use std::rc::Rc;
use rustc_hash::{FxHashMap, FxHashSet};
use super::Expander;
use super::budget_arena::BudgetId;
use super::problems::ExpandProblems;
use super::recur_check::RecurCheck;
use super::try_check::TryCheck;
use crate::core::{BindingId, Declaration, Expr};
use crate::diagnostic::Diagnostic;
use crate::interpret::{Env, Interpreter, Value};
use crate::reader::Form;
use crate::scope::Phase;
use crate::source::Span;
#[derive(serde::Serialize, serde::Deserialize)]
enum GlobalState {
Pending { value: Form, budget: BudgetId },
Lowering,
Lowered(Rc<Expr>),
Failed,
FailedDefinition(Declaration),
}
#[derive(Default, serde::Serialize, serde::Deserialize)]
pub struct GlobalTable {
states: FxHashMap<BindingId, GlobalState>,
values: FxHashMap<BindingId, Value>,
evaluating: FxHashSet<BindingId>,
compile_time_checks: FxHashMap<BindingId, CompileTimeCheck>,
failed_definition_count: usize,
}
#[derive(serde::Serialize, serde::Deserialize)]
pub struct LoweredGlobals(Vec<BindingId>);
#[derive(Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
pub enum CompileTimeCheck {
InProgress,
Passed,
Failed,
}
impl GlobalTable {
pub fn add_pending(&mut self, binding: BindingId, value: Form, budget: BudgetId) {
self.states
.insert(binding, GlobalState::Pending { value, budget });
}
pub fn compile_time_check(&self, binding: BindingId) -> Option<CompileTimeCheck> {
self.compile_time_checks.get(&binding).copied()
}
pub fn record_compile_time_check(&mut self, binding: BindingId, check: CompileTimeCheck) {
self.compile_time_checks.insert(binding, check);
}
pub fn macro_helpers(&self) -> FxHashSet<BindingId> {
self.compile_time_checks
.iter()
.filter(|(_, check)| **check == CompileTimeCheck::Passed)
.map(|(binding, _)| *binding)
.collect()
}
pub fn record_failed_definition(&mut self, binding: BindingId, declaration: Declaration) {
self.states
.insert(binding, GlobalState::FailedDefinition(declaration));
self.failed_definition_count += 1;
}
pub fn forget_failed_definition(&mut self, binding: BindingId) {
self.states.remove(&binding);
self.failed_definition_count -= 1;
}
pub fn has_failed_definitions(&self) -> bool {
self.failed_definition_count > 0
}
pub fn is_failed_macro_definition(&self, binding: BindingId) -> bool {
matches!(
self.states.get(&binding),
Some(GlobalState::FailedDefinition(Declaration::Macro))
)
}
pub fn is_failed_definition(&self, binding: BindingId) -> bool {
matches!(
self.states.get(&binding),
Some(GlobalState::FailedDefinition(_))
)
}
pub fn has_failed(&self, binding: BindingId) -> bool {
matches!(self.states.get(&binding), Some(GlobalState::Failed))
}
pub fn take_lowered<'m>(
&mut self,
definitions: impl Iterator<Item = (BindingId, &'m Rc<Expr>)>,
) -> LoweredGlobals {
let states = std::mem::take(&mut self.states);
let mut lowered: Vec<BindingId> = definitions
.filter(|(binding, value)| {
states
.get(binding)
.is_some_and(|state| state.is_lowered_to(value))
})
.map(|(binding, _)| binding)
.collect();
assert_eq!(
lowered.len(),
states.len(),
"every global to take is lowered to the expression of its definition"
);
lowered.sort_unstable();
LoweredGlobals(lowered)
}
pub fn restore_lowered<'m>(
&mut self,
lowered: &LoweredGlobals,
definitions: impl Iterator<Item = (BindingId, &'m Rc<Expr>)>,
) {
for (binding, value) in definitions.filter(|(binding, _)| lowered.contains(*binding)) {
self.states
.insert(binding, GlobalState::Lowered(Rc::clone(value)));
}
}
}
impl GlobalState {
fn is_lowered_to(&self, value: &Rc<Expr>) -> bool {
matches!(self, Self::Lowered(expr) if Rc::ptr_eq(expr, value))
}
}
impl LoweredGlobals {
fn contains(&self, binding: BindingId) -> bool {
self.0.binary_search(&binding).is_ok()
}
}
impl Expander<'_> {
pub(super) fn lowered_global(
&mut self,
binding: BindingId,
span: Span,
) -> Result<Rc<Expr>, Diagnostic> {
self.decode_saved_global(binding);
match self
.tables
.globals
.states
.insert(binding, GlobalState::Lowering)
{
Some(GlobalState::Pending { value, budget }) => {
self.spending(budget, |expander| expander.lower_global(binding, &value))
}
Some(GlobalState::Lowered(expr)) => {
self.tables
.globals
.states
.insert(binding, GlobalState::Lowered(Rc::clone(&expr)));
Ok(expr)
}
Some(failed @ (GlobalState::Failed | GlobalState::FailedDefinition(_))) => {
self.tables.globals.states.insert(binding, failed);
Err(ExpandProblems::broken_definition(
self.tables.bindings.get(binding).name(),
span,
))
}
