glsp-engine 0.2.0

use smallvec::{SmallVec};
use std::{usize};
use std::cell::{RefCell};
use std::collections::{HashMap, hash_map::Entry::{Occupied, Vacant}};
use std::iter::{FromIterator};
use std::rc::{Rc};
use super::{transform};
use super::ast::{Ast};
use super::code::{Bytecode, GFn, Stay};
use super::collections::{Arr, DequeAccess, DequeOps};
use super::encoder;
use super::engine::{glsp, Guard, RFn, stock_syms::*, Sym, with_vm};
use super::error::{GResult};
use super::gc::{Root, Slot};
use super::val::{Val};
use super::vm::{Frame};
use super::wrap::{CallableOps};

#[cfg(feature = "compiler")]
use super::compile::{Action};


//-------------------------------------------------------------------------------------------------
// entrypoints
//-------------------------------------------------------------------------------------------------

//successively expand and evaluate a number of toplevel forms, all in the same toplevel scope.
//the `to_record` flag determines whether or not any executed Bytecodes are recorded: this is
//true for (load) calls, but false for (eval) calls.
pub(crate) fn eval(
	forms: &[Val],
	env_mode: Option<EnvMode>,
	to_record: bool
) -> GResult<Val> {

	let mut context = Context::new(env_mode);

	//once fully-expanded, these forms all require special handling: (splice), (let-macro), (let),
	//(defer), (defer-yield). to facilitate (splice), we need an input stack.
	let mut input = Vec::from_iter(forms.iter().rev().cloned());
	let mut result = Ok(Val::Nil);

	while let Some(form) = input.pop() {
		let expanded = match fully_expand_form(&form, &mut context) {
			Ok(Some(expanded)) => expanded,
			Ok(None) => form,
			Err(error) => {
				let mut defer_result: GResult<Val> = Err(error);
				context.pop_defers(&mut defer_result);
				return defer_result
			}
		};

		if expanded.is_arr() && expanded.clone().unwrap_arr().len() > 0 {
			let arr = expanded.clone().unwrap_arr();
			match arr.get(0)? {
				Val::Sym(SPLICE_SYM) => {
					input.extend(arr.iter().skip(1).rev());
				}
				Val::Sym(LET_MACRO_SYM) => {
					result = context.push_let_macro_binding(arr).map(|_| Val::Nil);
				}
				Val::Sym(DEFER_SYM) => {
					result = context.push_defer(arr).map(|_| Val::Nil);
				}
				Val::Sym(DEFER_YIELD_SYM) => {
					result = Ok(Val::Nil);
				}
				Val::Sym(LET_SYM) => {
					result = context.register_toplevel_let(arr).map(|_| Val::Nil);
				}
				_ => result = evaluate_form(&expanded, &context.toplevel_lets, to_record)
			}
		} else {
			result = evaluate_form(&expanded, &context.toplevel_lets, to_record)
		}

		if let Err(error) = result {
			let mut defer_result: GResult<Val> = Err(error);
			context.pop_defers(&mut defer_result);
			return defer_result
		}
	}

	context.pop_defers(&mut result);
	result
}

//successively expand a number of toplevel forms, all in the same toplevel scope.
//`collapse_splices` will always return an output Vec of length 1, wrapping multiple results
//in a (splice ...) form if necessary.
pub(crate) fn expand(
	forms: &[Val],
	env_mode: Option<EnvMode>,
	collapse_splices: bool
) -> GResult<Vec<Val>> {
	let mut context = Context::new(env_mode);

	//we need to detect and handle toplevel (splice) and toplevel (let-macro). to facilitate
	//(splice), we need separate input and output stacks.
	let mut input = Vec::from_iter(forms.iter().rev().cloned());
	let mut output = Vec::<Val>::new();

	while let Some(form) = input.pop() {
		let expanded = fully_expand_form(&form, &mut context)?.unwrap_or(form);

		if expanded.is_arr() && expanded.clone().unwrap_arr().len() > 0 {
			let arr = expanded.clone().unwrap_arr();
			match arr.get(0)? {
				Val::Sym(SPLICE_SYM) => {
					input.extend(arr.iter().skip(1).rev());
				}
				Val::Sym(LET_MACRO_SYM) => {
					context.push_let_macro_binding(arr)?;
					output.push(Val::Nil);
				}
				_ => output.push(expanded)
			}
		} else {
			output.push(expanded);
		}
	}

