1 files changed, 105 insertions, 0 deletions
diff --git a/src/chomp/check/inline.rs b/src/chomp/check/inline.rs
new file mode 100644
index 0000000..a6a831c
--- /dev/null
+++ b/src/chomp/check/inline.rs
@@ -0,0 +1,105 @@
+use super::{
+    super::{
+        ast::{Alt, Call, Cat, Epsilon, Expression, Fix, Function, Literal, Parameter, Variable},
+        error::SubstituteError,
+        visit::{Folder, Visitable},
+    },
+    SubstituteParams,
+};
+
+#[derive(Clone, Debug)]
+pub struct InlineCalls {
+    function: Function,
+}
+
+impl InlineCalls {
+    pub fn new(function: Function) -> Self {
+        Self { function }
+    }
+}
+
+impl Folder for InlineCalls {
+    type Out = Result<Expression, SubstituteError>;
+
+    fn fold_epsilon(&mut self, eps: Epsilon) -> Self::Out {
+        Ok(eps.into())
+    }
+
+    fn fold_literal(&mut self, lit: Literal) -> Self::Out {
+        Ok(lit.into())
+    }
+
+    fn fold_cat(&mut self, mut cat: Cat) -> Self::Out {
+        cat.fst = Box::new(cat.fst.fold(self)?);
+        cat.snd = Box::new(cat.snd.fold(self)?);
+        Ok(cat.into())
+    }
+
+    fn fold_alt(&mut self, mut alt: Alt) -> Self::Out {
+        alt.left = Box::new(alt.left.fold(self)?);
+        alt.right = Box::new(alt.right.fold(self)?);
+        Ok(alt.into())
+    }
+
+    fn fold_fix(&mut self, mut fix: Fix) -> Self::Out {
+        fix.inner = Box::new(fix.inner.fold(self)?);
+        Ok(fix.into())
+    }
+
+    fn fold_variable(&mut self, var: Variable) -> Self::Out {
+        Ok(var.into())
+    }
+
+    fn fold_parameter(&mut self, param: Parameter) -> Self::Out {
+        Ok(param.into())
+    }
+
+    fn fold_call(&mut self, mut call: Call) -> Self::Out {
+        call.args = call
+            .args
+            .into_iter()
+            .map(|arg| arg.fold(self))
+            .collect::<Result<_, _>>()?;
+
+        if call.name != self.function.name {
+            Ok(call.into())
+        } else if call.args.len() != self.function.params {
+            Err(SubstituteError::WrongArgCount {
+                call,
+                expected: self.function.params,
+            })
+        } else {
+            self.function
+                .expr
+                .clone()
+                .fold(&mut SubstituteParams::new(call.args))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use proc_macro2::Span;
+    use syn::Ident;
+
+    use super::*;
+
+    const OPT_NAME: &str = "opt";
+    const OPT: Function = Function::new(
+        Ident::new(OPT_NAME, Span::call_site()),
+        1,
+        Expression::Alt(Alt::new(
+            Epsilon::default().into(),
+            None,
+            Parameter::new(None, 0).into(),
+        )),
+        None,
+    );
+
+    #[test]
+    fn test_inline_absent() {
+        let expr = Epsilon::default();
+        let inlined = expr.fold(&mut InlineCalls::new(OPT));
+        assert_eq!(inlined, Ok(Expression::from(Epsilon::default())))
+    }
+}