blob: 9c415400775a2dc119e8d5ff6ac8ca72ced0fbba [file] [log] [blame]
//! Unification and canonicalization logic.
use std::{fmt, iter, mem};
use chalk_ir::{
cast::Cast, fold::TypeFoldable, interner::HasInterner, zip::Zip, CanonicalVarKind, FloatTy,
IntTy, TyVariableKind, UniverseIndex,
};
use chalk_solve::infer::ParameterEnaVariableExt;
use either::Either;
use ena::unify::UnifyKey;
use hir_expand::name;
use triomphe::Arc;
use super::{InferOk, InferResult, InferenceContext, TypeError};
use crate::{
consteval::unknown_const, db::HirDatabase, fold_tys_and_consts, static_lifetime,
to_chalk_trait_id, traits::FnTrait, AliasEq, AliasTy, BoundVar, Canonical, Const, ConstValue,
DebruijnIndex, GenericArg, GenericArgData, Goal, Guidance, InEnvironment, InferenceVar,
Interner, Lifetime, ParamKind, ProjectionTy, ProjectionTyExt, Scalar, Solution, Substitution,
TraitEnvironment, Ty, TyBuilder, TyExt, TyKind, VariableKind,
};
impl InferenceContext<'_> {
pub(super) fn canonicalize<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>(
&mut self,
t: T,
) -> Canonicalized<T>
where
T: HasInterner<Interner = Interner>,
{
self.table.canonicalize(t)
}
}
#[derive(Debug, Clone)]
pub(crate) struct Canonicalized<T>
where
T: HasInterner<Interner = Interner>,
{
pub(crate) value: Canonical<T>,
free_vars: Vec<GenericArg>,
}
impl<T: HasInterner<Interner = Interner>> Canonicalized<T> {
pub(crate) fn apply_solution(
&self,
ctx: &mut InferenceTable<'_>,
solution: Canonical<Substitution>,
) {
// the solution may contain new variables, which we need to convert to new inference vars
let new_vars = Substitution::from_iter(
Interner,
solution.binders.iter(Interner).map(|k| match &k.kind {
VariableKind::Ty(TyVariableKind::General) => ctx.new_type_var().cast(Interner),
VariableKind::Ty(TyVariableKind::Integer) => ctx.new_integer_var().cast(Interner),
VariableKind::Ty(TyVariableKind::Float) => ctx.new_float_var().cast(Interner),
// Chalk can sometimes return new lifetime variables. We just use the static lifetime everywhere
VariableKind::Lifetime => static_lifetime().cast(Interner),
VariableKind::Const(ty) => ctx.new_const_var(ty.clone()).cast(Interner),
}),
);
for (i, v) in solution.value.iter(Interner).enumerate() {
let var = self.free_vars[i].clone();
if let Some(ty) = v.ty(Interner) {
// eagerly replace projections in the type; we may be getting types
// e.g. from where clauses where this hasn't happened yet
let ty = ctx.normalize_associated_types_in(new_vars.apply(ty.clone(), Interner));
ctx.unify(var.assert_ty_ref(Interner), &ty);
} else {
let _ = ctx.try_unify(&var, &new_vars.apply(v.clone(), Interner));
}
}
}
}
pub fn could_unify(
db: &dyn HirDatabase,
env: Arc<TraitEnvironment>,
tys: &Canonical<(Ty, Ty)>,
) -> bool {
unify(db, env, tys).is_some()
}
pub(crate) fn unify(
db: &dyn HirDatabase,
env: Arc<TraitEnvironment>,
tys: &Canonical<(Ty, Ty)>,
) -> Option<Substitution> {
let mut table = InferenceTable::new(db, env);
let vars = Substitution::from_iter(
Interner,
tys.binders.iter(Interner).map(|it| match &it.kind {
chalk_ir::VariableKind::Ty(_) => table.new_type_var().cast(Interner),
// FIXME: maybe wrong?
