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Extract unification code to unify module

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This commit is contained in:
Florian Diebold 2019-12-01 20:30:28 +01:00
parent cbf262a1bc
commit 599dab5982
6 changed files with 312 additions and 263 deletions
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255
crates/ra_hir_ty/src/infer.rs
View File

@ -18,7 +18,6 @@ use std::mem;
use std::ops::Index;
use std::sync::Arc;
use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
use rustc_hash::FxHashMap;
use hir_def::{
@ -33,12 +32,11 @@ use hir_def::{
use hir_expand::{diagnostics::DiagnosticSink, name};
use ra_arena::map::ArenaMap;
use ra_prof::profile;
use test_utils::tested_by;
use super::{
primitive::{FloatTy, IntTy},
traits::{Guidance, Obligation, ProjectionPredicate, Solution},
ApplicationTy, InEnvironment, ProjectionTy, Substs, TraitEnvironment, TraitRef, Ty, TypeCtor,
ApplicationTy, InEnvironment, ProjectionTy, TraitEnvironment, TraitRef, Ty, TypeCtor,
TypeWalk, Uncertain,
};
use crate::{db::HirDatabase, infer::diagnostics::InferenceDiagnostic};
@ -191,7 +189,7 @@ struct InferenceContext<'a, D: HirDatabase> {
owner: DefWithBodyId,
body: Arc<Body>,
resolver: Resolver,
var_unification_table: InPlaceUnificationTable<TypeVarId>,
table: unify::InferenceTable,
trait_env: Arc<TraitEnvironment>,
obligations: Vec<Obligation>,
result: InferenceResult,
@ -209,7 +207,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
fn new(db: &'a D, owner: DefWithBodyId, resolver: Resolver) -> Self {
InferenceContext {
result: InferenceResult::default(),
var_unification_table: InPlaceUnificationTable::new(),
table: unify::InferenceTable::new(),
obligations: Vec::default(),
return_ty: Ty::Unknown, // set in collect_fn_signature
trait_env: TraitEnvironment::lower(db, &resolver),
@ -224,13 +222,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
fn resolve_all(mut self) -> InferenceResult {
// FIXME resolve obligations as well (use Guidance if necessary)
let mut result = mem::replace(&mut self.result, InferenceResult::default());
let mut tv_stack = Vec::new();
for ty in result.type_of_expr.values_mut() {
let resolved = self.resolve_ty_completely(&mut tv_stack, mem::replace(ty, Ty::Unknown));
let resolved = self.table.resolve_ty_completely(mem::replace(ty, Ty::Unknown));
*ty = resolved;
}
for ty in result.type_of_pat.values_mut() {
let resolved = self.resolve_ty_completely(&mut tv_stack, mem::replace(ty, Ty::Unknown));
let resolved = self.table.resolve_ty_completely(mem::replace(ty, Ty::Unknown));
*ty = resolved;
}
result
@ -275,96 +272,15 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
self.normalize_associated_types_in(ty)
}
fn unify_substs(&mut self, substs1: &Substs, substs2: &Substs, depth: usize) -> bool {
substs1.0.iter().zip(substs2.0.iter()).all(|(t1, t2)| self.unify_inner(t1, t2, depth))
}
fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
self.unify_inner(ty1, ty2, 0)
}
fn unify_inner(&mut self, ty1: &Ty, ty2: &Ty, depth: usize) -> bool {
if depth > 1000 {
// prevent stackoverflows
panic!("infinite recursion in unification");
}
if ty1 == ty2 {
return true;
}
// try to resolve type vars first
let ty1 = self.resolve_ty_shallow(ty1);
let ty2 = self.resolve_ty_shallow(ty2);
match (&*ty1, &*ty2) {
(Ty::Apply(a_ty1), Ty::Apply(a_ty2)) if a_ty1.ctor == a_ty2.ctor => {
self.unify_substs(&a_ty1.parameters, &a_ty2.parameters, depth + 1)
}
_ => self.unify_inner_trivial(&ty1, &ty2),
}
}
fn unify_inner_trivial(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
match (ty1, ty2) {
(Ty::Unknown, _) | (_, Ty::Unknown) => true,
(Ty::Infer(InferTy::TypeVar(tv1)), Ty::Infer(InferTy::TypeVar(tv2)))
| (Ty::Infer(InferTy::IntVar(tv1)), Ty::Infer(InferTy::IntVar(tv2)))
| (Ty::Infer(InferTy::FloatVar(tv1)), Ty::Infer(InferTy::FloatVar(tv2)))
| (
Ty::Infer(InferTy::MaybeNeverTypeVar(tv1)),
Ty::Infer(InferTy::MaybeNeverTypeVar(tv2)),
) => {
// both type vars are unknown since we tried to resolve them
self.var_unification_table.union(*tv1, *tv2);
true
}
// The order of MaybeNeverTypeVar matters here.
