//! Type inference for expressions.
use std::iter::{repeat, repeat_with};
use std::{mem, sync::Arc};
use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
use hir_def::{
expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
path::{GenericArg, GenericArgs},
resolver::resolver_for_expr,
AssocContainerId, FieldId, Lookup,
};
use hir_expand::name::{name, Name};
use stdx::always;
use syntax::ast::RangeOp;
use crate::{
autoderef,
lower::lower_to_chalk_mutability,
method_resolution, op,
primitive::{self, UintTy},
to_assoc_type_id, to_chalk_trait_id,
traits::{chalk::from_chalk, FnTrait, InEnvironment},
utils::{generics, variant_data, Generics},
AdtId, Binders, CallableDefId, DomainGoal, FnPointer, FnSig, Interner, Rawness, Scalar,
Substitution, TraitRef, Ty, TyKind,
};
use super::{
find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
InferenceDiagnostic, TypeMismatch,
};
impl<'a> InferenceContext<'a> {
pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
let ty = self.infer_expr_inner(tgt_expr, expected);
if ty.is_never() {
// Any expression that produces a value of type `!` must have diverged
self.diverges = Diverges::Always;
}
let could_unify = self.unify(&ty, &expected.ty);
if !could_unify {
self.result.type_mismatches.insert(
tgt_expr,
TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
);
}
self.resolve_ty_as_possible(ty)
}
/// Infer type of expression with possibly implicit coerce to the expected type.
/// Return the type after possible coercion.
pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
let ty = self.infer_expr_inner(expr, &expected);
let ty = if !self.coerce(&ty, &expected.coercion_target()) {
self.result
.type_mismatches
.insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
// Return actual type when type mismatch.
// This is needed for diagnostic when return type mismatch.
ty
} else if expected.coercion_target().is_unknown() {
ty
} else {
expected.ty.clone()
};
self.resolve_ty_as_possible(ty)
}
fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
let krate = self.resolver.krate()?;
let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
let output_assoc_type =
self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
let generic_params = generics(self.db.upcast(), fn_once_trait.into());
if generic_params.len() != 2 {
return None;
}
let mut param_builder = Substitution::builder(num_args);
let mut arg_tys = vec![];
for _ in 0..num_args {
let arg = self.table.new_type_var();
param_builder = param_builder.push(arg.clone());
arg_tys.push(arg);
}
let parameters = param_builder.build();
let arg_ty = TyKind::Tuple(num_args, parameters).intern(&Interner);
let substs =
Substitution::build_for_generics(&generic_params).push(ty.clone()).push(arg_ty).build();
let trait_env = self.trait_env.env.clone();
let implements_fn_trait: DomainGoal =
TraitRef { trait_id: to_chalk_trait_id(fn_once_trait), substitution: substs.clone() }
.cast(&Interner);
let goal = self.canonicalizer().canonicalize_obligation(InEnvironment {
goal: implements_fn_trait.clone(),
environment: trait_env,
});
if self.db.trait_solve(krate, goal.value).is_some() {
self.obligations.push(implements_fn_trait);
let output_proj_ty = crate::ProjectionTy {
associated_ty_id: to_assoc_type_id(output_assoc_type),
substitution: substs,
};
let return_ty = self.normalize_projection_ty(output_proj_ty);
Some((arg_tys, return_ty))
} else {
None
}
}
pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
match ty.callable_sig(self.db) {
Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
None => self.callable_sig_from_fn_trait(ty, num_args),
}
}
fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
let body = Arc::clone(&self.body); // avoid borrow checker problem
let ty = match &body[tgt_expr] {
Expr::Missing => self.err_ty(),
Expr::If { condition, then_branch, else_branch } => {
// if let is desugared to match, so this is always simple if
self.infer_expr(
*condition,
&Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
);
let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
let mut both_arms_diverge = Diverges::Always;
let then_ty = self.infer_expr_inner(*then_branch, &expected);
both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
let else_ty = match else_branch {
Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
None => Ty::unit(),
};
both_arms_diverge &= self.diverges;
self.diverges = condition_diverges | both_arms_diverge;
self.coerce_merge_branch(&then_ty, &else_ty)
}
Expr::Block { statements, tail, label, id: _ } => {
let old_resolver = mem::replace(
&mut self.resolver,
resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
);
let ty = match label {
Some(_) => {
let break_ty = self.table.new_type_var();
self.breakables.push(BreakableContext {
may_break: false,
break_ty: break_ty.clone(),
label: label.map(|label| self.body[label].name.clone()),
});
let ty =
self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
let ctxt = self.breakables.pop().expect("breakable stack broken");
if ctxt.may_break {
ctxt.break_ty
} else {
ty
}
}
None => self.infer_block(statements, *tail, expected),
};
self.resolver = old_resolver;
ty
}
Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
Expr::TryBlock { body } => {
let _inner = self.infer_expr(*body, expected);
// FIXME should be std::result::Result<{inner}, _>
self.err_ty()
}
Expr::Async { body } => {
// Use the first type parameter as the output type of future.
// existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
let inner_ty = self.infer_expr(*body, &Expectation::none());
let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
TyKind::OpaqueType(opaque_ty_id, Substitution::single(inner_ty)).intern(&Interner)
}
Expr::Loop { body, label } => {
self.breakables.push(BreakableContext {
may_break: false,
break_ty: self.table.new_type_var(),
label: label.map(|label| self.body[label].name.clone()),
});
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let ctxt = self.breakables.pop().expect("breakable stack broken");
if ctxt.may_break {
self.diverges = Diverges::Maybe;
}
if ctxt.may_break {
ctxt.break_ty
} else {
TyKind::Never.intern(&Interner)
}
}
Expr::While { condition, body, label } => {
self.breakables.push(BreakableContext {
may_break: false,
break_ty: self.err_ty(),
label: label.map(|label| self.body[label].name.clone()),
});
// while let is desugared to a match loop, so this is always simple while
self.infer_expr(
*condition,
&Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
);
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let _ctxt = self.breakables.pop().expect("breakable stack broken");
// the body may not run, so it diverging doesn't mean we diverge
self.diverges = Diverges::Maybe;
Ty::unit()
}
Expr::For { iterable, body, pat, label } => {
let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
self.breakables.push(BreakableContext {
may_break: false,
break_ty: self.err_ty(),
label: label.map(|label| self.body[label].name.clone()),
});
let pat_ty =
self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
self.infer_pat(*pat, &pat_ty, BindingMode::default());
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
let _ctxt = self.breakables.pop().expect("breakable stack broken");
// the body may not run, so it diverging doesn't mean we diverge
self.diverges = Diverges::Maybe;
Ty::unit()
}
Expr::Lambda { body, args, ret_type, arg_types } => {
assert_eq!(args.len(), arg_types.len());
let mut sig_tys = Vec::new();
// collect explicitly written argument types
for arg_type in arg_types.iter() {
let arg_ty = if let Some(type_ref) = arg_type {
self.make_ty(type_ref)
} else {
self.table.new_type_var()
};
sig_tys.push(arg_ty);
}
// add return type
let ret_ty = match ret_type {
Some(type_ref) => self.make_ty(type_ref),
None => self.table.new_type_var(),
};
sig_tys.push(ret_ty.clone());
let sig_ty = TyKind::Function(FnPointer {
num_args: sig_tys.len() - 1,
sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
substs: Substitution(sig_tys.clone().into()),
})
.intern(&Interner);
let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
let closure_ty =
TyKind::Closure(closure_id, Substitution::single(sig_ty)).intern(&Interner);
// Eagerly try to relate the closure type with the expected
// type, otherwise we often won't have enough information to
// infer the body.
