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;
18 autoderef, dummy_usize_const,
19 lower::lower_to_chalk_mutability,
20 method_resolution, op,
21 primitive::{self, UintTy},
22 static_lifetime, to_chalk_trait_id,
23 traits::{chalk::from_chalk, FnTrait},
24 utils::{generics, variant_data, Generics},
25 AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
26 ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeWalk,
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])?;
77 let mut arg_tys = vec![];
78 let arg_ty = TyBuilder::tuple(num_args)
79 .fill(repeat_with(|| {
80 let arg = self.table.new_type_var();
81 arg_tys.push(arg.clone());
87 let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
88 if b.remaining() != 2 {
91 b.push(ty.clone()).push(arg_ty).build()
94 let trait_env = self.trait_env.env.clone();
95 let obligation = InEnvironment {
96 goal: projection.trait_ref(self.db).cast(&Interner),
97 environment: trait_env,
99 let canonical = self.canonicalizer().canonicalize_obligation(obligation.clone());
100 if self.db.trait_solve(krate, canonical.value).is_some() {
101 self.push_obligation(obligation.goal);
102 let return_ty = self.normalize_projection_ty(projection);
103 Some((arg_tys, return_ty))
109 pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
110 match ty.callable_sig(self.db) {
111 Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
112 None => self.callable_sig_from_fn_trait(ty, num_args),
116 fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
117 self.db.check_canceled();
119 let body = Arc::clone(&self.body); // avoid borrow checker problem
120 let ty = match &body[tgt_expr] {
121 Expr::Missing => self.err_ty(),
122 Expr::If { condition, then_branch, else_branch } => {
123 // if let is desugared to match, so this is always simple if
126 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
129 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
130 let mut both_arms_diverge = Diverges::Always;
132 let then_ty = self.infer_expr_inner(*then_branch, &expected);
133 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
134 let else_ty = match else_branch {
135 Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
136 None => TyBuilder::unit(),
138 both_arms_diverge &= self.diverges;
140 self.diverges = condition_diverges | both_arms_diverge;
142 self.coerce_merge_branch(&then_ty, &else_ty)
144 Expr::Block { statements, tail, label, id: _ } => {
145 let old_resolver = mem::replace(
147 resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
149 let ty = match label {
151 let break_ty = self.table.new_type_var();
152 self.breakables.push(BreakableContext {
154 break_ty: break_ty.clone(),
155 label: label.map(|label| self.body[label].name.clone()),
158 self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
159 let ctxt = self.breakables.pop().expect("breakable stack broken");
166 None => self.infer_block(statements, *tail, expected),
168 self.resolver = old_resolver;
171 Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
172 Expr::TryBlock { body } => {
173 let _inner = self.infer_expr(*body, expected);
174 // FIXME should be std::result::Result<{inner}, _>
177 Expr::Async { body } => {
178 // Use the first type parameter as the output type of future.
179 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
180 let inner_ty = self.infer_expr(*body, &Expectation::none());
181 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
182 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
183 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
186 Expr::Loop { body, label } => {
187 self.breakables.push(BreakableContext {
189 break_ty: self.table.new_type_var(),
190 label: label.map(|label| self.body[label].name.clone()),
192 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
194 let ctxt = self.breakables.pop().expect("breakable stack broken");
196 self.diverges = Diverges::Maybe;
202 TyKind::Never.intern(&Interner)
205 Expr::While { condition, body, label } => {
206 self.breakables.push(BreakableContext {
208 break_ty: self.err_ty(),
209 label: label.map(|label| self.body[label].name.clone()),
211 // while let is desugared to a match loop, so this is always simple while
214 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
216 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
217 let _ctxt = self.breakables.pop().expect("breakable stack broken");
218 // the body may not run, so it diverging doesn't mean we diverge
219 self.diverges = Diverges::Maybe;
222 Expr::For { iterable, body, pat, label } => {
223 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
225 self.breakables.push(BreakableContext {
227 break_ty: self.err_ty(),
228 label: label.map(|label| self.body[label].name.clone()),
231 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
233 self.infer_pat(*pat, &pat_ty, BindingMode::default());
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::Lambda { body, args, ret_type, arg_types } => {
242 assert_eq!(args.len(), arg_types.len());