	//we suppress splices in this roundabout way so that the children of forms like 
	//(splice (splice) (macro-invocation)) will still be expanded as normal
	if collapse_splices && output.len() != 1 {
		let splice = Val::Arr(arr![SPLICE_SYM, ..output]);
		output.clear();
		output.push(splice);
	}

	Ok(output)
}

//perform a single step of the expansion algorithm, with the option to override the expander
pub(crate) fn expand_1(
	form: &Val,
	expander: Option<Expander>,
	env_mode: Option<EnvMode>
) -> GResult<Expansion> {
	let mut context = Context::new(env_mode);
	maybe_call_expander(form, expander, &mut context)
}

/**

The return value for [`glsp::expand_1`](fn.expand_1.html).
*/

#[derive(Clone, PartialEq, Debug)]
pub enum Expansion {
	ExpandedTo(Val),
	MacroNoOp,
	NotAMacro
}

/**

A type-erased `expander`.

Used as a parameter or return value by [`glsp::bind_macro`](fn.bind_macro.html), 
[`glsp::expand_1`](fn.expand_1.html), and similar functions.
*/

#[derive(Clone, Debug)]
pub enum Expander {
	GFn(Root<GFn>),
	RFn(Root<RFn>)
}

/**

A lexical-environment capture mode.

Used as a parameter by [`glsp::eval`](fn.eval.html), [`glsp::expand`](fn.expand.html), and 
similar functions.
*/

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum EnvMode {
	Fresh,
	Copied
}

impl Default for EnvMode {
	fn default() -> EnvMode {
		EnvMode::Fresh
	}
}

//an initial expansion environment. this is made aliasable (as an Rc<Env>) so that we can store a
//copy of it in the Runtime when running a macro expander. then, when `env_mode` is Copied, the
//innermost Env can be copied into the new Context. we don't support toplevel (let)s in Env,
//because we'd also need to support local (let)s for consistency, which would be challenging.
#[derive(Clone, Default)]
pub(crate) struct Env {
	let_macros: RefCell<HashMap<Sym, Root<GFn>>>
}


//-------------------------------------------------------------------------------------------------
// Context
//-------------------------------------------------------------------------------------------------

//each entrypoint function creates a Context with which to expand or evaluate forms. it contains
//the state required by (let-macro), toplevel (let) and toplevel (defer).

struct Context {
	//keys are the variable bound by the toplevel `let`, values are the Stay used for storage.
	//when the same variable name is bound twice, the old one is simply erased from this map.
	toplevel_lets: HashMap<Sym, Root<Stay>>,

	//the active (let-macro)s. a reference to the current Env is stored in the Runtime every
	//time we invoke an expander, and it can be retrieved using glsp::env() or (env).
	env: Rc<Env>,

	//this stack is required so that we can keep the Env up to date when (let-macro) bindings 
	//shadow one another. the Option is the previous binding which is being shadowed, if any.
	let_stack: Vec<(Sym, Option<Root<GFn>>)>,

	//toplevel `defer`s are a bit simpler: we compile them when they're encountered, but we save
	//their bytecode rather than running it. we run that bytecode after the last toplevel form,
	//with some juggling to ensure that errors are reported properly. `defer-yield` is a silent 
	//no-op (it's not even compiled) because there's no way to yield from the toplevel.
	defers: Vec<Root<Bytecode>>
}

impl Context {
	fn new(env_mode: Option<EnvMode>) -> Context {
		let env = match env_mode {
			None | Some(EnvMode::Fresh) => Rc::new(Env::default()),
			Some(EnvMode::Copied) => {
				let env = match glsp::env() {
					Some(env) => (*env).clone(),
					None => Env::default()
				};

				Rc::new(env)
			}
		};

		Context {
			toplevel_lets: HashMap::new(),
			env,
			let_stack: Vec::new(),
			defers: Vec::new()
		}
	}

	fn push_let_macro_binding(
		&mut self,
		form: Root<Arr>
	) -> GResult<()> {

		//we extract the name, params and body from (let-macro name params ..body), use them to
		//make a gfn by evaluating (fn params ..body), then bind that gfn to `name` as a macro.
		let span = form.span();
		ensure_at!(span, form.len() >= 3, "let-macro form has too few arguments");

		let name = match form.get(1)? {
			Val::Sym(name) => name,
			_ => bail_at!(span, "the first argument to `let-macro` must be a sym")
		};

		let params_arr = match form.get(2)? {
			Val::Arr(arr) => arr,
			_ => bail_at!(span, "the second argument to `let-macro` must be an arr")
		};

		let fn_arr = arr![FN_SYM, FLAG_NAME_SYM, name, params_arr];
		fn_arr.set_span(span);
		fn_arr.extend(form.iter().skip(3))?;

