1 //! Type inference for expressions.
4 iter::{repeat, repeat_with},
9 use chalk_ir::{cast::Cast, fold::Shift, Mutability, TyVariableKind};
12 ArithOp, Array, BinaryOp, CmpOp, Expr, ExprId, Literal, MatchGuard, Ordering, Statement,
15 path::{GenericArg, GenericArgs},
16 resolver::resolver_for_expr,
17 AssocContainerId, FieldId, FunctionId, Lookup,
19 use hir_expand::name::{name, Name};
21 use syntax::ast::RangeOp;
24 autoderef::{self, Autoderef},
26 infer::coerce::CoerceMany,
27 lower::lower_to_chalk_mutability,
30 primitive::{self, UintTy},
31 static_lifetime, to_chalk_trait_id,
33 utils::{generics, Generics},
34 AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
35 ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
39 find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
40 InferenceDiagnostic, TypeMismatch,
43 impl<'a> InferenceContext<'a> {
44 pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
45 let ty = self.infer_expr_inner(tgt_expr, expected);
46 if self.resolve_ty_shallow(&ty).is_never() {
47 // Any expression that produces a value of type `!` must have diverged
48 self.diverges = Diverges::Always;
50 if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
51 let could_unify = self.unify(&ty, &expected_ty);
53 self.result.type_mismatches.insert(
55 TypeMismatch { expected: expected_ty, actual: ty.clone() },
62 /// Infer type of expression with possibly implicit coerce to the expected type.
63 /// Return the type after possible coercion.
64 pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
65 let ty = self.infer_expr_inner(expr, expected);
66 if let Some(target) = expected.only_has_type(&mut self.table) {
67 match self.coerce(Some(expr), &ty, &target) {
72 .insert(expr.into(), TypeMismatch { expected: target, actual: ty.clone() });
73 // Return actual type when type mismatch.
74 // This is needed for diagnostic when return type mismatch.
83 fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
84 let krate = self.resolver.krate()?;
85 let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
86 let output_assoc_type =
87 self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
89 let mut arg_tys = vec![];
90 let arg_ty = TyBuilder::tuple(num_args)
91 .fill(repeat_with(|| {
92 let arg = self.table.new_type_var();
93 arg_tys.push(arg.clone());
99 let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
100 if b.remaining() != 2 {
103 b.push(ty.clone()).push(arg_ty).build()
106 let trait_env = self.trait_env.env.clone();
107 let obligation = InEnvironment {
108 goal: projection.trait_ref(self.db).cast(&Interner),
109 environment: trait_env,
111 let canonical = self.canonicalize(obligation.clone());
112 if self.db.trait_solve(krate, canonical.value.cast(&Interner)).is_some() {
113 self.push_obligation(obligation.goal);
114 let return_ty = self.table.normalize_projection_ty(projection);
115 Some((arg_tys, return_ty))
121 pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
122 match ty.callable_sig(self.db) {
123 Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
124 None => self.callable_sig_from_fn_trait(ty, num_args),
128 fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
129 self.db.unwind_if_cancelled();
131 let body = Arc::clone(&self.body); // avoid borrow checker problem
132 let ty = match &body[tgt_expr] {
133 Expr::Missing => self.err_ty(),
134 &Expr::If { condition, then_branch, else_branch } => {
135 // if let is desugared to match, so this is always simple if
138 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
141 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
142 let mut both_arms_diverge = Diverges::Always;
144 let result_ty = self.table.new_type_var();
145 let then_ty = self.infer_expr_inner(then_branch, expected);
146 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
147 let mut coerce = CoerceMany::new(result_ty);
148 coerce.coerce(self, Some(then_branch), &then_ty);
149 let else_ty = match else_branch {
150 Some(else_branch) => self.infer_expr_inner(else_branch, expected),
151 None => TyBuilder::unit(),
153 both_arms_diverge &= self.diverges;
154 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
155 coerce.coerce(self, else_branch, &else_ty);
157 self.diverges = condition_diverges | both_arms_diverge;
161 Expr::Block { statements, tail, label, id: _ } => {
162 let old_resolver = mem::replace(
164 resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
166 let ty = match label {
168 let break_ty = self.table.new_type_var();
169 self.breakables.push(BreakableContext {
171 coerce: CoerceMany::new(break_ty.clone()),
172 label: label.map(|label| self.body[label].name.clone()),
174 let ty = self.infer_block(
178 &Expectation::has_type(break_ty),
180 let ctxt = self.breakables.pop().expect("breakable stack broken");
182 ctxt.coerce.complete()
187 None => self.infer_block(tgt_expr, statements, *tail, expected),
189 self.resolver = old_resolver;
192 Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
193 Expr::TryBlock { body } => {
194 let _inner = self.infer_expr(*body, expected);
195 // FIXME should be std::result::Result<{inner}, _>
198 Expr::Async { body } => {
199 // Use the first type parameter as the output type of future.