self.coerce(&closure_ty, &expected.ty);
// Now go through the argument patterns
for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
let resolved = self.resolve_ty_as_possible(arg_ty);
self.infer_pat(*arg_pat, &resolved, BindingMode::default());
}
let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
self.diverges = prev_diverges;
self.return_ty = prev_ret_ty;
closure_ty
}
Expr::Call { callee, args } => {
let callee_ty = self.infer_expr(*callee, &Expectation::none());
let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
let mut derefs = autoderef(
self.db,
self.resolver.krate(),
InEnvironment {
goal: canonicalized.value.clone(),
environment: self.trait_env.env.clone(),
},
);
let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
.find_map(|callee_deref_ty| {
self.callable_sig(
&canonicalized.decanonicalize_ty(callee_deref_ty.value),
args.len(),
)
})
.unwrap_or((Vec::new(), self.err_ty()));
self.register_obligations_for_call(&callee_ty);
self.check_call_arguments(args, ¶m_tys);
self.normalize_associated_types_in(ret_ty)
}
Expr::MethodCall { receiver, args, method_name, generic_args } => self
.infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
Expr::Match { expr, arms } => {
let input_ty = self.infer_expr(*expr, &Expectation::none());
let mut result_ty = if arms.is_empty() {
TyKind::Never.intern(&Interner)
} else {
self.table.new_type_var()
};
let matchee_diverges = self.diverges;
let mut all_arms_diverge = Diverges::Always;
for arm in arms {
self.diverges = Diverges::Maybe;
let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
if let Some(guard_expr) = arm.guard {
self.infer_expr(
guard_expr,
&Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
);
}
let arm_ty = self.infer_expr_inner(arm.expr, &expected);
all_arms_diverge &= self.diverges;
result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
}
self.diverges = matchee_diverges | all_arms_diverge;
result_ty
}
Expr::Path(p) => {
// FIXME this could be more efficient...
let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
}
Expr::Continue { .. } => TyKind::Never.intern(&Interner),
Expr::Break { expr, label } => {
let val_ty = if let Some(expr) = expr {
self.infer_expr(*expr, &Expectation::none())
} else {
Ty::unit()
};
let last_ty =
if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
ctxt.break_ty.clone()
} else {
self.err_ty()
};
let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
ctxt.break_ty = merged_type;
ctxt.may_break = true;
} else {
self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
expr: tgt_expr,
});
}
TyKind::Never.intern(&Interner)
}
Expr::Return { expr } => {
if let Some(expr) = expr {
self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
} else {
let unit = Ty::unit();
self.coerce(&unit, &self.return_ty.clone());
}
TyKind::Never.intern(&Interner)
}
Expr::Yield { expr } => {
// FIXME: track yield type for coercion
if let Some(expr) = expr {
self.infer_expr(*expr, &Expectation::none());
}
TyKind::Never.intern(&Interner)
}
Expr::RecordLit { path, fields, spread } => {
let (ty, def_id) = self.resolve_variant(path.as_ref());
if let Some(variant) = def_id {
self.write_variant_resolution(tgt_expr.into(), variant);
}
self.unify(&ty, &expected.ty);
let substs = ty.substs().cloned().unwrap_or_else(Substitution::empty);
let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
for field in fields.iter() {
let field_def =
variant_data.as_ref().and_then(|it| match it.field(&field.name) {
Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
None => {
self.push_diagnostic(InferenceDiagnostic::NoSuchField {
expr: field.expr,
});
None
}
});
if let Some(field_def) = field_def {
self.result.record_field_resolutions.insert(field.expr, field_def);
}
let field_ty = field_def.map_or(self.err_ty(), |it| {
field_types[it.local_id].clone().subst(&substs)
});
self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
}
if let Some(expr) = spread {
self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
}
ty
}
Expr::Field { expr, name } => {
let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
let ty = autoderef::autoderef(
self.db,
self.resolver.krate(),
InEnvironment {
goal: canonicalized.value.clone(),
environment: self.trait_env.env.clone(),
},
)
.find_map(|derefed_ty| {
let def_db = self.db.upcast();
let module = self.resolver.module();
let is_visible = |field_id: &FieldId| {
module
.map(|mod_id| {
self.db.field_visibilities(field_id.parent)[field_id.local_id]
.is_visible_from(def_db, mod_id)
})
.unwrap_or(true)
};
match canonicalized.decanonicalize_ty(derefed_ty.value).interned(&Interner) {
TyKind::Tuple(_, substs) => {
name.as_tuple_index().and_then(|idx| substs.0.get(idx).cloned())
}
TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
let local_id = self.db.struct_data(*s).variant_data.field(name)?;
let field = FieldId { parent: (*s).into(), local_id };
if is_visible(&field) {
self.write_field_resolution(tgt_expr, field);
Some(
self.db.field_types((*s).into())[field.local_id]
.clone()
.subst(¶meters),
)
} else {
None
}
}
TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
let local_id = self.db.union_data(*u).variant_data.field(name)?;
let field = FieldId { parent: (*u).into(), local_id };
if is_visible(&field) {
self.write_field_resolution(tgt_expr, field);
Some(
self.db.field_types((*u).into())[field.local_id]
.clone()
.subst(¶meters),
)
} else {
None
}
}
_ => None,
}
})
.unwrap_or(self.err_ty());
let ty = self.insert_type_vars(ty);
self.normalize_associated_types_in(ty)
}
Expr::Await { expr } => {
let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
}
Expr::Try { expr } => {
let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
}
Expr::Cast { expr, type_ref } => {
let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
let cast_ty = self.make_ty(type_ref);
// FIXME check the cast...
