1 //! Type inference for expressions.
3 use std::iter::{repeat, repeat_with};
4 use std::{mem, sync::Arc};
6 use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
8 expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
9 path::{GenericArg, GenericArgs},
10 resolver::resolver_for_expr,
11 AssocContainerId, FieldId, Lookup,
13 use hir_expand::name::{name, Name};
15 use syntax::ast::RangeOp;
19 lower::lower_to_chalk_mutability,
20 method_resolution, op,
21 primitive::{self, UintTy},
22 to_assoc_type_id, to_chalk_trait_id,
23 traits::{chalk::from_chalk, FnTrait, InEnvironment},
24 utils::{generics, variant_data, Generics},
25 AdtId, Binders, CallableDefId, DomainGoal, FnPointer, FnSig, Interner, Rawness, Scalar,
26 Substitution, TraitRef, Ty, TyKind,
30 find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
31 InferenceDiagnostic, TypeMismatch,
34 impl<'a> InferenceContext<'a> {
35 pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
36 let ty = self.infer_expr_inner(tgt_expr, expected);
38 // Any expression that produces a value of type `!` must have diverged
39 self.diverges = Diverges::Always;
41 let could_unify = self.unify(&ty, &expected.ty);
43 self.result.type_mismatches.insert(
45 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
48 self.resolve_ty_as_possible(ty)
51 /// Infer type of expression with possibly implicit coerce to the expected type.
52 /// Return the type after possible coercion.
53 pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
54 let ty = self.infer_expr_inner(expr, &expected);
55 let ty = if !self.coerce(&ty, &expected.coercion_target()) {
58 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
59 // Return actual type when type mismatch.
60 // This is needed for diagnostic when return type mismatch.
62 } else if expected.coercion_target().is_unknown() {
68 self.resolve_ty_as_possible(ty)
71 fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
72 let krate = self.resolver.krate()?;
73 let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
74 let output_assoc_type =
75 self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
76 let generic_params = generics(self.db.upcast(), fn_once_trait.into());
77 if generic_params.len() != 2 {
81 let mut param_builder = Substitution::builder(num_args);
82 let mut arg_tys = vec![];
83 for _ in 0..num_args {
84 let arg = self.table.new_type_var();
85 param_builder = param_builder.push(arg.clone());
88 let parameters = param_builder.build();
89 let arg_ty = TyKind::Tuple(num_args, parameters).intern(&Interner);
91 Substitution::build_for_generics(&generic_params).push(ty.clone()).push(arg_ty).build();
93 let trait_env = self.trait_env.env.clone();
94 let implements_fn_trait: DomainGoal =
95 TraitRef { trait_id: to_chalk_trait_id(fn_once_trait), substitution: substs.clone() }
97 let goal = self.canonicalizer().canonicalize_obligation(InEnvironment {
98 goal: implements_fn_trait.clone(),
99 environment: trait_env,
101 if self.db.trait_solve(krate, goal.value).is_some() {
102 self.obligations.push(implements_fn_trait);
103 let output_proj_ty = crate::ProjectionTy {
104 associated_ty_id: to_assoc_type_id(output_assoc_type),
105 substitution: substs,
107 let return_ty = self.normalize_projection_ty(output_proj_ty);
108 Some((arg_tys, return_ty))
114 pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
115 match ty.callable_sig(self.db) {
116 Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
117 None => self.callable_sig_from_fn_trait(ty, num_args),
121 fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
122 let body = Arc::clone(&self.body); // avoid borrow checker problem
123 let ty = match &body[tgt_expr] {
124 Expr::Missing => self.err_ty(),
125 Expr::If { condition, then_branch, else_branch } => {
126 // if let is desugared to match, so this is always simple if
129 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
132 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
133 let mut both_arms_diverge = Diverges::Always;
135 let then_ty = self.infer_expr_inner(*then_branch, &expected);
136 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
137 let else_ty = match else_branch {
138 Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
141 both_arms_diverge &= self.diverges;
143 self.diverges = condition_diverges | both_arms_diverge;
145 self.coerce_merge_branch(&then_ty, &else_ty)
147 Expr::Block { statements, tail, label, id: _ } => {
148 let old_resolver = mem::replace(
150 resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
152 let ty = match label {
154 let break_ty = self.table.new_type_var();
155 self.breakables.push(BreakableContext {
157 break_ty: break_ty.clone(),
158 label: label.map(|label| self.body[label].name.clone()),
161 self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
162 let ctxt = self.breakables.pop().expect("breakable stack broken");
169 None => self.infer_block(statements, *tail, expected),
171 self.resolver = old_resolver;
174 Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
175 Expr::TryBlock { body } => {
176 let _inner = self.infer_expr(*body, expected);
177 // FIXME should be std::result::Result<{inner}, _>
180 Expr::Async { body } => {
181 // Use the first type parameter as the output type of future.
