forked from M-Labs/nac3
677 lines
25 KiB
Rust
677 lines
25 KiB
Rust
use itertools::{chain, zip, Itertools};
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use std::borrow::Cow;
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use std::cell::RefCell;
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use std::collections::HashMap;
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use std::iter::once;
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use std::rc::Rc;
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use super::unification_table::{UnificationKey, UnificationTable};
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#[cfg(test)]
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mod test;
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/// Handle for a type, implementated as a key in the unification table.
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pub type Type = UnificationKey;
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pub type Mapping<K, V = Type> = HashMap<K, V>;
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type VarMap = Mapping<u32>;
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#[derive(Clone)]
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pub struct Call {
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pub posargs: Vec<Type>,
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pub kwargs: HashMap<String, Type>,
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pub ret: Type,
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pub fun: RefCell<Option<Type>>,
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}
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#[derive(Clone)]
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pub struct FuncArg {
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pub name: String,
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pub ty: Type,
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pub is_optional: bool,
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}
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#[derive(Clone)]
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pub struct FunSignature {
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pub args: Vec<FuncArg>,
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pub ret: Type,
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pub vars: VarMap,
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}
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#[derive(Clone)]
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pub enum TypeVarMeta {
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Generic,
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Sequence(RefCell<Mapping<i32>>),
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Record(RefCell<Mapping<String>>),
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}
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#[derive(Clone)]
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pub enum TypeEnum {
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TVar {
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id: u32,
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meta: TypeVarMeta,
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// empty indicates no restriction
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range: RefCell<Vec<Type>>,
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},
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TTuple {
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ty: Vec<Type>,
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},
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TList {
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ty: Type,
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},
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TObj {
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obj_id: usize,
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fields: Mapping<String>,
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params: VarMap,
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},
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TVirtual {
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ty: Type,
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},
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TCall(RefCell<Vec<Rc<Call>>>),
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TFunc(FunSignature),
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}
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impl TypeEnum {
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pub fn get_type_name(&self) -> &'static str {
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match self {
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TypeEnum::TVar { .. } => "TVar",
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TypeEnum::TTuple { .. } => "TTuple",
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TypeEnum::TList { .. } => "TList",
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TypeEnum::TObj { .. } => "TObj",
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TypeEnum::TVirtual { .. } => "TVirtual",
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TypeEnum::TCall { .. } => "TCall",
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TypeEnum::TFunc { .. } => "TFunc",
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}
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}
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pub fn is_concrete(&self) -> bool {
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!matches!(self, TypeEnum::TVar { .. })
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}
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}
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pub struct Unifier {
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unification_table: UnificationTable<Rc<TypeEnum>>,
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var_id: u32,
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}
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impl Unifier {
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/// Get an empty unifier
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pub fn new() -> Unifier {
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Unifier { unification_table: UnificationTable::new(), var_id: 0 }
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}
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/// Register a type to the unifier.
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/// Returns a key in the unification_table.
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pub fn add_ty(&mut self, a: TypeEnum) -> Type {
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self.unification_table.new_key(Rc::new(a))
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}
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pub fn add_record(&mut self, fields: Mapping<String>) -> Type {
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let id = self.var_id + 1;
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self.var_id += 1;
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self.add_ty(TypeEnum::TVar {
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id,
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range: vec![].into(),
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meta: TypeVarMeta::Record(fields.into()),
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})
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}
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pub fn add_sequence(&mut self, sequence: Mapping<i32>) -> Type {
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let id = self.var_id + 1;
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self.var_id += 1;
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self.add_ty(TypeEnum::TVar {
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id,
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range: vec![].into(),
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meta: TypeVarMeta::Sequence(sequence.into()),
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})
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}
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/// Get the TypeEnum of a type.
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pub fn get_ty(&mut self, a: Type) -> Rc<TypeEnum> {
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self.unification_table.probe_value(a).clone()
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}
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pub fn get_fresh_var(&mut self) -> (Type, u32) {
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self.get_fresh_var_with_range(&[])
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}
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/// Get a fresh type variable.