cast_ty
}
Expr::Ref { expr, rawness, mutability } => {
let mutability = lower_to_chalk_mutability(*mutability);
let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
&expected.ty.as_reference_or_ptr()
{
if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
// FIXME: throw type error - expected mut reference but found shared ref,
// which cannot be coerced
}
if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
// FIXME: throw type error - expected reference but found ptr,
// which cannot be coerced
}
Expectation::rvalue_hint(Ty::clone(exp_inner))
} else {
Expectation::none()
};
let inner_ty = self.infer_expr_inner(*expr, &expectation);
match rawness {
Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
Rawness::Ref => TyKind::Ref(mutability, inner_ty),
}
.intern(&Interner)
}
Expr::Box { expr } => {
let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
if let Some(box_) = self.resolve_boxed_box() {
let mut sb =
Substitution::build_for_generics(&generics(self.db.upcast(), box_.into()));
sb = sb.push(inner_ty);
match self.db.generic_defaults(box_.into()).get(1) {
Some(alloc_ty) if !alloc_ty.value.is_unknown() && sb.remaining() > 0 => {
sb = sb.push(alloc_ty.value.clone());
}
_ => (),
}
sb = sb.fill(repeat_with(|| self.table.new_type_var()));
Ty::adt_ty(box_, sb.build())
} else {
self.err_ty()
}
}
Expr::UnaryOp { expr, op } => {
let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
match op {
UnaryOp::Deref => match self.resolver.krate() {
Some(krate) => {
let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
match autoderef::deref(
self.db,
krate,
InEnvironment {
goal: &canonicalized.value,
environment: self.trait_env.env.clone(),
},
) {
Some(derefed_ty) => {
canonicalized.decanonicalize_ty(derefed_ty.value)
}
None => self.err_ty(),
}
}
None => self.err_ty(),
},
UnaryOp::Neg => {
match inner_ty.interned(&Interner) {
// Fast path for builtins
TyKind::Scalar(Scalar::Int(_))
| TyKind::Scalar(Scalar::Uint(_))
| TyKind::Scalar(Scalar::Float(_))
| TyKind::InferenceVar(_, TyVariableKind::Integer)
| TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
// Otherwise we resolve via the std::ops::Neg trait
_ => self
.resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
}
}
UnaryOp::Not => {
match inner_ty.interned(&Interner) {
// Fast path for builtins
TyKind::Scalar(Scalar::Bool)
| TyKind::Scalar(Scalar::Int(_))
| TyKind::Scalar(Scalar::Uint(_))
| TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
// Otherwise we resolve via the std::ops::Not trait
_ => self
.resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
}
}
}
}
Expr::BinaryOp { lhs, rhs, op } => match op {
Some(op) => {
let lhs_expectation = match op {
BinaryOp::LogicOp(..) => {
Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
}
_ => Expectation::none(),
};
let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
if ret.is_unknown() {
cov_mark::hit!(infer_expr_inner_binary_operator_overload);
self.resolve_associated_type_with_params(
lhs_ty,
self.resolve_binary_op_output(op),
&[rhs_ty],
)
} else {
ret
}
}
_ => self.err_ty(),
},
Expr::Range { lhs, rhs, range_type } => {
let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
let rhs_expect = lhs_ty
.as_ref()
.map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
match (range_type, lhs_ty, rhs_ty) {
(RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
Some(adt) => Ty::adt_ty(adt, Substitution::empty()),
None => self.err_ty(),
},
(RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
None => self.err_ty(),
},
(RangeOp::Inclusive, None, Some(ty)) => {
match self.resolve_range_to_inclusive() {
Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
None => self.err_ty(),
}
}
(RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
None => self.err_ty(),
},
(RangeOp::Inclusive, Some(_), Some(ty)) => {
match self.resolve_range_inclusive() {
Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
None => self.err_ty(),
}
}
(RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
