1 files changed, 17 insertions, 7 deletions

diff --git a/src/poem/read.rs b/src/poem/read.rs
index da13f76..3c4a720 100644
--- a/src/poem/read.rs
+++ b/src/poem/read.rs
@@ -42,8 +42,12 @@ impl fmt::Display for Mishap {
 /// A [Poem] can add more [Verse]s to itself
 trait Appendable {
     type Type;
-    fn add(&mut self, verse: &mut Self::Type, meter: Rune, env: &Environment)
-        -> Result<(), Mishap>;
+    fn add(
+        &mut self,
+        verse: &mut Self::Type,
+        meter: Rune,
+        env: &mut Environment,
+    ) -> Result<(), Mishap>;
 }
 
 impl Appendable for Poem {
@@ -57,7 +61,7 @@ impl Appendable for Poem {
         &mut self,
         verse: &mut Self::Type,
         meter: Rune,
-        env: &Environment,
+        env: &mut Environment,
     ) -> Result<(), Mishap> {
         if verse.is_empty() {
             return Ok(());
@@ -81,10 +85,16 @@ impl Appendable for Poem {
 
         // Check for aliases
         match env.aliases.get(&verse.verb()) {
-            Some(alias) => {
+            Some(alias) if env.cs == 0 => {
+                // Increase the callstack
+                env.cs = 1;
+
                 // Interpret the alias (could be a complex poem)
                 let mut poem = Poem::read(alias.to_string(), env)?;
 
+                // Decrease the callstack
+                env.cs = 0;
+
                 // Try and get the last verse
                 let lv = match poem.last_mut() {
                     Some(lv) => lv,
@@ -109,7 +119,7 @@ impl Appendable for Poem {
                     self.push(v.clone());
                 }
             }
-            None => {
+            Some(_) | None => {
                 // Push verse(s)
                 self.push(verse.clone());
             }
@@ -125,7 +135,7 @@ impl Appendable for Poem {
 
 /// A [Poem] can parse poetry
 pub trait Readable {
-    fn read(poetry: String, env: &Environment) -> Result<Poem, Mishap>;
+    fn read(poetry: String, env: &mut Environment) -> Result<Poem, Mishap>;
 }
 
 impl Readable for Poem {
@@ -135,7 +145,7 @@ impl Readable for Poem {
     /// machine-runnable [Poem]. If there is a parse error, [Poem::read] may
     /// return a [Mishap]. See [Poem::recite][super::recite] for how each
     /// [Verse] in a [Poem] is called.
-    fn read(poetry: String, env: &Environment) -> Result<Poem, Mishap> {
+    fn read(poetry: String, env: &mut Environment) -> Result<Poem, Mishap> {
         // Get all the characters in the input string as an iterator
         let mut chars = poetry.chars().into_iter();