// Unifying MaybeNeverTypeVar and TypeVar will let the latter become MaybeNeverTypeVar.
// Unifying MaybeNeverTypeVar and other concrete type will let the former become it.
(Ty::Infer(InferTy::TypeVar(tv)), other)
| (other, Ty::Infer(InferTy::TypeVar(tv)))
| (Ty::Infer(InferTy::MaybeNeverTypeVar(tv)), other)
| (other, Ty::Infer(InferTy::MaybeNeverTypeVar(tv)))
| (Ty::Infer(InferTy::IntVar(tv)), other @ ty_app!(TypeCtor::Int(_)))
| (other @ ty_app!(TypeCtor::Int(_)), Ty::Infer(InferTy::IntVar(tv)))
| (Ty::Infer(InferTy::FloatVar(tv)), other @ ty_app!(TypeCtor::Float(_)))
| (other @ ty_app!(TypeCtor::Float(_)), Ty::Infer(InferTy::FloatVar(tv))) => {
// the type var is unknown since we tried to resolve it
self.var_unification_table.union_value(*tv, TypeVarValue::Known(other.clone()));
true
}
_ => false,
}
}
fn new_type_var(&mut self) -> Ty {
Ty::Infer(InferTy::TypeVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
fn new_integer_var(&mut self) -> Ty {
Ty::Infer(InferTy::IntVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
fn new_float_var(&mut self) -> Ty {
Ty::Infer(InferTy::FloatVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
fn new_maybe_never_type_var(&mut self) -> Ty {
Ty::Infer(InferTy::MaybeNeverTypeVar(
self.var_unification_table.new_key(TypeVarValue::Unknown),
))
}
/// Replaces Ty::Unknown by a new type var, so we can maybe still infer it.
fn insert_type_vars_shallow(&mut self, ty: Ty) -> Ty {
match ty {
Ty::Unknown => self.new_type_var(),
Ty::Unknown => self.table.new_type_var(),
Ty::Apply(ApplicationTy { ctor: TypeCtor::Int(Uncertain::Unknown), .. }) => {
self.new_integer_var()
self.table.new_integer_var()
}
Ty::Apply(ApplicationTy { ctor: TypeCtor::Float(Uncertain::Unknown), .. }) => {
self.new_float_var()
self.table.new_float_var()
}
_ => ty,
}
@ -402,64 +318,22 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
}
fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
self.table.unify(ty1, ty2)
}
/// Resolves the type as far as currently possible, replacing type variables
/// by their known types. All types returned by the infer_* functions should
/// be resolved as far as possible, i.e. contain no type variables with
/// known type.
fn resolve_ty_as_possible(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
fn resolve_ty_as_possible(&mut self, ty: Ty) -> Ty {
self.resolve_obligations_as_possible();
ty.fold(&mut |ty| match ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
if tv_stack.contains(&inner) {
tested_by!(type_var_cycles_resolve_as_possible);
// recursive type
return tv.fallback_value();
}
if let Some(known_ty) =
self.var_unification_table.inlined_probe_value(inner).known()
{
// known_ty may contain other variables that are known by now
tv_stack.push(inner);
let result = self.resolve_ty_as_possible(tv_stack, known_ty.clone());
tv_stack.pop();
result
} else {
ty
}
}
_ => ty,
})
self.table.resolve_ty_as_possible(ty)
}
/// If `ty` is a type variable with known type, returns that type;
/// otherwise, return ty.