		//we have to expand the (fn ...) form here, rather than simply calling eval(), so that the
		//expansion is affected by any current `let-macro` bindings. we don't allow let-macros to
		//access toplevel `let`s, even though we could, because it would be inconsistent with
		//the fact that they can't access non-toplevel `let`s.
		let fn_form = Val::Arr(fn_arr);
		let expanded_fn = fully_expand_form(&fn_form, self)?.unwrap_or(fn_form);

		let gfn = match evaluate_form(&expanded_fn, &HashMap::new(), false)? {
			Val::GFn(gfn) => gfn,
			_ => panic!()
		};

		//assign the binding to the env and the let_stack
		match self.env.let_macros.borrow_mut().entry(name) {
			Occupied(mut occupied) => {
				let old_entry = occupied.insert(gfn);
				self.let_stack.push((name, Some(old_entry)));
			}
			Vacant(vacant) => {
				vacant.insert(gfn);
				self.let_stack.push((name, None));
			}
		}

		Ok(())
	}

	fn pop_binding(&mut self) {
		let (name, shadowed_entry) = self.let_stack.pop().unwrap();

		match self.env.let_macros.borrow_mut().entry(name) {
			Occupied(mut occupied) => {
				if let Some(shadowed_entry) = shadowed_entry {
					occupied.insert(shadowed_entry);
				} else {
					occupied.remove();
				}
			}
			Vacant(_) => panic!()
		}
	}

	fn lookup_let_macro(&mut self, name: Sym) -> Option<Root<GFn>> {
		self.env.let_macros.borrow().get(&name).cloned()
	}

	fn register_toplevel_let(&mut self, form: Root<Arr>) -> GResult<()> {
		let span = form.span();
		if form.len() != 3 {
			bail_at!(span, "the (let ...) special form expects two arguments")
		}

		let name = match form.get::<Val>(1)? {
			Val::Sym(name) => name,
			_ => bail_at!(span, "(let ...) special form has invalid arguments")
		};
		let init_form: Val = form.get(2)?;

		let stay = glsp::alloc(Stay::new(Slot::Nil));

		#[cfg(feature = "compiler")]
		glsp::record_action(Action::ToplevelLet(stay.clone()));

		let init_val = evaluate_form(&init_form, &self.toplevel_lets, true)?;
		stay.set(Slot::from_val(&init_val));

		//we don't actually bind the name until after its initializer has been evaluated,
		//for consistency with non-toplevel lets
		self.toplevel_lets.insert(name, stay.clone());

		Ok(())
	}

	fn push_defer(&mut self, form: Root<Arr>) -> GResult<()> {
		//paste the form's body into a (do) form
		let do_form = arr![DO_SYM];
		do_form.extend(form.iter().skip(1))?;

		//compile that (do) form into bytecode without evaluating it
		let mut ast = Ast::new();
		let node = ast.node_from_val(&Val::Arr(do_form), glsp::generated_span())?;
		transform::standard_passes(&mut ast, node);

		let bytecode = encoder::encode_fragment(&ast, node, &self.toplevel_lets)?;

		//stash that bytecode in the Context
		self.defers.push(bytecode);
		Ok(())
	}

	fn pop_defers(&mut self, result: &mut GResult<Val>) {
		//evaluate each toplevel (defer) form in reverse order. if one of them fails, chain its
		//error onto the GResult and then move on to the next (defer) form
		for bytecode in self.defers.drain(..).rev() {
			#[cfg(feature = "compiler")]
			glsp::record_action(Action::Execute(bytecode.clone()));

			let defer_result = with_vm(|vm| {
				vm.exec_bytecode(&bytecode)
			});

			if let Err(error) = defer_result {
				match *result {
					Ok(_) => *result = Err(error),
					Err(ref mut prev) => prev.chain_defer_error(error)
				}
			}
		}
	}
}


//-------------------------------------------------------------------------------------------------
// the implementation
//-------------------------------------------------------------------------------------------------