182 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
183 let inner_ty = self.infer_expr(*body, &Expectation::none());
184 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
185 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
186 TyKind::OpaqueType(opaque_ty_id, Substitution::single(inner_ty)).intern(&Interner)
188 Expr::Loop { body, label } => {
189 self.breakables.push(BreakableContext {
191 break_ty: self.table.new_type_var(),
192 label: label.map(|label| self.body[label].name.clone()),
194 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
196 let ctxt = self.breakables.pop().expect("breakable stack broken");
198 self.diverges = Diverges::Maybe;
204 TyKind::Never.intern(&Interner)
207 Expr::While { condition, body, label } => {
208 self.breakables.push(BreakableContext {
210 break_ty: self.err_ty(),
211 label: label.map(|label| self.body[label].name.clone()),
213 // while let is desugared to a match loop, so this is always simple while
216 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
218 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
219 let _ctxt = self.breakables.pop().expect("breakable stack broken");
220 // the body may not run, so it diverging doesn't mean we diverge
221 self.diverges = Diverges::Maybe;
224 Expr::For { iterable, body, pat, label } => {
225 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
227 self.breakables.push(BreakableContext {
229 break_ty: self.err_ty(),
230 label: label.map(|label| self.body[label].name.clone()),
233 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
235 self.infer_pat(*pat, &pat_ty, BindingMode::default());
237 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
238 let _ctxt = self.breakables.pop().expect("breakable stack broken");
239 // the body may not run, so it diverging doesn't mean we diverge
240 self.diverges = Diverges::Maybe;
243 Expr::Lambda { body, args, ret_type, arg_types } => {
244 assert_eq!(args.len(), arg_types.len());
246 let mut sig_tys = Vec::new();
248 // collect explicitly written argument types
249 for arg_type in arg_types.iter() {
250 let arg_ty = if let Some(type_ref) = arg_type {
251 self.make_ty(type_ref)
253 self.table.new_type_var()
255 sig_tys.push(arg_ty);
259 let ret_ty = match ret_type {
260 Some(type_ref) => self.make_ty(type_ref),
261 None => self.table.new_type_var(),
263 sig_tys.push(ret_ty.clone());
264 let sig_ty = TyKind::Function(FnPointer {
265 num_args: sig_tys.len() - 1,
266 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
267 substs: Substitution(sig_tys.clone().into()),
270 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
272 TyKind::Closure(closure_id, Substitution::single(sig_ty)).intern(&Interner);
274 // Eagerly try to relate the closure type with the expected
275 // type, otherwise we often won't have enough information to
277 self.coerce(&closure_ty, &expected.ty);
279 // Now go through the argument patterns
280 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
281 let resolved = self.resolve_ty_as_possible(arg_ty);
282 self.infer_pat(*arg_pat, &resolved, BindingMode::default());
285 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
286 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
288 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
290 self.diverges = prev_diverges;
291 self.return_ty = prev_ret_ty;
295 Expr::Call { callee, args } => {
296 let callee_ty = self.infer_expr(*callee, &Expectation::none());
297 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
298 let mut derefs = autoderef(
300 self.resolver.krate(),
302 goal: canonicalized.value.clone(),
303 environment: self.trait_env.env.clone(),
306 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
307 .find_map(|callee_deref_ty| {
309 &canonicalized.decanonicalize_ty(callee_deref_ty.value),
313 .unwrap_or((Vec::new(), self.err_ty()));
314 self.register_obligations_for_call(&callee_ty);
315 self.check_call_arguments(args, ¶m_tys);
316 self.normalize_associated_types_in(ret_ty)
318 Expr::MethodCall { receiver, args, method_name, generic_args } => self
319 .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
320 Expr::Match { expr, arms } => {
321 let input_ty = self.infer_expr(*expr, &Expectation::none());
323 let mut result_ty = if arms.is_empty() {
324 TyKind::Never.intern(&Interner)
326 self.table.new_type_var()
329 let matchee_diverges = self.diverges;
330 let mut all_arms_diverge = Diverges::Always;
333 self.diverges = Diverges::Maybe;