200 // existential type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
201 let inner_ty = self.infer_expr(*body, &Expectation::none());
202 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
203 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
204 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
207 Expr::Loop { body, label } => {
208 self.breakables.push(BreakableContext {
210 coerce: CoerceMany::new(self.table.new_type_var()),
211 label: label.map(|label| self.body[label].name.clone()),
213 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
215 let ctxt = self.breakables.pop().expect("breakable stack broken");
218 self.diverges = Diverges::Maybe;
219 ctxt.coerce.complete()
221 TyKind::Never.intern(&Interner)
224 Expr::While { condition, body, label } => {
225 self.breakables.push(BreakableContext {
227 coerce: CoerceMany::new(self.err_ty()),
228 label: label.map(|label| self.body[label].name.clone()),
230 // while let is desugared to a match loop, so this is always simple while
233 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
235 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
236 let _ctxt = self.breakables.pop().expect("breakable stack broken");
237 // the body may not run, so it diverging doesn't mean we diverge
238 self.diverges = Diverges::Maybe;
241 Expr::For { iterable, body, pat, label } => {
242 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
244 self.breakables.push(BreakableContext {
246 coerce: CoerceMany::new(self.err_ty()),
247 label: label.map(|label| self.body[label].name.clone()),
250 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
252 self.infer_pat(*pat, &pat_ty, BindingMode::default());
254 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
255 let _ctxt = self.breakables.pop().expect("breakable stack broken");
256 // the body may not run, so it diverging doesn't mean we diverge
257 self.diverges = Diverges::Maybe;
260 Expr::Lambda { body, args, ret_type, arg_types } => {
261 assert_eq!(args.len(), arg_types.len());
263 let mut sig_tys = Vec::new();
265 // collect explicitly written argument types
266 for arg_type in arg_types.iter() {
267 let arg_ty = match arg_type {
268 Some(type_ref) => self.make_ty(type_ref),
269 None => self.table.new_type_var(),
271 sig_tys.push(arg_ty);
275 let ret_ty = match ret_type {
276 Some(type_ref) => self.make_ty(type_ref),
277 None => self.table.new_type_var(),
279 sig_tys.push(ret_ty.clone());
280 let sig_ty = TyKind::Function(FnPointer {
282 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
283 substitution: FnSubst(
284 Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
288 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
290 TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty.clone()))
293 // Eagerly try to relate the closure type with the expected
294 // type, otherwise we often won't have enough information to
296 self.deduce_closure_type_from_expectations(
303 // Now go through the argument patterns
304 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
305 self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
308 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
309 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
311 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
313 self.diverges = prev_diverges;
314 self.return_ty = prev_ret_ty;
318 Expr::Call { callee, args } => {
319 let callee_ty = self.infer_expr(*callee, &Expectation::none());
320 let canonicalized = self.canonicalize(callee_ty.clone());
321 let mut derefs = Autoderef::new(
323 self.resolver.krate(),
325 goal: canonicalized.value.clone(),
326 environment: self.table.trait_env.env.clone(),
329 let res = derefs.by_ref().find_map(|(callee_deref_ty, _)| {
330 let ty = &canonicalized.decanonicalize_ty(&mut self.table, callee_deref_ty);
331 self.callable_sig(ty, args.len())
333 let (param_tys, ret_ty): (Vec<Ty>, Ty) = match res {
335 self.write_expr_adj(*callee, self.auto_deref_adjust_steps(&derefs));
338 None => (Vec::new(), self.err_ty()),
340 self.register_obligations_for_call(&callee_ty);
342 let expected_inputs = self.expected_inputs_for_expected_output(
348 self.check_call_arguments(args, &expected_inputs, ¶m_tys);
349 self.normalize_associated_types_in(ret_ty)
351 Expr::MethodCall { receiver, args, method_name, generic_args } => self
357 generic_args.as_deref(),
360 Expr::Match { expr, arms } => {
361 let input_ty = self.infer_expr(*expr, &Expectation::none());
363 let expected = expected.adjust_for_branches(&mut self.table);
365 let result_ty = if arms.is_empty() {
366 TyKind::Never.intern(&Interner)
369 Expectation::HasType(ty) => ty.clone(),
370 _ => self.table.new_type_var(),
373 let mut coerce = CoerceMany::new(result_ty);
375 let matchee_diverges = self.diverges;
376 let mut all_arms_diverge = Diverges::Always;
379 self.diverges = Diverges::Maybe;
380 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
382 Some(MatchGuard::If { expr: guard_expr }) => {
385 &Expectation::has_type(
386 TyKind::Scalar(Scalar::Bool).intern(&Interner),
390 Some(MatchGuard::IfLet { expr, pat }) => {
391 let input_ty = self.infer_expr(expr, &Expectation::none());
392 let _pat_ty = self.infer_pat(pat, &input_ty, BindingMode::default());
397 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
398 all_arms_diverge &= self.diverges;
399 coerce.coerce(self, Some(arm.expr), &arm_ty);
402 self.diverges = matchee_diverges | all_arms_diverge;
407 // FIXME this could be more efficient...