fn resolve_ty_shallow<'b>(&mut self, ty: &'b Ty) -> Cow<'b, Ty> {
let mut ty = Cow::Borrowed(ty);
// The type variable could resolve to a int/float variable. Hence try
// resolving up to three times; each type of variable shouldn't occur
// more than once
for i in 0..3 {
if i > 0 {
tested_by!(type_var_resolves_to_int_var);
}
match &*ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
match self.var_unification_table.inlined_probe_value(inner).known() {
Some(known_ty) => {
// The known_ty can't be a type var itself
ty = Cow::Owned(known_ty.clone());
}
_ => return ty,
}
}
_ => return ty,
}
}
log::error!("Inference variable still not resolved: {:?}", ty);
ty
self.table.resolve_ty_shallow(ty)
}
/// Recurses through the given type, normalizing associated types mentioned
@ -469,7 +343,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
/// call). `make_ty` handles this already, but e.g. for field types we need
/// to do it as well.
fn normalize_associated_types_in(&mut self, ty: Ty) -> Ty {
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
ty.fold(&mut |ty| match ty {
Ty::Projection(proj_ty) => self.normalize_projection_ty(proj_ty),
_ => ty,
@ -477,40 +351,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
fn normalize_projection_ty(&mut self, proj_ty: ProjectionTy) -> Ty {
let var = self.new_type_var();
let var = self.table.new_type_var();
let predicate = ProjectionPredicate { projection_ty: proj_ty, ty: var.clone() };
let obligation = Obligation::Projection(predicate);
self.obligations.push(obligation);
var
}
/// Resolves the type completely; type variables without known type are
/// replaced by Ty::Unknown.
fn resolve_ty_completely(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
ty.fold(&mut |ty| match ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
if tv_stack.contains(&inner) {
tested_by!(type_var_cycles_resolve_completely);
// recursive type
return tv.fallback_value();
}
if let Some(known_ty) =
self.var_unification_table.inlined_probe_value(inner).known()
{
// known_ty may contain other variables that are known by now
tv_stack.push(inner);
let result = self.resolve_ty_completely(tv_stack, known_ty.clone());
tv_stack.pop();
result
} else {
tv.fallback_value()
}
}
_ => ty,
})
}
fn resolve_variant(&mut self, path: Option<&Path>) -> (Ty, Option<VariantId>) {
let path = match path {
Some(path) => path,
@ -615,78 +462,20 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
}
/// The ID of a type variable.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub struct TypeVarId(pub(super) u32);
impl UnifyKey for TypeVarId {
type Value = TypeVarValue;
fn index(&self) -> u32 {
self.0
}
fn from_index(i: u32) -> Self {
TypeVarId(i)
}
fn tag() -> &'static str {
"TypeVarId"
}
}
/// The value of a type variable: either we already know the type, or we don't
/// know it yet.
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum TypeVarValue {
Known(Ty),
Unknown,
}
impl TypeVarValue {
fn known(&self) -> Option<&Ty> {
match self {
TypeVarValue::Known(ty) => Some(ty),
TypeVarValue::Unknown => None,
}
}
}
impl UnifyValue for TypeVarValue {
type Error = NoError;
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
match (value1, value2) {
// We should never equate two type variables, both of which have
// known types. Instead, we recursively equate those types.
(TypeVarValue::Known(t1), TypeVarValue::Known(t2)) => panic!(
"equating two type variables, both of which have known types: {:?} and {:?}",
t1, t2
),
// If one side is known, prefer that one.
(TypeVarValue::Known(..), TypeVarValue::Unknown) => Ok(value1.clone()),
(TypeVarValue::Unknown, TypeVarValue::Known(..)) => Ok(value2.clone()),
(TypeVarValue::Unknown, TypeVarValue::Unknown) => Ok(TypeVarValue::Unknown),
}
}
}
/// The kinds of placeholders we need during type inference. There's separate
/// values for general types, and for integer and float variables. The latter
/// two are used for inference of literal values (e.g. `100` could be one of
/// several integer types).
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum InferTy {
TypeVar(TypeVarId),
IntVar(TypeVarId),
FloatVar(TypeVarId),
MaybeNeverTypeVar(TypeVarId),
TypeVar(unify::TypeVarId),
IntVar(unify::TypeVarId),
FloatVar(unify::TypeVarId),
MaybeNeverTypeVar(unify::TypeVarId),
}
impl InferTy {
fn to_inner(self) -> TypeVarId {
fn to_inner(self) -> unify::TypeVarId {
match self {
InferTy::TypeVar(ty)
| InferTy::IntVar(ty)

10
crates/ra_hir_ty/src/infer/coerce.rs
View File

@ -10,7 +10,7 @@ use test_utils::tested_by;
use crate::{autoderef, db::HirDatabase, Substs, Ty, TypeCtor, TypeWalk};
use super::{InEnvironment, InferTy, InferenceContext, TypeVarValue};
use super::{InEnvironment, InferTy, InferenceContext, unify::TypeVarValue};
impl<'a, D: HirDatabase> InferenceContext<'a, D> {
/// Unify two types, but may coerce the first one to the second one
@ -85,8 +85,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
match (&from_ty, to_ty) {
// Never type will make type variable to fallback to Never Type instead of Unknown.
