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 = if let Some(type_ref) = arg_type {
268 self.make_ty(type_ref)
270 self.table.new_type_var()
272 sig_tys.push(arg_ty);
276 let ret_ty = match ret_type {
277 Some(type_ref) => self.make_ty(type_ref),
278 None => self.table.new_type_var(),
280 sig_tys.push(ret_ty.clone());
281 let sig_ty = TyKind::Function(FnPointer {
283 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
284 substitution: FnSubst(
285 Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
289 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
291 TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty.clone()))
294 // Eagerly try to relate the closure type with the expected
295 // type, otherwise we often won't have enough information to
297 self.deduce_closure_type_from_expectations(
304 // Now go through the argument patterns
305 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
306 self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
309 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
310 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
312 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
314 self.diverges = prev_diverges;
315 self.return_ty = prev_ret_ty;
319 Expr::Call { callee, args } => {
320 let callee_ty = self.infer_expr(*callee, &Expectation::none());
321 let canonicalized = self.canonicalize(callee_ty.clone());
322 let mut derefs = Autoderef::new(
324 self.resolver.krate(),
326 goal: canonicalized.value.clone(),
327 environment: self.table.trait_env.env.clone(),
330 let res = derefs.by_ref().find_map(|(callee_deref_ty, _)| {
331 let ty = &canonicalized.decanonicalize_ty(&mut self.table, callee_deref_ty);
332 self.callable_sig(ty, args.len())
334 let (param_tys, ret_ty): (Vec<Ty>, Ty) = match res {
336 self.write_expr_adj(*callee, self.auto_deref_adjust_steps(&derefs));
339 None => (Vec::new(), self.err_ty()),
341 self.register_obligations_for_call(&callee_ty);
343 let expected_inputs = self.expected_inputs_for_expected_output(
349 self.check_call_arguments(args, &expected_inputs, ¶m_tys);
350 self.normalize_associated_types_in(ret_ty)
352 Expr::MethodCall { receiver, args, method_name, generic_args } => self
358 generic_args.as_deref(),
361 Expr::Match { expr, arms } => {
362 let input_ty = self.infer_expr(*expr, &Expectation::none());
364 let expected = expected.adjust_for_branches(&mut self.table);
366 let result_ty = if arms.is_empty() {
367 TyKind::Never.intern(&Interner)
370 Expectation::HasType(ty) => ty.clone(),
371 _ => self.table.new_type_var(),
374 let mut coerce = CoerceMany::new(result_ty);
376 let matchee_diverges = self.diverges;
377 let mut all_arms_diverge = Diverges::Always;
380 self.diverges = Diverges::Maybe;
381 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
383 Some(MatchGuard::If { expr: guard_expr }) => {
386 &Expectation::has_type(
387 TyKind::Scalar(Scalar::Bool).intern(&Interner),
391 Some(MatchGuard::IfLet { expr, pat }) => {
392 let input_ty = self.infer_expr(expr, &Expectation::none());
393 let _pat_ty = self.infer_pat(pat, &input_ty, BindingMode::default());
398 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
399 all_arms_diverge &= self.diverges;
400 coerce.coerce(self, Some(arm.expr), &arm_ty);
403 self.diverges = matchee_diverges | all_arms_diverge;
408 // FIXME this could be more efficient...