408 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
409 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or_else(|| self.err_ty())
411 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
412 Expr::Break { expr, label } => {
413 let mut coerce = match find_breakable(&mut self.breakables, label.as_ref()) {
415 // avoiding the borrowck
418 CoerceMany::new(self.result.standard_types.unknown.clone()),
421 None => CoerceMany::new(self.result.standard_types.unknown.clone()),
424 let val_ty = if let Some(expr) = *expr {
425 self.infer_expr(expr, &Expectation::none())
430 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
431 coerce.coerce(self, *expr, &val_ty);
433 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
434 ctxt.coerce = coerce;
435 ctxt.may_break = true;
437 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
442 TyKind::Never.intern(&Interner)
444 Expr::Return { expr } => {
445 if let Some(expr) = expr {
446 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
448 let unit = TyBuilder::unit();
449 let _ = self.coerce(Some(tgt_expr), &unit, &self.return_ty.clone());
451 TyKind::Never.intern(&Interner)
453 Expr::Yield { expr } => {
454 // FIXME: track yield type for coercion
455 if let Some(expr) = expr {
456 self.infer_expr(*expr, &Expectation::none());
458 TyKind::Never.intern(&Interner)
460 Expr::RecordLit { path, fields, spread } => {
461 let (ty, def_id) = self.resolve_variant(path.as_deref(), false);
462 if let Some(variant) = def_id {
463 self.write_variant_resolution(tgt_expr.into(), variant);
466 if let Some(t) = expected.only_has_type(&mut self.table) {
472 .map(|(_, s)| s.clone())
473 .unwrap_or_else(|| Substitution::empty(&Interner));
474 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
475 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
476 for field in fields.iter() {
478 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
479 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
481 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
487 let field_ty = field_def.map_or(self.err_ty(), |it| {
488 field_types[it.local_id].clone().substitute(&Interner, &substs)
490 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
492 if let Some(expr) = spread {
493 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
497 Expr::Field { expr, name } => {
498 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
499 let canonicalized = self.canonicalize(receiver_ty);
501 let mut autoderef = Autoderef::new(
503 self.resolver.krate(),
505 goal: canonicalized.value.clone(),
506 environment: self.trait_env.env.clone(),
509 let ty = autoderef.by_ref().find_map(|(derefed_ty, _)| {
510 let module = self.resolver.module();
512 let is_visible = |field_id: &FieldId| {
515 db.field_visibilities(field_id.parent)[field_id.local_id]
516 .is_visible_from(db.upcast(), mod_id)
521 .decanonicalize_ty(&mut self.table, derefed_ty)
524 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
528 .map(|a| a.assert_ty_ref(&Interner))
531 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
532 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
533 let field = FieldId { parent: (*s).into(), local_id };
534 if is_visible(&field) {
535 self.write_field_resolution(tgt_expr, field);
537 self.db.field_types((*s).into())[field.local_id]
539 .substitute(&Interner, ¶meters),
545 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
546 let local_id = self.db.union_data(*u).variant_data.field(name)?;
547 let field = FieldId { parent: (*u).into(), local_id };
548 if is_visible(&field) {
549 self.write_field_resolution(tgt_expr, field);
551 self.db.field_types((*u).into())[field.local_id]
553 .substitute(&Interner, ¶meters),
564 self.write_expr_adj(*expr, self.auto_deref_adjust_steps(&autoderef));
567 None => self.err_ty(),
569 let ty = self.insert_type_vars(ty);
570 self.normalize_associated_types_in(ty)
572 Expr::Await { expr } => {
573 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
574 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
576 Expr::Try { expr } => {
577 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
578 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
580 Expr::Cast { expr, type_ref } => {
581 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
582 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
583 let cast_ty = self.make_ty(type_ref);
584 // FIXME check the cast...
