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Cleanup the unification engine to use associated types, making the code much easier to read.

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This commit is contained in:
Niko Matsakis 2015-01-21 20:25:24 -05:00
parent 984dc03df6
commit 60db57e7ec
4 changed files with 89 additions and 88 deletions
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9
src/librustc/middle/infer/mod.rs
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@ -79,16 +79,13 @@ pub struct InferCtxt<'a, 'tcx: 'a> {
type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
// Map from integral variable to the kind of integer it represents
int_unification_table:
RefCell<UnificationTable<ty::IntVid, Option<IntVarValue>>>,
int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
// Map from floating variable to the kind of float it represents
float_unification_table:
RefCell<UnificationTable<ty::FloatVid, Option<ast::FloatTy>>>,
float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
// For region variables.
region_vars:
RegionVarBindings<'a, 'tcx>,
region_vars: RegionVarBindings<'a, 'tcx>,
}
/// A map returned by `skolemize_late_bound_regions()` indicating the skolemized

11
src/librustc/middle/infer/type_variable.rs
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@ -19,7 +19,7 @@ use std::u32;
use util::snapshot_vec as sv;
pub struct TypeVariableTable<'tcx> {
values: sv::SnapshotVec<TypeVariableData<'tcx>,UndoEntry,Delegate>,
values: sv::SnapshotVec<Delegate<'tcx>>,
}
struct TypeVariableData<'tcx> {
@ -42,7 +42,7 @@ enum UndoEntry {
Relate(ty::TyVid, ty::TyVid),
}
struct Delegate;
struct Delegate<'tcx>;
type Relation = (RelationDir, ty::TyVid);
@ -195,9 +195,12 @@ impl<'tcx> TypeVariableTable<'tcx> {
}
}
impl<'tcx> sv::SnapshotVecDelegate<TypeVariableData<'tcx>,UndoEntry> for Delegate {
impl<'tcx> sv::SnapshotVecDelegate for Delegate<'tcx> {
type Value = TypeVariableData<'tcx>;
type Undo = UndoEntry;
fn reverse(&mut self,
values: &mut Vec<TypeVariableData>,
values: &mut Vec<TypeVariableData<'tcx>>,
action: UndoEntry) {
match action {
SpecifyVar(vid, relations) => {

121
src/librustc/middle/infer/unify.rs
View File

@ -19,7 +19,6 @@ use middle::infer::InferCtxt;
use std::cell::RefCell;
use std::fmt::Debug;
use syntax::ast;
use util::ppaux::Repr;
use util::snapshot_vec as sv;
/// This trait is implemented by any type that can serve as a type
@ -32,7 +31,9 @@ use util::snapshot_vec as sv;
/// (possibly not yet known) sort of integer.
///
/// Implementations of this trait are at the end of this file.
pub trait UnifyKey<'tcx, V> : Clone + Debug + PartialEq + Repr<'tcx> {
pub trait UnifyKey : Clone + Debug + PartialEq {
type Value : UnifyValue;
fn index(&self) -> uint;
fn from_index(u: uint) -> Self;
@ -40,7 +41,7 @@ pub trait UnifyKey<'tcx, V> : Clone + Debug + PartialEq + Repr<'tcx> {
// Given an inference context, returns the unification table
// appropriate to this key type.
fn unification_table<'v>(infcx: &'v InferCtxt)
-> &'v RefCell<UnificationTable<Self,V>>;
-> &'v RefCell<UnificationTable<Self>>;
fn tag(k: Option<Self>) -> &'static str;
}
@ -51,7 +52,7 @@ pub trait UnifyKey<'tcx, V> : Clone + Debug + PartialEq + Repr<'tcx> {
/// whose value is not yet set).
///
/// Implementations of this trait are at the end of this file.
pub trait UnifyValue<'tcx> : Clone + Repr<'tcx> + PartialEq {
pub trait UnifyValue : Clone + PartialEq + Debug {
}
/// Value of a unification key. We implement Tarjan's union-find
@ -62,21 +63,21 @@ pub trait UnifyValue<'tcx> : Clone + Repr<'tcx> + PartialEq {
/// to keep the DAG relatively balanced, which helps keep the running
/// time of the algorithm under control. For more information, see
/// <http://en.wikipedia.org/wiki/Disjoint-set_data_structure>.