409 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
410 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or_else(|| self.err_ty())
412 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
413 Expr::Break { expr, label } => {
414 let mut coerce = match find_breakable(&mut self.breakables, label.as_ref()) {
416 // avoiding the borrowck
419 CoerceMany::new(self.result.standard_types.unknown.clone()),
422 None => CoerceMany::new(self.result.standard_types.unknown.clone()),
425 let val_ty = if let Some(expr) = *expr {
426 self.infer_expr(expr, &Expectation::none())
431 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
432 coerce.coerce(self, *expr, &val_ty);
434 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
435 ctxt.coerce = coerce;
436 ctxt.may_break = true;
438 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
443 TyKind::Never.intern(&Interner)
445 Expr::Return { expr } => {
446 if let Some(expr) = expr {
447 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
449 let unit = TyBuilder::unit();
450 let _ = self.coerce(Some(tgt_expr), &unit, &self.return_ty.clone());
452 TyKind::Never.intern(&Interner)
454 Expr::Yield { expr } => {
455 // FIXME: track yield type for coercion
456 if let Some(expr) = expr {
457 self.infer_expr(*expr, &Expectation::none());
459 TyKind::Never.intern(&Interner)
461 Expr::RecordLit { path, fields, spread } => {
462 let (ty, def_id) = self.resolve_variant(path.as_deref(), false);
463 if let Some(variant) = def_id {
464 self.write_variant_resolution(tgt_expr.into(), variant);
467 if let Some(t) = expected.only_has_type(&mut self.table) {
473 .map(|(_, s)| s.clone())
474 .unwrap_or_else(|| Substitution::empty(&Interner));
475 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
476 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
477 for field in fields.iter() {
479 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
480 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
482 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
488 let field_ty = field_def.map_or(self.err_ty(), |it| {
489 field_types[it.local_id].clone().substitute(&Interner, &substs)
491 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
493 if let Some(expr) = spread {
494 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
498 Expr::Field { expr, name } => {
499 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
500 let canonicalized = self.canonicalize(receiver_ty);
502 let mut autoderef = Autoderef::new(
504 self.resolver.krate(),
506 goal: canonicalized.value.clone(),
507 environment: self.trait_env.env.clone(),
510 let ty = autoderef.by_ref().find_map(|(derefed_ty, _)| {
511 let module = self.resolver.module();
513 let is_visible = |field_id: &FieldId| {
516 db.field_visibilities(field_id.parent)[field_id.local_id]
517 .is_visible_from(db.upcast(), mod_id)
522 .decanonicalize_ty(&mut self.table, derefed_ty)
525 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
529 .map(|a| a.assert_ty_ref(&Interner))
532 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
533 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
534 let field = FieldId { parent: (*s).into(), local_id };
535 if is_visible(&field) {
536 self.write_field_resolution(tgt_expr, field);
538 self.db.field_types((*s).into())[field.local_id]
540 .substitute(&Interner, ¶meters),
546 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
547 let local_id = self.db.union_data(*u).variant_data.field(name)?;
548 let field = FieldId { parent: (*u).into(), local_id };
549 if is_visible(&field) {
550 self.write_field_resolution(tgt_expr, field);
552 self.db.field_types((*u).into())[field.local_id]
554 .substitute(&Interner, ¶meters),
565 self.write_expr_adj(*expr, self.auto_deref_adjust_steps(&autoderef));
568 None => self.err_ty(),
570 let ty = self.insert_type_vars(ty);
571 self.normalize_associated_types_in(ty)
573 Expr::Await { expr } => {
574 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
575 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
577 Expr::Try { expr } => {
578 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
579 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
581 Expr::Cast { expr, type_ref } => {
582 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
583 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
584 let cast_ty = self.make_ty(type_ref);
585 // FIXME check the cast...