587 Expr::Ref { expr, rawness, mutability } => {
588 let mutability = lower_to_chalk_mutability(*mutability);
589 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
590 .only_has_type(&mut self.table)
592 .and_then(|t| t.as_reference_or_ptr())
594 if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
595 // FIXME: record type error - expected mut reference but found shared ref,
596 // which cannot be coerced
598 if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
599 // FIXME: record type error - expected reference but found ptr,
600 // which cannot be coerced
602 Expectation::rvalue_hint(&mut self.table, Ty::clone(exp_inner))
606 let inner_ty = self.infer_expr_inner(*expr, &expectation);
608 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
609 Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
613 Expr::Box { expr } => {
614 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
615 if let Some(box_) = self.resolve_boxed_box() {
616 TyBuilder::adt(self.db, box_)
618 .fill_with_defaults(self.db, || self.table.new_type_var())
624 Expr::UnaryOp { expr, op } => {
625 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
626 let inner_ty = self.resolve_ty_shallow(&inner_ty);
628 UnaryOp::Deref => match self.resolver.krate() {
630 let canonicalized = self.canonicalize(inner_ty);
631 match autoderef::deref(
635 goal: &canonicalized.value,
636 environment: self.trait_env.env.clone(),
639 Some(derefed_ty) => {
640 canonicalized.decanonicalize_ty(&mut self.table, derefed_ty)
642 None => self.err_ty(),
645 None => self.err_ty(),
648 match inner_ty.kind(&Interner) {
649 // Fast path for builtins
650 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
651 | TyKind::InferenceVar(
653 TyVariableKind::Integer | TyVariableKind::Float,
655 // Otherwise we resolve via the std::ops::Neg trait
657 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
661 match inner_ty.kind(&Interner) {
662 // Fast path for builtins
663 TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
664 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
665 // Otherwise we resolve via the std::ops::Not trait
667 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
672 Expr::BinaryOp { lhs, rhs, op } => match op {
673 Some(BinaryOp::Assignment { op: None }) => {
674 let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
675 self.infer_expr_coerce(*rhs, &Expectation::has_type(lhs_ty));
676 self.result.standard_types.unit.clone()
678 Some(BinaryOp::LogicOp(_)) => {
679 let bool_ty = self.result.standard_types.bool_.clone();
680 self.infer_expr_coerce(*lhs, &Expectation::HasType(bool_ty.clone()));
681 let lhs_diverges = self.diverges;
682 self.infer_expr_coerce(*rhs, &Expectation::HasType(bool_ty.clone()));
683 // Depending on the LHS' value, the RHS can never execute.
684 self.diverges = lhs_diverges;
687 Some(op) => self.infer_overloadable_binop(*lhs, *op, *rhs, tgt_expr),
690 Expr::Range { lhs, rhs, range_type } => {
691 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
692 let rhs_expect = lhs_ty
694 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
695 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
696 match (range_type, lhs_ty, rhs_ty) {
697 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
698 Some(adt) => TyBuilder::adt(self.db, adt).build(),
699 None => self.err_ty(),
701 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
702 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
703 None => self.err_ty(),
705 (RangeOp::Inclusive, None, Some(ty)) => {
706 match self.resolve_range_to_inclusive() {
707 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
708 None => self.err_ty(),
711 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
712 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
713 None => self.err_ty(),
715 (RangeOp::Inclusive, Some(_), Some(ty)) => {
716 match self.resolve_range_inclusive() {
717 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
718 None => self.err_ty(),
721 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
722 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
723 None => self.err_ty(),
725 (RangeOp::Inclusive, _, None) => self.err_ty(),
728 Expr::Index { base, index } => {
729 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
730 let index_ty = self.infer_expr(*index, &Expectation::none());
732 if let (Some(index_trait), Some(krate)) =
733 (self.resolve_ops_index(), self.resolver.krate())
735 let canonicalized = self.canonicalize(base_ty);
736 let self_ty = method_resolution::resolve_indexing_op(
738 &canonicalized.value,
739 self.trait_env.clone(),