#[derive(PartialEq,Clone)]
pub enum VarValue<K,V> {
#[derive(PartialEq,Clone,Show)]
pub enum VarValue<K:UnifyKey> {
Redirect(K),
Root(V, uint),
Root(K::Value, uint),
}
/// Table of unification keys and their values.
pub struct UnificationTable<K,V> {
pub struct UnificationTable<K:UnifyKey> {
/// Indicates the current value of each key.
values: sv::SnapshotVec<VarValue<K,V>,(),Delegate>,
values: sv::SnapshotVec<Delegate<K>>,
}
/// At any time, users may snapshot a unification table. The changes
/// made during the snapshot may either be *committed* or *rolled back*.
pub struct Snapshot<K> {
pub struct Snapshot<K:UnifyKey> {
// Link snapshot to the key type `K` of the table.
marker: marker::CovariantType<K>,
snapshot: sv::Snapshot,
@ -84,22 +85,22 @@ pub struct Snapshot<K> {
/// Internal type used to represent the result of a `get()` operation.
/// Conveys the current root and value of the key.
pub struct Node<K,V> {
pub struct Node<K:UnifyKey> {
pub key: K,
pub value: V,
pub value: K::Value,
pub rank: uint,
}
#[derive(Copy)]
pub struct Delegate;
pub struct Delegate<K>;
// We can't use V:LatticeValue, much as I would like to,
// because frequently the pattern is that V=Option<U> for some
// other type parameter U, and we have no way to say
// Option<U>:LatticeValue.
impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K,V> {
pub fn new() -> UnificationTable<K,V> {
impl<K:UnifyKey> UnificationTable<K> {
pub fn new() -> UnificationTable<K> {
UnificationTable {
values: sv::SnapshotVec::new(Delegate),
}
@ -126,7 +127,7 @@ impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K
self.values.commit(snapshot.snapshot);
}
pub fn new_key(&mut self, value: V) -> K {
pub fn new_key(&mut self, value: K::Value) -> K {
let index = self.values.push(Root(value, 0));
let k = UnifyKey::from_index(index);
debug!("{}: created new key: {:?}",
@ -137,12 +138,12 @@ impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K
/// Find the root node for `vid`. This uses the standard union-find algorithm with path
/// compression: http://en.wikipedia.org/wiki/Disjoint-set_data_structure
pub fn get(&mut self, tcx: &ty::ctxt, vid: K) -> Node<K,V> {
pub fn get(&mut self, tcx: &ty::ctxt, vid: K) -> Node<K> {
let index = vid.index();
let value = (*self.values.get(index)).clone();
match value {
Redirect(redirect) => {
let node: Node<K,V> = self.get(tcx, redirect.clone());
let node: Node<K> = self.get(tcx, redirect.clone());
if node.key != redirect {
// Path compression
self.values.set(index, Redirect(node.key.clone()));
@ -164,16 +165,15 @@ impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K
/// Sets the value for `vid` to `new_value`. `vid` MUST be a root node! Also, we must be in the
/// middle of a snapshot.
pub fn set(&mut self,
tcx: &ty::ctxt<'tcx>,
key: K,
new_value: VarValue<K,V>)
pub fn set<'tcx>(&mut self,
_tcx: &ty::ctxt<'tcx>,
key: K,
new_value: VarValue<K>)
{
assert!(self.is_root(&key));
debug!("Updating variable {} to {}",
key.repr(tcx),
new_value.repr(tcx));
debug!("Updating variable {:?} to {:?}",
key, new_value);
self.values.set(key.index(), new_value);
}
@ -181,16 +181,16 @@ impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K
/// Either redirects node_a to node_b or vice versa, depending on the relative rank. Returns
/// the new root and rank. You should then update the value of the new root to something
/// suitable.
pub fn unify(&mut self,
tcx: &ty::ctxt<'tcx>,
node_a: &Node<K,V>,
node_b: &Node<K,V>)
-> (K, uint)
pub fn unify<'tcx>(&mut self,
tcx: &ty::ctxt<'tcx>,
node_a: &Node<K>,
node_b: &Node<K>)
-> (K, uint)
{
debug!("unify(node_a(id={}, rank={}), node_b(id={}, rank={}))",
node_a.key.repr(tcx),
debug!("unify(node_a(id={:?}, rank={:?}), node_b(id={:?}, rank={:?}))",
node_a.key,
node_a.rank,
node_b.key.repr(tcx),
node_b.key,
node_b.rank);
if node_a.rank > node_b.rank {
@ -212,8 +212,11 @@ impl<'tcx, V:PartialEq+Clone+Repr<'tcx>, K:UnifyKey<'tcx, V>> UnificationTable<K
}
}
impl<K,V> sv::SnapshotVecDelegate<VarValue<K,V>,()> for Delegate {
fn reverse(&mut self, _: &mut Vec<VarValue<K,V>>, _: ()) {
impl<K> sv::SnapshotVecDelegate for Delegate<K> {
type Value = VarValue<K>;
type Undo = ();
fn reverse(&mut self, _: &mut Vec<VarValue<K>>, _: ()) {
panic!("Nothing to reverse");
}
}
@ -224,7 +227,7 @@ impl<K,V> sv::SnapshotVecDelegate<VarValue<K,V>,()> for Delegate {
/// Indicates a type that does not have any kind of subtyping
/// relationship.