588 Expr::Ref { expr, rawness, mutability } => {
589 let mutability = lower_to_chalk_mutability(*mutability);
590 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
591 .only_has_type(&mut self.table)
593 .and_then(|t| t.as_reference_or_ptr())
595 if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
596 // FIXME: record type error - expected mut reference but found shared ref,
597 // which cannot be coerced
599 if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
600 // FIXME: record type error - expected reference but found ptr,
601 // which cannot be coerced
603 Expectation::rvalue_hint(&mut self.table, Ty::clone(exp_inner))
607 let inner_ty = self.infer_expr_inner(*expr, &expectation);
609 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
610 Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
614 Expr::Box { expr } => {
615 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
616 if let Some(box_) = self.resolve_boxed_box() {
617 TyBuilder::adt(self.db, box_)
619 .fill_with_defaults(self.db, || self.table.new_type_var())
625 Expr::UnaryOp { expr, op } => {
626 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
627 let inner_ty = self.resolve_ty_shallow(&inner_ty);
629 UnaryOp::Deref => match self.resolver.krate() {
631 let canonicalized = self.canonicalize(inner_ty);
632 match autoderef::deref(
636 goal: &canonicalized.value,
637 environment: self.trait_env.env.clone(),
640 Some(derefed_ty) => {
641 canonicalized.decanonicalize_ty(&mut self.table, derefed_ty)
643 None => self.err_ty(),
646 None => self.err_ty(),
649 match inner_ty.kind(&Interner) {
650 // Fast path for builtins
651 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
652 | TyKind::InferenceVar(
654 TyVariableKind::Integer | TyVariableKind::Float,
656 // Otherwise we resolve via the std::ops::Neg trait
658 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
662 match inner_ty.kind(&Interner) {
663 // Fast path for builtins
664 TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
665 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
666 // Otherwise we resolve via the std::ops::Not trait
668 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
673 Expr::BinaryOp { lhs, rhs, op } => match op {
674 Some(BinaryOp::Assignment { op: None }) => {
675 let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
676 self.infer_expr_coerce(*rhs, &Expectation::has_type(lhs_ty));
677 self.result.standard_types.unit.clone()
679 Some(BinaryOp::LogicOp(_)) => {
680 let bool_ty = self.result.standard_types.bool_.clone();
681 self.infer_expr_coerce(*lhs, &Expectation::HasType(bool_ty.clone()));
682 let lhs_diverges = self.diverges;
683 self.infer_expr_coerce(*rhs, &Expectation::HasType(bool_ty.clone()));
684 // Depending on the LHS' value, the RHS can never execute.
685 self.diverges = lhs_diverges;
688 Some(op) => self.infer_overloadable_binop(*lhs, *op, *rhs, tgt_expr),
691 Expr::Range { lhs, rhs, range_type } => {
692 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
693 let rhs_expect = lhs_ty
695 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
696 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
697 match (range_type, lhs_ty, rhs_ty) {
698 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
699 Some(adt) => TyBuilder::adt(self.db, adt).build(),
700 None => self.err_ty(),
702 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
703 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
704 None => self.err_ty(),
706 (RangeOp::Inclusive, None, Some(ty)) => {
707 match self.resolve_range_to_inclusive() {
708 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
709 None => self.err_ty(),
712 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
713 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
714 None => self.err_ty(),
716 (RangeOp::Inclusive, Some(_), Some(ty)) => {
717 match self.resolve_range_inclusive() {
718 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
719 None => self.err_ty(),
722 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
723 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
724 None => self.err_ty(),
726 (RangeOp::Inclusive, _, None) => self.err_ty(),
729 Expr::Index { base, index } => {
730 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
731 let index_ty = self.infer_expr(*index, &Expectation::none());
733 if let (Some(index_trait), Some(krate)) =
734 (self.resolve_ops_index(), self.resolver.krate())
736 let canonicalized = self.canonicalize(base_ty);
737 let self_ty = method_resolution::resolve_indexing_op(
739 &canonicalized.value,
740 self.trait_env.clone(),
