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.push_obligation(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 self.db.check_canceled();
124 let body = Arc::clone(&self.body); // avoid borrow checker problem
125 let ty = match &body[tgt_expr] {
126 Expr::Missing => self.err_ty(),
127 Expr::If { condition, then_branch, else_branch } => {
128 // if let is desugared to match, so this is always simple if
131 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
134 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
135 let mut both_arms_diverge = Diverges::Always;
137 let then_ty = self.infer_expr_inner(*then_branch, &expected);
138 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
139 let else_ty = match else_branch {
140 Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
143 both_arms_diverge &= self.diverges;
145 self.diverges = condition_diverges | both_arms_diverge;
147 self.coerce_merge_branch(&then_ty, &else_ty)
149 Expr::Block { statements, tail, label, id: _ } => {
150 let old_resolver = mem::replace(
152 resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
154 let ty = match label {
156 let break_ty = self.table.new_type_var();
157 self.breakables.push(BreakableContext {
159 break_ty: break_ty.clone(),
160 label: label.map(|label| self.body[label].name.clone()),
163 self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
164 let ctxt = self.breakables.pop().expect("breakable stack broken");
171 None => self.infer_block(statements, *tail, expected),
173 self.resolver = old_resolver;
176 Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
177 Expr::TryBlock { body } => {
178 let _inner = self.infer_expr(*body, expected);
179 // FIXME should be std::result::Result<{inner}, _>
182 Expr::Async { body } => {
183 // Use the first type parameter as the output type of future.
184 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
185 let inner_ty = self.infer_expr(*body, &Expectation::none());
186 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
187 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
188 TyKind::OpaqueType(opaque_ty_id, Substitution::single(inner_ty)).intern(&Interner)
190 Expr::Loop { body, label } => {
191 self.breakables.push(BreakableContext {
193 break_ty: self.table.new_type_var(),
194 label: label.map(|label| self.body[label].name.clone()),
196 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
198 let ctxt = self.breakables.pop().expect("breakable stack broken");
200 self.diverges = Diverges::Maybe;
206 TyKind::Never.intern(&Interner)
209 Expr::While { condition, body, label } => {
210 self.breakables.push(BreakableContext {
212 break_ty: self.err_ty(),
213 label: label.map(|label| self.body[label].name.clone()),
215 // while let is desugared to a match loop, so this is always simple while
218 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
220 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
221 let _ctxt = self.breakables.pop().expect("breakable stack broken");
222 // the body may not run, so it diverging doesn't mean we diverge
223 self.diverges = Diverges::Maybe;
226 Expr::For { iterable, body, pat, label } => {
227 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
229 self.breakables.push(BreakableContext {
231 break_ty: self.err_ty(),
232 label: label.map(|label| self.body[label].name.clone()),
235 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
237 self.infer_pat(*pat, &pat_ty, BindingMode::default());
239 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
240 let _ctxt = self.breakables.pop().expect("breakable stack broken");
241 // the body may not run, so it diverging doesn't mean we diverge
242 self.diverges = Diverges::Maybe;
245 Expr::Lambda { body, args, ret_type, arg_types } => {
246 assert_eq!(args.len(), arg_types.len());
248 let mut sig_tys = Vec::new();
250 // collect explicitly written argument types
251 for arg_type in arg_types.iter() {
252 let arg_ty = if let Some(type_ref) = arg_type {
253 self.make_ty(type_ref)
255 self.table.new_type_var()
257 sig_tys.push(arg_ty);
261 let ret_ty = match ret_type {
262 Some(type_ref) => self.make_ty(type_ref),
263 None => self.table.new_type_var(),
265 sig_tys.push(ret_ty.clone());
266 let sig_ty = TyKind::Function(FnPointer {
267 num_args: sig_tys.len() - 1,
268 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
269 substs: Substitution::from_iter(&Interner, sig_tys.clone()),
272 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
274 TyKind::Closure(closure_id, Substitution::single(sig_ty)).intern(&Interner);
276 // Eagerly try to relate the closure type with the expected
277 // type, otherwise we often won't have enough information to
279 self.coerce(&closure_ty, &expected.ty);
281 // Now go through the argument patterns
282 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
283 let resolved = self.resolve_ty_as_possible(arg_ty);
284 self.infer_pat(*arg_pat, &resolved, BindingMode::default());
287 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
288 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
290 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
292 self.diverges = prev_diverges;
293 self.return_ty = prev_ret_ty;
297 Expr::Call { callee, args } => {
298 let callee_ty = self.infer_expr(*callee, &Expectation::none());
299 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
300 let mut derefs = autoderef(
