1 //! Type inference for expressions.
3 use std::iter::{repeat, repeat_with};
4 use std::{mem, sync::Arc};
6 use chalk_ir::{cast::Cast, fold::Shift, ConstData, Mutability, TyVariableKind};
8 expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
9 path::{GenericArg, GenericArgs},
10 resolver::resolver_for_expr,
11 type_ref::ConstScalar,
12 AssocContainerId, FieldId, Lookup,
14 use hir_expand::name::{name, Name};
16 use syntax::ast::RangeOp;
20 lower::lower_to_chalk_mutability,
22 method_resolution, op,
23 primitive::{self, UintTy},
24 static_lifetime, to_chalk_trait_id,
26 utils::{generics, Generics},
27 AdtId, Binders, CallableDefId, ConcreteConst, ConstValue, FnPointer, FnSig, FnSubst,
28 InEnvironment, Interner, ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty,
29 TyBuilder, TyExt, TyKind,
33 find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
34 InferenceDiagnostic, TypeMismatch,
37 impl<'a> InferenceContext<'a> {
38 pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
39 let ty = self.infer_expr_inner(tgt_expr, expected);
41 // Any expression that produces a value of type `!` must have diverged
42 self.diverges = Diverges::Always;
44 let could_unify = self.unify(&ty, &expected.ty);
46 self.result.type_mismatches.insert(
48 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
51 self.resolve_ty_as_possible(ty)
54 /// Infer type of expression with possibly implicit coerce to the expected type.
55 /// Return the type after possible coercion.
56 pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
57 let ty = self.infer_expr_inner(expr, &expected);
58 let ty = if !self.coerce(&ty, &expected.coercion_target()) {
61 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
62 // Return actual type when type mismatch.
63 // This is needed for diagnostic when return type mismatch.
65 } else if expected.coercion_target().is_unknown() {
71 self.resolve_ty_as_possible(ty)
74 fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
75 let krate = self.resolver.krate()?;
76 let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
77 let output_assoc_type =
78 self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
80 let mut arg_tys = vec![];
81 let arg_ty = TyBuilder::tuple(num_args)
82 .fill(repeat_with(|| {
83 let arg = self.table.new_type_var();
84 arg_tys.push(arg.clone());
90 let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
91 if b.remaining() != 2 {
94 b.push(ty.clone()).push(arg_ty).build()
97 let trait_env = self.trait_env.env.clone();
98 let obligation = InEnvironment {
99 goal: projection.trait_ref(self.db).cast(&Interner),
100 environment: trait_env,
102 let canonical = self.canonicalizer().canonicalize_obligation(obligation.clone());
103 if self.db.trait_solve(krate, canonical.value).is_some() {
104 self.push_obligation(obligation.goal);
105 let return_ty = self.normalize_projection_ty(projection);
106 Some((arg_tys, return_ty))
112 pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
113 match ty.callable_sig(self.db) {
114 Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
115 None => self.callable_sig_from_fn_trait(ty, num_args),
119 fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
120 self.db.check_canceled();
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),
139 None => TyBuilder::unit(),
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::from1(&Interner, inner_ty))
189 Expr::Loop { body, label } => {
190 self.breakables.push(BreakableContext {
192 break_ty: self.table.new_type_var(),
193 label: label.map(|label| self.body[label].name.clone()),
195 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
197 let ctxt = self.breakables.pop().expect("breakable stack broken");
199 self.diverges = Diverges::Maybe;
205 TyKind::Never.intern(&Interner)
208 Expr::While { condition, body, label } => {
209 self.breakables.push(BreakableContext {
211 break_ty: self.err_ty(),
212 label: label.map(|label| self.body[label].name.clone()),
214 // while let is desugared to a match loop, so this is always simple while
217 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
219 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
220 let _ctxt = self.breakables.pop().expect("breakable stack broken");
221 // the body may not run, so it diverging doesn't mean we diverge
222 self.diverges = Diverges::Maybe;
225 Expr::For { iterable, body, pat, label } => {
226 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
228 self.breakables.push(BreakableContext {
230 break_ty: self.err_ty(),
231 label: label.map(|label| self.body[label].name.clone()),
234 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
236 self.infer_pat(*pat, &pat_ty, BindingMode::default());
238 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
239 let _ctxt = self.breakables.pop().expect("breakable stack broken");
240 // the body may not run, so it diverging doesn't mean we diverge
241 self.diverges = Diverges::Maybe;
244 Expr::Lambda { body, args, ret_type, arg_types } => {
245 assert_eq!(args.len(), arg_types.len());
247 let mut sig_tys = Vec::new();
249 // collect explicitly written argument types
250 for arg_type in arg_types.iter() {
