diff --git a/src/lib.rs b/src/lib.rs
index 5f09888..ea71efa 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,148 +1,22 @@
-pub fn process_ast(program: &str, ast: &Program) {
-    dbg(ast);
+pub fn foo(parent: Parent<'_>) {
+    requires_parent_fulfill_trait(parent);
 }
 
-pub fn dbg(x: impl dbg_pls::DebugPls) {
-    eprintln!("{}", dbg_pls::pretty(&x))
+pub fn requires_parent_fulfill_trait(_: impl dbg_pls::DebugPls) {}
+
+#[derive(dbg_pls::DebugPls)]
+pub enum Parent<'a> {
+    A(&'a A<'a>),
+    B(&'a B<'a>),
+}
+
+
+#[derive(dbg_pls::DebugPls)]
+pub struct A<'a> {
+    parent: Parent<'a>,
 }
 
 #[derive(dbg_pls::DebugPls)]
-pub struct Span {
-    pub start: usize,
-    pub end: usize,
-}
-
-type Symbol = usize;
-
-#[derive(dbg_pls::DebugPls)]
-pub struct Ident {
-    pub sym: Symbol,
-    pub span: Span,
-}
-
-pub type Program<'ast> = Block<'ast>;
-
-#[derive(dbg_pls::DebugPls)]
-pub struct Block<'ast> {
-    pub stmts: &'ast [Stmt<'ast>],
-    pub span: Span,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum Stmt<'ast> {
-    FnDecl(FnDecl<'ast>),
-    Loop(Block<'ast>, Span),
-    While(WhileStmt<'ast>),
-    Break(Span),
-    Return(Option<Expr<'ast>>, Span),
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub struct FnDecl<'ast> {
-    pub span: Span,
-    pub name: Ident,
-    pub params: &'ast [Ident],
-    pub body: Block<'ast>,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub struct WhileStmt<'ast> {
-    pub span: Span,
-    pub cond: Expr<'ast>,
-    pub body: Block<'ast>,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum Expr<'ast> {
-    Ident(Ident),
-    Literal(Literal<'ast>),
-    UnaryOp(&'ast UnaryOp<'ast>),
-    BinaryOp(&'ast BinaryOp<'ast>),
-    Call(&'ast Call<'ast>),
-}
-
-impl Expr<'_> {
-    pub fn span(&self) -> Span {
-        match self {
-            Expr::Literal(lit) => lit.span(),
-            Expr::UnaryOp(unary) => unary.span,
-            Expr::BinaryOp(binary) => binary.span,
-            Expr::Ident(Ident { span, .. }) => *span,
-            Expr::Call(call) => call.span,
-        }
-    }
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum Literal<'ast> {
-    String(Symbol, Span),
-    Number(f64, Span),
-    Array(&'ast [Expr<'ast>], Span),
-    Object(Span),
-    Boolean(bool, Span),
-    Null(Span),
-}
-
-impl Literal<'_> {
-    pub fn span(&self) -> Span {
-        match self {
-            Literal::String(_, span)
-            | Literal::Number(_, span)
-            | Literal::Array(_, span)
-            | Literal::Object(span)
-            | Literal::Boolean(_, span)
-            | Literal::Null(span) => *span,
-        }
-    }
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub struct UnaryOp<'ast> {
-    pub span: Span,
-    pub expr: Expr<'ast>,
-    pub kind: UnaryOpKind,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum UnaryOpKind {
-    Not,
-    Neg,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub struct BinaryOp<'ast> {
-    pub span: Span,
-    pub lhs: Expr<'ast>,
-    pub rhs: Expr<'ast>,
-    pub kind: BinaryOpKind,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum BinaryOpKind {
-    And,
-    Or,
-    Equal,
-    GreaterEqual,
-    Greater,
-    LessEqual,
-    Less,
-    NotEqual,
-    Add,
-    Sub,
-    Mul,
-    Div,
-    Mod,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub struct Call<'ast> {
-    pub callee: Expr<'ast>,
-    pub span: Span,
-    pub kind: CallKind<'ast>,
-}
-
-#[derive(dbg_pls::DebugPls)]
-pub enum CallKind<'ast> {
-    Field(Ident),
-    Fn(&'ast [Expr<'ast>]),
+pub struct B<'a> {
+    parent: Parent<'a>,
 }