744 let self_ty = self_ty.map_or(self.err_ty(), |t| {
745 canonicalized.decanonicalize_ty(&mut self.table, t)
747 self.resolve_associated_type_with_params(
749 self.resolve_ops_index_output(),
756 Expr::Tuple { exprs } => {
757 let mut tys = match expected
758 .only_has_type(&mut self.table)
760 .map(|t| t.kind(&Interner))
762 Some(TyKind::Tuple(_, substs)) => substs
764 .map(|a| a.assert_ty_ref(&Interner).clone())
765 .chain(repeat_with(|| self.table.new_type_var()))
767 .collect::<Vec<_>>(),
768 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
771 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
772 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
775 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
777 Expr::Array(array) => {
779 match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(&Interner)) {
780 Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
781 _ => self.table.new_type_var(),
783 let mut coerce = CoerceMany::new(elem_ty.clone());
785 let expected = Expectation::has_type(elem_ty.clone());
786 let len = match array {
787 Array::ElementList(items) => {
788 for &expr in items.iter() {
789 let cur_elem_ty = self.infer_expr_inner(expr, &expected);
790 coerce.coerce(self, Some(expr), &cur_elem_ty);
792 Some(items.len() as u64)
794 &Array::Repeat { initializer, repeat } => {
795 self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
798 &Expectation::has_type(
799 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
803 let repeat_expr = &self.body.exprs[repeat];
804 consteval::eval_usize(repeat_expr)
808 TyKind::Array(coerce.complete(), consteval::usize_const(len)).intern(&Interner)
810 Expr::Literal(lit) => match lit {
811 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
812 Literal::String(..) => {
813 TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
816 Literal::ByteString(bs) => {
817 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
819 let len = consteval::usize_const(Some(bs.len() as u64));
821 let array_type = TyKind::Array(byte_type, len).intern(&Interner);
822 TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
824 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
825 Literal::Int(_v, ty) => match ty {
827 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
830 None => self.table.new_integer_var(),
832 Literal::Uint(_v, ty) => match ty {
834 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
837 None => self.table.new_integer_var(),
839 Literal::Float(_v, ty) => match ty {
841 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
844 None => self.table.new_float_var(),
847 Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
849 // use a new type variable if we got unknown here
850 let ty = self.insert_type_vars_shallow(ty);
851 self.write_expr_ty(tgt_expr, ty.clone());
855 fn infer_overloadable_binop(
862 let lhs_expectation = Expectation::none();
863 let lhs_ty = self.infer_expr(lhs, &lhs_expectation);
864 let rhs_ty = self.table.new_type_var();
866 let func = self.resolve_binop_method(op);
867 let func = match func {
870 let rhs_ty = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone());
871 let rhs_ty = self.infer_expr_coerce(rhs, &Expectation::from_option(rhs_ty));
873 .builtin_binary_op_return_ty(op, lhs_ty, rhs_ty)
874 .unwrap_or_else(|| self.err_ty());
878 let subst = TyBuilder::subst_for_def(self.db, func)
879 .push(lhs_ty.clone())
880 .push(rhs_ty.clone())
882 self.write_method_resolution(tgt_expr, func, subst.clone());
884 let method_ty = self.db.value_ty(func.into()).substitute(&Interner, &subst);
885 self.register_obligations_for_call(&method_ty);
887 self.infer_expr_coerce(rhs, &Expectation::has_type(rhs_ty.clone()));
889 let ret_ty = match method_ty.callable_sig(self.db) {
890 Some(sig) => sig.ret().clone(),
891 None => self.err_ty(),
894 let ret_ty = self.normalize_associated_types_in(ret_ty);
896 // FIXME: record autoref adjustments
898 // use knowledge of built-in binary ops, which can sometimes help inference
899 if let Some(builtin_rhs) = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone()) {
900 self.unify(&builtin_rhs, &rhs_ty);
902 if let Some(builtin_ret) = self.builtin_binary_op_return_ty(op, lhs_ty, rhs_ty) {
903 self.unify(&builtin_ret, &ret_ty);
912 statements: &[Statement],
913 tail: Option<ExprId>,
914 expected: &Expectation,
916 for stmt in statements {
918 Statement::Let { pat, type_ref, initializer } => {
919 let decl_ty = type_ref
921 .map(|tr| self.make_ty(tr))
922 .unwrap_or_else(|| self.err_ty());
924 // Always use the declared type when specified
925 let mut ty = decl_ty.clone();
927 if let Some(expr) = initializer {