(ty_app!(TypeCtor::Never), Ty::Infer(InferTy::TypeVar(tv))) => {
let var = self.new_maybe_never_type_var();
self.var_unification_table.union_value(*tv, TypeVarValue::Known(var));
let var = self.table.new_maybe_never_type_var();
self.table.var_unification_table.union_value(*tv, TypeVarValue::Known(var));
return true;
}
(ty_app!(TypeCtor::Never), _) => return true,
@ -94,7 +94,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
// Trivial cases, this should go after `never` check to
// avoid infer result type to be never
_ => {
if self.unify_inner_trivial(&from_ty, &to_ty) {
if self.table.unify_inner_trivial(&from_ty, &to_ty) {
return true;
}
}
@ -330,7 +330,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
// Stop when constructor matches.
(ty_app!(from_ctor, st1), ty_app!(to_ctor, st2)) if from_ctor == to_ctor => {
// It will not recurse to `coerce`.
return self.unify_substs(st1, st2, 0);
return self.table.unify_substs(st1, st2, 0);
}
_ => {}
}

30
crates/ra_hir_ty/src/infer/expr.rs
View File

@ -32,7 +32,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
);
}
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
ty
}
@ -53,7 +53,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
expected.ty.clone()
};
self.resolve_ty_as_possible(&mut vec![], ty)
self.resolve_ty_as_possible(ty)
}
fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
@ -94,7 +94,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let pat_ty = match self.resolve_into_iter_item() {
Some(into_iter_item_alias) => {
let pat_ty = self.new_type_var();
let pat_ty = self.table.new_type_var();
let projection = ProjectionPredicate {
ty: pat_ty.clone(),
projection_ty: ProjectionTy {
@ -103,7 +103,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
},
};
self.obligations.push(Obligation::Projection(projection));
self.resolve_ty_as_possible(&mut vec![], pat_ty)
self.resolve_ty_as_possible(pat_ty)
}
None => Ty::Unknown,
};
@ -128,7 +128,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
// add return type
let ret_ty = self.new_type_var();
let ret_ty = self.table.new_type_var();
sig_tys.push(ret_ty.clone());
let sig_ty = Ty::apply(
TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1 },
@ -167,7 +167,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
Expr::Match { expr, arms } => {
let input_ty = self.infer_expr(*expr, &Expectation::none());
let mut result_ty = self.new_maybe_never_type_var();
let mut result_ty = self.table.new_maybe_never_type_var();
for arm in arms {
for &pat in &arm.pats {
@ -283,7 +283,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let inner_ty = self.infer_expr(*expr, &Expectation::none());
let ty = match self.resolve_future_future_output() {
Some(future_future_output_alias) => {
let ty = self.new_type_var();
let ty = self.table.new_type_var();
let projection = ProjectionPredicate {
ty: ty.clone(),
projection_ty: ProjectionTy {
@ -292,7 +292,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
},
};
self.obligations.push(Obligation::Projection(projection));
self.resolve_ty_as_possible(&mut vec![], ty)
self.resolve_ty_as_possible(ty)
}
None => Ty::Unknown,
};
@ -302,7 +302,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let inner_ty = self.infer_expr(*expr, &Expectation::none());
let ty = match self.resolve_ops_try_ok() {
Some(ops_try_ok_alias) => {
let ty = self.new_type_var();
let ty = self.table.new_type_var();
let projection = ProjectionPredicate {
ty: ty.clone(),
projection_ty: ProjectionTy {
@ -311,7 +311,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
},
};
self.obligations.push(Obligation::Projection(projection));
self.resolve_ty_as_possible(&mut vec![], ty)
self.resolve_ty_as_possible(ty)
}
None => Ty::Unknown,
};