244 let mut sig_tys = Vec::new();
246 // collect explicitly written argument types
247 for arg_type in arg_types.iter() {
248 let arg_ty = if let Some(type_ref) = arg_type {
249 self.make_ty(type_ref)
251 self.table.new_type_var()
253 sig_tys.push(arg_ty);
257 let ret_ty = match ret_type {
258 Some(type_ref) => self.make_ty(type_ref),
259 None => self.table.new_type_var(),
261 sig_tys.push(ret_ty.clone());
262 let sig_ty = TyKind::Function(FnPointer {
264 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
265 substitution: FnSubst(
266 Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
270 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
272 TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty))
275 // Eagerly try to relate the closure type with the expected
276 // type, otherwise we often won't have enough information to
278 self.coerce(&closure_ty, &expected.ty);
280 // Now go through the argument patterns
281 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
282 let resolved = self.resolve_ty_as_possible(arg_ty);
283 self.infer_pat(*arg_pat, &resolved, BindingMode::default());
286 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
287 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
289 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
291 self.diverges = prev_diverges;
292 self.return_ty = prev_ret_ty;
296 Expr::Call { callee, args } => {
297 let callee_ty = self.infer_expr(*callee, &Expectation::none());
298 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
299 let mut derefs = autoderef(
301 self.resolver.krate(),
303 goal: canonicalized.value.clone(),
304 environment: self.trait_env.env.clone(),
307 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
308 .find_map(|callee_deref_ty| {
310 &canonicalized.decanonicalize_ty(callee_deref_ty.value),
314 .unwrap_or((Vec::new(), self.err_ty()));
315 self.register_obligations_for_call(&callee_ty);
316 self.check_call_arguments(args, ¶m_tys);
317 self.normalize_associated_types_in(ret_ty)
319 Expr::MethodCall { receiver, args, method_name, generic_args } => self
320 .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
321 Expr::Match { expr, arms } => {
322 let input_ty = self.infer_expr(*expr, &Expectation::none());
324 let mut result_ty = if arms.is_empty() {
325 TyKind::Never.intern(&Interner)
327 self.table.new_type_var()
330 let matchee_diverges = self.diverges;
331 let mut all_arms_diverge = Diverges::Always;
334 self.diverges = Diverges::Maybe;
335 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
336 if let Some(guard_expr) = arm.guard {
339 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
343 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
344 all_arms_diverge &= self.diverges;
345 result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
348 self.diverges = matchee_diverges | all_arms_diverge;
353 // FIXME this could be more efficient...
354 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
355 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
357 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
358 Expr::Break { expr, label } => {
359 let val_ty = if let Some(expr) = expr {
360 self.infer_expr(*expr, &Expectation::none())
366 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
367 ctxt.break_ty.clone()
372 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
374 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
375 ctxt.break_ty = merged_type;
376 ctxt.may_break = true;
378 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
382 TyKind::Never.intern(&Interner)
384 Expr::Return { expr } => {
385 if let Some(expr) = expr {
386 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
388 let unit = TyBuilder::unit();
389 self.coerce(&unit, &self.return_ty.clone());
391 TyKind::Never.intern(&Interner)
393 Expr::Yield { expr } => {
394 // FIXME: track yield type for coercion
395 if let Some(expr) = expr {
396 self.infer_expr(*expr, &Expectation::none());
398 TyKind::Never.intern(&Interner)
400 Expr::RecordLit { path, fields, spread } => {
401 let (ty, def_id) = self.resolve_variant(path.as_ref());
402 if let Some(variant) = def_id {
403 self.write_variant_resolution(tgt_expr.into(), variant);
406 self.unify(&ty, &expected.ty);
408 let substs = ty.substs().cloned().unwrap_or_else(|| Substitution::empty(&Interner));
409 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
410 let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
411 for field in fields.iter() {
413 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
414 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
416 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
422 if let Some(field_def) = field_def {
423 self.result.record_field_resolutions.insert(field.expr, field_def);
425 let field_ty = field_def.map_or(self.err_ty(), |it| {
426 field_types[it.local_id].clone().substitute(&Interner, &substs)
428 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
430 if let Some(expr) = spread {