929 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
930 if decl_ty.is_unknown() {
935 self.infer_pat(*pat, &ty, BindingMode::default());
937 Statement::Expr { expr, .. } => {
938 self.infer_expr(*expr, &Expectation::none());
943 if let Some(expr) = tail {
944 self.infer_expr_coerce(expr, expected)
946 // Citing rustc: if there is no explicit tail expression,
947 // that is typically equivalent to a tail expression
948 // of `()` -- except if the block diverges. In that
949 // case, there is no value supplied from the tail
950 // expression (assuming there are no other breaks,
951 // this implies that the type of the block will be
953 if self.diverges.is_always() {
954 // we don't even make an attempt at coercion
955 self.table.new_maybe_never_var()
957 if let Some(t) = expected.only_has_type(&mut self.table) {
958 let _ = self.coerce(Some(expr), &TyBuilder::unit(), &t);
965 fn infer_method_call(
971 generic_args: Option<&GenericArgs>,
972 expected: &Expectation,
974 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
975 let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
977 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
979 let resolved = self.resolver.krate().and_then(|krate| {
980 method_resolution::lookup_method(
981 &canonicalized_receiver.value,
983 self.trait_env.clone(),
986 self.resolver.module(),
990 let (receiver_ty, method_ty, substs) = match resolved {
991 Some((ty, func)) => {
992 let ty = canonicalized_receiver.decanonicalize_ty(&mut self.table, ty);
993 let generics = generics(self.db.upcast(), func.into());
994 let substs = self.substs_for_method_call(generics, generic_args, &ty);
995 self.write_method_resolution(tgt_expr, func, substs.clone());
996 (ty, self.db.value_ty(func.into()), substs)
1000 Binders::empty(&Interner, self.err_ty()),
1001 Substitution::empty(&Interner),
1004 let method_ty = method_ty.substitute(&Interner, &substs);
1005 self.register_obligations_for_call(&method_ty);
1006 let (formal_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
1008 if !sig.params().is_empty() {
1009 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
1011 (self.err_ty(), Vec::new(), sig.ret().clone())
1014 None => (self.err_ty(), Vec::new(), self.err_ty()),
1016 self.unify(&formal_receiver_ty, &receiver_ty);
1018 let expected_inputs =
1019 self.expected_inputs_for_expected_output(expected, ret_ty.clone(), param_tys.clone());
1021 self.check_call_arguments(args, &expected_inputs, ¶m_tys);
1022 self.normalize_associated_types_in(ret_ty)
1025 fn expected_inputs_for_expected_output(
1027 expected_output: &Expectation,
1031 if let Some(expected_ty) = expected_output.to_option(&mut self.table) {
1032 self.table.fudge_inference(|table| {
1033 if table.try_unify(&expected_ty, &output).is_ok() {
1034 table.resolve_with_fallback(inputs, |var, kind, _, _| match kind {
1035 chalk_ir::VariableKind::Ty(tk) => var.to_ty(&Interner, tk).cast(&Interner),
1036 chalk_ir::VariableKind::Lifetime => {
1037 var.to_lifetime(&Interner).cast(&Interner)
1039 chalk_ir::VariableKind::Const(ty) => {
1040 var.to_const(&Interner, ty).cast(&Interner)
1052 fn check_call_arguments(&mut self, args: &[ExprId], expected_inputs: &[Ty], param_tys: &[Ty]) {
1053 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
1054 // We do this in a pretty awful way: first we type-check any arguments
1055 // that are not closures, then we type-check the closures. This is so
1056 // that we have more information about the types of arguments when we
1057 // type-check the functions. This isn't really the right way to do this.
1058 for &check_closures in &[false, true] {
1059 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
1060 let expected_iter = expected_inputs
1063 .chain(param_iter.clone().skip(expected_inputs.len()));
1064 for ((&arg, param_ty), expected_ty) in args.iter().zip(param_iter).zip(expected_iter) {
1065 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
1066 if is_closure != check_closures {
1070 // the difference between param_ty and expected here is that
1071 // expected is the parameter when the expected *return* type is
1072 // taken into account. So in `let _: &[i32] = identity(&[1, 2])`
1073 // the expected type is already `&[i32]`, whereas param_ty is
1074 // still an unbound type variable. We don't always want to force
1075 // the parameter to coerce to the expected type (for example in
1076 // `coerce_unsize_expected_type_4`).
1077 let param_ty = self.normalize_associated_types_in(param_ty);
1078 let expected = Expectation::rvalue_hint(&mut self.table, expected_ty);
1079 // infer with the expected type we have...