chalk_ir::VariableKind::Lifetime => table.new_type_var().cast(Interner),
chalk_ir::VariableKind::Const(ty) => table.new_const_var(ty.clone()).cast(Interner),
}),
);
let ty1_with_vars = vars.apply(tys.value.0.clone(), Interner);
let ty2_with_vars = vars.apply(tys.value.1.clone(), Interner);
if !table.unify(&ty1_with_vars, &ty2_with_vars) {
return None;
}
// default any type vars that weren't unified back to their original bound vars
// (kind of hacky)
let find_var = |iv| {
vars.iter(Interner).position(|v| match v.data(Interner) {
GenericArgData::Ty(ty) => ty.inference_var(Interner),
GenericArgData::Lifetime(lt) => lt.inference_var(Interner),
GenericArgData::Const(c) => c.inference_var(Interner),
} == Some(iv))
};
let fallback = |iv, kind, default, binder| match kind {
chalk_ir::VariableKind::Ty(_ty_kind) => find_var(iv)
.map_or(default, |i| BoundVar::new(binder, i).to_ty(Interner).cast(Interner)),
chalk_ir::VariableKind::Lifetime => find_var(iv)
.map_or(default, |i| BoundVar::new(binder, i).to_lifetime(Interner).cast(Interner)),
chalk_ir::VariableKind::Const(ty) => find_var(iv)
.map_or(default, |i| BoundVar::new(binder, i).to_const(Interner, ty).cast(Interner)),
};
Some(Substitution::from_iter(
Interner,
vars.iter(Interner).map(|v| table.resolve_with_fallback(v.clone(), &fallback)),
))
}
bitflags::bitflags! {
#[derive(Default, Clone, Copy)]
pub(crate) struct TypeVariableFlags: u8 {
const DIVERGING = 1 << 0;
const INTEGER = 1 << 1;
const FLOAT = 1 << 2;
}
}
type ChalkInferenceTable = chalk_solve::infer::InferenceTable<Interner>;
#[derive(Clone)]
pub(crate) struct InferenceTable<'a> {
pub(crate) db: &'a dyn HirDatabase,
pub(crate) trait_env: Arc<TraitEnvironment>,
var_unification_table: ChalkInferenceTable,
type_variable_table: Vec<TypeVariableFlags>,
pending_obligations: Vec<Canonicalized<InEnvironment<Goal>>>,
/// Double buffer used in [`Self::resolve_obligations_as_possible`] to cut down on
/// temporary allocations.
resolve_obligations_buffer: Vec<Canonicalized<InEnvironment<Goal>>>,
}
pub(crate) struct InferenceTableSnapshot {
var_table_snapshot: chalk_solve::infer::InferenceSnapshot<Interner>,
pending_obligations: Vec<Canonicalized<InEnvironment<Goal>>>,
type_variable_table_snapshot: Vec<TypeVariableFlags>,
}
impl<'a> InferenceTable<'a> {
pub(crate) fn new(db: &'a dyn HirDatabase, trait_env: Arc<TraitEnvironment>) -> Self {
InferenceTable {
db,
trait_env,
var_unification_table: ChalkInferenceTable::new(),
type_variable_table: Vec::new(),
pending_obligations: Vec::new(),
resolve_obligations_buffer: Vec::new(),
}
}
/// Chalk doesn't know about the `diverging` flag, so when it unifies two
/// type variables of which one is diverging, the chosen root might not be
/// diverging and we have no way of marking it as such at that time. This
/// function goes through all type variables and make sure their root is
/// marked as diverging if necessary, so that resolving them gives the right
/// result.