334 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
335 if let Some(guard_expr) = arm.guard {
338 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
342 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
343 all_arms_diverge &= self.diverges;
344 result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
347 self.diverges = matchee_diverges | all_arms_diverge;
352 // FIXME this could be more efficient...
353 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
354 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
356 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
357 Expr::Break { expr, label } => {
358 let val_ty = if let Some(expr) = expr {
359 self.infer_expr(*expr, &Expectation::none())
365 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
366 ctxt.break_ty.clone()
371 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
373 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
374 ctxt.break_ty = merged_type;
375 ctxt.may_break = true;
377 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
381 TyKind::Never.intern(&Interner)
383 Expr::Return { expr } => {
384 if let Some(expr) = expr {
385 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
387 let unit = Ty::unit();
388 self.coerce(&unit, &self.return_ty.clone());
390 TyKind::Never.intern(&Interner)
392 Expr::Yield { expr } => {
393 // FIXME: track yield type for coercion
394 if let Some(expr) = expr {
395 self.infer_expr(*expr, &Expectation::none());
397 TyKind::Never.intern(&Interner)
399 Expr::RecordLit { path, fields, spread } => {
400 let (ty, def_id) = self.resolve_variant(path.as_ref());
401 if let Some(variant) = def_id {
402 self.write_variant_resolution(tgt_expr.into(), variant);
405 self.unify(&ty, &expected.ty);
407 let substs = ty.substs().cloned().unwrap_or_else(Substitution::empty);
408 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
409 let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
410 for field in fields.iter() {
412 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
413 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
415 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
421 if let Some(field_def) = field_def {
422 self.result.record_field_resolutions.insert(field.expr, field_def);
424 let field_ty = field_def.map_or(self.err_ty(), |it| {
425 field_types[it.local_id].clone().subst(&substs)
427 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
429 if let Some(expr) = spread {
430 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
434 Expr::Field { expr, name } => {
435 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
436 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
437 let ty = autoderef::autoderef(
439 self.resolver.krate(),
441 goal: canonicalized.value.clone(),
442 environment: self.trait_env.env.clone(),
445 .find_map(|derefed_ty| {
446 let def_db = self.db.upcast();
447 let module = self.resolver.module();
448 let is_visible = |field_id: &FieldId| {
451 self.db.field_visibilities(field_id.parent)[field_id.local_id]
452 .is_visible_from(def_db, mod_id)
456 match canonicalized.decanonicalize_ty(derefed_ty.value).interned(&Interner) {
457 TyKind::Tuple(_, substs) => {
458 name.as_tuple_index().and_then(|idx| substs.0.get(idx).cloned())
460 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
461 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
462 let field = FieldId { parent: (*s).into(), local_id };
463 if is_visible(&field) {
464 self.write_field_resolution(tgt_expr, field);
466 self.db.field_types((*s).into())[field.local_id]
474 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
475 let local_id = self.db.union_data(*u).variant_data.field(name)?;
476 let field = FieldId { parent: (*u).into(), local_id };
477 if is_visible(&field) {
478 self.write_field_resolution(tgt_expr, field);
480 self.db.field_types((*u).into())[field.local_id]
491 .unwrap_or(self.err_ty());
492 let ty = self.insert_type_vars(ty);
493 self.normalize_associated_types_in(ty)
495 Expr::Await { expr } => {
496 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
497 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
499 Expr::Try { expr } => {
500 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
501 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
503 Expr::Cast { expr, type_ref } => {
504 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
505 let cast_ty = self.make_ty(type_ref);
506 // FIXME check the cast...