//evaluates a form which has already been fully expanded.
fn evaluate_form(
	form: &Val,
	toplevel_lets: &HashMap<Sym, Root<Stay>>,
	_to_record: bool
) -> GResult<Val> {

	let mut ast = Ast::new();
	let node = ast.node_from_val(form, glsp::generated_span())?;
	transform::standard_passes(&mut ast, node);

	let bytecode = encoder::encode_fragment(&ast, node, toplevel_lets)?;

	#[cfg(feature = "compiler")]
	if _to_record {
		glsp::record_action(Action::Execute(bytecode.clone()));
	}

	with_vm(|vm| {
		vm.exec_bytecode(&bytecode)
	})
}

//recursively performs the full expansion algorithm for a single form. note that this fn's result
//may be a (splice) form, but any child (splice) forms are handled appropriately. similarly,
//if the expansion result is a (let-macro) then it's just returned, but inner (let-macro)s
//are handled properly.
fn fully_expand_form(
	form: &Val,
	context: &mut Context
) -> GResult<Option<Val>> {

	let mut form = form.clone();
	let mut form_mutated = false;

	loop {
		//step 1: if it's not an array, or if it's an empty array, do nothing.
		if !form.is_arr() {
			return if form_mutated { Ok(Some(form)) } else { Ok(None) }
		}

		let mut arr = form.unwrap_arr();
		if arr.len() == 0 {
			return if form_mutated { Ok(Some(Val::Arr(arr))) } else { Ok(None) }
		}

		//the value being expanded is copy-on-write. if nothing changes, there's no need to clone 
		//the form, and we return None. this helps to minimize copying.
		let mut arr_owned = false;

		//expand_element repeatedly (splice)s and fully-expands the form at a single array index, 
		//in-place, cloning the array if it needs to be mutated. bear in mind that empty (splice)s
		//will cause an element to be deleted - we continue looping until its replacement, if any,
		//is fully-expanded. 
		fn expand_element(
			mut arr: Root<Arr>, 
			i: usize, 
			arr_owned: &mut bool, 
			context: &mut Context
		) -> GResult<Root<Arr>> {
			loop {
				if arr.len() <= i {
					return Ok(arr)
				}

				let elem = arr.get::<Val>(i).unwrap();

				if elem.is_arr() && elem.clone().unwrap_arr().len() > 0 &&
				   elem.clone().unwrap_arr().get::<Val>(0).unwrap() == Val::Sym(SPLICE_SYM) {

					if !*arr_owned {
						arr = arr.shallow_clone();
						*arr_owned = true;
					}

					let to_splice = elem.clone().unwrap_arr();
					if to_splice.len() == 1 {
						let _discarded: Val = arr.remove(i)?;
						if arr.len() <= i {
							return Ok(arr)
						}
					} else {
						arr.set(i, to_splice.get::<Val>(1).unwrap())?;

						//this is wildly inefficient, but (splice) is usually small so it probably
						//doesn't matter. todo: revisit this when we have DequeOps::insert_multi()
						for src_i in (2 .. to_splice.len()).rev() {
							arr.insert(i + 1, to_splice.get::<Val>(src_i).unwrap())?;
						}
					}
				} else {
					//note that there's no easy way to check two forms for deep-equality: all we
					//can do is check whether they've been reallocated. therefore, to avoid
					//endless loops here, we *must not* take ownership of an arr unless we're 
					//actually mutating it in some way.
					match fully_expand_form(&elem, context)? {
						Some(replacement) => {
							if !*arr_owned {
								arr = arr.shallow_clone();
								*arr_owned = true;
							}

							arr.set(i, replacement)?;
						}
						None => return Ok(arr)
					}
				}
			}
		}

		//step 2: recurse for the array's first element
		arr = expand_element(arr, 0, &mut arr_owned, context)?;

		//step 3: try to call an expander for this form *once*. if an expander was called and it 
		//wasn't a macro-no-op, replace the form with the expansion result and start over from 1.
		match maybe_call_expander(&Val::Arr(arr.clone()), None, context)? {
			Expansion::ExpandedTo(expanded_to) => {
				form = expanded_to;

				//the `expanded_to` form completely replaces the arr, and it could be *anything*
				//returned from a macro, including something immutable or aliased. don't get any
				//clever ideas about setting `arr_owned` to true here...