pub(super) fn propagate_diverging_flag(&mut self) {
for i in 0..self.type_variable_table.len() {
if !self.type_variable_table[i].contains(TypeVariableFlags::DIVERGING) {
continue;
}
let v = InferenceVar::from(i as u32);
let root = self.var_unification_table.inference_var_root(v);
if let Some(data) = self.type_variable_table.get_mut(root.index() as usize) {
*data |= TypeVariableFlags::DIVERGING;
}
}
}
pub(super) fn set_diverging(&mut self, iv: InferenceVar, diverging: bool) {
self.type_variable_table[iv.index() as usize].set(TypeVariableFlags::DIVERGING, diverging);
}
fn fallback_value(&self, iv: InferenceVar, kind: TyVariableKind) -> Ty {
match kind {
_ if self
.type_variable_table
.get(iv.index() as usize)
.map_or(false, |data| data.contains(TypeVariableFlags::DIVERGING)) =>
{
TyKind::Never
}
TyVariableKind::General => TyKind::Error,
TyVariableKind::Integer => TyKind::Scalar(Scalar::Int(IntTy::I32)),
TyVariableKind::Float => TyKind::Scalar(Scalar::Float(FloatTy::F64)),
}
.intern(Interner)
}
pub(crate) fn canonicalize<T: TypeFoldable<Interner> + HasInterner<Interner = Interner>>(
&mut self,
t: T,
) -> Canonicalized<T>
where
T: HasInterner<Interner = Interner>,
{
// try to resolve obligations before canonicalizing, since this might
// result in new knowledge about variables
self.resolve_obligations_as_possible();
let result = self.var_unification_table.canonicalize(Interner, t);
let free_vars = result
.free_vars
.into_iter()
.map(|free_var| free_var.to_generic_arg(Interner))
.collect();
Canonicalized { value: result.quantified, free_vars }
}
/// Recurses through the given type, normalizing associated types mentioned
/// in it by replacing them by type variables and registering obligations to
/// resolve later. This should be done once for every type we get from some
/// type annotation (e.g. from a let type annotation, field type or function
/// call). `make_ty` handles this already, but e.g. for field types we need
/// to do it as well.
pub(crate) fn normalize_associated_types_in<T>(&mut self, ty: T) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
{
fold_tys_and_consts(
ty,
|e, _| match e {
Either::Left(ty) => Either::Left(match ty.kind(Interner) {
TyKind::Alias(AliasTy::Projection(proj_ty)) => {
self.normalize_projection_ty(proj_ty.clone())
}
_ => ty,
}),
Either::Right(c) => Either::Right(match &c.data(Interner).value {
chalk_ir::ConstValue::Concrete(cc) => match &cc.interned {
crate::ConstScalar::UnevaluatedConst(c_id, subst) => {
// FIXME: Ideally here we should do everything that we do with type alias, i.e. adding a variable
// and registering an obligation. But it needs chalk support, so we handle the most basic
// case (a non associated const without generic parameters) manually.
if subst.len(Interner) == 0 {
if let Ok(eval) = self.db.const_eval(*c_id, subst.clone(), None) {
eval
} else {
unknown_const(c.data(Interner).ty.clone())
}
} else {
unknown_const(c.data(Interner).ty.clone())
}
}
_ => c,
},
_ => c,
}),
},
DebruijnIndex::INNERMOST,
)
}
pub(crate) fn normalize_projection_ty(&mut self, proj_ty: ProjectionTy) -> Ty {
let var = self.new_type_var();
let alias_eq = AliasEq { alias: AliasTy::Projection(proj_ty), ty: var.clone() };
let obligation = alias_eq.cast(Interner);
self.register_obligation(obligation);
var
}
fn extend_type_variable_table(&mut self, to_index: usize) {
let count = to_index - self.type_variable_table.len() + 1;
self.type_variable_table.extend(iter::repeat(TypeVariableFlags::default()).take(count));
}
fn new_var(&mut self, kind: TyVariableKind, diverging: bool) -> Ty {
let var = self.var_unification_table.new_variable(UniverseIndex::ROOT);
// Chalk might have created some type variables for its own purposes that we don't know about...