743 let self_ty = self_ty.map_or(self.err_ty(), |t| {
744 canonicalized.decanonicalize_ty(&mut self.table, t)
746 self.resolve_associated_type_with_params(
748 self.resolve_ops_index_output(),
755 Expr::Tuple { exprs } => {
756 let mut tys = match expected
757 .only_has_type(&mut self.table)
759 .map(|t| t.kind(&Interner))
761 Some(TyKind::Tuple(_, substs)) => substs
763 .map(|a| a.assert_ty_ref(&Interner).clone())
764 .chain(repeat_with(|| self.table.new_type_var()))
766 .collect::<Vec<_>>(),
767 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
770 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
771 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
774 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
776 Expr::Array(array) => {
778 match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(&Interner)) {
779 Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
780 _ => self.table.new_type_var(),
782 let mut coerce = CoerceMany::new(elem_ty.clone());
784 let expected = Expectation::has_type(elem_ty.clone());
785 let len = match array {
786 Array::ElementList(items) => {
787 for &expr in items.iter() {
788 let cur_elem_ty = self.infer_expr_inner(expr, &expected);
789 coerce.coerce(self, Some(expr), &cur_elem_ty);
791 Some(items.len() as u64)
793 &Array::Repeat { initializer, repeat } => {
794 self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
797 &Expectation::has_type(
798 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
802 let repeat_expr = &self.body.exprs[repeat];
803 consteval::eval_usize(repeat_expr)
807 TyKind::Array(coerce.complete(), consteval::usize_const(len)).intern(&Interner)
809 Expr::Literal(lit) => match lit {
810 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
811 Literal::String(..) => {
812 TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
815 Literal::ByteString(bs) => {
816 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
818 let len = consteval::usize_const(Some(bs.len() as u64));
820 let array_type = TyKind::Array(byte_type, len).intern(&Interner);
821 TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
823 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
824 Literal::Int(_v, ty) => match ty {
826 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
829 None => self.table.new_integer_var(),
831 Literal::Uint(_v, ty) => match ty {
833 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
836 None => self.table.new_integer_var(),
838 Literal::Float(_v, ty) => match ty {
840 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
843 None => self.table.new_float_var(),
846 Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
848 // use a new type variable if we got unknown here
849 let ty = self.insert_type_vars_shallow(ty);
850 self.write_expr_ty(tgt_expr, ty.clone());
854 fn infer_overloadable_binop(
861 let lhs_expectation = Expectation::none();
862 let lhs_ty = self.infer_expr(lhs, &lhs_expectation);
863 let rhs_ty = self.table.new_type_var();
865 let func = self.resolve_binop_method(op);
866 let func = match func {
869 let rhs_ty = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone());
870 let rhs_ty = self.infer_expr_coerce(rhs, &Expectation::from_option(rhs_ty));
872 .builtin_binary_op_return_ty(op, lhs_ty, rhs_ty)
873 .unwrap_or_else(|| self.err_ty());
877 let subst = TyBuilder::subst_for_def(self.db, func)
878 .push(lhs_ty.clone())
879 .push(rhs_ty.clone())
881 self.write_method_resolution(tgt_expr, func, subst.clone());
883 let method_ty = self.db.value_ty(func.into()).substitute(&Interner, &subst);
884 self.register_obligations_for_call(&method_ty);
886 self.infer_expr_coerce(rhs, &Expectation::has_type(rhs_ty.clone()));
888 let ret_ty = match method_ty.callable_sig(self.db) {
889 Some(sig) => sig.ret().clone(),
890 None => self.err_ty(),
893 let ret_ty = self.normalize_associated_types_in(ret_ty);
895 // FIXME: record autoref adjustments
897 // use knowledge of built-in binary ops, which can sometimes help inference
898 if let Some(builtin_rhs) = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone()) {
899 self.unify(&builtin_rhs, &rhs_ty);
901 if let Some(builtin_ret) = self.builtin_binary_op_return_ty(op, lhs_ty, rhs_ty) {
902 self.unify(&builtin_ret, &ret_ty);
911 statements: &[Statement],
912 tail: Option<ExprId>,
913 expected: &Expectation,
915 for stmt in statements {
917 Statement::Let { pat, type_ref, initializer, else_branch } => {
918 let decl_ty = type_ref
920 .map(|tr| self.make_ty(tr))
921 .unwrap_or_else(|| self.err_ty());
923 // Always use the declared type when specified
924 let mut ty = decl_ty.clone();