509 Expr::Ref { expr, rawness, mutability } => {
510 let mutability = lower_to_chalk_mutability(*mutability);
511 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
512 &expected.ty.as_reference_or_ptr()
514 if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
515 // FIXME: throw type error - expected mut reference but found shared ref,
516 // which cannot be coerced
518 if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
519 // FIXME: throw type error - expected reference but found ptr,
520 // which cannot be coerced
522 Expectation::rvalue_hint(Ty::clone(exp_inner))
526 let inner_ty = self.infer_expr_inner(*expr, &expectation);
528 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
529 Rawness::Ref => TyKind::Ref(mutability, inner_ty),
533 Expr::Box { expr } => {
534 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
535 if let Some(box_) = self.resolve_boxed_box() {
537 Substitution::build_for_generics(&generics(self.db.upcast(), box_.into()));
538 sb = sb.push(inner_ty);
539 match self.db.generic_defaults(box_.into()).get(1) {
540 Some(alloc_ty) if !alloc_ty.value.is_unknown() && sb.remaining() > 0 => {
541 sb = sb.push(alloc_ty.value.clone());
545 sb = sb.fill(repeat_with(|| self.table.new_type_var()));
546 Ty::adt_ty(box_, sb.build())
551 Expr::UnaryOp { expr, op } => {
552 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
554 UnaryOp::Deref => match self.resolver.krate() {
556 let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
557 match autoderef::deref(
561 goal: &canonicalized.value,
562 environment: self.trait_env.env.clone(),
565 Some(derefed_ty) => {
566 canonicalized.decanonicalize_ty(derefed_ty.value)
568 None => self.err_ty(),
571 None => self.err_ty(),
574 match inner_ty.interned(&Interner) {
575 // Fast path for builtins
576 TyKind::Scalar(Scalar::Int(_))
577 | TyKind::Scalar(Scalar::Uint(_))
578 | TyKind::Scalar(Scalar::Float(_))
579 | TyKind::InferenceVar(_, TyVariableKind::Integer)
580 | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
581 // Otherwise we resolve via the std::ops::Neg trait
583 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
587 match inner_ty.interned(&Interner) {
588 // Fast path for builtins
589 TyKind::Scalar(Scalar::Bool)
590 | TyKind::Scalar(Scalar::Int(_))
591 | TyKind::Scalar(Scalar::Uint(_))
592 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
593 // Otherwise we resolve via the std::ops::Not trait
595 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
600 Expr::BinaryOp { lhs, rhs, op } => match op {
602 let lhs_expectation = match op {
603 BinaryOp::LogicOp(..) => {
604 Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
606 _ => Expectation::none(),
608 let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
609 let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
610 let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
612 let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
614 if ret.is_unknown() {
615 cov_mark::hit!(infer_expr_inner_binary_operator_overload);
617 self.resolve_associated_type_with_params(
619 self.resolve_binary_op_output(op),
628 Expr::Range { lhs, rhs, range_type } => {
629 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
630 let rhs_expect = lhs_ty
632 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
633 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
634 match (range_type, lhs_ty, rhs_ty) {
635 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
636 Some(adt) => Ty::adt_ty(adt, Substitution::empty()),
637 None => self.err_ty(),
639 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
640 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
641 None => self.err_ty(),
643 (RangeOp::Inclusive, None, Some(ty)) => {
644 match self.resolve_range_to_inclusive() {
645 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
646 None => self.err_ty(),
649 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
650 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
651 None => self.err_ty(),
653 (RangeOp::Inclusive, Some(_), Some(ty)) => {
654 match self.resolve_range_inclusive() {
655 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
656 None => self.err_ty(),
659 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
660 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
661 None => self.err_ty(),
