diff --git a/crates/fuse-ast/src/ast.rs b/crates/fuse-ast/src/ast.rs
index 01ac54d..9a7f79d 100644
--- a/crates/fuse-ast/src/ast.rs
+++ b/crates/fuse-ast/src/ast.rs
@@ -1,4 +1,4 @@
-use fuse_common::Span;
+use fuse_common::{ReferenceId, Span};
 use fuse_common_proc::serializable;
 use std::{cell::Cell, rc::Rc};
 
@@ -94,7 +94,7 @@ pub struct TypeAnnotation {
 }
 
 #[serializable]
-#[derive(Debug, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Atom(pub Rc<str>);
 
 #[serializable]
@@ -188,10 +188,6 @@ pub struct Identifier {
     pub reference: Cell<Option<ReferenceId>>,
 }
 
-#[serializable]
-#[derive(Debug, PartialEq, Clone, Copy)]
-pub struct ReferenceId(u32);
-
 #[serializable]
 #[derive(Debug, PartialEq)]
 pub struct Function {
diff --git a/crates/fuse-ast/src/visit.rs b/crates/fuse-ast/src/visit.rs
index 6a50c36..d6cb5fd 100644
--- a/crates/fuse-ast/src/visit.rs
+++ b/crates/fuse-ast/src/visit.rs
@@ -19,7 +19,19 @@ macro_rules! visit_list {
     };
 }
 
+macro_rules! visit_scope {
+    ($visitor:ident => $block:block) => {
+        $visitor.enter_scope();
+        $block
+        $visitor.leave_scope();
+    };
+}
+
 pub trait Visitor<'ast>: Sized {
+    fn enter_scope(&mut self) {}
+
+    fn leave_scope(&mut self) {}
+
     fn visit_chunk(&mut self, chunk: &'ast Chunk) {
         walk_block(self, &chunk.body)
     }
@@ -164,7 +176,9 @@ pub trait Visitor<'ast>: Sized {
 }
 
 pub fn walk_block<'ast, V: Visitor<'ast>>(visitor: &mut V, block: &'ast Block) {
-    visit_list!(visitor.visit_statement(&block.statements))
+    visit_scope!(visitor => {
+        visit_list!(visitor.visit_statement(&block.statements));
+    });
 }
 
 pub fn walk_statement<'ast, V: Visitor<'ast>>(visitor: &mut V, statement: &'ast Statement) {
@@ -216,8 +230,10 @@ pub fn walk_expression<'ast, V: Visitor<'ast>>(visitor: &mut V, expression: &'as
 }
 
 pub fn walk_function<'ast, V: Visitor<'ast>>(visitor: &mut V, func: &'ast Function) {
-    visit!(visitor.visit_function_signature(&func.signature));
-    visit!(visitor.visit_function_body(&func.body));
+    visit_scope!(visitor => {
+        visit!(visitor.visit_function_signature(&func.signature));
+        visit!(visitor.visit_function_body(&func.body));
+    });
 }
 
 pub fn walk_function_signature<'ast, V: Visitor<'ast>>(
@@ -260,8 +276,10 @@ pub fn walk_function_body<'ast, V: Visitor<'ast>>(visitor: &mut V, body: &'ast F
 }
 
 pub fn walk_enum_declaration<'ast, V: Visitor<'ast>>(visitor: &mut V, decl: &'ast EnumDeclaration) {
-    visit!(visitor.visit_identifier(&decl.identifier));
-    visit_list!(visitor.visit_enum_variant(&decl.variants));
+    visit_scope!(visitor => {
+        visit!(visitor.visit_identifier(&decl.identifier));
+        visit_list!(visitor.visit_enum_variant(&decl.variants));
+    });
 }
 