302 self.resolver.krate(),
304 goal: canonicalized.value.clone(),
305 environment: self.trait_env.env.clone(),
308 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
309 .find_map(|callee_deref_ty| {
311 &canonicalized.decanonicalize_ty(callee_deref_ty.value),
315 .unwrap_or((Vec::new(), self.err_ty()));
316 self.register_obligations_for_call(&callee_ty);
317 self.check_call_arguments(args, ¶m_tys);
318 self.normalize_associated_types_in(ret_ty)
320 Expr::MethodCall { receiver, args, method_name, generic_args } => self
321 .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
322 Expr::Match { expr, arms } => {
323 let input_ty = self.infer_expr(*expr, &Expectation::none());
325 let mut result_ty = if arms.is_empty() {
326 TyKind::Never.intern(&Interner)
328 self.table.new_type_var()
331 let matchee_diverges = self.diverges;
332 let mut all_arms_diverge = Diverges::Always;
335 self.diverges = Diverges::Maybe;
336 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
337 if let Some(guard_expr) = arm.guard {
340 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
344 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
345 all_arms_diverge &= self.diverges;
346 result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
349 self.diverges = matchee_diverges | all_arms_diverge;
354 // FIXME this could be more efficient...
355 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
356 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
358 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
359 Expr::Break { expr, label } => {
360 let val_ty = if let Some(expr) = expr {
361 self.infer_expr(*expr, &Expectation::none())
367 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
368 ctxt.break_ty.clone()
373 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
375 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
376 ctxt.break_ty = merged_type;
377 ctxt.may_break = true;
379 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
383 TyKind::Never.intern(&Interner)
385 Expr::Return { expr } => {
386 if let Some(expr) = expr {
387 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
389 let unit = Ty::unit();
390 self.coerce(&unit, &self.return_ty.clone());
392 TyKind::Never.intern(&Interner)
394 Expr::Yield { expr } => {
395 // FIXME: track yield type for coercion
396 if let Some(expr) = expr {
397 self.infer_expr(*expr, &Expectation::none());
399 TyKind::Never.intern(&Interner)
401 Expr::RecordLit { path, fields, spread } => {
402 let (ty, def_id) = self.resolve_variant(path.as_ref());
403 if let Some(variant) = def_id {
404 self.write_variant_resolution(tgt_expr.into(), variant);
407 self.unify(&ty, &expected.ty);
409 let substs = ty.substs().cloned().unwrap_or_else(|| Substitution::empty(&Interner));
410 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
411 let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
412 for field in fields.iter() {
414 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
415 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
417 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
423 if let Some(field_def) = field_def {
424 self.result.record_field_resolutions.insert(field.expr, field_def);
426 let field_ty = field_def.map_or(self.err_ty(), |it| {
427 field_types[it.local_id].clone().subst(&substs)
429 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
431 if let Some(expr) = spread {
432 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
436 Expr::Field { expr, name } => {
437 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
438 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
439 let ty = autoderef::autoderef(
441 self.resolver.krate(),
443 goal: canonicalized.value.clone(),
444 environment: self.trait_env.env.clone(),
447 .find_map(|derefed_ty| {
448 let def_db = self.db.upcast();
449 let module = self.resolver.module();
450 let is_visible = |field_id: &FieldId| {
453 self.db.field_visibilities(field_id.parent)[field_id.local_id]
454 .is_visible_from(def_db, mod_id)
458 match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
459 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
463 .map(|a| a.assert_ty_ref(&Interner))
466 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
467 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
468 let field = FieldId { parent: (*s).into(), local_id };
469 if is_visible(&field) {
470 self.write_field_resolution(tgt_expr, field);
472 self.db.field_types((*s).into())[field.local_id]
480 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
481 let local_id = self.db.union_data(*u).variant_data.field(name)?;
482 let field = FieldId { parent: (*u).into(), local_id };
483 if is_visible(&field) {
484 self.write_field_resolution(tgt_expr, field);
486 self.db.field_types((*u).into())[field.local_id]
497 .unwrap_or(self.err_ty());
498 let ty = self.insert_type_vars(ty);
499 self.normalize_associated_types_in(ty)
501 Expr::Await { expr } => {
502 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
503 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
505 Expr::Try { expr } => {
506 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
507 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
509 Expr::Cast { expr, type_ref } => {
510 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
511 let cast_ty = self.make_ty(type_ref);
512 // FIXME check the cast...