663 (RangeOp::Inclusive, _, None) => self.err_ty(),
666 Expr::Index { base, index } => {
667 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
668 let index_ty = self.infer_expr(*index, &Expectation::none());
670 if let (Some(index_trait), Some(krate)) =
671 (self.resolve_ops_index(), self.resolver.krate())
673 let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
674 let self_ty = method_resolution::resolve_indexing_op(
676 &canonicalized.value,
677 self.trait_env.clone(),
682 self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
683 self.resolve_associated_type_with_params(
685 self.resolve_ops_index_output(),
692 Expr::Tuple { exprs } => {
693 let mut tys = match expected.ty.interned(&Interner) {
694 TyKind::Tuple(_, substs) => substs
697 .chain(repeat_with(|| self.table.new_type_var()))
699 .collect::<Vec<_>>(),
700 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
703 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
704 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
707 TyKind::Tuple(tys.len(), Substitution(tys.into())).intern(&Interner)
709 Expr::Array(array) => {
710 let elem_ty = match expected.ty.interned(&Interner) {
711 TyKind::Array(st) | TyKind::Slice(st) => st.clone(),
712 _ => self.table.new_type_var(),
716 Array::ElementList(items) => {
717 for expr in items.iter() {
718 self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
721 Array::Repeat { initializer, repeat } => {
722 self.infer_expr_coerce(
724 &Expectation::has_type(elem_ty.clone()),
728 &Expectation::has_type(
729 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
735 TyKind::Array(elem_ty).intern(&Interner)
737 Expr::Literal(lit) => match lit {
738 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
739 Literal::String(..) => {
740 TyKind::Ref(Mutability::Not, TyKind::Str.intern(&Interner)).intern(&Interner)
742 Literal::ByteString(..) => {
743 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
744 let array_type = TyKind::Array(byte_type).intern(&Interner);
745 TyKind::Ref(Mutability::Not, array_type).intern(&Interner)
747 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
748 Literal::Int(_v, ty) => match ty {
750 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
753 None => self.table.new_integer_var(),
755 Literal::Uint(_v, ty) => match ty {
757 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
760 None => self.table.new_integer_var(),
762 Literal::Float(_v, ty) => match ty {
764 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
767 None => self.table.new_float_var(),
771 // use a new type variable if we got unknown here
772 let ty = self.insert_type_vars_shallow(ty);
773 let ty = self.resolve_ty_as_possible(ty);
774 self.write_expr_ty(tgt_expr, ty.clone());
780 statements: &[Statement],
781 tail: Option<ExprId>,
782 expected: &Expectation,
784 for stmt in statements {
786 Statement::Let { pat, type_ref, initializer } => {
788 type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
790 // Always use the declared type when specified
791 let mut ty = decl_ty.clone();
793 if let Some(expr) = initializer {
795 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
796 if decl_ty.is_unknown() {
801 let ty = self.resolve_ty_as_possible(ty);
802 self.infer_pat(*pat, &ty, BindingMode::default());
804 Statement::Expr(expr) => {
805 self.infer_expr(*expr, &Expectation::none());
810 let ty = if let Some(expr) = tail {
811 self.infer_expr_coerce(expr, expected)
813 // Citing rustc: if there is no explicit tail expression,
814 // that is typically equivalent to a tail expression
815 // of `()` -- except if the block diverges. In that
816 // case, there is no value supplied from the tail
817 // expression (assuming there are no other breaks,
818 // this implies that the type of the block will be
820 if self.diverges.is_always() {
821 // we don't even make an attempt at coercion
822 self.table.new_maybe_never_var()
824 self.coerce(&Ty::unit(), &expected.coercion_target());
831 fn infer_method_call(
837 generic_args: Option<&GenericArgs>,
839 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
840 let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
842 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
844 let resolved = self.resolver.krate().and_then(|krate| {
845 method_resolution::lookup_method(
846 &canonicalized_receiver.value,
