diff --git a/src/twopass.rs b/src/twopass.rs
index bf6692c..a8ec575 100644
--- a/src/twopass.rs
+++ b/src/twopass.rs
@@ -128,7 +128,12 @@ fn lookup(scope: &BuildContext<'_>, loc: &ast::Location) -> Location {
 }
 
 fn build_expression(scope: &BuildContext<'_>, code: &ast::Expression) -> Expression {
-	todo!()
+	match code {
+		ast::Expression::Constant(c) => Expression::Constant(c.clone()),
+		ast::Expression::Variable(loc) => Expression::Variable(lookup(scope, loc)),
+		ast::Expression::Call(call) => Expression::Call(build_call(scope, call)),
+		ast::Expression::Function(f) => Expression::Function(build_in_scope(scope, f)),
+	}
 }
 
 fn build_call(scope: &BuildContext<'_>, code: &ast::Call) -> Call {