515 Expr::Ref { expr, rawness, mutability } => {
516 let mutability = lower_to_chalk_mutability(*mutability);
517 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
518 &expected.ty.as_reference_or_ptr()
520 if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
521 // FIXME: throw type error - expected mut reference but found shared ref,
522 // which cannot be coerced
524 if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
525 // FIXME: throw type error - expected reference but found ptr,
526 // which cannot be coerced
528 Expectation::rvalue_hint(Ty::clone(exp_inner))
532 let inner_ty = self.infer_expr_inner(*expr, &expectation);
534 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
535 Rawness::Ref => TyKind::Ref(mutability, inner_ty),
539 Expr::Box { expr } => {
540 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
541 if let Some(box_) = self.resolve_boxed_box() {
543 Substitution::build_for_generics(&generics(self.db.upcast(), box_.into()));
544 sb = sb.push(inner_ty);
545 match self.db.generic_defaults(box_.into()).get(1) {
546 Some(alloc_ty) if !alloc_ty.value.is_unknown() && sb.remaining() > 0 => {
547 sb = sb.push(alloc_ty.value.clone());
551 sb = sb.fill(repeat_with(|| self.table.new_type_var()));
552 Ty::adt_ty(box_, sb.build())
557 Expr::UnaryOp { expr, op } => {
558 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
560 UnaryOp::Deref => match self.resolver.krate() {
562 let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
563 match autoderef::deref(
567 goal: &canonicalized.value,
568 environment: self.trait_env.env.clone(),
571 Some(derefed_ty) => {
572 canonicalized.decanonicalize_ty(derefed_ty.value)
574 None => self.err_ty(),
577 None => self.err_ty(),
580 match inner_ty.kind(&Interner) {
581 // Fast path for builtins
582 TyKind::Scalar(Scalar::Int(_))
583 | TyKind::Scalar(Scalar::Uint(_))
584 | TyKind::Scalar(Scalar::Float(_))
585 | TyKind::InferenceVar(_, TyVariableKind::Integer)
586 | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
587 // Otherwise we resolve via the std::ops::Neg trait
589 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
593 match inner_ty.kind(&Interner) {
594 // Fast path for builtins
595 TyKind::Scalar(Scalar::Bool)
596 | TyKind::Scalar(Scalar::Int(_))
597 | TyKind::Scalar(Scalar::Uint(_))
598 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
599 // Otherwise we resolve via the std::ops::Not trait
601 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
606 Expr::BinaryOp { lhs, rhs, op } => match op {
608 let lhs_expectation = match op {
609 BinaryOp::LogicOp(..) => {
610 Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
612 _ => Expectation::none(),
614 let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
615 let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
616 let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
618 let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
620 if ret.is_unknown() {
621 cov_mark::hit!(infer_expr_inner_binary_operator_overload);
623 self.resolve_associated_type_with_params(
625 self.resolve_binary_op_output(op),
634 Expr::Range { lhs, rhs, range_type } => {
635 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
636 let rhs_expect = lhs_ty
638 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
639 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
640 match (range_type, lhs_ty, rhs_ty) {
641 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
642 Some(adt) => Ty::adt_ty(adt, Substitution::empty(&Interner)),
643 None => self.err_ty(),
645 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
646 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
647 None => self.err_ty(),
649 (RangeOp::Inclusive, None, Some(ty)) => {
650 match self.resolve_range_to_inclusive() {
651 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
652 None => self.err_ty(),
655 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
656 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
657 None => self.err_ty(),
659 (RangeOp::Inclusive, Some(_), Some(ty)) => {
660 match self.resolve_range_inclusive() {
661 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
662 None => self.err_ty(),
665 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
666 Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
667 None => self.err_ty(),
669 (RangeOp::Inclusive, _, None) => self.err_ty(),