 pub fn walk_enum_variant<'ast, V: Visitor<'ast>>(visitor: &mut V, var: &'ast EnumVariant) {
@@ -275,8 +293,10 @@ pub fn walk_struct_declaration<'ast, V: Visitor<'ast>>(
     visitor: &mut V,
     decl: &'ast StructDeclaration,
 ) {
-    visit!(visitor.visit_identifier(&decl.identifier));
-    visit_list!(visitor.visit_struct_field(&decl.fields));
+    visit_scope!(visitor => {
+        visit!(visitor.visit_identifier(&decl.identifier));
+        visit_list!(visitor.visit_struct_field(&decl.fields));
+    });
 }
 
 pub fn walk_struct_field<'ast, V: Visitor<'ast>>(visitor: &mut V, decl: &'ast StructField) {
@@ -286,18 +306,22 @@ pub fn walk_struct_field<'ast, V: Visitor<'ast>>(visitor: &mut V, decl: &'ast St
 }
 
 pub fn walk_if<'ast, V: Visitor<'ast>>(visitor: &mut V, r#if: &'ast If) {
-    visit!(visitor.visit_expression(&r#if.cond));
-    visit!(visitor.visit_block(&r#if.body));
-    if let Some(r#else) = &r#if.r#else {
-        visit!(visitor.visit_else(r#else));
-    }
+    visit_scope!(visitor => {
+        visit!(visitor.visit_expression(&r#if.cond));
+        visit!(visitor.visit_block(&r#if.body));
+        if let Some(r#else) = &r#if.r#else {
+            visit!(visitor.visit_else(r#else));
+        }
+    });
 }
 
 pub fn walk_else<'ast, V: Visitor<'ast>>(visitor: &mut V, r#else: &'ast Else) {
-    match r#else {
-        Else::If(r#if) => visit!(visitor.visit_if(r#if)),
-        Else::Block(block) => visit!(visitor.visit_block(block)),
-    }
+    visit_scope!(visitor => {
+        match r#else {
+            Else::If(r#if) => visit!(visitor.visit_if(r#if)),
+            Else::Block(block) => visit!(visitor.visit_block(block)),
+        }
+    });
 }
 
 pub fn walk_unary_operator<'ast, V: Visitor<'ast>>(visitor: &mut V, op: &'ast UnaryOperator) {
diff --git a/crates/fuse-common/src/lib.rs b/crates/fuse-common/src/lib.rs
index 398b34b..df4960b 100644
--- a/crates/fuse-common/src/lib.rs
+++ b/crates/fuse-common/src/lib.rs
@@ -4,3 +4,5 @@ mod debug;
 
 pub use span::*;
 pub use span_view::*;
+
+pub type ReferenceId = usize;
diff --git a/crates/fuse-semantic/src/lib.rs b/crates/fuse-semantic/src/lib.rs
index b25970b..2bcf6b1 100644
--- a/crates/fuse-semantic/src/lib.rs
+++ b/crates/fuse-semantic/src/lib.rs
@@ -1,12 +1,135 @@
-use fuse_ast::Chunk;
+use std::collections::HashMap;
 
