Update cycle error message

cspell.json

@@ -36,6 +36,7 @@
     "interner",
     "itertools",
     "lcons",
+    "linearization",
     "linearizes",
     "linearizing",
     "lnet",

docs/lazy-definitions.md

@@ -40,7 +40,7 @@ This code will work as expected, because `Nat.add` is unrolled lazily only when
 
 ### Automatic optimization
 
-HVM-lang carries out [match linearization](compiler-options#linearize-matches) and [combinator floating](compiler-options#float-combinators) optimizations, enabled through the CLI, which is active by default in strict mode.
+HVM-lang carries out [match linearization](compiler-options#linearize-matches) and [combinator floating](compiler-options#float-combinators) optimizations, enabled through the CLI, which are active by default in strict mode.
 
 Consider the code below:
 

src/hvmc_net/mutual_recursion.rs

@@ -13,7 +13,17 @@ pub fn check_cycles(book: &Book) -> Result<(), String> {
   let graph = Graph::from(book);
   let cycles = graph.cycles();
 
-  if cycles.is_empty() { Ok(()) } else { Err(pretty_print_cycles(&cycles)) }
+  if cycles.is_empty() {
+    Ok(())
+  } else {
+    Err(format!(
+      "{}\n{}\n{}\n{}",
+      "Mutual recursion cycle detected in compiled funcions:",
+      pretty_print_cycles(&cycles),
+      "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."
+    ))
+  }
 }
 
 fn pretty_print_cycles(cycles: &[Vec<Ref>]) -> String {

tests/golden_tests/mutual_recursion/multiple.hvm

@@ -0,0 +1,11 @@
+(A) = (B)
+(B) = (C)
+(C) = (A)
+
+(H) = (I)
+(I) = (H)
+
+(M) = (N)
+(N) = (M)
+
+(Main) = *

tests/snapshots/mutual_recursion__a_b_c.hvm.snap

@@ -2,4 +2,7 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/mutual_recursion/a_b_c.hvm
 ---
+Mutual recursion cycle detected in compiled funcions:
 Cycle 1: A -> B -> C
+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

@@ -0,0 +1,10 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/mutual_recursion/multiple.hvm
+---
+Mutual recursion cycle detected in compiled funcions:
+Cycle 1: A -> B -> C
+Cycle 2: H -> I
+Cycle 3: M -> 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

@@ -2,4 +2,7 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/mutual_recursion/odd_even.hvm
 ---
+Mutual recursion cycle detected in compiled funcions:
 Cycle 1: isEven -> isOdd
+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.