431 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
435 Expr::Field { expr, name } => {
436 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
437 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
438 let ty = autoderef::autoderef(
440 self.resolver.krate(),
442 goal: canonicalized.value.clone(),
443 environment: self.trait_env.env.clone(),
446 .find_map(|derefed_ty| {
447 let def_db = self.db.upcast();
448 let module = self.resolver.module();
449 let is_visible = |field_id: &FieldId| {
452 self.db.field_visibilities(field_id.parent)[field_id.local_id]
453 .is_visible_from(def_db, mod_id)
457 match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
458 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
459 substs.interned().get(idx).map(|a| a.assert_ty_ref(&Interner)).cloned()
461 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
462 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
463 let field = FieldId { parent: (*s).into(), local_id };
464 if is_visible(&field) {
465 self.write_field_resolution(tgt_expr, field);
467 self.db.field_types((*s).into())[field.local_id]
469 .substitute(&Interner, ¶meters),
475 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
476 let local_id = self.db.union_data(*u).variant_data.field(name)?;
477 let field = FieldId { parent: (*u).into(), local_id };
478 if is_visible(&field) {
479 self.write_field_resolution(tgt_expr, field);
481 self.db.field_types((*u).into())[field.local_id]
483 .substitute(&Interner, ¶meters),
492 .unwrap_or(self.err_ty());
493 let ty = self.insert_type_vars(ty);
494 self.normalize_associated_types_in(ty)
496 Expr::Await { expr } => {
497 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
498 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
500 Expr::Try { expr } => {
501 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
502 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
504 Expr::Cast { expr, type_ref } => {
505 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
506 let cast_ty = self.make_ty(type_ref);
507 // FIXME check the cast...
510 Expr::Ref { expr, rawness, mutability } => {
511 let mutability = lower_to_chalk_mutability(*mutability);
512 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
513 &expected.ty.as_reference_or_ptr()
515 if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
516 // FIXME: throw type error - expected mut reference but found shared ref,
517 // which cannot be coerced
519 if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
520 // FIXME: throw type error - expected reference but found ptr,
521 // which cannot be coerced
523 Expectation::rvalue_hint(Ty::clone(exp_inner))
527 let inner_ty = self.infer_expr_inner(*expr, &expectation);
529 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
530 Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
534 Expr::Box { expr } => {
535 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
536 if let Some(box_) = self.resolve_boxed_box() {
537 TyBuilder::adt(self.db, box_)
539 .fill_with_defaults(self.db, || self.table.new_type_var())
545 Expr::UnaryOp { expr, op } => {
546 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
548 UnaryOp::Deref => match self.resolver.krate() {
550 let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
551 match autoderef::deref(
555 goal: &canonicalized.value,
556 environment: self.trait_env.env.clone(),
559 Some(derefed_ty) => {
560 canonicalized.decanonicalize_ty(derefed_ty.value)
562 None => self.err_ty(),
565 None => self.err_ty(),
568 match inner_ty.kind(&Interner) {
569 // Fast path for builtins
570 TyKind::Scalar(Scalar::Int(_))
571 | TyKind::Scalar(Scalar::Uint(_))
572 | TyKind::Scalar(Scalar::Float(_))
573 | TyKind::InferenceVar(_, TyVariableKind::Integer)
574 | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
575 // Otherwise we resolve via the std::ops::Neg trait
577 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
581 match inner_ty.kind(&Interner) {
582 // Fast path for builtins
583 TyKind::Scalar(Scalar::Bool)
584 | TyKind::Scalar(Scalar::Int(_))
585 | TyKind::Scalar(Scalar::Uint(_))
586 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
587 // Otherwise we resolve via the std::ops::Not trait
589 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
594 Expr::BinaryOp { lhs, rhs, op } => match op {
596 let lhs_expectation = match op {
597 BinaryOp::LogicOp(..) => {
598 Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
600 _ => Expectation::none(),
602 let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
603 let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
604 let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
606 let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
608 if ret.is_unknown() {
609 cov_mark::hit!(infer_expr_inner_binary_operator_overload);
611 self.resolve_associated_type_with_params(
613 self.resolve_binary_op_output(op),
622 Expr::Range { lhs, rhs, range_type } => {
623 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