self.extend_type_variable_table(var.index() as usize);
assert_eq!(var.index() as usize, self.type_variable_table.len() - 1);
let flags = self.type_variable_table.get_mut(var.index() as usize).unwrap();
if diverging {
*flags |= TypeVariableFlags::DIVERGING;
}
if matches!(kind, TyVariableKind::Integer) {
*flags |= TypeVariableFlags::INTEGER;
} else if matches!(kind, TyVariableKind::Float) {
*flags |= TypeVariableFlags::FLOAT;
}
var.to_ty_with_kind(Interner, kind)
}
pub(crate) fn new_type_var(&mut self) -> Ty {
self.new_var(TyVariableKind::General, false)
}
pub(crate) fn new_integer_var(&mut self) -> Ty {
self.new_var(TyVariableKind::Integer, false)
}
pub(crate) fn new_float_var(&mut self) -> Ty {
self.new_var(TyVariableKind::Float, false)
}
pub(crate) fn new_maybe_never_var(&mut self) -> Ty {
self.new_var(TyVariableKind::General, true)
}
pub(crate) fn new_const_var(&mut self, ty: Ty) -> Const {
let var = self.var_unification_table.new_variable(UniverseIndex::ROOT);
var.to_const(Interner, ty)
}
pub(crate) fn new_lifetime_var(&mut self) -> Lifetime {
let var = self.var_unification_table.new_variable(UniverseIndex::ROOT);
var.to_lifetime(Interner)
}
pub(crate) fn resolve_with_fallback<T>(
&mut self,
t: T,
fallback: &dyn Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg,
) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
{
self.resolve_with_fallback_inner(&mut Vec::new(), t, &fallback)
}
pub(crate) fn fresh_subst(&mut self, binders: &[CanonicalVarKind<Interner>]) -> Substitution {
Substitution::from_iter(
Interner,
binders.iter().map(|kind| {
let param_infer_var =
kind.map_ref(|&ui| self.var_unification_table.new_variable(ui));
param_infer_var.to_generic_arg(Interner)
}),
)
}
pub(crate) fn instantiate_canonical<T>(&mut self, canonical: Canonical<T>) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner> + std::fmt::Debug,
{
let subst = self.fresh_subst(canonical.binders.as_slice(Interner));
subst.apply(canonical.value, Interner)
}
fn resolve_with_fallback_inner<T>(
&mut self,
var_stack: &mut Vec<InferenceVar>,
t: T,
fallback: &dyn Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg,
) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
{
t.fold_with(
&mut resolve::Resolver { table: self, var_stack, fallback },
DebruijnIndex::INNERMOST,
)
}
pub(crate) fn resolve_completely<T>(&mut self, t: T) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
{
self.resolve_with_fallback(t, &|_, _, d, _| d)
}
/// Apply a fallback to unresolved scalar types. Integer type variables and float type
/// variables are replaced with i32 and f64, respectively.
///
/// This method is only intended to be called just before returning inference results (i.e. in
/// `InferenceContext::resolve_all()`).
///
/// FIXME: This method currently doesn't apply fallback to unconstrained general type variables
/// whereas rustc replaces them with `()` or `!`.
pub(super) fn fallback_if_possible(&mut self) {
let int_fallback = TyKind::Scalar(Scalar::Int(IntTy::I32)).intern(Interner);
let float_fallback = TyKind::Scalar(Scalar::Float(FloatTy::F64)).intern(Interner);
let scalar_vars: Vec<_> = self
.type_variable_table
.iter()
.enumerate()
.filter_map(|(index, flags)| {
let kind = if flags.contains(TypeVariableFlags::INTEGER) {
TyVariableKind::Integer
} else if flags.contains(TypeVariableFlags::FLOAT) {
TyVariableKind::Float
} else {
return None;
};
// FIXME: This is not really the nicest way to get `InferenceVar`s. Can we get them
// without directly constructing them from `index`?
let var = InferenceVar::from(index as u32).to_ty(Interner, kind);
Some(var)
})
.collect();
for var in scalar_vars {
let maybe_resolved = self.resolve_ty_shallow(&var);
if let TyKind::InferenceVar(_, kind) = maybe_resolved.kind(Interner) {
let fallback = match kind {
TyVariableKind::Integer => &int_fallback,
TyVariableKind::Float => &float_fallback,
TyVariableKind::General => unreachable!(),
};
self.unify(&var, fallback);
}
}
}
/// Unify two relatable values (e.g. `Ty`) and register new trait goals that arise from that.