pub trait SimplyUnifiable<'tcx> : Clone + PartialEq + Repr<'tcx> {
pub trait SimplyUnifiable<'tcx> : Clone + PartialEq + Debug {
fn to_type(&self, tcx: &ty::ctxt<'tcx>) -> Ty<'tcx>;
fn to_type_err(expected_found<Self>) -> ty::type_err<'tcx>;
}
@ -242,8 +245,11 @@ pub fn err<'tcx, V:SimplyUnifiable<'tcx>>(a_is_expected: bool,
}
}
pub trait InferCtxtMethodsForSimplyUnifiableTypes<'tcx, V:SimplyUnifiable<'tcx>,
K:UnifyKey<'tcx, Option<V>>> {
pub trait InferCtxtMethodsForSimplyUnifiableTypes<'tcx,K,V>
where K : UnifyKey<Value=Option<V>>,
V : SimplyUnifiable<'tcx>,
Option<V> : UnifyValue,
{
fn simple_vars(&self,
a_is_expected: bool,
a_id: K,
@ -257,8 +263,10 @@ pub trait InferCtxtMethodsForSimplyUnifiableTypes<'tcx, V:SimplyUnifiable<'tcx>,
fn probe_var(&self, a_id: K) -> Option<Ty<'tcx>>;
}
impl<'a,'tcx,V:SimplyUnifiable<'tcx>,K:UnifyKey<'tcx, Option<V>>>
InferCtxtMethodsForSimplyUnifiableTypes<'tcx, V, K> for InferCtxt<'a, 'tcx>
impl<'a,'tcx,V,K> InferCtxtMethodsForSimplyUnifiableTypes<'tcx,K,V> for InferCtxt<'a,'tcx>
where K : UnifyKey<Value=Option<V>>,
V : SimplyUnifiable<'tcx>,
Option<V> : UnifyValue,
{
/// Unifies two simple keys. Because simple keys do not have any subtyping relationships, if
/// both keys have already been associated with a value, then those two values must be the
@ -271,8 +279,8 @@ impl<'a,'tcx,V:SimplyUnifiable<'tcx>,K:UnifyKey<'tcx, Option<V>>>
{
let tcx = self.tcx;
let table = UnifyKey::unification_table(self);
let node_a = table.borrow_mut().get(tcx, a_id);
let node_b = table.borrow_mut().get(tcx, b_id);
let node_a: Node<K> = table.borrow_mut().get(tcx, a_id);
let node_b: Node<K> = table.borrow_mut().get(tcx, b_id);
let a_id = node_a.key.clone();
let b_id = node_b.key.clone();
@ -346,14 +354,14 @@ impl<'a,'tcx,V:SimplyUnifiable<'tcx>,K:UnifyKey<'tcx, Option<V>>>
// Integral type keys
impl<'tcx> UnifyKey<'tcx, Option<IntVarValue>> for ty::IntVid {
impl UnifyKey for ty::IntVid {
type Value = Option<IntVarValue>;
fn index(&self) -> uint { self.index as uint }
fn from_index(i: uint) -> ty::IntVid { ty::IntVid { index: i as u32 } }
fn unification_table<'v>(infcx: &'v InferCtxt)
-> &'v RefCell<UnificationTable<ty::IntVid, Option<IntVarValue>>>
{
fn unification_table<'v>(infcx: &'v InferCtxt) -> &'v RefCell<UnificationTable<ty::IntVid>> {
return &infcx.int_unification_table;
}
@ -375,18 +383,18 @@ impl<'tcx> SimplyUnifiable<'tcx> for IntVarValue {
}
}
impl<'tcx> UnifyValue<'tcx> for Option<IntVarValue> { }
impl UnifyValue for Option<IntVarValue> { }
// Floating point type keys
impl<'tcx> UnifyKey<'tcx, Option<ast::FloatTy>> for ty::FloatVid {
impl UnifyKey for ty::FloatVid {
type Value = Option<ast::FloatTy>;
fn index(&self) -> uint { self.index as uint }
fn from_index(i: uint) -> ty::FloatVid { ty::FloatVid { index: i as u32 } }
fn unification_table<'v>(infcx: &'v InferCtxt)
-> &'v RefCell<UnificationTable<ty::FloatVid, Option<ast::FloatTy>>>
{
fn unification_table<'v>(infcx: &'v InferCtxt) -> &'v RefCell<UnificationTable<ty::FloatVid>> {
return &infcx.float_unification_table;
}
@ -395,7 +403,7 @@ impl<'tcx> UnifyKey<'tcx, Option<ast::FloatTy>> for ty::FloatVid {
}
}
impl<'tcx> UnifyValue<'tcx> for Option<ast::FloatTy> {
impl UnifyValue for Option<ast::FloatTy> {
}
impl<'tcx> SimplyUnifiable<'tcx> for ast::FloatTy {
@ -407,12 +415,3 @@ impl<'tcx> SimplyUnifiable<'tcx> for ast::FloatTy {
ty::terr_float_mismatch(err)
}
}
impl<'tcx, K:Repr<'tcx>, V:Repr<'tcx>> Repr<'tcx> for VarValue<K,V> {
fn repr(&self, tcx: &ty::ctxt<'tcx>) -> String {
match *self {
Redirect(ref k) => format!("Redirect({})", k.repr(tcx)),
Root(ref v, r) => format!("Root({}, {})", v.repr(tcx), r)
}
}
}

36
src/librustc/util/snapshot_vec.rs
View File

@ -22,8 +22,7 @@ use self::UndoLog::*;
use std::mem;
#[derive(PartialEq)]
pub enum UndoLog<T,U> {
pub enum UndoLog<D:SnapshotVecDelegate> {
/// Indicates where a snapshot started.
