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#![allow(dead_code)]
use super::super::objects::{DeclInfoKey, ObjKey, TCObjects};
use super::check::{Checker, Initializer};
use super::resolver::DeclInfo;
use std::cell::RefCell;
use std::collections::{HashMap, HashSet};
use std::rc::Rc;
#[derive(Debug)]
struct GraphEdges {
pred: Rc<RefCell<HashSet<ObjKey>>>,
succ: Rc<RefCell<HashSet<ObjKey>>>,
}
struct GraphNode {
obj: ObjKey,
ndeps: usize,
pos: usize,
}
impl GraphEdges {
fn new(succ: Rc<RefCell<HashSet<ObjKey>>>) -> GraphEdges {
GraphEdges {
pred: Rc::new(RefCell::new(HashSet::new())),
succ: succ,
}
}
}
impl<'a> Checker<'a> {
pub fn init_order(&mut self) {
let (mut nodes, edges) = self.dependency_graph();
nodes.sort_by(|a, b| a.ndeps.cmp(&b.ndeps)); // sort by n_deps
let len = nodes.len();
let mut nodes = &mut nodes[0..len];
let mut order: Vec<ObjKey> = vec![];
let mut emitted: HashSet<DeclInfoKey> = HashSet::new();
loop {
if nodes.len() == 0 {
break;
}
let mut first_dependant = nodes
.iter()
.enumerate()
.find(|(_, n)| n.ndeps > 0)
.map_or(nodes.len(), |(i, _)| i);
if first_dependant == 0 {
// we have a cycle with the first node
let visited = &mut HashSet::new();
let obj = nodes[0].obj;
// If obj is not part of the cycle (e.g., obj->b->c->d->c),
// cycle will be nil. Don't report anything in that case since
// the cycle is reported when the algorithm gets to an object
// in the cycle.
// Furthermore, once an object in the cycle is encountered,
// the cycle will be broken (dependency count will be reduced
// below), and so the remaining nodes in the cycle don't trigger
// another error (unless they are part of multiple cycles).
if let Some(cycle) = find_path(&self.obj_map, obj, obj, visited, self.tc_objs) {
self.report_cycle(&cycle);
}
// Ok to continue, but the variable initialization order
// will be incorrect at this point since it assumes no
// cycle errors.
// set first_dependant to 1 to remove the first node,
first_dependant = 1;
}
let mut indep: Vec<ObjKey> = nodes[0..first_dependant].iter().map(|n| n.obj).collect();
indep.sort_by(|a, b| self.lobj(*a).order().cmp(&self.lobj(*b).order()));
order.append(&mut indep);
// reduce dependency count of all dependent nodes
let to_sub: HashMap<ObjKey, usize> =
nodes[0..first_dependant]
.iter()
.fold(HashMap::new(), |mut init, x| {
for p in edges[&x.obj].pred.borrow().iter() {
*init.entry(*p).or_insert(0) += 1;
}
init
});
// remove resolved nodes
nodes = &mut nodes[first_dependant..];
for n in nodes.iter_mut() {
n.ndeps -= *to_sub.get(&n.obj).unwrap_or(&0);
}
// sort nodes, shoud be fast as it's almost sorted
nodes.sort_by(|a, b| a.ndeps.cmp(&b.ndeps));
}
// record the init order for variables with initializers only
let init_order = order
.into_iter()
.filter_map(|x| {
let decl_key = self.obj_map[&x];
match &self.tc_objs.decls[decl_key] {
DeclInfo::Var(var) => {
if var.init.is_none() {
return None;
}
// n:1 variable declarations such as: a, b = f()
// introduce a node for each lhs variable (here: a, b);
// but they all have the same initializer - emit only
// one, for the first variable seen
if emitted.contains(&decl_key) {
return None;
}
emitted.insert(decl_key);
let lhs = var.lhs.clone().unwrap_or(vec![x]);
Some(Initializer {
lhs: lhs,
rhs: var.init.clone().unwrap(),
})
}
_ => None,
}
})
.collect();
self.result.record_init_order(init_order);
}
/// dependency_graph returns the object dependency graph from the given obj_map,
/// with any function nodes removed. The resulting graph contains only constants
/// and variables.
fn dependency_graph(&self) -> (Vec<GraphNode>, HashMap<ObjKey, GraphEdges>) {
// map is the dependency (Object) -> graphNode mapping
let map: HashMap<ObjKey, GraphEdges> = self.obj_map.iter().fold(
HashMap::new(),
|mut init: HashMap<ObjKey, GraphEdges>, (&x, &decl_key)| {
let decl = &self.tc_objs.decls[decl_key];
if decl.has_initializer(self.ast_objs) {
let deps: HashSet<ObjKey> = decl.deps().iter().map(|z| *z).collect();
init.insert(x, GraphEdges::new(Rc::new(RefCell::new(deps))));
}
init
},
);
// add the edges for the other direction
for (o, node) in map.iter() {
for s in node.succ.borrow().iter() {
let decl = &self.tc_objs.decls[self.obj_map[s]];
if decl.has_initializer(self.ast_objs) {
map[s].pred.borrow_mut().insert(*o);
}
}
}
// remove function nodes and collect remaining graph nodes in graph
// (Mutually recursive functions may introduce cycles among themselves
// which are permitted. Yet such cycles may incorrectly inflate the dependency
// count for variables which in turn may not get scheduled for initialization
// in correct order.)
let mut nodes: Vec<GraphNode> = map
.iter()
.filter_map(|(o, node)| {
if self.lobj(*o).entity_type().is_func() {
for p in node.pred.borrow().iter() {
if p != o {
for s in node.succ.borrow().iter() {
if s != o {
map[p].succ.borrow_mut().insert(*s);
map[s].pred.borrow_mut().insert(*p);
map[s].pred.borrow_mut().remove(o);
}
}
map[p].succ.borrow_mut().remove(o);
}
}
None
} else {
Some(GraphNode {
obj: *o,
ndeps: node.succ.borrow().len(),
pos: self.lobj(*o).pos(),
})
}
})
.collect();
nodes.sort_by(|a, b| a.pos.cmp(&b.pos)); // sort by pos
(nodes, map)
}
fn report_cycle(&self, cycle: &Vec<ObjKey>) {
let o = self.lobj(cycle[0]);
self.error(o.pos(), format!("initialization cycle for {}", o.name()));
self.error(o.pos(), format!("\t{} refers to", o.name()));
for okey in cycle[1..].iter().rev() {
let o = self.lobj(*okey);
self.error(o.pos(), format!("\t{} refers to", o.name()));
}
let o = self.lobj(cycle[0]);
self.error(o.pos(), format!("\t{}", o.name()));
}
}
/// find_path returns the (reversed) list of objects Vec<ObjKey>{to, ... from}
/// such that there is a path of object dependencies from 'from' to 'to'.
/// If there is no such path, the result is None.
fn find_path(
map: &HashMap<ObjKey, DeclInfoKey>,
from: ObjKey,
to: ObjKey,
visited: &mut HashSet<ObjKey>,
tc_objs: &TCObjects,
) -> Option<Vec<ObjKey>> {
if visited.contains(&from) {
return None;
}
visited.insert(from);
let decl = &tc_objs.decls[map[&from]];
for &d in decl.deps().iter() {
if d == to {
return Some(vec![d]);
}
if let Some(mut p) = find_path(map, d, to, visited, tc_objs) {
p.push(d);
return Some(p);
}
}
None
}