A fairly major refactor / simplification.

src/syntax/simplify.rs

@@ -0,0 +1,49 @@
+use crate::syntax::ast::{Program, Statement, Expression};
+
+impl Program {
+    pub fn simplify(mut self) -> Self {
+        let mut new_statements = Vec::new();
+        let mut gensym_index = 1;
+
+        for stmt in self.statements.drain(..) {
+            match stmt {
+                Statement::Print(_, _) => new_statements.push(stmt),
+                Statement::Binding(_, _, Expression::Reference(_, _)) => new_statements.push(stmt),
+                Statement::Binding(_, _, Expression::Value(_, _)) => new_statements.push(stmt),
+                Statement::Binding(loc, name, value) => {
+                    let (mut prereqs, new_value) = value.rebind(&name, &mut gensym_index);
+                    new_statements.append(&mut prereqs);
+                    new_statements.push(Statement::Binding(loc, name, new_value))
+                }
+            }
+        }
+
+        self.statements = new_statements;
+        self
+    }
+}
+
+impl Expression {
+    fn rebind(self, base_name: &str, gensym_index: &mut usize) -> (Vec<Statement>, Expression) {
+        match self {
+            Expression::Value(_, _) => (vec![], self),
+            Expression::Reference(_, _) => (vec![], self),
+            Expression::Primitive(loc, prim, mut expressions) => {
+                let mut prereqs = Vec::new();
+                let mut new_exprs = Vec::new();
+
+                for expr in expressions.drain(..) {
+                    let (mut cur_prereqs, arg) = expr.rebind(base_name, gensym_index);
+                    prereqs.append(&mut cur_prereqs);
+                    new_exprs.push(arg);
+                }
+
+                let new_name = format!("<{}:{}>", base_name, *gensym_index);
+                *gensym_index += 1;
+                prereqs.push(Statement::Binding(loc.clone(), new_name.clone(), Expression::Primitive(loc.clone(), prim, new_exprs)));
+
+                (prereqs, Expression::Reference(loc, new_name))
+            }
+        }
+    }
+}