Update cycle error message

docs/lazy-definitions.md

@@ -17,7 +17,7 @@ Nat.add = (Y λaddλaλb match a {
 main = (Nat.add (S (S (S Z))) (S Z))
 ```
 
-Because of that, is recommended to use [supercombinator](https://en.wikipedia.org/wiki/Supercombinator) formulation to make terms be unrolled lazily, preventing infinite expansion in recursive function bodies.
+Because of that, its recommended to use a [supercombinator](https://en.wikipedia.org/wiki/Supercombinator) formulation to make terms be unrolled lazily, preventing infinite expansion in recursive function bodies.
 
 The `Nat.add` definition below can be a supercombinator if linearized.
 

src/hvmc_net/mutual_recursion.rs

@@ -30,7 +30,10 @@ fn pretty_print_cycles(cycles: &[Vec<Ref>]) -> String {
   cycles
     .iter()
     .enumerate()
-    .map(|(i, cycles)| format!("Cycle {}: {}", 1 + i, cycles.join(" -> ")))
+    .map(|(i, cycle)| {
+      let cycle_str = cycle.iter().chain(cycle.first()).cloned().collect::<Vec<_>>().join(" -> ");
+      format!("Cycle {}: {}", 1 + i, cycle_str)
+    })
     .collect::<Vec<String>>()
     .join("\n")
 }

tests/golden_tests/mutual_recursion/multiple.hvm

@@ -5,7 +5,8 @@
 (H) = (I)
 (I) = (H)
 
-(M) = (N)
-(N) = (M)
+(N x) = (x (N x))
+
+(M) = (M)
 
 (Main) = *

tests/snapshots/mutual_recursion__a_b_c.hvm.snap

@@ -3,6 +3,6 @@ source: tests/golden_tests.rs
 input_file: tests/golden_tests/mutual_recursion/a_b_c.hvm
 ---
 Mutual recursion cycle detected in compiled functions:
-Cycle 1: A -> B -> C
+Cycle 1: A -> B -> C -> A
 This program will expand infinitely in strict evaluation mode.
 Read https://github.com/HigherOrderCO/hvm-lang/blob/main/docs/lazy-definitions.md for more information.

tests/snapshots/mutual_recursion__multiple.hvm.snap

@@ -3,8 +3,9 @@ source: tests/golden_tests.rs
 input_file: tests/golden_tests/mutual_recursion/multiple.hvm
 ---
 Mutual recursion cycle detected in compiled functions:
-Cycle 1: A -> B -> C
-Cycle 2: H -> I
-Cycle 3: M -> N
+Cycle 1: A -> B -> C -> A
+Cycle 2: H -> I -> H
+Cycle 3: M -> M
+Cycle 4: N -> N
 This program will expand infinitely in strict evaluation mode.
 Read https://github.com/HigherOrderCO/hvm-lang/blob/main/docs/lazy-definitions.md for more information.

tests/snapshots/mutual_recursion__odd_even.hvm.snap

@@ -3,6 +3,6 @@ source: tests/golden_tests.rs
 input_file: tests/golden_tests/mutual_recursion/odd_even.hvm
 ---
 Mutual recursion cycle detected in compiled functions:
-Cycle 1: isEven -> isOdd
+Cycle 1: isEven -> isOdd -> isEven
 This program will expand infinitely in strict evaluation mode.
 Read https://github.com/HigherOrderCO/hvm-lang/blob/main/docs/lazy-definitions.md for more information.