@ -465,10 +465,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
ty_app!(TypeCtor::Tuple { .. }, st) => st
.iter()
.cloned()
.chain(repeat_with(|| self.new_type_var()))
.chain(repeat_with(|| self.table.new_type_var()))
.take(exprs.len())
.collect::<Vec<_>>(),
_ => (0..exprs.len()).map(|_| self.new_type_var()).collect(),
_ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
};
for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
@ -482,7 +482,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
ty_app!(TypeCtor::Array, st) | ty_app!(TypeCtor::Slice, st) => {
st.as_single().clone()
}
_ => self.new_type_var(),
_ => self.table.new_type_var(),
};
match array {
@ -524,7 +524,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
};
// use a new type variable if we got Ty::Unknown here
let ty = self.insert_type_vars_shallow(ty);
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
self.write_expr_ty(tgt_expr, ty.clone());
ty
}
@ -553,7 +553,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
}
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
self.infer_pat(*pat, &ty, BindingMode::default());
}
Statement::Expr(expr) => {

4
crates/ra_hir_ty/src/infer/pat.rs
View File

@ -170,7 +170,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
BindingMode::Move => inner_ty.clone(),
};
let bound_ty = self.resolve_ty_as_possible(&mut vec![], bound_ty);
let bound_ty = self.resolve_ty_as_possible(bound_ty);
self.write_pat_ty(pat, bound_ty);
return inner_ty;
}
@ -179,7 +179,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
// use a new type variable if we got Ty::Unknown here
let ty = self.insert_type_vars_shallow(ty);
self.unify(&ty, expected);
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
self.write_pat_ty(pat, ty.clone());
ty
}

4
crates/ra_hir_ty/src/infer/path.rs
View File

@ -57,7 +57,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let typable: ValueTyDefId = match value {
ValueNs::LocalBinding(pat) => {
let ty = self.result.type_of_pat.get(pat)?.clone();
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
let ty = self.resolve_ty_as_possible(ty);
return Some(ty);
}
ValueNs::FunctionId(it) => it.into(),
@ -211,7 +211,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
// we're picking this method
let trait_substs = Substs::build_for_def(self.db, trait_)
.push(ty.clone())
.fill(std::iter::repeat_with(|| self.new_type_var()))
.fill(std::iter::repeat_with(|| self.table.new_type_var()))
.build();
let substs = Substs::build_for_def(self.db, item)
.use_parent_substs(&trait_substs)

272
crates/ra_hir_ty/src/infer/unify.rs
View File

@ -1,9 +1,15 @@
//! Unification and canonicalization logic.
use std::borrow::Cow;
use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
use test_utils::tested_by;
use super::{InferenceContext, Obligation};
use crate::{
db::HirDatabase, utils::make_mut_slice, Canonical, InEnvironment, InferTy, ProjectionPredicate,
ProjectionTy, Substs, TraitRef, Ty, TypeWalk,
ProjectionTy, Substs, TraitRef, Ty, TypeCtor, TypeWalk,
};
impl<'a, D: HirDatabase> InferenceContext<'a, D> {
@ -24,7 +30,7 @@ where
/// A stack of type variables that is used to detect recursive types (which
/// are an error, but we need to protect against them to avoid stack
/// overflows).
var_stack: Vec<super::TypeVarId>,
var_stack: Vec<TypeVarId>,
}
pub(super) struct Canonicalized<T> {
@ -53,14 +59,14 @@ where
return tv.fallback_value();
}
if let Some(known_ty) =
self.ctx.var_unification_table.inlined_probe_value(inner).known()
self.ctx.table.var_unification_table.inlined_probe_value(inner).known()
{
self.var_stack.push(inner);
let result = self.do_canonicalize_ty(known_ty.clone());
self.var_stack.pop();
result
} else {
let root = self.ctx.var_unification_table.find(inner);
