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Remove unused TailCallRequest variant

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The `TailCallRequest` enum variant and its associated logic have been
removed. Instead, the VM now uses an `Option<(Rc<dyn Object>,
Vec<Value>)>` field named `tail_call` to manage tail-call requests. This
change simplifies the `Value` enum and centralizes tail-call handling
within the `VM` struct.
This commit is contained in:
Brummel
2026-03-22 19:20:18 +01:00
parent f6c963cb41
commit 37d7ed3e75
2 changed files with 68 additions and 78 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/ast/vm.rs
+68 -72
View File
@@ -133,6 +133,9 @@ pub struct VM {
stack: Vec<Value>,
globals: Rc<RefCell<Vec<Value>>>,
frames: Vec<CallFrame>,
/// Side-channel for tail-call signaling. Set by `eval_internal` when a tail-call
/// is requested; consumed by `resolve_tail_calls` and the inline TCO loop.
tail_call: Option<(Rc<dyn Object>, Vec<Value>)>,
}
impl VM {
@@ -141,6 +144,7 @@ impl VM {
stack: Vec::new(),
globals,
frames: Vec::new(),
tail_call: None,
}
}
@@ -154,65 +158,63 @@ impl VM {
mut result: Result<Value, String>,
) -> Result<Value, String> {
loop {
match result {
Ok(Value::TailCallRequest(payload)) => {
let (next_obj, next_args) = *payload;
if let Ok(closure_rc) = next_obj.clone().into_rc_any().downcast::<Closure>() {
self.stack.clear();
// frames should be empty here since we popped before entering the loop
self.frames.push(CallFrame {
stack_base: 0,
closure: Some(closure_rc.clone()),
});
let closure = closure_rc.as_ref();
if let Some(count) = closure.positional_count
&& next_args.len() == count as usize
{
self.stack.extend(next_args);
} else {
self.unpack(closure.parameter_node.as_ref(), &next_args, &mut 0)?;
}
// PRE-ALLOCATION
let current_stack = self.stack.len() as u32;
if closure.stack_size > current_stack {
self.stack.resize(closure.stack_size as usize, Value::Void);
}
result = self.eval_observed(observer, &closure.exec_node);
self.frames.pop();
} else if let Some(series) = next_obj.as_series() {
if next_args.len() != 1 {
return Err(format!(
"{} indexer expects exactly 1 argument (the lookback index), got {}",
next_obj.type_name(),
next_args.len()
));
}
if let Value::Int(idx) = &next_args[0] {
if *idx < 0 {
return Err(format!(
"{} lookback index cannot be negative: {}",
next_obj.type_name(),
idx
));
}
result = Ok(series.get_item(*idx as usize).unwrap_or(Value::Void));
} else {
return Err(format!(
"{} index must be an integer, got {}",
next_obj.type_name(),
next_args[0]
));
}
if let Some((next_obj, next_args)) = self.tail_call.take() {
if let Ok(closure_rc) = next_obj.clone().into_rc_any().downcast::<Closure>() {
self.stack.clear();
// frames should be empty here since we popped before entering the loop
self.frames.push(CallFrame {
stack_base: 0,
closure: Some(closure_rc.clone()),
});
let closure = closure_rc.as_ref();
if let Some(count) = closure.positional_count
&& next_args.len() == count as usize
{
self.stack.extend(next_args);
} else {
self.unpack(closure.parameter_node.as_ref(), &next_args, &mut 0)?;
}
// PRE-ALLOCATION
let current_stack = self.stack.len() as u32;
if closure.stack_size > current_stack {
self.stack.resize(closure.stack_size as usize, Value::Void);
}
result = self.eval_observed(observer, &closure.exec_node);
self.frames.pop();
} else if let Some(series) = next_obj.as_series() {
if next_args.len() != 1 {
return Err(format!(
"Tail call target is not callable: {}",
next_obj.type_name()
"{} indexer expects exactly 1 argument (the lookback index), got {}",
next_obj.type_name(),
next_args.len()
));
}
if let Value::Int(idx) = &next_args[0] {
if *idx < 0 {
return Err(format!(
"{} lookback index cannot be negative: {}",
next_obj.type_name(),
idx
));
}
result = Ok(series.get_item(*idx as usize).unwrap_or(Value::Void));
} else {
return Err(format!(
"{} index must be an integer, got {}",
next_obj.type_name(),
next_args[0]
));
}
} else {
return Err(format!(
"Tail call target is not callable: {}",
next_obj.type_name()
));
}
_ => return result,
} else {
return result;
}
}
}
@@ -527,7 +529,8 @@ impl VM {
match func_val {
Value::Object(obj) => {
return Ok(Value::TailCallRequest(Box::new((obj, arg_vals))));
self.tail_call = Some((obj, arg_vals));
return Ok(Value::Void);
}
Value::Function(f) => return Ok((f.func)(&arg_vals)),
Value::FieldAccessor(k) => {
@@ -753,24 +756,19 @@ impl VM {
Value::Function(_) => "Function",
Value::Object(_) => "Object",
Value::Cell(_) => "Cell",
Value::TailCallRequest(_) => "TailCallRequest",
};
return Err(format!("Attempt to call non-function: {} (Variant: {})", current_func, variant_name));
}
};
match result {
Ok(Value::TailCallRequest(payload)) => {
let (next_obj, next_args) = *payload;
current_func = Value::Object(next_obj);
self.stack.truncate(base);
self.stack.extend(next_args);
continue;
}
res => {
self.stack.truncate(base);
return res;
}
if let Some((next_obj, next_args)) = self.tail_call.take() {
current_func = Value::Object(next_obj);
self.stack.truncate(base);
self.stack.extend(next_args);
continue;
} else {
self.stack.truncate(base);
return result;
}
}
}
@@ -785,10 +783,8 @@ impl VM {
let frame = self.frames.last().ok_or("No call frame for 'again'")?;
if let Some(closure_obj) = &frame.closure {
Ok(Value::TailCallRequest(Box::new((
closure_obj.clone(),
arg_vals,
))))
self.tail_call = Some((closure_obj.clone() as Rc<dyn Object>, arg_vals));
Ok(Value::Void)
} else {
Err("'again' called outside of a closure".to_string())
}