Refactor evaluator for stackless execution

Author: swernli

compiler/qsc_eval/src/lib.rs

@@ -2,13 +2,15 @@
 // Licensed under the MIT License.
 
 #![warn(clippy::mod_module_files, clippy::pedantic, clippy::unwrap_used)]
+#![allow(unused)]
 
 #[cfg(test)]
 mod tests;
 
 pub mod debug;
 mod intrinsic;
 pub mod output;
+mod stackless;
 pub mod val;
 
 use crate::val::{ConversionError, FunctorApp, Value};
@@ -217,50 +219,54 @@ impl<'a, F: Fn(GlobalId) -> Option<&'a CallableDecl>> GlobalLookup<'a> for F {
 /// # Errors
 /// Returns the first error encountered during execution.
 pub fn eval_stmt<'a>(
-    stmt: &Stmt,
+    stmt: &'a Stmt,
     globals: &'a impl GlobalLookup<'a>,
     package: PackageId,
-    env: &mut Env,
+    env: &'a mut Env,
     out: &'a mut dyn Receiver,
 ) -> Result<Value, (Error, CallStack)> {
-    let mut eval = Evaluator {
-        globals,
-        package,
-        env: take(env),
-        call_stack: CallStack::default(),
-        out: Some(out),
-    };
-    let res = match eval.eval_stmt(stmt) {
-        Continue(res) | Break(Reason::Return(res)) => Ok(res),
-        Break(Reason::Error(error)) => Err((error, eval.call_stack.clone())),
-    };
-    *env = take(&mut eval.env);
-    res
+    stackless::eval_stmt(stmt, globals, package, env, out)
+
+    // let mut eval = Evaluator {
+    //     globals,
+    //     package,
+    //     env: take(env),
+    //     call_stack: CallStack::default(),
+    //     out: Some(out),
+    // };
+    // let res = match eval.eval_stmt(stmt) {
+    //     Continue(res) | Break(Reason::Return(res)) => Ok(res),
+    //     Break(Reason::Error(error)) => Err((error, eval.call_stack.clone())),
+    // };
+    // *env = take(&mut eval.env);
+    // res
 }
 
 /// Evaluates the given expression with the given context.
 /// # Errors
 /// Returns the first error encountered during execution.
 pub fn eval_expr<'a>(
-    expr: &Expr,
+    expr: &'a Expr,
     globals: &'a impl GlobalLookup<'a>,
     package: PackageId,
-    env: &mut Env,
+    env: &'a mut Env,
     out: &'a mut dyn Receiver,
 ) -> Result<Value, (Error, CallStack)> {
-    let mut eval = Evaluator {
-        globals,
-        package,
-        env: take(env),
-        call_stack: CallStack::default(),
-        out: Some(out),
-    };
-    let res = match eval.eval_expr(expr) {
-        Continue(res) | Break(Reason::Return(res)) => Ok(res),
-        Break(Reason::Error(error)) => Err((error, eval.call_stack.clone())),
-    };
-    *env = take(&mut eval.env);
-    res
+    stackless::eval_expr(expr, globals, package, env, out)
+
+    // let mut eval = Evaluator {
+    //     globals,
+    //     package,
+    //     env: take(env),
+    //     call_stack: CallStack::default(),
+    //     out: Some(out),
+    // };
+    // let res = match eval.eval_expr(expr) {
+    //     Continue(res) | Break(Reason::Return(res)) => Ok(res),
+    //     Break(Reason::Error(error)) => Err((error, eval.call_stack.clone())),
+    // };
+    // *env = take(&mut eval.env);
+    // res
 }
 
 pub fn init() {