672 Expr::Index { base, index } => {
673 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
674 let index_ty = self.infer_expr(*index, &Expectation::none());
676 if let (Some(index_trait), Some(krate)) =
677 (self.resolve_ops_index(), self.resolver.krate())
679 let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
680 let self_ty = method_resolution::resolve_indexing_op(
682 &canonicalized.value,
683 self.trait_env.clone(),
688 self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
689 self.resolve_associated_type_with_params(
691 self.resolve_ops_index_output(),
698 Expr::Tuple { exprs } => {
699 let mut tys = match expected.ty.kind(&Interner) {
700 TyKind::Tuple(_, substs) => substs
702 .map(|a| a.assert_ty_ref(&Interner).clone())
703 .chain(repeat_with(|| self.table.new_type_var()))
705 .collect::<Vec<_>>(),
706 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
709 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
710 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
713 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
715 Expr::Array(array) => {
716 let elem_ty = match expected.ty.kind(&Interner) {
717 TyKind::Array(st) | TyKind::Slice(st) => st.clone(),
718 _ => self.table.new_type_var(),
722 Array::ElementList(items) => {
723 for expr in items.iter() {
724 self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
727 Array::Repeat { initializer, repeat } => {
728 self.infer_expr_coerce(
730 &Expectation::has_type(elem_ty.clone()),
734 &Expectation::has_type(
735 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
741 TyKind::Array(elem_ty).intern(&Interner)
743 Expr::Literal(lit) => match lit {
744 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
745 Literal::String(..) => {
746 TyKind::Ref(Mutability::Not, TyKind::Str.intern(&Interner)).intern(&Interner)
748 Literal::ByteString(..) => {
749 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
750 let array_type = TyKind::Array(byte_type).intern(&Interner);
751 TyKind::Ref(Mutability::Not, array_type).intern(&Interner)
753 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
754 Literal::Int(_v, ty) => match ty {
756 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
759 None => self.table.new_integer_var(),
761 Literal::Uint(_v, ty) => match ty {
763 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
766 None => self.table.new_integer_var(),
768 Literal::Float(_v, ty) => match ty {
770 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
773 None => self.table.new_float_var(),
776 Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
778 // use a new type variable if we got unknown here
779 let ty = self.insert_type_vars_shallow(ty);
780 let ty = self.resolve_ty_as_possible(ty);
781 self.write_expr_ty(tgt_expr, ty.clone());
787 statements: &[Statement],
788 tail: Option<ExprId>,
789 expected: &Expectation,
791 for stmt in statements {
793 Statement::Let { pat, type_ref, initializer } => {
795 type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
797 // Always use the declared type when specified
798 let mut ty = decl_ty.clone();
800 if let Some(expr) = initializer {
802 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
803 if decl_ty.is_unknown() {
808 let ty = self.resolve_ty_as_possible(ty);
809 self.infer_pat(*pat, &ty, BindingMode::default());
811 Statement::Expr(expr) => {
812 self.infer_expr(*expr, &Expectation::none());
817 let ty = if let Some(expr) = tail {
818 self.infer_expr_coerce(expr, expected)
820 // Citing rustc: if there is no explicit tail expression,
821 // that is typically equivalent to a tail expression
822 // of `()` -- except if the block diverges. In that
823 // case, there is no value supplied from the tail
824 // expression (assuming there are no other breaks,
825 // this implies that the type of the block will be
827 if self.diverges.is_always() {
828 // we don't even make an attempt at coercion
829 self.table.new_maybe_never_var()
831 self.coerce(&Ty::unit(), &expected.coercion_target());
838 fn infer_method_call(
844 generic_args: Option<&GenericArgs>,
846 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
847 let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
849 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
851 let resolved = self.resolver.krate().and_then(|krate| {
852 method_resolution::lookup_method(