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pub fn get_fresh_var_with_range(&mut self, range: &[Type]) -> (Type, u32) {
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let id = self.var_id + 1;
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self.var_id += 1;
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let range = range.to_vec().into();
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(self.add_ty(TypeEnum::TVar { id, range, meta: TypeVarMeta::Generic }), id)
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}
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pub fn unify(&mut self, a: Type, b: Type) -> Result<(), String> {
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if self.unification_table.unioned(a, b) {
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Ok(())
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} else {
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self.unify_impl(a, b, false)
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}
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}
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fn unify_impl(&mut self, a: Type, b: Type, swapped: bool) -> Result<(), String> {
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use TypeEnum::*;
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use TypeVarMeta::*;
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let (ty_a, ty_b) = {
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(
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self.unification_table.probe_value(a).clone(),
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self.unification_table.probe_value(b).clone(),
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)
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};
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match (&*ty_a, &*ty_b) {
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(TVar { meta: meta1, range: range1, .. }, TVar { meta: meta2, range: range2, .. }) => {
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self.occur_check(a, b)?;
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self.occur_check(b, a)?;
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match (meta1, meta2) {
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(Generic, _) => {}
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(_, Generic) => {
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return self.unify_impl(b, a, true);
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}
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(Record(fields1), Record(fields2)) => {
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let mut fields2 = fields2.borrow_mut();
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for (key, value) in fields1.borrow().iter() {
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if let Some(ty) = fields2.get(key) {
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self.unify(*ty, *value)?;
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} else {
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fields2.insert(key.clone(), *value);
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}
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}
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}
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(Sequence(map1), Sequence(map2)) => {
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let mut map2 = map2.borrow_mut();
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for (key, value) in map1.borrow().iter() {
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if let Some(ty) = map2.get(key) {
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self.unify(*ty, *value)?;
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} else {
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map2.insert(*key, *value);
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}
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}
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}
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_ => {
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return Err("Incompatible".to_string());
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}
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}
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let range1 = range1.borrow();
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// new range is the intersection of them
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// empty range indicates no constraint
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if !range1.is_empty() {
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let old_range2 = range2.take();
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let mut range2 = range2.borrow_mut();
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if old_range2.is_empty() {
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range2.extend_from_slice(&range1);
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}
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for v1 in old_range2.iter() {
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for v2 in range1.iter() {
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if !self.shape_match(*v1, *v2) {
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continue;
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}
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self.unify(*v1, *v2)?;
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range2.push(*v2);
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}
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}
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if range2.is_empty() {
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return Err(
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"cannot unify type variables with incompatible value range".to_string()
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);
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}
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}
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self.set_a_to_b(a, b);
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}
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(TVar { meta: Generic, id, range, .. }, _) => {
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self.occur_check(a, b)?;
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self.check_var_range(*id, b, &range.borrow())?;
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self.set_a_to_b(a, b);
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}
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(TVar { meta: Sequence(map), id, range, .. }, TTuple { ty }) => {
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self.occur_check(a, b)?;
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let len = ty.len() as i32;
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for (k, v) in map.borrow().iter() {
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// handle negative index
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let ind = if *k < 0 { len + *k } else { *k };
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if ind >= len || ind < 0 {
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return Err(format!(
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"Tuple index out of range. (Length: {}, Index: {})",
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len, k
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));
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}
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self.unify(*v, ty[ind as usize])?;
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}
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self.check_var_range(*id, b, &range.borrow())?;
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self.set_a_to_b(a, b);
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}
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(TVar { meta: Sequence(map), id, range, .. }, TList { ty }) => {
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self.occur_check(a, b)?;
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for v in map.borrow().values() {
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self.unify(*v, *ty)?;
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}
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self.check_var_range(*id, b, &range.borrow())?;
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self.set_a_to_b(a, b);
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}
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(TTuple { ty: ty1 }, TTuple { ty: ty2 }) => {
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if ty1.len() != ty2.len() {
