 }
 
 struct Cat {
+mut:
 	breed string
 }
 
@@ -25,6 +26,10 @@ fn (c Cat) name_detailed(pet_name string) string {
 	return '$pet_name the ${typeof(c)}, breed:${c.breed}'
 }
 
+fn (c mut Cat) set_breed(new string) {
+	c.breed = new
+}
+
 // utility function to convert to string, as a sample
 fn (c Cat) str() string {
 	return 'Cat: $c.breed'
@@ -44,6 +49,10 @@ fn (d Dog) name_detailed(pet_name string) string {
 	return '$pet_name the ${typeof(d)}, breed:${d.breed}'
 }
 
+fn (d mut Dog) set_breed(new string) {
+	println('Nah')
+}
+
 // do not add to Dog the utility function 'str', as a sample
 fn test_todo() {
 	if true {
@@ -62,11 +71,23 @@ fn perform_speak(a Animal) {
 	println(a.name())
 }
 
+fn perform_speak_on_ptr(a &Animal) {
+	a.speak('Hi !')
+	assert true
+	name := a.name()
+	assert name == 'Dog' || name == 'Cat'
+	// if a is Dog {
+	// assert name == 'Dog'
+	// }
+	println(a.name())
+}
+
 fn test_perform_speak() {
 	dog := Dog{
 		breed: 'Labrador Retriever'
 	}
 	perform_speak(dog)
+	perform_speak_on_ptr(dog)
 	cat := Cat{
 		breed: 'Persian'
 	}
@@ -74,6 +95,10 @@ fn test_perform_speak() {
 	perform_speak(Cat{
 		breed: 'Persian'
 	})
+	perform_speak_on_ptr(cat)
+	perform_speak_on_ptr(Cat{
+		breed: 'Persian'
+	})
 	handle_animals([dog, cat])
 	/*
 	f := Foo {
@@ -82,6 +107,19 @@ fn test_perform_speak() {
 	*/
 }
 
+fn change_animal_breed(a &Animal, new string) {
+	a.set_breed(new)
+}
+
+fn test_interface_ptr_modification() {
+	mut cat := Cat{
+		breed: 'Persian'
+	}
+	// TODO Should fail and require `mut cat`
+	change_animal_breed(cat, 'Siamese')
+	assert cat.breed == 'Siamese'
+}
+
 fn perform_name_detailed(a Animal) {
 	name_full := a.name_detailed('MyPet')
 	println(name_full)
@@ -142,6 +180,7 @@ interface Animal {
 	name() string
 	name_detailed(pet_name string) string
 	speak(s string)
+	set_breed(s string)
 }
 
 fn test_interface_array() {
@@ -150,6 +189,7 @@ fn test_interface_array() {
 	animals = [Cat{}, Dog{
 		breed: 'Labrador Retriever'
 	}]
+	assert true
 	animals << Cat{}
 	assert true
 	// TODO .str() from the real types should be called
@@ -157,3 +197,14 @@ fn test_interface_array() {
 	// println('Animals array contains: ${animals}') // implicit call to 'str' function
 	assert animals.len == 3
 }
+
+fn test_interface_ptr_array() {
+	mut animals := []&Animal{}
+	animals = [Cat{}, Dog{
+		breed: 'Labrador Retriever'
+	}]
+	assert true
+	animals << Cat{}
+	assert true
+	assert animals.len == 3
+}