853 &canonicalized_receiver.value,
855 self.trait_env.clone(),
858 self.resolver.module(),
862 let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
863 Some((ty, func)) => {
864 let ty = canonicalized_receiver.decanonicalize_ty(ty);
865 self.write_method_resolution(tgt_expr, func);
866 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
868 None => (receiver_ty, Binders::new(0, self.err_ty()), None),
870 let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
871 let method_ty = method_ty.subst(&substs);
872 let method_ty = self.insert_type_vars(method_ty);
873 self.register_obligations_for_call(&method_ty);
874 let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
876 if !sig.params().is_empty() {
877 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
879 (self.err_ty(), Vec::new(), sig.ret().clone())
882 None => (self.err_ty(), Vec::new(), self.err_ty()),
884 // Apply autoref so the below unification works correctly
885 // FIXME: return correct autorefs from lookup_method
886 let actual_receiver_ty = match expected_receiver_ty.as_reference() {
887 Some((_, mutability)) => TyKind::Ref(mutability, derefed_receiver_ty).intern(&Interner),
888 _ => derefed_receiver_ty,
890 self.unify(&expected_receiver_ty, &actual_receiver_ty);
892 self.check_call_arguments(args, ¶m_tys);
893 self.normalize_associated_types_in(ret_ty)
896 fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
897 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
898 // We do this in a pretty awful way: first we type-check any arguments
899 // that are not closures, then we type-check the closures. This is so
900 // that we have more information about the types of arguments when we
901 // type-check the functions. This isn't really the right way to do this.
902 for &check_closures in &[false, true] {
903 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
904 for (&arg, param_ty) in args.iter().zip(param_iter) {
905 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
906 if is_closure != check_closures {
910 let param_ty = self.normalize_associated_types_in(param_ty);
911 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
916 fn substs_for_method_call(
918 def_generics: Option<Generics>,
919 generic_args: Option<&GenericArgs>,
922 let (parent_params, self_params, type_params, impl_trait_params) =
923 def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
924 assert_eq!(self_params, 0); // method shouldn't have another Self param
925 let total_len = parent_params + type_params + impl_trait_params;
926 let mut substs = Vec::with_capacity(total_len);
927 // Parent arguments are unknown, except for the receiver type
928 if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
929 for (_id, param) in parent_generics {
930 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
931 substs.push(receiver_ty.clone());
933 substs.push(self.err_ty());
937 // handle provided type arguments
938 if let Some(generic_args) = generic_args {
939 // if args are provided, it should be all of them, but we can't rely on that
940 for arg in generic_args
943 .filter(|arg| matches!(arg, GenericArg::Type(_)))
947 GenericArg::Type(type_ref) => {
948 let ty = self.make_ty(type_ref);
951 GenericArg::Lifetime(_) => {}
955 let supplied_params = substs.len();
956 for _ in supplied_params..total_len {
957 substs.push(self.err_ty());
959 assert_eq!(substs.len(), total_len);
960 Substitution::from_iter(&Interner, substs)
963 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
964 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
965 let def: CallableDefId = from_chalk(self.db, *fn_def);
966 let generic_predicates = self.db.generic_predicates(def.into());
967 for predicate in generic_predicates.iter() {
968 let (predicate, binders) =
969 predicate.clone().subst(parameters).into_value_and_skipped_binders();
970 always!(binders == 0); // quantified where clauses not yet handled
971 self.push_obligation(predicate.cast(&Interner));
973 // add obligation for trait implementation, if this is a trait method
975 CallableDefId::FunctionId(f) => {
976 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
978 // construct a TraitRef
980 parameters.prefix(generics(self.db.upcast(), trait_.into()).len());
981 self.push_obligation(
982 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
987 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}