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return Err(format!(
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"Cannot unify tuples with length {} and {}",
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ty1.len(),
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ty2.len()
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));
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}
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for (x, y) in ty1.iter().zip(ty2.iter()) {
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self.unify(*x, *y)?;
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}
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self.set_a_to_b(a, b);
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}
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(TList { ty: ty1 }, TList { ty: ty2 }) => {
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self.unify(*ty1, *ty2)?;
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self.set_a_to_b(a, b);
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}
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(TVar { meta: Record(map), id, range, .. }, TObj { fields, .. }) => {
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self.occur_check(a, b)?;
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for (k, v) in map.borrow().iter() {
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if let Some(ty) = fields.get(k) {
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self.unify(*ty, *v)?;
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} else {
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return Err(format!("No such attribute {}", k));
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}
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}
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self.check_var_range(*id, b, &range.borrow())?;
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self.set_a_to_b(a, b);
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}
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(TVar { meta: Record(_), id, range, .. }, TVirtual { ty }) => {
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// TODO: look at this rule
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self.occur_check(a, b)?;
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self.check_var_range(*id, b, &range.borrow())?;
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self.unify(a, *ty)?;
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}
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(
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TObj { obj_id: id1, params: params1, .. },
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TObj { obj_id: id2, params: params2, .. },
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) => {
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if id1 != id2 {
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return Err(format!("Cannot unify objects with ID {} and {}", id1, id2));
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}
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for (x, y) in zip(params1.values(), params2.values()) {
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self.unify(*x, *y)?;
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}
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self.set_a_to_b(a, b);
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}
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(TVirtual { ty: ty1 }, TVirtual { ty: ty2 }) => {
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self.unify(*ty1, *ty2)?;
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self.set_a_to_b(a, b);
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}
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(TCall(calls1), TCall(calls2)) => {
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calls2.borrow_mut().extend_from_slice(&calls1.borrow());
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}
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(TCall(calls), TFunc(signature)) => {
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self.occur_check(a, b)?;
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let required: Vec<String> = signature
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.args
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.iter()
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.filter(|v| !v.is_optional)
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.map(|v| v.name.clone())
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.rev()
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.collect();
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for c in calls.borrow().iter() {
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let Call { posargs, kwargs, ret, fun } = c.as_ref();
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let instantiated = self.instantiate_fun(b, signature);
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let signature;
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let r = self.get_ty(instantiated);
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let r = r.as_ref();
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if let TypeEnum::TFunc(s) = &*r {
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signature = s;
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} else {
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unreachable!();
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}
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let mut required = required.clone();
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let mut all_names: Vec<_> =
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signature.args.iter().map(|v| (v.name.clone(), v.ty)).rev().collect();
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for (i, t) in posargs.iter().enumerate() {
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if signature.args.len() <= i {
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return Err("Too many arguments.".to_string());
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}
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if !required.is_empty() {
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required.pop();
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}
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self.unify(all_names.pop().unwrap().1, *t)?;
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}
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for (k, t) in kwargs.iter() {
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if let Some(i) = required.iter().position(|v| v == k) {
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required.remove(i);
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}
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if let Some(i) = all_names.iter().position(|v| &v.0 == k) {
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self.unify(all_names.remove(i).1, *t)?;
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} else {
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return Err(format!("Unknown keyword argument {}", k));
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}
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}
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if !required.is_empty() {
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return Err("Expected more arguments".to_string());
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}
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self.unify(*ret, signature.ret)?;
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*fun.borrow_mut() = Some(instantiated);
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}
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self.set_a_to_b(a, b);
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}
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(TFunc(sign1), TFunc(sign2)) => {
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if !sign1.vars.is_empty() || !sign2.vars.is_empty() {
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return Err("Polymorphic function pointer is prohibited.".to_string());
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}
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if sign1.args.len() != sign2.args.len() {
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return Err("Functions differ in number of parameters.".to_string());
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}
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for (x, y) in sign1.args.iter().zip(sign2.args.iter()) {
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if x.name != y.name {