624 let rhs_expect = lhs_ty
626 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
627 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
628 match (range_type, lhs_ty, rhs_ty) {
629 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
630 Some(adt) => TyBuilder::adt(self.db, adt).build(),
631 None => self.err_ty(),
633 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
634 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
635 None => self.err_ty(),
637 (RangeOp::Inclusive, None, Some(ty)) => {
638 match self.resolve_range_to_inclusive() {
639 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
640 None => self.err_ty(),
643 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
644 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
645 None => self.err_ty(),
647 (RangeOp::Inclusive, Some(_), Some(ty)) => {
648 match self.resolve_range_inclusive() {
649 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
650 None => self.err_ty(),
653 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
654 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
655 None => self.err_ty(),
657 (RangeOp::Inclusive, _, None) => self.err_ty(),
660 Expr::Index { base, index } => {
661 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
662 let index_ty = self.infer_expr(*index, &Expectation::none());
664 if let (Some(index_trait), Some(krate)) =
665 (self.resolve_ops_index(), self.resolver.krate())
667 let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
668 let self_ty = method_resolution::resolve_indexing_op(
670 &canonicalized.value,
671 self.trait_env.clone(),
676 self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
677 self.resolve_associated_type_with_params(
679 self.resolve_ops_index_output(),
686 Expr::Tuple { exprs } => {
687 let mut tys = match expected.ty.kind(&Interner) {
688 TyKind::Tuple(_, substs) => substs
690 .map(|a| a.assert_ty_ref(&Interner).clone())
691 .chain(repeat_with(|| self.table.new_type_var()))
693 .collect::<Vec<_>>(),
694 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
697 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
698 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
701 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
703 Expr::Array(array) => {
704 let elem_ty = match expected.ty.kind(&Interner) {
705 TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
706 _ => self.table.new_type_var(),
710 Array::ElementList(items) => {
711 for expr in items.iter() {
712 self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
715 Array::Repeat { initializer, repeat } => {
716 self.infer_expr_coerce(
718 &Expectation::has_type(elem_ty.clone()),
722 &Expectation::has_type(
723 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
729 TyKind::Array(elem_ty, dummy_usize_const()).intern(&Interner)
731 Expr::Literal(lit) => match lit {
732 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
733 Literal::String(..) => {
734 TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
737 Literal::ByteString(..) => {
738 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
740 TyKind::Array(byte_type, dummy_usize_const()).intern(&Interner);
741 TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
743 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
744 Literal::Int(_v, ty) => match ty {
746 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
749 None => self.table.new_integer_var(),
751 Literal::Uint(_v, ty) => match ty {
753 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
756 None => self.table.new_integer_var(),
758 Literal::Float(_v, ty) => match ty {
760 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
763 None => self.table.new_float_var(),
766 Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
768 // use a new type variable if we got unknown here
769 let ty = self.insert_type_vars_shallow(ty);
770 let ty = self.resolve_ty_as_possible(ty);
771 self.write_expr_ty(tgt_expr, ty.clone());
777 statements: &[Statement],
778 tail: Option<ExprId>,
779 expected: &Expectation,
781 for stmt in statements {
783 Statement::Let { pat, type_ref, initializer } => {
785 type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
787 // Always use the declared type when specified
788 let mut ty = decl_ty.clone();
790 if let Some(expr) = initializer {
792 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
793 if decl_ty.is_unknown() {
798 let ty = self.resolve_ty_as_possible(ty);
799 self.infer_pat(*pat, &ty, BindingMode::default());
801 Statement::Expr(expr) => {
802 self.infer_expr(*expr, &Expectation::none());
807 let ty = if let Some(expr) = tail {
808 self.infer_expr_coerce(expr, expected)
810 // Citing rustc: if there is no explicit tail expression,
811 // that is typically equivalent to a tail expression
812 // of `()` -- except if the block diverges. In that
813 // case, there is no value supplied from the tail
814 // expression (assuming there are no other breaks,
815 // this implies that the type of the block will be