				form_mutated = true;
				continue
			}
			Expansion::MacroNoOp | Expansion::NotAMacro => ()
		}

		//step 4: the callee form is now fully-expanded. recurse for the "argument" forms.
		//some callees have a special traversal order, and they may permit (let-macro) children,
		//which we'll need to process.
		fn expand_do_elements(
			mut arr: Root<Arr>,
			first_child_i: usize,
			arr_owned: &mut bool,
			context: &mut Context
		) -> GResult<Root<Arr>> {

			let mut let_macro_count = 0;

			let mut i = first_child_i;
			while i < arr.len() {
				arr = expand_element(arr, i, arr_owned, context)?;

				if arr.len() <= i {
					break
				}

				if let Val::Arr(expanded_arr) = arr.get::<Val>(i)? {
					if expanded_arr.len() >= 1 &&
					   expanded_arr.get::<Val>(0)? == Val::Sym(LET_MACRO_SYM) {

						context.push_let_macro_binding(expanded_arr)?;
						let_macro_count += 1;

						//we replace (let-macro) forms with #n so they won't upset the evaluator
						if !*arr_owned {
							arr = arr.shallow_clone();
							*arr_owned = true;
						}

						arr.set(i, Val::Nil)?;
					}
				}

				i += 1;
			}

			for _ in 0 .. let_macro_count {
				context.pop_binding();
			}

			Ok(arr)
		}

		/*fn expand_fn_params(
			mut fn_arr: Root<Arr>,
			fn_arr_owned: &mut bool,
			context: &mut Context
		) -> GResult<Root<Arr>> {
			//for params, we *mostly* want to skip them, but we still need to expand the 
			//initializers for optional arguments
			assert!(fn_arr.len() >= 2);
			let mut params = match fn_arr.get(1)? {
				Val::Arr(params) => params,
				_ => bail_at!(fn_arr.span(), "invalid (fn) form passed to expander")
			};

			//if there are no &opt params, we do nothing
			let rest_index = params.iter().rposition(|val| val == Val::Sym(REST_SYM))
			                              .unwrap_or(params.len());

			let opt_index = match params.iter().rposition(|val| val == Val::Sym(OPT_SYM)) {
				Some(opt_index) if opt_index < rest_index => opt_index,
				_ => return Ok(fn_arr)
			};

			//iterate over each &opt param. when it's a nonempty arr, in-place-expand each of its 
			//elements beyond the first.
			let mut params_owned = false;

			for param_i in opt_index + 1 .. rest_index {
				let param: Val = params.get(param_i)?;
				match param {
					Val::Arr(mut param) => {
						let mut param_owned = false;
						let mut elem_i = 1;
						while elem_i < param.len() {
							param = expand_element(param, elem_i, &mut param_owned, context)?;
							elem_i += 1;
						}

						//replacing any param has a cascading effect for the entire (fn) form...
						if param_owned {
							if !params_owned {
								params = params.shallow_clone();
								params_owned = true;

								if !*fn_arr_owned {
									fn_arr = fn_arr.shallow_clone();
									*fn_arr_owned = true;
								}

								fn_arr.set(1, &params)?;
							}

							params.set(param_i, param)?;
						}
					}
					_ => ()
				}
			}

			Ok(fn_arr)
		}*/

		match arr.get::<Val>(0).unwrap() {
			Val::Sym(QUOTE_SYM) => {
				//the argument to a (quote) form is not expanded
				ensure_at!(arr.span(), arr.len() == 2, "invalid (quote) form passed to expander");
			}
			Val::Sym(SPLICE_SYM) | Val::Sym(LET_MACRO_SYM) => {
				//we return (splice) and (let-macro) to the caller unchanged, without attempting
				//any further expansion at this stage.
			}
			Val::Sym(DO_SYM) | Val::Sym(DEFER_SYM) => {
				//the arguments to a (do) special form may be (let-macro), so we need to handle 
				//that: pushing any (let-macro) children and then popping them at the end.
				arr = expand_do_elements(arr, 1, &mut arr_owned, context)?;
			}
			Val::Sym(BLOCK_SYM) => {
				//for a (block) form, we expand its first form like a function argument and its
				//subsequent forms as an implicit (do)
				ensure_at!(arr.span(), arr.len() >= 2, "invalid (block) form passed to expander");
				arr = expand_element(arr, 1, &mut arr_owned, context)?;
				arr = expand_do_elements(arr, 2, &mut arr_owned, context)?;
			}
			Val::Sym(FN_SYM) => {
				//for a (fn) form, we skip expanding the parameter list, and we treat its body 
				//as an implicit "do"
				let params_i = match arr.iter().position(|v| v.is_arr()) {
					Some(i) => i,
					None => bail_at!(arr.span(), "invalid (fn) form passed to expander")
				};
				//arr = expand_fn_params(arr, &mut arr_owned, context)?;
				arr = expand_do_elements(arr, params_i + 1, &mut arr_owned, context)?;