pub(crate) fn unify<T: ?Sized + Zip<Interner>>(&mut self, ty1: &T, ty2: &T) -> bool {
let result = match self.try_unify(ty1, ty2) {
Ok(r) => r,
Err(_) => return false,
};
self.register_infer_ok(result);
true
}
/// Unify two relatable values (e.g. `Ty`) and return new trait goals arising from it, so the
/// caller needs to deal with them.
pub(crate) fn try_unify<T: ?Sized + Zip<Interner>>(
&mut self,
t1: &T,
t2: &T,
) -> InferResult<()> {
match self.var_unification_table.relate(
Interner,
&self.db,
&self.trait_env.env,
chalk_ir::Variance::Invariant,
t1,
t2,
) {
Ok(result) => Ok(InferOk { goals: result.goals, value: () }),
Err(chalk_ir::NoSolution) => Err(TypeError),
}
}
/// If `ty` is a type variable with known type, returns that type;
/// otherwise, return ty.
pub(crate) fn resolve_ty_shallow(&mut self, ty: &Ty) -> Ty {
self.resolve_obligations_as_possible();
self.var_unification_table.normalize_ty_shallow(Interner, ty).unwrap_or_else(|| ty.clone())
}
pub(crate) fn snapshot(&mut self) -> InferenceTableSnapshot {
let var_table_snapshot = self.var_unification_table.snapshot();
let type_variable_table_snapshot = self.type_variable_table.clone();
let pending_obligations = self.pending_obligations.clone();
InferenceTableSnapshot {
var_table_snapshot,
pending_obligations,
type_variable_table_snapshot,
}
}
pub(crate) fn rollback_to(&mut self, snapshot: InferenceTableSnapshot) {
self.var_unification_table.rollback_to(snapshot.var_table_snapshot);
self.type_variable_table = snapshot.type_variable_table_snapshot;
self.pending_obligations = snapshot.pending_obligations;
}
pub(crate) fn run_in_snapshot<T>(&mut self, f: impl FnOnce(&mut InferenceTable<'_>) -> T) -> T {
let snapshot = self.snapshot();
let result = f(self);
self.rollback_to(snapshot);
result
}
/// Checks an obligation without registering it. Useful mostly to check
/// whether a trait *might* be implemented before deciding to 'lock in' the
/// choice (during e.g. method resolution or deref).
pub(crate) fn try_obligation(&mut self, goal: Goal) -> Option<Solution> {
let in_env = InEnvironment::new(&self.trait_env.env, goal);
let canonicalized = self.canonicalize(in_env);
self.db.trait_solve(self.trait_env.krate, self.trait_env.block, canonicalized.value)
}
pub(crate) fn register_obligation(&mut self, goal: Goal) {
let in_env = InEnvironment::new(&self.trait_env.env, goal);
self.register_obligation_in_env(in_env)
}
fn register_obligation_in_env(&mut self, goal: InEnvironment<Goal>) {
let canonicalized = self.canonicalize(goal);
if !self.try_resolve_obligation(&canonicalized) {
self.pending_obligations.push(canonicalized);
}
}
pub(crate) fn register_infer_ok<T>(&mut self, infer_ok: InferOk<T>) {
infer_ok.goals.into_iter().for_each(|goal| self.register_obligation_in_env(goal));
}
pub(crate) fn resolve_obligations_as_possible(&mut self) {
let _span = profile::span("resolve_obligations_as_possible");
let mut changed = true;
let mut obligations = mem::take(&mut self.resolve_obligations_buffer);
while mem::take(&mut changed) {
mem::swap(&mut self.pending_obligations, &mut obligations);
for canonicalized in obligations.drain(..) {
if !self.check_changed(&canonicalized) {
self.pending_obligations.push(canonicalized);
continue;
}
changed = true;
let uncanonical = chalk_ir::Substitute::apply(