-pub struct Semantic<'a> {
-    source: &'a str,
-    chunk: Chunk,
+use fuse_ast::{
+    walk_binding_pattern, walk_variable_declaration, Atom, BindingPattern, BindingPatternKind,
+    Chunk, Identifier, VariableDeclaration, Visitor,
+};
+use fuse_common::ReferenceId;
+
+type ScopeId = ReferenceId;
+
+struct IdentifierMap(HashMap<Atom, ReferenceId>);
+
+impl IdentifierMap {
+    fn new() -> Self {
+        Self(HashMap::new())
+    }
+
+    fn insert(&mut self, atom: Atom, ref_id: ReferenceId) {
+        debug_assert!(!self.0.contains_key(&atom));
+        self.0.insert(atom, ref_id);
+    }
+}
+
+struct ScopeTree {
+    current: ScopeId,
+    identifier_maps: Vec<IdentifierMap>,
+    parent_ids: Vec<ScopeId>,
+}
+
+impl ScopeTree {
+    fn root_scope() -> Self {
+        Self {
+            current: 0,
+            parent_ids: vec![0],
+            identifier_maps: vec![IdentifierMap::new()],
+        }
+    }
+
+    fn push_stack(&mut self) -> ScopeId {
+        self.identifier_maps.push(IdentifierMap::new());
+        self.parent_ids.push(self.current);
+
+        let scope_id = self.identifier_maps.len() - 1;
+
+        // length of all arrays should be same.
+        debug_assert!(self.identifier_maps.len() == self.parent_ids.len());
+        self.current = scope_id;
+        scope_id
+    }
+
+    fn pop_stack(&mut self) {
+        assert_ne!(
+            self.current, 0,
+            "Attempt to pop the root scope from the stack."
+        );
+
+        self.current = self.parent();
+    }
+
+    fn push_identifier(&mut self, atom: Atom, ref_id: ReferenceId) {
+        self.identifier_maps[self.current].insert(atom, ref_id);
+    }
+
+    fn parent(&self) -> ScopeId {
+        assert_ne!(
+            self.current, 0,
+            "Attempt to access the root scope's parent."
+        );
+        self.parent_ids[self.current]
+    }
+}
+
+pub struct Semantic<'ast> {
+    source: &'ast str,
+    chunk: &'ast Chunk,
+    scope: ScopeTree,
+    last_reference: ReferenceId,
+}
+
+impl<'ast> Semantic<'ast> {
+    pub fn new(source: &'ast str, chunk: &'ast Chunk) -> Self {
+        Self {
+            source,
+            chunk,
+            scope: ScopeTree::root_scope(),
+            last_reference: 0,
+        }
+    }
+
+    pub fn build(mut self) {
+        self.visit_chunk(&self.chunk)
+    }
+
+    fn reference_identifier(&mut self, ident: &Identifier) {
+        self.last_reference += 1;
+        self.scope
+            .push_identifier(ident.name.clone(), self.last_reference);
+        ident.reference.set(Some(self.last_reference))
+    }
 }
 
-impl<'a> Semantic<'a> {
-    pub fn new(source: &'a str, chunk: Chunk) -> Self {
-        Self { source, chunk }
+impl<'ast> Visitor<'ast> for Semantic<'ast> {
+    fn enter_scope(&mut self) {
+        println!("IN");
+        self.scope.push_stack();
+    }
+
+    fn leave_scope(&mut self) {
+        println!("OUT");
+        self.scope.pop_stack();
+    }
+
+    fn visit_identifier(&mut self, ident: &Identifier) {
+        println!("{ident:?}")
+    }
+
+    fn visit_variable_declaration(&mut self, decl: &'ast VariableDeclaration) {
+        match &decl.binding.kind {
+            BindingPatternKind::Identifier(bind) => self.reference_identifier(&bind.identifier),
+            _ => todo!(),
+        }
+
+        walk_variable_declaration(self, decl)
+    }
+
+    fn visit_binding_pattern(&mut self, pattern: &'ast BindingPattern) {
+        match &pattern.kind {
+            BindingPatternKind::Identifier(ident) => {
+                println!("{ident:?}")
+            }
+            _ => {}
+        }
+        walk_binding_pattern(self, pattern)
     }
 }
diff --git a/crates/fusec/src/lib.rs b/crates/fusec/src/lib.rs
index 029efeb..3795074 100644
--- a/crates/fusec/src/lib.rs
+++ b/crates/fusec/src/lib.rs
@@ -3,7 +3,8 @@ use fuse_semantic::Semantic;
 
 fn compile_chunk(source: &str) {
     let parsed = Parser::new(source).parse();
-    let semantic = Semantic::new(source, parsed.chunk.unwrap());
+    let semantic = Semantic::new(source, &parsed.chunk.unwrap()).build();
+    // panic!()
 }
 
 #[test]