926 if let Some(expr) = initializer {
928 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
929 if decl_ty.is_unknown() {
934 if let Some(expr) = else_branch {
935 self.infer_expr_coerce(
937 &Expectation::has_type(Ty::new(&Interner, TyKind::Never)),
941 self.infer_pat(*pat, &ty, BindingMode::default());
943 Statement::Expr { expr, .. } => {
944 self.infer_expr(*expr, &Expectation::none());
949 if let Some(expr) = tail {
950 self.infer_expr_coerce(expr, expected)
952 // Citing rustc: if there is no explicit tail expression,
953 // that is typically equivalent to a tail expression
954 // of `()` -- except if the block diverges. In that
955 // case, there is no value supplied from the tail
956 // expression (assuming there are no other breaks,
957 // this implies that the type of the block will be
959 if self.diverges.is_always() {
960 // we don't even make an attempt at coercion
961 self.table.new_maybe_never_var()
963 if let Some(t) = expected.only_has_type(&mut self.table) {
964 let _ = self.coerce(Some(expr), &TyBuilder::unit(), &t);
971 fn infer_method_call(
977 generic_args: Option<&GenericArgs>,
978 expected: &Expectation,
980 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
981 let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
983 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
985 let resolved = self.resolver.krate().and_then(|krate| {
986 method_resolution::lookup_method(
987 &canonicalized_receiver.value,
989 self.trait_env.clone(),
992 self.resolver.module(),
996 let (receiver_ty, method_ty, substs) = match resolved {
997 Some((ty, func)) => {
998 let ty = canonicalized_receiver.decanonicalize_ty(&mut self.table, ty);
999 let generics = generics(self.db.upcast(), func.into());
1000 let substs = self.substs_for_method_call(generics, generic_args, &ty);
1001 self.write_method_resolution(tgt_expr, func, substs.clone());
1002 (ty, self.db.value_ty(func.into()), substs)
1006 Binders::empty(&Interner, self.err_ty()),
1007 Substitution::empty(&Interner),
1010 let method_ty = method_ty.substitute(&Interner, &substs);
1011 self.register_obligations_for_call(&method_ty);
1012 let (formal_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
1014 if !sig.params().is_empty() {
1015 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
1017 (self.err_ty(), Vec::new(), sig.ret().clone())
1020 None => (self.err_ty(), Vec::new(), self.err_ty()),
1022 self.unify(&formal_receiver_ty, &receiver_ty);
1024 let expected_inputs =
1025 self.expected_inputs_for_expected_output(expected, ret_ty.clone(), param_tys.clone());
1027 self.check_call_arguments(args, &expected_inputs, ¶m_tys);
1028 self.normalize_associated_types_in(ret_ty)
1031 fn expected_inputs_for_expected_output(
1033 expected_output: &Expectation,
1037 if let Some(expected_ty) = expected_output.to_option(&mut self.table) {
1038 self.table.fudge_inference(|table| {
1039 if table.try_unify(&expected_ty, &output).is_ok() {
1040 table.resolve_with_fallback(inputs, &|var, kind, _, _| match kind {
1041 chalk_ir::VariableKind::Ty(tk) => var.to_ty(&Interner, tk).cast(&Interner),
1042 chalk_ir::VariableKind::Lifetime => {
1043 var.to_lifetime(&Interner).cast(&Interner)
1045 chalk_ir::VariableKind::Const(ty) => {
1046 var.to_const(&Interner, ty).cast(&Interner)
1058 fn check_call_arguments(&mut self, args: &[ExprId], expected_inputs: &[Ty], param_tys: &[Ty]) {
1059 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
1060 // We do this in a pretty awful way: first we type-check any arguments
1061 // that are not closures, then we type-check the closures. This is so
1062 // that we have more information about the types of arguments when we
1063 // type-check the functions. This isn't really the right way to do this.
1064 for &check_closures in &[false, true] {
1065 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
1066 let expected_iter = expected_inputs
1069 .chain(param_iter.clone().skip(expected_inputs.len()));
1070 for ((&arg, param_ty), expected_ty) in args.iter().zip(param_iter).zip(expected_iter) {
1071 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
1072 if is_closure != check_closures {
1076 // the difference between param_ty and expected here is that
1077 // expected is the parameter when the expected *return* type is
1078 // taken into account. So in `let _: &[i32] = identity(&[1, 2])`
1079 // the expected type is already `&[i32]`, whereas param_ty is
1080 // still an unbound type variable. We don't always want to force
1081 // the parameter to coerce to the expected type (for example in
1082 // `coerce_unsize_expected_type_4`).