&canonicalized.free_vars,
canonicalized.value.value,
Interner,
);
self.register_obligation_in_env(uncanonical);
}
}
self.resolve_obligations_buffer = obligations;
self.resolve_obligations_buffer.clear();
}
pub(crate) fn fudge_inference<T: TypeFoldable<Interner>>(
&mut self,
f: impl FnOnce(&mut Self) -> T,
) -> T {
use chalk_ir::fold::TypeFolder;
#[derive(chalk_derive::FallibleTypeFolder)]
#[has_interner(Interner)]
struct VarFudger<'a, 'b> {
table: &'a mut InferenceTable<'b>,
highest_known_var: InferenceVar,
}
impl TypeFolder<Interner> for VarFudger<'_, '_> {
fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
self
}
fn interner(&self) -> Interner {
Interner
}
fn fold_inference_ty(
&mut self,
var: chalk_ir::InferenceVar,
kind: TyVariableKind,
_outer_binder: chalk_ir::DebruijnIndex,
) -> chalk_ir::Ty<Interner> {
if var < self.highest_known_var {
var.to_ty(Interner, kind)
} else {
self.table.new_type_var()
}
}
fn fold_inference_lifetime(
&mut self,
var: chalk_ir::InferenceVar,
_outer_binder: chalk_ir::DebruijnIndex,
) -> chalk_ir::Lifetime<Interner> {
if var < self.highest_known_var {
var.to_lifetime(Interner)
} else {
self.table.new_lifetime_var()
}
}
fn fold_inference_const(
&mut self,
ty: chalk_ir::Ty<Interner>,
var: chalk_ir::InferenceVar,
_outer_binder: chalk_ir::DebruijnIndex,
) -> chalk_ir::Const<Interner> {
if var < self.highest_known_var {
var.to_const(Interner, ty)
} else {
self.table.new_const_var(ty)
}
}
}
let snapshot = self.snapshot();
let highest_known_var = self.new_type_var().inference_var(Interner).expect("inference_var");
let result = f(self);
self.rollback_to(snapshot);
result
.fold_with(&mut VarFudger { table: self, highest_known_var }, DebruijnIndex::INNERMOST)
}
/// This checks whether any of the free variables in the `canonicalized`
/// have changed (either been unified with another variable, or with a
/// value). If this is not the case, we don't need to try to solve the goal
/// again -- it'll give the same result as last time.
fn check_changed(&mut self, canonicalized: &Canonicalized<InEnvironment<Goal>>) -> bool {
canonicalized.free_vars.iter().any(|var| {
let iv = match var.data(Interner) {
GenericArgData::Ty(ty) => ty.inference_var(Interner),
GenericArgData::Lifetime(lt) => lt.inference_var(Interner),
GenericArgData::Const(c) => c.inference_var(Interner),
}
.expect("free var is not inference var");
if self.var_unification_table.probe_var(iv).is_some() {
return true;
}
let root = self.var_unification_table.inference_var_root(iv);
iv != root
})
}
fn try_resolve_obligation(
&mut self,
canonicalized: &Canonicalized<InEnvironment<Goal>>,
) -> bool {
let solution = self.db.trait_solve(
self.trait_env.krate,
self.trait_env.block,
canonicalized.value.clone(),
);
match solution {
Some(Solution::Unique(canonical_subst)) => {
canonicalized.apply_solution(
self,
Canonical {
binders: canonical_subst.binders,
// FIXME: handle constraints
value: canonical_subst.value.subst,
},
);
true
}
Some(Solution::Ambig(Guidance::Definite(substs))) => {
canonicalized.apply_solution(self, substs);
false
}
Some(_) => {
// FIXME use this when trying to resolve everything at the end
false
}
None => {
// FIXME obligation cannot be fulfilled => diagnostic
true
}
}
}
pub(crate) fn callable_sig(
&mut self,
ty: &Ty,
num_args: usize,
