From b27fcf38e53cff280c364c356ccbeb8cd7d73caf Mon Sep 17 00:00:00 2001
From: rvcas <x@rvcas.dev>
Date: Tue, 2 Apr 2024 19:45:16 -0400
Subject: [PATCH] fix(check): collapse_links on tuple_index access closes #905

---
 crates/aiken-lang/src/tests/check.rs | 21 +++++++++++++++++++++
 crates/aiken-lang/src/tipo/expr.rs   |  2 +-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/crates/aiken-lang/src/tests/check.rs b/crates/aiken-lang/src/tests/check.rs
index 865f83f0..a188efc4 100644
--- a/crates/aiken-lang/src/tests/check.rs
+++ b/crates/aiken-lang/src/tests/check.rs
@@ -2274,3 +2274,24 @@ fn validator_private_everything() {
 
     assert!(check_validator(parse(source_code)).is_ok())
 }
+
+#[test]
+fn tuple_access_on_call() {
+    let source_code = r#"
+        use aiken/builtin
+
+        pub fn list_at(xs: List<a>, index: Int) -> a {
+          if index == 0 {
+            builtin.head_list(xs)
+          } else {
+            list_at(builtin.tail_list(xs), index - 1)
+          }
+        }
+
+        fn foo() {
+          [list_at([(1, 2)], 0).2nd, ..[1, 2]]
+        }
+    "#;
+
+    assert!(check(parse(source_code)).is_ok())
+}
diff --git a/crates/aiken-lang/src/tipo/expr.rs b/crates/aiken-lang/src/tipo/expr.rs
index 8875506a..7aa932f9 100644
--- a/crates/aiken-lang/src/tipo/expr.rs
+++ b/crates/aiken-lang/src/tipo/expr.rs
@@ -2045,7 +2045,7 @@ impl<'a, 'b> ExprTyper<'a, 'b> {
     ) -> Result<TypedExpr, Error> {
         let tuple = self.infer(tuple)?;
 
-        let tipo = match *tuple.tipo() {
+        let tipo = match *collapse_links(tuple.tipo()) {
             Type::Tuple {
                 ref elems,
                 alias: _,