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return Err("Functions differ in parameter names.".to_string());
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}
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if x.is_optional != y.is_optional {
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return Err("Functions differ in optional parameters.".to_string());
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}
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self.unify(x.ty, y.ty)?;
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}
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self.unify(sign1.ret, sign2.ret)?;
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self.set_a_to_b(a, b);
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}
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_ => {
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if swapped {
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return self.incompatible_types(&*ty_a, &*ty_b);
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} else {
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self.unify_impl(b, a, true)?;
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}
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}
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}
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Ok(())
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}
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/// Get string representation of the type
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pub fn stringify<F, G>(&mut self, ty: Type, obj_to_name: &mut F, var_to_name: &mut G) -> String
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where
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F: FnMut(usize) -> String,
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G: FnMut(u32) -> String,
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{
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use TypeVarMeta::*;
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let ty = self.unification_table.probe_value(ty).clone();
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match ty.as_ref() {
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TypeEnum::TVar { id, meta: Generic, .. } => var_to_name(*id),
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TypeEnum::TVar { meta: Sequence(map), .. } => {
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let fields = map.borrow().iter().map(|(k, v)| {
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format!("{}={}", k, self.stringify(*v, obj_to_name, var_to_name))
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}).join(", ");
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format!("seq[{}]", fields)
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}
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TypeEnum::TVar { meta: Record(fields), .. } => {
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let fields = fields.borrow().iter().map(|(k, v)| {
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format!("{}={}", k, self.stringify(*v, obj_to_name, var_to_name))
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}).join(", ");
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format!("record[{}]", fields)
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}
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TypeEnum::TTuple { ty } => {
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let mut fields = ty
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.iter()
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.map(|v| self.stringify(*v, obj_to_name, var_to_name));
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format!("tuple[{}]", fields.join(", "))
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}
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TypeEnum::TList { ty } => {
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format!("list[{}]", self.stringify(*ty, obj_to_name, var_to_name))
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}
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TypeEnum::TVirtual { ty } => {
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format!("virtual[{}]", self.stringify(*ty, obj_to_name, var_to_name))
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}
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TypeEnum::TObj { obj_id, params, .. } => {
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let name = obj_to_name(*obj_id);
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if !params.is_empty() {
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let mut params = params
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.values()
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.map(|v| self.stringify(*v, obj_to_name, var_to_name));
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format!("{}[{}]", name, params.join(", "))
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} else {
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name
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}
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}
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TypeEnum::TCall { .. } => "call".to_owned(),
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TypeEnum::TFunc(signature) => {
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let params = signature
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.args
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.iter()
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.map(|arg| {
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format!(
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"{}={}",
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arg.name,
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self.stringify(arg.ty, obj_to_name, var_to_name)
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)
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})
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.join(", ");
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let ret = self.stringify(signature.ret, obj_to_name, var_to_name);
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format!("fn[[{}], {}]", params, ret)
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}
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}
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}
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fn check_var_range(&mut self, id: u32, b: Type, range: &[Type]) -> Result<(), String> {
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let mut in_range = range.is_empty();
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for t in range.iter() {
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if self.shape_match(*t, b) {
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self.unify(*t, b)?;
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in_range = true;
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}
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}
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if !in_range {
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return Err(format!(
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"Cannot unify {} with {} due to incompatible value range",
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id,
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self.get_ty(b).get_type_name()
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));
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}
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Ok(())
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}
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fn set_a_to_b(&mut self, a: Type, b: Type) {
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// unify a and b together, and set the value to b's value.
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let table = &mut self.unification_table;
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let ty_b = table.probe_value(b).clone();
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table.unify(a, b);
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table.set_value(a, ty_b)
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}
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fn incompatible_types(&self, a: &TypeEnum, b: &TypeEnum) -> Result<(), String> {
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Err(format!("Cannot unify {} with {}", a.get_type_name(), b.get_type_name()))
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}
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|
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/// Instantiate a function if it hasn't been instntiated.
