tests: add more generic structs tests (#10095)

vlib/v/tests/generics_return_inconsistent_types_generics_struct_test.v

@@ -0,0 +1,97 @@
+// test generics function that return generics struct
+pub struct Optional<T> {
+mut:
+	value T
+	some  bool
+	typ   string
+}
+
+pub fn new_some<T, B>(value T, b B) Optional<T> {
+	return {
+		value: value
+		some: true
+		typ: typeof(b).name
+	}
+}
+
+pub fn some<T>(opt Optional<T>) bool {
+	return opt.some
+}
+
+pub fn get_value<T>(opt Optional<T>) T {
+	return opt.value
+}
+
+pub fn get_typ<T>(opt Optional<T>) string {
+	return opt.typ
+}
+
+pub fn set<T, B>(mut opt Optional<T>, value T, b B) {
+	opt.value = value
+	opt.some = true
+	opt.typ = typeof(b).name
+}
+
+fn test_inconsistent_types_generics_fn_return_generics_struct() {
+	mut o := new_some<int, string>(23, 'aaa')
+	println(some<int>(o))
+	assert some<int>(o) == true
+
+	println(get_value<int>(o))
+	assert get_value<int>(o) == 23
+
+	set<int, string>(mut o, 42, 'aaa')
+	println(get_value<int>(o))
+	assert get_value<int>(o) == 42
+
+	println(get_typ<int>(o))
+	assert get_typ<int>(o) == 'string'
+}
+
+// test generics method that return generics struct
+pub struct Foo {
+	foo int
+}
+
+pub fn (f Foo) new_some<T, B>(value T, b B) Optional<T> {
+	return {
+		value: value
+		some: true
+		typ: typeof(b).name
+	}
+}
+
+pub fn (f Foo) some<T>(opt Optional<T>) bool {
+	return opt.some
+}
+
+pub fn (f Foo) get_value<T>(opt Optional<T>) T {
+	return opt.value
+}
+
+pub fn (f Foo) get_typ<T>(opt Optional<T>) string {
+	return opt.typ
+}
+
+pub fn (f Foo) set<T, B>(mut opt Optional<T>, value T, b B) {
+	opt.value = value
+	opt.some = true
+	opt.typ = typeof(b).name
+}
+
+fn test_inconstent_types_generics_method_return_generics_struct() {
+	foo := Foo{}
+	mut o := foo.new_some<int, string>(23, 'aaa')
+	println(foo.some<int>(o))
+	assert foo.some<int>(o) == true
+
+	println(foo.get_value<int>(o))
+	assert foo.get_value<int>(o) == 23
+
+	foo.set<int, string>(mut o, 42, 'aaa')
+	println(foo.get_value<int>(o))
+	assert foo.get_value<int>(o) == 42
+
+	println(foo.get_typ<int>(o))
+	assert foo.get_typ<int>(o) == 'string'
+}