) -> Option<(Option<FnTrait>, Vec<Ty>, Ty)> {
match ty.callable_sig(self.db) {
Some(sig) => Some((None, sig.params().to_vec(), sig.ret().clone())),
None => {
let (f, args_ty, return_ty) = self.callable_sig_from_fn_trait(ty, num_args)?;
Some((Some(f), args_ty, return_ty))
}
}
}
fn callable_sig_from_fn_trait(
&mut self,
ty: &Ty,
num_args: usize,
) -> Option<(FnTrait, Vec<Ty>, Ty)> {
let krate = self.trait_env.krate;
let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
let trait_data = self.db.trait_data(fn_once_trait);
let output_assoc_type = trait_data.associated_type_by_name(&name![Output])?;
let mut arg_tys = vec![];
let arg_ty = TyBuilder::tuple(num_args)
.fill(|it| {
let arg = match it {
ParamKind::Type => self.new_type_var(),
ParamKind::Const(_) => unreachable!("Tuple with const parameter"),
};
arg_tys.push(arg.clone());
arg.cast(Interner)
})
.build();
let projection = {
let b = TyBuilder::subst_for_def(self.db, fn_once_trait, None);
if b.remaining() != 2 {
return None;
}
let fn_once_subst = b.push(ty.clone()).push(arg_ty).build();
TyBuilder::assoc_type_projection(self.db, output_assoc_type, Some(fn_once_subst))
.build()
};
let trait_env = self.trait_env.env.clone();
let mut trait_ref = projection.trait_ref(self.db);
let obligation = InEnvironment {
goal: trait_ref.clone().cast(Interner),
environment: trait_env.clone(),
};
let canonical = self.canonicalize(obligation.clone());
if self
.db
.trait_solve(krate, self.trait_env.block, canonical.value.cast(Interner))
.is_some()
{
self.register_obligation(obligation.goal);
let return_ty = self.normalize_projection_ty(projection);
for fn_x in [FnTrait::Fn, FnTrait::FnMut, FnTrait::FnOnce] {
let fn_x_trait = fn_x.get_id(self.db, krate)?;
trait_ref.trait_id = to_chalk_trait_id(fn_x_trait);
let obligation: chalk_ir::InEnvironment<chalk_ir::Goal<Interner>> = InEnvironment {
goal: trait_ref.clone().cast(Interner),
environment: trait_env.clone(),
};
let canonical = self.canonicalize(obligation.clone());
if self
.db
.trait_solve(krate, self.trait_env.block, canonical.value.cast(Interner))
.is_some()
{
return Some((fn_x, arg_tys, return_ty));
}
}
unreachable!("It should at least implement FnOnce at this point");
} else {
None
}
}
pub(super) fn insert_type_vars<T>(&mut self, ty: T) -> T
where
T: HasInterner<Interner = Interner> + TypeFoldable<Interner>,
{
fold_tys_and_consts(
ty,
|it, _| match it {
Either::Left(ty) => Either::Left(self.insert_type_vars_shallow(ty)),
Either::Right(c) => Either::Right(self.insert_const_vars_shallow(c)),
},
DebruijnIndex::INNERMOST,
)
}
/// Replaces `Ty::Error` by a new type var, so we can maybe still infer it.
pub(super) fn insert_type_vars_shallow(&mut self, ty: Ty) -> Ty {
match ty.kind(Interner) {
TyKind::Error => self.new_type_var(),
TyKind::InferenceVar(..) => {
let ty_resolved = self.resolve_ty_shallow(&ty);
if ty_resolved.is_unknown() {
self.new_type_var()
} else {
ty
}
}
_ => ty,
}
}
/// Replaces ConstScalar::Unknown by a new type var, so we can maybe still infer it.
pub(super) fn insert_const_vars_shallow(&mut self, c: Const) -> Const {
let data = c.data(Interner);
match &data.value {
ConstValue::Concrete(cc) => match &cc.interned {
crate::ConstScalar::Unknown => self.new_const_var(data.ty.clone()),
// try to evaluate unevaluated const. Replace with new var if const eval failed.