				//we currently don't need to expand the parameter list of a (fn) special form at
				//all. see macros.rs: the output of the (fn) macro guarantees that any initializer
				//forms which remain in the param list are trivial, e.g. 5 or 'something.
			}
			_ => {
				//for all other forms, like (if) and function calls, we can just expand their
				//arguments in order. we forbid (let-macro) forms outside of an implicit "do".
				let mut i = 1;
				while i < arr.len() {
					arr = expand_element(arr, i, &mut arr_owned, context)?;
					i += 1;
				}
			}
		}

		//all finished! if the array was never mutated, it's always safe to return None.
		return if arr_owned || form_mutated { Ok(Some(Val::Arr(arr))) } else { Ok(None) }
	}
}

//performs step 3 of the expansion algorithm, once. this is the same functionality exposed as the
//(expand-1) function: it can optionally receive a custom expander, and it notifies the caller 
//whether or not an expander was called, and whether or not (macro-no-op) occurred.
fn maybe_call_expander(
	form: &Val,
	expander: Option<Expander>,
	context: &mut Context
) -> GResult<Expansion> {

	fn invoke_macro_expander(
		arr: &Root<Arr>,
		overridden: bool,
		expander: &Expander,
		context: &mut Context
	) -> GResult<Expansion> {

		let prev_expanding = glsp::enter_expander(arr, Rc::clone(&context.env));
		let _guard = Guard::new(|| glsp::leave_expander(prev_expanding));

		let args = SmallVec::<[Val; 16]>::from_iter(arr.iter().skip(1));

		let result = match expander {
			Expander::RFn(ref rfn) => {
				let override_name = if overridden {
					Some(rfn.name())
				} else {
					None
				};

				glsp::push_frame(Frame::Expand(arr.to_raw(), override_name));
				let _guard = Guard::new(|| glsp::pop_frame());

				glsp::call(rfn, &args[..])
			}
			Expander::GFn(ref gfn) => {
				let override_name = if overridden {
					Some(gfn.name())
				} else {
					None
				};

				glsp::push_frame(Frame::Expand(arr.to_raw(), override_name));
				let _guard = Guard::new(|| glsp::pop_frame());

				glsp::call(gfn, &args[..])
			}
		};

		match result {
			Ok(val) => Ok(Expansion::ExpandedTo(val)),
			Err(err) => {
				if err.is_macro_no_op() {
					Ok(Expansion::MacroNoOp)
				} else {
					Err(err)
				}
			}
		}
	}

	match expander {
		Some(expander) => {
			ensure!(form.is_arr(), "attempted to macro-expand a form with a custom expander, \
			                        but the form is not an arr");
			let arr = form.clone().unwrap_arr();

			ensure!(arr.len() > 0, "attempted to macro-expand a form with a custom expander, \
			                        but the form is an empty arr");
			ensure!(arr.get::<Val>(0)?.is_sym(), "attempted to macro-expand a form with a custom \
			                                      expander, but it doesn't start with a sym");

			invoke_macro_expander(&arr, true, &expander, context)
		}
		None => {
			match *form {
				Val::Arr(ref arr) if arr.len() > 0 && arr.get::<Val>(0).unwrap().is_sym() => {
					let sym = arr.get::<Sym>(0).unwrap();

					//local macro bindings
					if let Some(expander_gfn) = context.lookup_let_macro(sym) {
						let expander = Expander::GFn(expander_gfn.clone());
						return invoke_macro_expander(&arr, false, &expander, context)
					}

					//global macro bindings
					if glsp::has_macro(sym).unwrap() {
						let expander = glsp::get_macro(sym).unwrap();
						return invoke_macro_expander(&arr, false, &expander, context)
					}

					Ok(Expansion::NotAMacro)
				}
				_ => Ok(Expansion::NotAMacro)
			}
		}
	}
}