OpenSnapshot,
@ -34,15 +33,15 @@ pub enum UndoLog<T,U> {
NewElem(uint),
/// Variable with given index was changed *from* the given value.
SetElem(uint, T),
SetElem(uint, D::Value),
/// Extensible set of actions
Other(U)
Other(D::Undo)
}
pub struct SnapshotVec<T,U,D> {
values: Vec<T>,
undo_log: Vec<UndoLog<T,U>>,
pub struct SnapshotVec<D:SnapshotVecDelegate> {
values: Vec<D::Value>,
undo_log: Vec<UndoLog<D>>,
delegate: D
}
@ -53,12 +52,15 @@ pub struct Snapshot {
length: uint,
}
pub trait SnapshotVecDelegate<T,U> {
fn reverse(&mut self, values: &mut Vec<T>, action: U);
pub trait SnapshotVecDelegate {
type Value;
type Undo;
fn reverse(&mut self, values: &mut Vec<Self::Value>, action: Self::Undo);
}
impl<T,U,D:SnapshotVecDelegate<T,U>> SnapshotVec<T,U,D> {
pub fn new(delegate: D) -> SnapshotVec<T,U,D> {
impl<D:SnapshotVecDelegate> SnapshotVec<D> {
pub fn new(delegate: D) -> SnapshotVec<D> {
SnapshotVec {
values: Vec::new(),
undo_log: Vec::new(),
@ -70,13 +72,13 @@ impl<T,U,D:SnapshotVecDelegate<T,U>> SnapshotVec<T,U,D> {
!self.undo_log.is_empty()
}
pub fn record(&mut self, action: U) {
pub fn record(&mut self, action: D::Undo) {
if self.in_snapshot() {
self.undo_log.push(Other(action));
}
}
pub fn push(&mut self, elem: T) -> uint {
pub fn push(&mut self, elem: D::Value) -> uint {
let len = self.values.len();
self.values.push(elem);
@ -87,20 +89,20 @@ impl<T,U,D:SnapshotVecDelegate<T,U>> SnapshotVec<T,U,D> {
len
}
pub fn get<'a>(&'a self, index: uint) -> &'a T {
pub fn get<'a>(&'a self, index: uint) -> &'a D::Value {
&self.values[index]
}
/// Returns a mutable pointer into the vec; whatever changes you make here cannot be undone
/// automatically, so you should be sure call `record()` with some sort of suitable undo
/// action.
pub fn get_mut<'a>(&'a mut self, index: uint) -> &'a mut T {
pub fn get_mut<'a>(&'a mut self, index: uint) -> &'a mut D::Value {
&mut self.values[index]
}
/// Updates the element at the given index. The old value will saved (and perhaps restored) if
/// a snapshot is active.
pub fn set(&mut self, index: uint, new_elem: T) {
pub fn set(&mut self, index: uint, new_elem: D::Value) {
let old_elem = mem::replace(&mut self.values[index], new_elem);
if self.in_snapshot() {
self.undo_log.push(SetElem(index, old_elem));
@ -115,7 +117,7 @@ impl<T,U,D:SnapshotVecDelegate<T,U>> SnapshotVec<T,U,D> {
pub fn actions_since_snapshot(&self,
snapshot: &Snapshot)
-> &[UndoLog<T,U>] {
-> &[UndoLog<D>] {
&self.undo_log[snapshot.length..]
}