deny empty tuplets

src/compiler.rs

@@ -170,6 +170,9 @@ pub struct Tuplet(pub TokenVec);
 impl Token for Tuplet {
     fn apply(&self, mut context: Context) -> Result<Context, CompilerError> {
         debug!("⚡ {}", type_name::<Self>());
+        if self.0.as_ref().is_empty() {
+            return Err(CompilerError::Nilplet);
+        }
         let mut old_result = context.result.clone();
         context.result.clear();
         let mut new_context = self
@@ -294,10 +297,14 @@ pub struct SlopeNotFoundError(String);
 pub enum CompilerError {
     #[error("expression evaluation: {0:?}")]
     FastEval(#[from] fasteval::Error),
-    #[error("{0}")]
+    #[error(transparent)]
     VariableNotFound(#[from] VariableNotFoundError),
-    #[error("{0}")]
+    #[error(transparent)]
     SlopeNotFound(#[from] SlopeNotFoundError),
+    #[error(
+        "You successfully made a nilplet / noplet (and I don't know what to do with it).\nTo resume compilation, remove any occurrence of \"[]\" in your sheet music."
+    )]
+    Nilplet,
 }
 
 impl Context {