1083 let param_ty = self.normalize_associated_types_in(param_ty);
1084 let expected = Expectation::rvalue_hint(&mut self.table, expected_ty);
1085 // infer with the expected type we have...
1086 let ty = self.infer_expr_inner(arg, &expected);
1088 // then coerce to either the expected type or just the formal parameter type
1089 let coercion_target = if let Some(ty) = expected.only_has_type(&mut self.table) {
1090 // if we are coercing to the expectation, unify with the
1091 // formal parameter type to connect everything
1092 self.unify(&ty, ¶m_ty);
1097 if !coercion_target.is_unknown() {
1098 if self.coerce(Some(arg), &ty, &coercion_target).is_err() {
1099 self.result.type_mismatches.insert(
1101 TypeMismatch { expected: coercion_target, actual: ty.clone() },
1109 fn substs_for_method_call(
1111 def_generics: Generics,
1112 generic_args: Option<&GenericArgs>,
1115 let (parent_params, self_params, type_params, impl_trait_params) =
1116 def_generics.provenance_split();
1117 assert_eq!(self_params, 0); // method shouldn't have another Self param
1118 let total_len = parent_params + type_params + impl_trait_params;
1119 let mut substs = Vec::with_capacity(total_len);
1120 // Parent arguments are unknown, except for the receiver type
1121 for (_id, param) in def_generics.iter_parent() {
1122 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
1123 substs.push(receiver_ty.clone());
1125 substs.push(self.table.new_type_var());
1128 // handle provided type arguments
1129 if let Some(generic_args) = generic_args {
1130 // if args are provided, it should be all of them, but we can't rely on that
1131 for arg in generic_args
1134 .filter(|arg| matches!(arg, GenericArg::Type(_)))
1138 GenericArg::Type(type_ref) => {
1139 let ty = self.make_ty(type_ref);
1142 GenericArg::Lifetime(_) => {}
1146 let supplied_params = substs.len();
1147 for _ in supplied_params..total_len {
1148 substs.push(self.table.new_type_var());
1150 assert_eq!(substs.len(), total_len);
1151 Substitution::from_iter(&Interner, substs)
1154 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1155 let callable_ty = self.resolve_ty_shallow(callable_ty);
1156 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
1157 let def: CallableDefId = from_chalk(self.db, *fn_def);
1158 let generic_predicates = self.db.generic_predicates(def.into());
1159 for predicate in generic_predicates.iter() {
1160 let (predicate, binders) = predicate
1162 .substitute(&Interner, parameters)
1163 .into_value_and_skipped_binders();
1164 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
1165 self.push_obligation(predicate.cast(&Interner));
1167 // add obligation for trait implementation, if this is a trait method
1169 CallableDefId::FunctionId(f) => {
1170 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1172 // construct a TraitRef
1173 let substs = crate::subst_prefix(
1175 generics(self.db.upcast(), trait_.into()).len(),
1177 self.push_obligation(
1178 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1183 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1188 fn builtin_binary_op_return_ty(&mut self, op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Option<Ty> {
1189 let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
1190 let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
1192 BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => {
1193 Some(TyKind::Scalar(Scalar::Bool).intern(&Interner))
1195 BinaryOp::Assignment { .. } => Some(TyBuilder::unit()),
1196 BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => {
1197 // all integer combinations are valid here
1199 lhs_ty.kind(&Interner),
1200 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1201 | TyKind::InferenceVar(_, TyVariableKind::Integer)
1203 rhs_ty.kind(&Interner),
1204 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1205 | TyKind::InferenceVar(_, TyVariableKind::Integer)