None => self.err_ty(),
},
(RangeOp::Inclusive, _, None) => self.err_ty(),
}
}
Expr::Index { base, index } => {
let base_ty = self.infer_expr_inner(*base, &Expectation::none());
let index_ty = self.infer_expr(*index, &Expectation::none());
if let (Some(index_trait), Some(krate)) =
(self.resolve_ops_index(), self.resolver.krate())
{
let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
let self_ty = method_resolution::resolve_indexing_op(
self.db,
&canonicalized.value,
self.trait_env.clone(),
krate,
index_trait,
);
let self_ty =
self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
self.resolve_associated_type_with_params(
self_ty,
self.resolve_ops_index_output(),
&[index_ty],
)
} else {
self.err_ty()
}
}
Expr::Tuple { exprs } => {
let mut tys = match expected.ty.interned(&Interner) {
TyKind::Tuple(_, substs) => substs
.iter()
.cloned()
.chain(repeat_with(|| self.table.new_type_var()))
.take(exprs.len())
.collect::<Vec<_>>(),
_ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
};
for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
}
TyKind::Tuple(tys.len(), Substitution(tys.into())).intern(&Interner)
}
Expr::Array(array) => {
let elem_ty = match expected.ty.interned(&Interner) {
TyKind::Array(st) | TyKind::Slice(st) => st.clone(),
_ => self.table.new_type_var(),
};
match array {
Array::ElementList(items) => {
for expr in items.iter() {
self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
}
}
Array::Repeat { initializer, repeat } => {
self.infer_expr_coerce(
*initializer,
&Expectation::has_type(elem_ty.clone()),
);
self.infer_expr(
*repeat,
&Expectation::has_type(
TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
),
);
}
}
TyKind::Array(elem_ty).intern(&Interner)
}
Expr::Literal(lit) => match lit {
Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
Literal::String(..) => {
TyKind::Ref(Mutability::Not, TyKind::Str.intern(&Interner)).intern(&Interner)
}
Literal::ByteString(..) => {
let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
let array_type = TyKind::Array(byte_type).intern(&Interner);
TyKind::Ref(Mutability::Not, array_type).intern(&Interner)
}
Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
Literal::Int(_v, ty) => match ty {
Some(int_ty) => {
TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
.intern(&Interner)
}
None => self.table.new_integer_var(),
},
Literal::Uint(_v, ty) => match ty {
Some(int_ty) => {
TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
.intern(&Interner)
}
None => self.table.new_integer_var(),
},
Literal::Float(_v, ty) => match ty {
Some(float_ty) => {
TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
.intern(&Interner)
}
None => self.table.new_float_var(),
},
},
};
// use a new type variable if we got unknown here
let ty = self.insert_type_vars_shallow(ty);
let ty = self.resolve_ty_as_possible(ty);
self.write_expr_ty(tgt_expr, ty.clone());
ty
}
fn infer_block(
&mut self,
statements: &[Statement],
tail: Option<ExprId>,
expected: &Expectation,
) -> Ty {
for stmt in statements {
match stmt {
Statement::Let { pat, type_ref, initializer } => {
let decl_ty =
type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
// Always use the declared type when specified
let mut ty = decl_ty.clone();
if let Some(expr) = initializer {
let actual_ty =
self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
if decl_ty.is_unknown() {
ty = actual_ty;
}
}
let ty = self.resolve_ty_as_possible(ty);
self.infer_pat(*pat, &ty, BindingMode::default());
}
Statement::Expr(expr) => {
self.infer_expr(*expr, &Expectation::none());
}
}
}
let ty = if let Some(expr) = tail {
self.infer_expr_coerce(expr, expected)
} else {
// Citing rustc: if there is no explicit tail expression,
// that is typically equivalent to a tail expression
// of `()` -- except if the block diverges. In that
// case, there is no value supplied from the tail
// expression (assuming there are no other breaks,
// this implies that the type of the block will be
// `!`).