1080 let ty = self.infer_expr_inner(arg, &expected);
1082 // then coerce to either the expected type or just the formal parameter type
1083 let coercion_target = if let Some(ty) = expected.only_has_type(&mut self.table) {
1084 // if we are coercing to the expectation, unify with the
1085 // formal parameter type to connect everything
1086 self.unify(&ty, ¶m_ty);
1091 if !coercion_target.is_unknown() {
1092 if self.coerce(Some(arg), &ty, &coercion_target).is_err() {
1093 self.result.type_mismatches.insert(
1095 TypeMismatch { expected: coercion_target, actual: ty.clone() },
1103 fn substs_for_method_call(
1105 def_generics: Generics,
1106 generic_args: Option<&GenericArgs>,
1109 let (parent_params, self_params, type_params, impl_trait_params) =
1110 def_generics.provenance_split();
1111 assert_eq!(self_params, 0); // method shouldn't have another Self param
1112 let total_len = parent_params + type_params + impl_trait_params;
1113 let mut substs = Vec::with_capacity(total_len);
1114 // Parent arguments are unknown, except for the receiver type
1115 for (_id, param) in def_generics.iter_parent() {
1116 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
1117 substs.push(receiver_ty.clone());
1119 substs.push(self.table.new_type_var());
1122 // handle provided type arguments
1123 if let Some(generic_args) = generic_args {
1124 // if args are provided, it should be all of them, but we can't rely on that
1125 for arg in generic_args
1128 .filter(|arg| matches!(arg, GenericArg::Type(_)))
1132 GenericArg::Type(type_ref) => {
1133 let ty = self.make_ty(type_ref);
1136 GenericArg::Lifetime(_) => {}
1140 let supplied_params = substs.len();
1141 for _ in supplied_params..total_len {
1142 substs.push(self.table.new_type_var());
1144 assert_eq!(substs.len(), total_len);
1145 Substitution::from_iter(&Interner, substs)
1148 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1149 let callable_ty = self.resolve_ty_shallow(callable_ty);
1150 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
1151 let def: CallableDefId = from_chalk(self.db, *fn_def);
1152 let generic_predicates = self.db.generic_predicates(def.into());
1153 for predicate in generic_predicates.iter() {
1154 let (predicate, binders) = predicate
1156 .substitute(&Interner, parameters)
1157 .into_value_and_skipped_binders();
1158 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
1159 self.push_obligation(predicate.cast(&Interner));
1161 // add obligation for trait implementation, if this is a trait method
1163 CallableDefId::FunctionId(f) => {
1164 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1166 // construct a TraitRef
1167 let substs = crate::subst_prefix(
1169 generics(self.db.upcast(), trait_.into()).len(),
1171 self.push_obligation(
1172 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1177 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1182 fn builtin_binary_op_return_ty(&mut self, op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Option<Ty> {
1183 let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
1184 let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
1186 BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => {
1187 Some(TyKind::Scalar(Scalar::Bool).intern(&Interner))
1189 BinaryOp::Assignment { .. } => Some(TyBuilder::unit()),
1190 BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => {
1191 // all integer combinations are valid here
1193 lhs_ty.kind(&Interner),
1194 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1195 | TyKind::InferenceVar(_, TyVariableKind::Integer)
1197 rhs_ty.kind(&Interner),
1198 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1199 | TyKind::InferenceVar(_, TyVariableKind::Integer)
1206 BinaryOp::ArithOp(_) => match (lhs_ty.kind(&Interner), rhs_ty.kind(&Interner)) {
1207 // (int, int) | (uint, uint) | (float, float)