1212 BinaryOp::ArithOp(_) => match (lhs_ty.kind(&Interner), rhs_ty.kind(&Interner)) {
1213 // (int, int) | (uint, uint) | (float, float)
1214 (TyKind::Scalar(Scalar::Int(_)), TyKind::Scalar(Scalar::Int(_)))
1215 | (TyKind::Scalar(Scalar::Uint(_)), TyKind::Scalar(Scalar::Uint(_)))
1216 | (TyKind::Scalar(Scalar::Float(_)), TyKind::Scalar(Scalar::Float(_))) => {
1219 // ({int}, int) | ({int}, uint)
1221 TyKind::InferenceVar(_, TyVariableKind::Integer),
1222 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1224 // (int, {int}) | (uint, {int})
1226 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1227 TyKind::InferenceVar(_, TyVariableKind::Integer),
1229 // ({float} | float)
1231 TyKind::InferenceVar(_, TyVariableKind::Float),
1232 TyKind::Scalar(Scalar::Float(_)),
1236 TyKind::Scalar(Scalar::Float(_)),
1237 TyKind::InferenceVar(_, TyVariableKind::Float),
1239 // ({int}, {int}) | ({float}, {float})
1241 TyKind::InferenceVar(_, TyVariableKind::Integer),
1242 TyKind::InferenceVar(_, TyVariableKind::Integer),
1245 TyKind::InferenceVar(_, TyVariableKind::Float),
1246 TyKind::InferenceVar(_, TyVariableKind::Float),
1253 fn builtin_binary_op_rhs_expectation(&mut self, op: BinaryOp, lhs_ty: Ty) -> Option<Ty> {
1255 BinaryOp::LogicOp(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
1256 BinaryOp::Assignment { op: None } => lhs_ty,
1257 BinaryOp::CmpOp(CmpOp::Eq { .. }) => match self
1258 .resolve_ty_shallow(&lhs_ty)
1261 TyKind::Scalar(_) | TyKind::Str => lhs_ty,
1262 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1265 BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => return None,
1266 BinaryOp::CmpOp(CmpOp::Ord { .. })
1267 | BinaryOp::Assignment { op: Some(_) }
1268 | BinaryOp::ArithOp(_) => match self.resolve_ty_shallow(&lhs_ty).kind(&Interner) {
1269 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_)) => lhs_ty,
1270 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1276 fn resolve_binop_method(&self, op: BinaryOp) -> Option<FunctionId> {
1277 let (name, lang_item) = match op {
1278 BinaryOp::LogicOp(_) => return None,
1279 BinaryOp::ArithOp(aop) => match aop {
1280 ArithOp::Add => (name!(add), "add"),
1281 ArithOp::Mul => (name!(mul), "mul"),
1282 ArithOp::Sub => (name!(sub), "sub"),
1283 ArithOp::Div => (name!(div), "div"),
1284 ArithOp::Rem => (name!(rem), "rem"),
1285 ArithOp::Shl => (name!(shl), "shl"),
1286 ArithOp::Shr => (name!(shr), "shr"),
1287 ArithOp::BitXor => (name!(bitxor), "bitxor"),
1288 ArithOp::BitOr => (name!(bitor), "bitor"),
1289 ArithOp::BitAnd => (name!(bitand), "bitand"),
1291 BinaryOp::Assignment { op: Some(aop) } => match aop {
1292 ArithOp::Add => (name!(add_assign), "add_assign"),
1293 ArithOp::Mul => (name!(mul_assign), "mul_assign"),
1294 ArithOp::Sub => (name!(sub_assign), "sub_assign"),
1295 ArithOp::Div => (name!(div_assign), "div_assign"),
1296 ArithOp::Rem => (name!(rem_assign), "rem_assign"),
1297 ArithOp::Shl => (name!(shl_assign), "shl_assign"),
1298 ArithOp::Shr => (name!(shr_assign), "shr_assign"),
1299 ArithOp::BitXor => (name!(bitxor_assign), "bitxor_assign"),
1300 ArithOp::BitOr => (name!(bitor_assign), "bitor_assign"),
1301 ArithOp::BitAnd => (name!(bitand_assign), "bitand_assign"),
1303 BinaryOp::CmpOp(cop) => match cop {
1304 CmpOp::Eq { negated: false } => (name!(eq), "eq"),
1305 CmpOp::Eq { negated: true } => (name!(ne), "eq"),
1306 CmpOp::Ord { ordering: Ordering::Less, strict: false } => {
1307 (name!(le), "partial_ord")
1309 CmpOp::Ord { ordering: Ordering::Less, strict: true } => (name!(lt), "partial_ord"),
1310 CmpOp::Ord { ordering: Ordering::Greater, strict: false } => {
1311 (name!(ge), "partial_ord")
1313 CmpOp::Ord { ordering: Ordering::Greater, strict: true } => {
1314 (name!(gt), "partial_ord")
1317 BinaryOp::Assignment { op: None } => return None,
1320 let trait_ = self.resolve_lang_item(lang_item)?.as_trait()?;
1322 self.db.trait_data(trait_).method_by_name(&name)