if self.diverges.is_always() {
// we don't even make an attempt at coercion
self.table.new_maybe_never_var()
} else {
self.coerce(&Ty::unit(), &expected.coercion_target());
Ty::unit()
}
};
ty
}
fn infer_method_call(
&mut self,
tgt_expr: ExprId,
receiver: ExprId,
args: &[ExprId],
method_name: &Name,
generic_args: Option<&GenericArgs>,
) -> Ty {
let receiver_ty = self.infer_expr(receiver, &Expectation::none());
let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
let resolved = self.resolver.krate().and_then(|krate| {
method_resolution::lookup_method(
&canonicalized_receiver.value,
self.db,
self.trait_env.clone(),
krate,
&traits_in_scope,
self.resolver.module(),
method_name,
)
});
let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
Some((ty, func)) => {
let ty = canonicalized_receiver.decanonicalize_ty(ty);
self.write_method_resolution(tgt_expr, func);
(ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
}
None => (receiver_ty, Binders::new(0, self.err_ty()), None),
};
let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
let method_ty = method_ty.subst(&substs);
let method_ty = self.insert_type_vars(method_ty);
self.register_obligations_for_call(&method_ty);
let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
Some(sig) => {
if !sig.params().is_empty() {
(sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
} else {
(self.err_ty(), Vec::new(), sig.ret().clone())
}
}
None => (self.err_ty(), Vec::new(), self.err_ty()),
};
// Apply autoref so the below unification works correctly
// FIXME: return correct autorefs from lookup_method
let actual_receiver_ty = match expected_receiver_ty.as_reference() {
Some((_, mutability)) => TyKind::Ref(mutability, derefed_receiver_ty).intern(&Interner),
_ => derefed_receiver_ty,
};
self.unify(&expected_receiver_ty, &actual_receiver_ty);
self.check_call_arguments(args, ¶m_tys);
self.normalize_associated_types_in(ret_ty)
}
fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
// Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
// We do this in a pretty awful way: first we type-check any arguments
// that are not closures, then we type-check the closures. This is so
// that we have more information about the types of arguments when we
// type-check the functions. This isn't really the right way to do this.
for &check_closures in &[false, true] {
let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
for (&arg, param_ty) in args.iter().zip(param_iter) {
let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
if is_closure != check_closures {
continue;
}
let param_ty = self.normalize_associated_types_in(param_ty);
self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
}
}
}
fn substs_for_method_call(
&mut self,
def_generics: Option<Generics>,
generic_args: Option<&GenericArgs>,
receiver_ty: &Ty,
) -> Substitution {
let (parent_params, self_params, type_params, impl_trait_params) =
def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
assert_eq!(self_params, 0); // method shouldn't have another Self param
let total_len = parent_params + type_params + impl_trait_params;
let mut substs = Vec::with_capacity(total_len);
// Parent arguments are unknown, except for the receiver type
if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
for (_id, param) in parent_generics {
if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
substs.push(receiver_ty.clone());
} else {
substs.push(self.err_ty());
}
}
}
// handle provided type arguments
if let Some(generic_args) = generic_args {
// if args are provided, it should be all of them, but we can't rely on that
for arg in generic_args
.args
.iter()
.filter(|arg| matches!(arg, GenericArg::Type(_)))
.take(type_params)
{
match arg {
GenericArg::Type(type_ref) => {
let ty = self.make_ty(type_ref);
substs.push(ty);
}
GenericArg::Lifetime(_) => {}
}
}
};
let supplied_params = substs.len();
for _ in supplied_params..total_len {
substs.push(self.err_ty());
}
assert_eq!(substs.len(), total_len);
Substitution(substs.into())
}
fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
if let TyKind::FnDef(fn_def, parameters) = callable_ty.interned(&Interner) {
let def: CallableDefId = from_chalk(self.db, *fn_def);
let generic_predicates = self.db.generic_predicates(def.into());
for predicate in generic_predicates.iter() {
let (predicate, binders) =
predicate.clone().subst(parameters).into_value_and_skipped_binders();
always!(binders == 0); // quantified where clauses not yet handled
self.obligations.push(predicate.cast(&Interner));
}
// add obligation for trait implementation, if this is a trait method
match def {
CallableDefId::FunctionId(f) => {
if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
{
// construct a TraitRef
let substs =
parameters.prefix(generics(self.db.upcast(), trait_.into()).len());
self.obligations.push(
TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
.cast(&Interner),
);
}
}
CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
}
}
}
}