crate::ConstScalar::UnevaluatedConst(id, subst) => {
if let Ok(eval) = self.db.const_eval(*id, subst.clone(), None) {
eval
} else {
self.new_const_var(data.ty.clone())
}
}
_ => c,
},
_ => c,
}
}
}
impl fmt::Debug for InferenceTable<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("InferenceTable").field("num_vars", &self.type_variable_table.len()).finish()
}
}
mod resolve {
use super::InferenceTable;
use crate::{
ConcreteConst, Const, ConstData, ConstScalar, ConstValue, DebruijnIndex, GenericArg,
InferenceVar, Interner, Lifetime, Ty, TyVariableKind, VariableKind,
};
use chalk_ir::{
cast::Cast,
fold::{TypeFoldable, TypeFolder},
};
#[derive(chalk_derive::FallibleTypeFolder)]
#[has_interner(Interner)]
pub(super) struct Resolver<
'a,
'b,
F: Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg,
> {
pub(super) table: &'a mut InferenceTable<'b>,
pub(super) var_stack: &'a mut Vec<InferenceVar>,
pub(super) fallback: F,
}
impl<F> TypeFolder<Interner> for Resolver<'_, '_, F>
where
F: Fn(InferenceVar, VariableKind, GenericArg, DebruijnIndex) -> GenericArg,
{
fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner, Error = Self::Error> {
self
}
fn interner(&self) -> Interner {
Interner
}
fn fold_inference_ty(
&mut self,
var: InferenceVar,
kind: TyVariableKind,
outer_binder: DebruijnIndex,
) -> Ty {
let var = self.table.var_unification_table.inference_var_root(var);
if self.var_stack.contains(&var) {
// recursive type
let default = self.table.fallback_value(var, kind).cast(Interner);
return (self.fallback)(var, VariableKind::Ty(kind), default, outer_binder)
.assert_ty_ref(Interner)
.clone();
}
let result = if let Some(known_ty) = self.table.var_unification_table.probe_var(var) {
// known_ty may contain other variables that are known by now
self.var_stack.push(var);
let result = known_ty.fold_with(self, outer_binder);
self.var_stack.pop();
result.assert_ty_ref(Interner).clone()
} else {
let default = self.table.fallback_value(var, kind).cast(Interner);
(self.fallback)(var, VariableKind::Ty(kind), default, outer_binder)
.assert_ty_ref(Interner)
.clone()
};
result
}
fn fold_inference_const(
&mut self,
ty: Ty,
var: InferenceVar,
outer_binder: DebruijnIndex,
) -> Const {
let var = self.table.var_unification_table.inference_var_root(var);
let default = ConstData {
ty: ty.clone(),
value: ConstValue::Concrete(ConcreteConst { interned: ConstScalar::Unknown }),
}
.intern(Interner)
.cast(Interner);
if self.var_stack.contains(&var) {
// recursive
return (self.fallback)(var, VariableKind::Const(ty), default, outer_binder)
.assert_const_ref(Interner)
.clone();
}
if let Some(known_ty) = self.table.var_unification_table.probe_var(var) {
// known_ty may contain other variables that are known by now
self.var_stack.push(var);
let result = known_ty.fold_with(self, outer_binder);
self.var_stack.pop();
result.assert_const_ref(Interner).clone()
} else {
(self.fallback)(var, VariableKind::Const(ty), default, outer_binder)
.assert_const_ref(Interner)
.clone()
}
}
fn fold_inference_lifetime(
&mut self,
_var: InferenceVar,
_outer_binder: DebruijnIndex,
) -> Lifetime {
// fall back all lifetimes to 'static -- currently we don't deal
// with any lifetimes, but we can sometimes get some lifetime
// variables through Chalk's unification, and this at least makes
// sure we don't leak them outside of inference
crate::static_lifetime()
}
}
}