docs: add a note on initializing structs with reference fields (#7913)

doc/docs.md

@@ -2737,6 +2737,42 @@ surrounding code).
 
 * Note: This is work in progress.
 
+### Structs with reference fields
+
+Structs with references require explicitly setting the initial value to a
+reference value unless the struct already defines its own initial value.
+
+Zero-value references, or nil pointers, will **NOT** be supported in the future,
+for now data structures such as Linked Lists or Binary Trees that rely on reference
+fields that can use the value `0`, understanding that it is unsafe, and that it can
+cause a panic.
+
+```v
+struct Node {
+	a &Node
+	b &Node = 0 // Auto-initialized to nil, use with caution!
+}
+
+// Reference fields must be initialized unless an initial value is declared.
+// Zero (0) is OK but use with caution, it's a nil pointer.
+foo := Node{
+	a: 0
+}
+bar := Node{
+	a: &foo
+}
+baz := Node{
+	a: 0
+	b: 0
+}
+qux := Node{
+	a: &foo
+	b: &bar
+}
+println(baz)
+println(qux)
+```
+
 ## Calling C functions from V
 
 ```v