add (commented-out) problematic multiple-nested struct test-case

vlib/toml/tests/encode_and_decode_test.v

@@ -15,6 +15,11 @@ struct Pet {
 	has_furr  bool
 	title     JobTitle
 	address   Address
+	// *¹ Currently it is only possible to decode a single nested struct generically.
+	// As soon as we decode another nested struct (e.g. within this struct, like `contact` below)
+	// or only one nested struct within another struct, it results in wrong values or errors.
+	// Related issue: https://github.com/vlang/v/issues/18110
+	// contact Contact
 }
 
 struct Address {
@@ -22,6 +27,12 @@ struct Address {
 	city   string
 }
 
+// *¹
+/*
+struct Contact {
+	phone string
+}*/
+
 struct Employee {
 mut:
 	name     string
@@ -45,6 +56,8 @@ struct Arrs {
 }
 
 fn test_encode_and_decode() {
+	// *¹
+	// p := Pet{'Mr. Scratchy McEvilPaws', ['Freddy', 'Fred', 'Charles'], 8, -1, 0.8, true, .manager, Address{'1428 Elm Street', 'Springwood'}, Contact{'123-456-7890'}}
 	p := Pet{'Mr. Scratchy McEvilPaws', ['Freddy', 'Fred', 'Charles'], 8, -1, 0.8, true, .manager, Address{'1428 Elm Street', 'Springwood'}}
 	s := 'name = "Mr. Scratchy McEvilPaws"
 nicknames = [
@@ -58,6 +71,7 @@ height = 0.8
 has_furr = true
 title = 2
 address = { street = "1428 Elm Street", city = "Springwood" }'
+	// contact = { phone = "123-456-7890" }' // *¹
 
 	assert toml.encode[Pet](p) == s
 	assert toml.decode[Pet](s)! == p