848 self.trait_env.clone(),
851 self.resolver.module(),
855 let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
856 Some((ty, func)) => {
857 let ty = canonicalized_receiver.decanonicalize_ty(ty);
858 self.write_method_resolution(tgt_expr, func);
859 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
861 None => (receiver_ty, Binders::new(0, self.err_ty()), None),
863 let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
864 let method_ty = method_ty.subst(&substs);
865 let method_ty = self.insert_type_vars(method_ty);
866 self.register_obligations_for_call(&method_ty);
867 let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
869 if !sig.params().is_empty() {
870 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
872 (self.err_ty(), Vec::new(), sig.ret().clone())
875 None => (self.err_ty(), Vec::new(), self.err_ty()),
877 // Apply autoref so the below unification works correctly
878 // FIXME: return correct autorefs from lookup_method
879 let actual_receiver_ty = match expected_receiver_ty.as_reference() {
880 Some((_, mutability)) => TyKind::Ref(mutability, derefed_receiver_ty).intern(&Interner),
881 _ => derefed_receiver_ty,
883 self.unify(&expected_receiver_ty, &actual_receiver_ty);
885 self.check_call_arguments(args, ¶m_tys);
886 self.normalize_associated_types_in(ret_ty)
889 fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
890 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
891 // We do this in a pretty awful way: first we type-check any arguments
892 // that are not closures, then we type-check the closures. This is so
893 // that we have more information about the types of arguments when we
894 // type-check the functions. This isn't really the right way to do this.
895 for &check_closures in &[false, true] {
896 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
897 for (&arg, param_ty) in args.iter().zip(param_iter) {
898 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
899 if is_closure != check_closures {
903 let param_ty = self.normalize_associated_types_in(param_ty);
904 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
909 fn substs_for_method_call(
911 def_generics: Option<Generics>,
912 generic_args: Option<&GenericArgs>,
915 let (parent_params, self_params, type_params, impl_trait_params) =
916 def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
917 assert_eq!(self_params, 0); // method shouldn't have another Self param
918 let total_len = parent_params + type_params + impl_trait_params;
919 let mut substs = Vec::with_capacity(total_len);
920 // Parent arguments are unknown, except for the receiver type
921 if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
922 for (_id, param) in parent_generics {
923 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
924 substs.push(receiver_ty.clone());
926 substs.push(self.err_ty());
930 // handle provided type arguments
931 if let Some(generic_args) = generic_args {
932 // if args are provided, it should be all of them, but we can't rely on that
933 for arg in generic_args
936 .filter(|arg| matches!(arg, GenericArg::Type(_)))
940 GenericArg::Type(type_ref) => {
941 let ty = self.make_ty(type_ref);
944 GenericArg::Lifetime(_) => {}
948 let supplied_params = substs.len();
949 for _ in supplied_params..total_len {
950 substs.push(self.err_ty());
952 assert_eq!(substs.len(), total_len);
953 Substitution(substs.into())
956 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
957 if let TyKind::FnDef(fn_def, parameters) = callable_ty.interned(&Interner) {
958 let def: CallableDefId = from_chalk(self.db, *fn_def);
959 let generic_predicates = self.db.generic_predicates(def.into());
960 for predicate in generic_predicates.iter() {
961 let (predicate, binders) =
962 predicate.clone().subst(parameters).into_value_and_skipped_binders();
963 always!(binders == 0); // quantified where clauses not yet handled
964 self.obligations.push(predicate.cast(&Interner));
966 // add obligation for trait implementation, if this is a trait method
968 CallableDefId::FunctionId(f) => {
969 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
971 // construct a TraitRef
973 parameters.prefix(generics(self.db.upcast(), trait_.into()).len());
974 self.obligations.push(
975 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
980 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}