let root = self.ctx.table.var_unification_table.find(inner);
let free_var = match tv {
InferTy::TypeVar(_) => InferTy::TypeVar(root),
InferTy::IntVar(_) => InferTy::IntVar(root),
@ -153,10 +159,264 @@ impl<T> Canonicalized<T> {
solution: Canonical<Vec<Ty>>,
) {
// the solution may contain new variables, which we need to convert to new inference vars
let new_vars = Substs((0..solution.num_vars).map(|_| ctx.new_type_var()).collect());
let new_vars = Substs((0..solution.num_vars).map(|_| ctx.table.new_type_var()).collect());
for (i, ty) in solution.value.into_iter().enumerate() {
let var = self.free_vars[i];
ctx.unify(&Ty::Infer(var), &ty.subst_bound_vars(&new_vars));
ctx.table.unify(&Ty::Infer(var), &ty.subst_bound_vars(&new_vars));
}
}
}
pub fn unify(ty1: Canonical<&Ty>, ty2: &Ty) -> Substs {
let mut table = InferenceTable::new();
let vars = Substs::builder(ty1.num_vars)
.fill(std::iter::repeat_with(|| table.new_type_var())).build();
let ty_with_vars = ty1.value.clone().subst_bound_vars(&vars);
table.unify(&ty_with_vars, ty2);
Substs::builder(ty1.num_vars).fill(vars.iter().map(|v| table.resolve_ty_completely(v.clone()))).build()
}
#[derive(Clone, Debug)]
pub(crate) struct InferenceTable {
pub(super) var_unification_table: InPlaceUnificationTable<TypeVarId>,
}
impl InferenceTable {
pub fn new() -> Self {
InferenceTable {
var_unification_table: InPlaceUnificationTable::new(),
}
}
pub fn new_type_var(&mut self) -> Ty {
Ty::Infer(InferTy::TypeVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
pub fn new_integer_var(&mut self) -> Ty {
Ty::Infer(InferTy::IntVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
pub fn new_float_var(&mut self) -> Ty {
Ty::Infer(InferTy::FloatVar(self.var_unification_table.new_key(TypeVarValue::Unknown)))
}
pub fn new_maybe_never_type_var(&mut self) -> Ty {
Ty::Infer(InferTy::MaybeNeverTypeVar(
self.var_unification_table.new_key(TypeVarValue::Unknown),
))
}
pub fn resolve_ty_completely(&mut self, ty: Ty) -> Ty {
self.resolve_ty_completely_inner(&mut Vec::new(), ty)
}
pub fn resolve_ty_as_possible(&mut self, ty: Ty) -> Ty {
self.resolve_ty_as_possible_inner(&mut Vec::new(), ty)
}
pub fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
self.unify_inner(ty1, ty2, 0)
}
pub fn unify_substs(&mut self, substs1: &Substs, substs2: &Substs, depth: usize) -> bool {
substs1.0.iter().zip(substs2.0.iter()).all(|(t1, t2)| self.unify_inner(t1, t2, depth))
}
fn unify_inner(&mut self, ty1: &Ty, ty2: &Ty, depth: usize) -> bool {
if depth > 1000 {
// prevent stackoverflows
panic!("infinite recursion in unification");
}
if ty1 == ty2 {
return true;
}
// try to resolve type vars first
let ty1 = self.resolve_ty_shallow(ty1);
let ty2 = self.resolve_ty_shallow(ty2);
match (&*ty1, &*ty2) {
(Ty::Apply(a_ty1), Ty::Apply(a_ty2)) if a_ty1.ctor == a_ty2.ctor => {
self.unify_substs(&a_ty1.parameters, &a_ty2.parameters, depth + 1)
}
_ => self.unify_inner_trivial(&ty1, &ty2),
}
}
pub(super) fn unify_inner_trivial(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
match (ty1, ty2) {
(Ty::Unknown, _) | (_, Ty::Unknown) => true,
(Ty::Infer(InferTy::TypeVar(tv1)), Ty::Infer(InferTy::TypeVar(tv2)))
| (Ty::Infer(InferTy::IntVar(tv1)), Ty::Infer(InferTy::IntVar(tv2)))
| (Ty::Infer(InferTy::FloatVar(tv1)), Ty::Infer(InferTy::FloatVar(tv2)))
| (
Ty::Infer(InferTy::MaybeNeverTypeVar(tv1)),
Ty::Infer(InferTy::MaybeNeverTypeVar(tv2)),
) => {
// both type vars are unknown since we tried to resolve them
self.var_unification_table.union(*tv1, *tv2);
true
}
// The order of MaybeNeverTypeVar matters here.
// Unifying MaybeNeverTypeVar and TypeVar will let the latter become MaybeNeverTypeVar.
// Unifying MaybeNeverTypeVar and other concrete type will let the former become it.