1208 (TyKind::Scalar(Scalar::Int(_)), TyKind::Scalar(Scalar::Int(_)))
1209 | (TyKind::Scalar(Scalar::Uint(_)), TyKind::Scalar(Scalar::Uint(_)))
1210 | (TyKind::Scalar(Scalar::Float(_)), TyKind::Scalar(Scalar::Float(_))) => {
1213 // ({int}, int) | ({int}, uint)
1215 TyKind::InferenceVar(_, TyVariableKind::Integer),
1216 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1218 // (int, {int}) | (uint, {int})
1220 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1221 TyKind::InferenceVar(_, TyVariableKind::Integer),
1223 // ({float} | float)
1225 TyKind::InferenceVar(_, TyVariableKind::Float),
1226 TyKind::Scalar(Scalar::Float(_)),
1230 TyKind::Scalar(Scalar::Float(_)),
1231 TyKind::InferenceVar(_, TyVariableKind::Float),
1233 // ({int}, {int}) | ({float}, {float})
1235 TyKind::InferenceVar(_, TyVariableKind::Integer),
1236 TyKind::InferenceVar(_, TyVariableKind::Integer),
1239 TyKind::InferenceVar(_, TyVariableKind::Float),
1240 TyKind::InferenceVar(_, TyVariableKind::Float),
1247 fn builtin_binary_op_rhs_expectation(&mut self, op: BinaryOp, lhs_ty: Ty) -> Option<Ty> {
1249 BinaryOp::LogicOp(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
1250 BinaryOp::Assignment { op: None } => lhs_ty,
1251 BinaryOp::CmpOp(CmpOp::Eq { .. }) => match self
1252 .resolve_ty_shallow(&lhs_ty)
1255 TyKind::Scalar(_) | TyKind::Str => lhs_ty,
1256 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1259 BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => return None,
1260 BinaryOp::CmpOp(CmpOp::Ord { .. })
1261 | BinaryOp::Assignment { op: Some(_) }
1262 | BinaryOp::ArithOp(_) => match self.resolve_ty_shallow(&lhs_ty).kind(&Interner) {
1263 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_)) => lhs_ty,
1264 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1270 fn resolve_binop_method(&self, op: BinaryOp) -> Option<FunctionId> {
1271 let (name, lang_item) = match op {
1272 BinaryOp::LogicOp(_) => return None,
1273 BinaryOp::ArithOp(aop) => match aop {
1274 ArithOp::Add => (name!(add), "add"),
1275 ArithOp::Mul => (name!(mul), "mul"),
1276 ArithOp::Sub => (name!(sub), "sub"),
1277 ArithOp::Div => (name!(div), "div"),
1278 ArithOp::Rem => (name!(rem), "rem"),
1279 ArithOp::Shl => (name!(shl), "shl"),
1280 ArithOp::Shr => (name!(shr), "shr"),
1281 ArithOp::BitXor => (name!(bitxor), "bitxor"),
1282 ArithOp::BitOr => (name!(bitor), "bitor"),
1283 ArithOp::BitAnd => (name!(bitand), "bitand"),
1285 BinaryOp::Assignment { op: Some(aop) } => match aop {
1286 ArithOp::Add => (name!(add_assign), "add_assign"),
1287 ArithOp::Mul => (name!(mul_assign), "mul_assign"),
1288 ArithOp::Sub => (name!(sub_assign), "sub_assign"),
1289 ArithOp::Div => (name!(div_assign), "div_assign"),
1290 ArithOp::Rem => (name!(rem_assign), "rem_assign"),
1291 ArithOp::Shl => (name!(shl_assign), "shl_assign"),
1292 ArithOp::Shr => (name!(shr_assign), "shr_assign"),
1293 ArithOp::BitXor => (name!(bitxor_assign), "bitxor_assign"),
1294 ArithOp::BitOr => (name!(bitor_assign), "bitor_assign"),
1295 ArithOp::BitAnd => (name!(bitand_assign), "bitand_assign"),
1297 BinaryOp::CmpOp(cop) => match cop {
1298 CmpOp::Eq { negated: false } => (name!(eq), "eq"),
1299 CmpOp::Eq { negated: true } => (name!(ne), "eq"),
1300 CmpOp::Ord { ordering: Ordering::Less, strict: false } => {
1301 (name!(le), "partial_ord")
1303 CmpOp::Ord { ordering: Ordering::Less, strict: true } => (name!(lt), "partial_ord"),
1304 CmpOp::Ord { ordering: Ordering::Greater, strict: false } => {
1305 (name!(ge), "partial_ord")
1307 CmpOp::Ord { ordering: Ordering::Greater, strict: true } => {
1308 (name!(gt), "partial_ord")
1311 BinaryOp::Assignment { op: None } => return None,
1314 let trait_ = self.resolve_lang_item(lang_item)?.as_trait()?;
1316 self.db.trait_data(trait_).method_by_name(&name)