817 if self.diverges.is_always() {
818 // we don't even make an attempt at coercion
819 self.table.new_maybe_never_var()
821 self.coerce(&TyBuilder::unit(), &expected.coercion_target());
828 fn infer_method_call(
834 generic_args: Option<&GenericArgs>,
836 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
837 let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
839 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
841 let resolved = self.resolver.krate().and_then(|krate| {
842 method_resolution::lookup_method(
843 &canonicalized_receiver.value,
845 self.trait_env.clone(),
848 self.resolver.module(),
852 let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
853 Some((ty, func)) => {
854 let ty = canonicalized_receiver.decanonicalize_ty(ty);
855 self.write_method_resolution(tgt_expr, func);
856 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
858 None => (receiver_ty, Binders::empty(&Interner, self.err_ty()), None),
860 let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
861 let method_ty = method_ty.substitute(&Interner, &substs);
862 let method_ty = self.insert_type_vars(method_ty);
863 self.register_obligations_for_call(&method_ty);
864 let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
866 if !sig.params().is_empty() {
867 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
869 (self.err_ty(), Vec::new(), sig.ret().clone())
872 None => (self.err_ty(), Vec::new(), self.err_ty()),
874 // Apply autoref so the below unification works correctly
875 // FIXME: return correct autorefs from lookup_method
876 let actual_receiver_ty = match expected_receiver_ty.as_reference() {
877 Some((_, lifetime, mutability)) => {
878 TyKind::Ref(mutability, lifetime, derefed_receiver_ty).intern(&Interner)
880 _ => derefed_receiver_ty,
882 self.unify(&expected_receiver_ty, &actual_receiver_ty);
884 self.check_call_arguments(args, ¶m_tys);
885 self.normalize_associated_types_in(ret_ty)
888 fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
889 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
890 // We do this in a pretty awful way: first we type-check any arguments
891 // that are not closures, then we type-check the closures. This is so
892 // that we have more information about the types of arguments when we
893 // type-check the functions. This isn't really the right way to do this.
894 for &check_closures in &[false, true] {
895 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
896 for (&arg, param_ty) in args.iter().zip(param_iter) {
897 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
898 if is_closure != check_closures {
902 let param_ty = self.normalize_associated_types_in(param_ty);
903 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
908 fn substs_for_method_call(
910 def_generics: Option<Generics>,
911 generic_args: Option<&GenericArgs>,
914 let (parent_params, self_params, type_params, impl_trait_params) =
915 def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
916 assert_eq!(self_params, 0); // method shouldn't have another Self param
917 let total_len = parent_params + type_params + impl_trait_params;
918 let mut substs = Vec::with_capacity(total_len);
919 // Parent arguments are unknown, except for the receiver type
920 if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
921 for (_id, param) in parent_generics {
922 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
923 substs.push(receiver_ty.clone());
925 substs.push(self.err_ty());
929 // handle provided type arguments
930 if let Some(generic_args) = generic_args {
931 // if args are provided, it should be all of them, but we can't rely on that
932 for arg in generic_args
935 .filter(|arg| matches!(arg, GenericArg::Type(_)))
939 GenericArg::Type(type_ref) => {
940 let ty = self.make_ty(type_ref);
943 GenericArg::Lifetime(_) => {}
947 let supplied_params = substs.len();
948 for _ in supplied_params..total_len {
949 substs.push(self.err_ty());
951 assert_eq!(substs.len(), total_len);
952 Substitution::from_iter(&Interner, substs)
955 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
956 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
957 let def: CallableDefId = from_chalk(self.db, *fn_def);
958 let generic_predicates = self.db.generic_predicates(def.into());
959 for predicate in generic_predicates.iter() {
960 let (predicate, binders) = predicate
962 .substitute(&Interner, parameters)
963 .into_value_and_skipped_binders();
964 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
965 self.push_obligation(predicate.cast(&Interner));
967 // add obligation for trait implementation, if this is a trait method
969 CallableDefId::FunctionId(f) => {
970 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
972 // construct a TraitRef
973 let substs = crate::subst_prefix(
975 generics(self.db.upcast(), trait_.into()).len(),
977 self.push_obligation(
978 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
983 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}