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/// Returns Some(T) where T is the instantiated type.
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/// Returns None if the function is already instantiated.
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fn instantiate_fun(&mut self, ty: Type, fun: &FunSignature) -> Type {
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let mut instantiated = false;
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let mut vars = Vec::new();
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for (k, v) in fun.vars.iter() {
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if let TypeEnum::TVar { id, range, .. } =
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self.unification_table.probe_value(*v).as_ref()
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{
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if k != id {
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instantiated = true;
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break;
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}
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// actually, if the first check succeeded, the function should be uninstatiated.
|
|
// The cloned values must be used and would not be wasted.
|
|
vars.push((*k, range.clone()));
|
|
} else {
|
|
instantiated = true;
|
|
break;
|
|
}
|
|
}
|
|
if instantiated {
|
|
ty
|
|
} else {
|
|
let mapping = vars
|
|
.into_iter()
|
|
.map(|(k, range)| (k, self.get_fresh_var_with_range(range.borrow().as_ref()).0))
|
|
.collect();
|
|
self.subst(ty, &mapping).unwrap_or(ty)
|
|
}
|
|
}
|
|
|
|
/// Substitute type variables within a type into other types.
|
|
/// If this returns Some(T), T would be the substituted type.
|
|
/// If this returns None, the result type would be the original type
|
|
/// (no substitution has to be done).
|
|
fn subst(&mut self, a: Type, mapping: &VarMap) -> Option<Type> {
|
|
use TypeVarMeta::*;
|
|
let ty = self.unification_table.probe_value(a).clone();
|
|
// this function would only be called when we instantiate functions.
|
|
// function type signature should ONLY contain concrete types and type
|
|
// variables, i.e. things like TRecord, TCall should not occur, and we
|
|
// should be safe to not implement the substitution for those variants.
|
|
match &*ty {
|
|
TypeEnum::TVar { id, meta: Generic, .. } => mapping.get(&id).cloned(),
|
|
TypeEnum::TTuple { ty } => {
|
|
let mut new_ty = Cow::from(ty);
|
|
for (i, t) in ty.iter().enumerate() {
|
|
if let Some(t1) = self.subst(*t, mapping) {
|
|
new_ty.to_mut()[i] = t1;
|
|
}
|
|
}
|
|
if matches!(new_ty, Cow::Owned(_)) {
|
|
Some(self.add_ty(TypeEnum::TTuple { ty: new_ty.into_owned() }))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
TypeEnum::TList { ty } => {
|
|
self.subst(*ty, mapping).map(|t| self.add_ty(TypeEnum::TList { ty: t }))
|
|
}
|
|
TypeEnum::TVirtual { ty } => {
|
|
self.subst(*ty, mapping).map(|t| self.add_ty(TypeEnum::TVirtual { ty: t }))
|
|
}
|
|
TypeEnum::TObj { obj_id, fields, params } => {
|
|
// Type variables in field types must be present in the type parameter.
|
|
// If the mapping does not contain any type variables in the
|
|
// parameter list, we don't need to substitute the fields.
|
|
// This is also used to prevent infinite substitution...