(Ty::Infer(InferTy::TypeVar(tv)), other)
| (other, Ty::Infer(InferTy::TypeVar(tv)))
| (Ty::Infer(InferTy::MaybeNeverTypeVar(tv)), other)
| (other, Ty::Infer(InferTy::MaybeNeverTypeVar(tv)))
| (Ty::Infer(InferTy::IntVar(tv)), other @ ty_app!(TypeCtor::Int(_)))
| (other @ ty_app!(TypeCtor::Int(_)), Ty::Infer(InferTy::IntVar(tv)))
| (Ty::Infer(InferTy::FloatVar(tv)), other @ ty_app!(TypeCtor::Float(_)))
| (other @ ty_app!(TypeCtor::Float(_)), Ty::Infer(InferTy::FloatVar(tv))) => {
// the type var is unknown since we tried to resolve it
self.var_unification_table.union_value(*tv, TypeVarValue::Known(other.clone()));
true
}
_ => false,
}
}
/// If `ty` is a type variable with known type, returns that type;
/// otherwise, return ty.
pub fn resolve_ty_shallow<'b>(&mut self, ty: &'b Ty) -> Cow<'b, Ty> {
let mut ty = Cow::Borrowed(ty);
// The type variable could resolve to a int/float variable. Hence try
// resolving up to three times; each type of variable shouldn't occur
// more than once
for i in 0..3 {
if i > 0 {
tested_by!(type_var_resolves_to_int_var);
}
match &*ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
match self.var_unification_table.inlined_probe_value(inner).known() {
Some(known_ty) => {
// The known_ty can't be a type var itself
ty = Cow::Owned(known_ty.clone());
}
_ => return ty,
}
}
_ => return ty,
}
}
log::error!("Inference variable still not resolved: {:?}", ty);
ty
}
/// Resolves the type as far as currently possible, replacing type variables
/// by their known types. All types returned by the infer_* functions should
/// be resolved as far as possible, i.e. contain no type variables with
/// known type.
fn resolve_ty_as_possible_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
ty.fold(&mut |ty| match ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
if tv_stack.contains(&inner) {
tested_by!(type_var_cycles_resolve_as_possible);
// recursive type
return tv.fallback_value();
}
if let Some(known_ty) =
self.var_unification_table.inlined_probe_value(inner).known()
{
// known_ty may contain other variables that are known by now
tv_stack.push(inner);
let result = self.resolve_ty_as_possible_inner(tv_stack, known_ty.clone());
tv_stack.pop();
result
} else {
ty
}
}
_ => ty,
})
}
/// Resolves the type completely; type variables without known type are
/// replaced by Ty::Unknown.
fn resolve_ty_completely_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
ty.fold(&mut |ty| match ty {
Ty::Infer(tv) => {
let inner = tv.to_inner();
if tv_stack.contains(&inner) {
tested_by!(type_var_cycles_resolve_completely);
// recursive type
return tv.fallback_value();
}
if let Some(known_ty) =
self.var_unification_table.inlined_probe_value(inner).known()
{
// known_ty may contain other variables that are known by now
tv_stack.push(inner);
let result = self.resolve_ty_completely_inner(tv_stack, known_ty.clone());
tv_stack.pop();
result
} else {
tv.fallback_value()
}
}
_ => ty,
})
}
}
/// The ID of a type variable.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub struct TypeVarId(pub(super) u32);
impl UnifyKey for TypeVarId {
type Value = TypeVarValue;
fn index(&self) -> u32 {
self.0
}
fn from_index(i: u32) -> Self {
TypeVarId(i)
}
fn tag() -> &'static str {
"TypeVarId"
}
}
/// The value of a type variable: either we already know the type, or we don't
/// know it yet.
#[derive(Clone, PartialEq, Eq, Debug)]
pub enum TypeVarValue {
Known(Ty),
Unknown,
}
impl TypeVarValue {
fn known(&self) -> Option<&Ty> {
match self {
TypeVarValue::Known(ty) => Some(ty),
TypeVarValue::Unknown => None,
}
}
}
impl UnifyValue for TypeVarValue {
type Error = NoError;
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
match (value1, value2) {
// We should never equate two type variables, both of which have
// known types. Instead, we recursively equate those types.
(TypeVarValue::Known(t1), TypeVarValue::Known(t2)) => panic!(
"equating two type variables, both of which have known types: {:?} and {:?}",
t1, t2
),
// If one side is known, prefer that one.
(TypeVarValue::Known(..), TypeVarValue::Unknown) => Ok(value1.clone()),
(TypeVarValue::Unknown, TypeVarValue::Known(..)) => Ok(value2.clone()),
(TypeVarValue::Unknown, TypeVarValue::Unknown) => Ok(TypeVarValue::Unknown),
}
}
}