Some(GlobalState::Lowering) | None => Err(ExpandProblems::compile_time_cycle(
self.tables.bindings.get(binding).name(),
span,
)),
}
}
fn decode_saved_global(&mut self, binding: BindingId) {
let states = &mut self.tables.globals.states;
if !states.contains_key(&binding)
&& let Some(value) = self.saved_definitions.value_of(binding)
{
states.insert(binding, GlobalState::Lowered(value));
}
}
pub(super) fn evaluate_global(
&mut self,
binding: BindingId,
span: Span,
) -> Result<Value, Diagnostic> {
if let Some(value) = self.tables.globals.values.get(&binding) {
return Ok(value.clone());
}
if !self.tables.globals.evaluating.insert(binding) {
return Err(ExpandProblems::compile_time_cycle(
self.tables.bindings.get(binding).name(),
span,
));
}
let result = self
.lowered_global(binding, span)
.and_then(|expr| Interpreter::new(self, span).eval(&expr, &Env::default()));
self.tables.globals.evaluating.remove(&binding);
let value = result?;
self.tables.globals.values.insert(binding, value.clone());
Ok(value)
}
fn lower_global(&mut self, binding: BindingId, form: &Form) -> Result<Rc<Expr>, Diagnostic> {
let outer_phase = std::mem::replace(&mut self.phase, Phase::Runtime);
let errors_before = self.recovered_diagnostics.len();
let lowered = self.lower_expr(form);
self.phase = outer_phase;
match lowered {
Ok(expr) => {
if self.recovered_diagnostics.len() > errors_before {
self.tables
.globals
.states
.insert(binding, GlobalState::Failed);
return Err(self.recovered_diagnostics.remove(errors_before));
}
RecurCheck::outside().value(&expr)?;
TryCheck::outside().value(&expr)?;
let expr = Rc::new(expr);
self.tables
.globals
.states
.insert(binding, GlobalState::Lowered(Rc::clone(&expr)));
Ok(expr)
}
Err(diagnostic) => {
self.tables
.globals
.states
.insert(binding, GlobalState::Failed);
Err(diagnostic)
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::core::{BindingArena, BindingInfo, BindingKind, ExprKind, Leaf, Literal, ModuleId};
use crate::source::SourceId;
struct Definitions {
bindings: BindingArena,
values: Vec<(BindingId, Rc<Expr>)>,
}
impl Definitions {
fn new() -> Self {
Self {
bindings: BindingArena::default(),
values: Vec::new(),
}
}
fn define(&mut self, name: &str) -> BindingId {
let kind = BindingKind::Global(ModuleId::new(0));
let binding = self.bindings.add(BindingInfo::new(name.into(), kind, None));
let span = Span::new(SourceId::new(0), 0..0);
let value = Expr::new(ExprKind::Leaf(Leaf::Literal(Literal::Bool(true))), span);
self.values.push((binding, Rc::new(value)));
binding
}
fn lower(&self, table: &mut GlobalTable, binding: BindingId) {
table.states.insert(
binding,
GlobalState::Lowered(Rc::clone(self.value(binding))),
);
}
fn value(&self, binding: BindingId) -> &Rc<Expr> {
&self
.values
.iter()
.find(|(defined, _)| *defined == binding)
.expect("the binding is defined")
.1
}
fn newest_first(&self) -> impl Iterator<Item = (BindingId, &Rc<Expr>)> {
self.values
.iter()
.rev()
.map(|(binding, value)| (*binding, value))
}
}
#[test]
fn a_restore_brings_back_only_the_lowered_globals() {
let mut definitions = Definitions::new();
let lowered = [definitions.define("fuel"), definitions.define("range")];
let method = definitions.define("charge");
let mut built = GlobalTable::default();
lowered
.iter()
.for_each(|binding| definitions.lower(&mut built, *binding));
let taken = built.take_lowered(definitions.newest_first());
let mut restored = GlobalTable::default();
restored.restore_lowered(&taken, definitions.newest_first());
assert!(lowered.iter().all(|binding| {
restored.states[binding].is_lowered_to(definitions.value(*binding))
}));
assert!(!restored.states.contains_key(&method));
}
#[test]
fn a_take_leaves_no_state_behind() {
let mut definitions = Definitions::new();
let binding = definitions.define("fuel");
let mut table = GlobalTable::default();
definitions.lower(&mut table, binding);
table.take_lowered(definitions.newest_first());
assert!(table.states.is_empty());
}
#[test]
#[should_panic(
expected = "every global to take is lowered to the expression of its definition"
)]
fn a_global_lowered_to_another_expression_stops_the_take() {
let mut definitions = Definitions::new();
let binding = definitions.define("fuel");
let mut table = GlobalTable::default();
let copy = Expr::clone(definitions.value(binding));
table
.states
.insert(binding, GlobalState::Lowered(Rc::new(copy)));
table.take_lowered(definitions.newest_first());
}
}