|
|
let need_subst = params.values().any(|v| {
|
|
let ty = self.unification_table.probe_value(*v);
|
|
if let TypeEnum::TVar { id, .. } = ty.as_ref() {
|
|
mapping.contains_key(&id)
|
|
} else {
|
|
false
|
|
}
|
|
});
|
|
if need_subst {
|
|
let obj_id = *obj_id;
|
|
let params = self.subst_map(¶ms, mapping).unwrap_or_else(|| params.clone());
|
|
let fields = self.subst_map(&fields, mapping).unwrap_or_else(|| fields.clone());
|
|
Some(self.add_ty(TypeEnum::TObj { obj_id, params, fields }))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
TypeEnum::TFunc(FunSignature { args, ret, vars: params }) => {
|
|
let new_params = self.subst_map(params, mapping);
|
|
let new_ret = self.subst(*ret, mapping);
|
|
let mut new_args = Cow::from(args);
|
|
for (i, t) in args.iter().enumerate() {
|
|
if let Some(t1) = self.subst(t.ty, mapping) {
|
|
let mut t = t.clone();
|
|
t.ty = t1;
|
|
new_args.to_mut()[i] = t;
|
|
}
|
|
}
|
|
if new_params.is_some() || new_ret.is_some() || matches!(new_args, Cow::Owned(..)) {
|
|
let params = new_params.unwrap_or_else(|| params.clone());
|
|
let ret = new_ret.unwrap_or_else(|| *ret);
|
|
let args = new_args.into_owned();
|
|
Some(self.add_ty(TypeEnum::TFunc(FunSignature { args, ret, vars: params })))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
_ => unimplemented!(),
|
|
}
|
|
}
|
|
|
|
fn subst_map<K>(&mut self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
|
|
where
|
|
K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
|
|
{
|
|
let mut map2 = None;
|
|
for (k, v) in map.iter() {
|
|
if let Some(v1) = self.subst(*v, mapping) {
|
|
if map2.is_none() {
|
|
map2 = Some(map.clone());
|
|
}
|
|
*map2.as_mut().unwrap().get_mut(k).unwrap() = v1;
|
|
}
|
|
}
|
|
map2
|
|
}
|
|
|
|
fn occur_check(&mut self, a: Type, b: Type) -> Result<(), String> {
|
|
use TypeVarMeta::*;
|
|
if self.unification_table.unioned(a, b) {
|
|
return Err("Recursive type is prohibited.".to_owned());
|
|
}
|
|
let ty = self.unification_table.probe_value(b).clone();
|
|
|
|
match ty.as_ref() {
|
|
TypeEnum::TVar { meta: Generic, .. } => {}
|
|
TypeEnum::TVar { meta: Sequence(map), .. } => {
|
|
for t in map.borrow().values() {
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
TypeEnum::TVar { meta: Record(map), .. } => {
|
|
for t in map.borrow().values() {
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
TypeEnum::TCall(calls) => {
|
|
for t in calls
|
|
.borrow()
|
|
.iter()
|
|
.map(|call| chain!(call.posargs.iter(), call.kwargs.values(), once(&call.ret)))
|
|
.flatten()
|
|
{
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
TypeEnum::TTuple { ty } => {
|
|
for t in ty.iter() {
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
TypeEnum::TList { ty } | TypeEnum::TVirtual { ty } => {
|
|
self.occur_check(a, *ty)?;
|
|
}
|
|
TypeEnum::TObj { params: map, .. } => {
|
|
for t in map.values() {
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
TypeEnum::TFunc(FunSignature { args, ret, vars: params }) => {
|
|
for t in chain!(args.iter().map(|v| &v.ty), params.values(), once(ret)) {
|
|
self.occur_check(a, *t)?;
|
|
}
|
|
}
|
|
}
|
|
Ok(())
|
|
}
|
|
|
|
pub fn shape_match(&mut self, a: Type, b: Type) -> bool {
|
|
use TypeEnum::*;
|
|
let a = self.get_ty(a);
|
|
let b = self.get_ty(b);
|
|
match (a.as_ref(), b.as_ref()) {
|
|
(TVar { .. }, _) => true,
|
|
(_, TVar { .. }) => true,
|
|
(TTuple { ty: ty1 }, TTuple { ty: ty2 }) => {
|
|
ty1.len() == ty2.len()
|
|
&& zip(ty1.iter(), ty2.iter()).all(|(a, b)| self.shape_match(*a, *b))
|
|
}
|
|
(TList { ty: ty1 }, TList { ty: ty2 })
|
|
| (TVirtual { ty: ty1 }, TVirtual { ty: ty2 }) => self.shape_match(*ty1, *ty2),
|
|
(TObj { obj_id: id1, .. }, TObj { obj_id: id2, .. }) => id1 == id2,
|
|
// don't deal with function shape for now
|
|
_ => false,
|
|
}
|
|
}
|
|
}
|