251 let arg_ty = if let Some(type_ref) = arg_type {
252 self.make_ty(type_ref)
254 self.table.new_type_var()
256 sig_tys.push(arg_ty);
260 let ret_ty = match ret_type {
261 Some(type_ref) => self.make_ty(type_ref),
262 None => self.table.new_type_var(),
264 sig_tys.push(ret_ty.clone());
265 let sig_ty = TyKind::Function(FnPointer {
267 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
268 substitution: FnSubst(
269 Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
273 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
275 TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty))
278 // Eagerly try to relate the closure type with the expected
279 // type, otherwise we often won't have enough information to
281 self.coerce(&closure_ty, &expected.ty);
283 // Now go through the argument patterns
284 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
285 let resolved = self.resolve_ty_as_possible(arg_ty);
286 self.infer_pat(*arg_pat, &resolved, BindingMode::default());
289 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
290 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
292 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
294 self.diverges = prev_diverges;
295 self.return_ty = prev_ret_ty;
299 Expr::Call { callee, args } => {
300 let callee_ty = self.infer_expr(*callee, &Expectation::none());
301 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
302 let mut derefs = autoderef(
304 self.resolver.krate(),
306 goal: canonicalized.value.clone(),
307 environment: self.trait_env.env.clone(),
310 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
311 .find_map(|callee_deref_ty| {
313 &canonicalized.decanonicalize_ty(callee_deref_ty.value),
317 .unwrap_or((Vec::new(), self.err_ty()));
318 self.register_obligations_for_call(&callee_ty);
319 self.check_call_arguments(args, ¶m_tys);
320 self.normalize_associated_types_in(ret_ty)
322 Expr::MethodCall { receiver, args, method_name, generic_args } => self
328 generic_args.as_deref(),
330 Expr::Match { expr, arms } => {
331 let input_ty = self.infer_expr(*expr, &Expectation::none());
333 let mut result_ty = if arms.is_empty() {
334 TyKind::Never.intern(&Interner)
336 self.table.new_type_var()
339 let matchee_diverges = self.diverges;
340 let mut all_arms_diverge = Diverges::Always;
343 self.diverges = Diverges::Maybe;
344 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
345 if let Some(guard_expr) = arm.guard {
348 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
352 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
353 all_arms_diverge &= self.diverges;
354 result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
357 self.diverges = matchee_diverges | all_arms_diverge;
362 // FIXME this could be more efficient...
363 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
364 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
366 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
367 Expr::Break { expr, label } => {
368 let val_ty = if let Some(expr) = expr {
369 self.infer_expr(*expr, &Expectation::none())
375 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
376 ctxt.break_ty.clone()
381 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
383 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
384 ctxt.break_ty = merged_type;
385 ctxt.may_break = true;
387 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
391 TyKind::Never.intern(&Interner)
393 Expr::Return { expr } => {
394 if let Some(expr) = expr {
395 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
397 let unit = TyBuilder::unit();
398 self.coerce(&unit, &self.return_ty.clone());
400 TyKind::Never.intern(&Interner)
402 Expr::Yield { expr } => {
403 // FIXME: track yield type for coercion
404 if let Some(expr) = expr {
405 self.infer_expr(*expr, &Expectation::none());
407 TyKind::Never.intern(&Interner)
409 Expr::RecordLit { path, fields, spread } => {
410 let (ty, def_id) = self.resolve_variant(path.as_deref());
411 if let Some(variant) = def_id {
412 self.write_variant_resolution(tgt_expr.into(), variant);
415 self.unify(&ty, &expected.ty);
419 .map(|(_, s)| s.clone())
420 .unwrap_or_else(|| Substitution::empty(&Interner));
421 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
422 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
423 for field in fields.iter() {
425 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
426 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
428 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
434 let field_ty = field_def.map_or(self.err_ty(), |it| {
435 field_types[it.local_id].clone().substitute(&Interner, &substs)
437 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
439 if let Some(expr) = spread {
440 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
444 Expr::Field { expr, name } => {
445 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
446 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
447 let ty = autoderef::autoderef(
449 self.resolver.krate(),
451 goal: canonicalized.value.clone(),
452 environment: self.trait_env.env.clone(),
455 .find_map(|derefed_ty| {
456 let def_db = self.db.upcast();
457 let module = self.resolver.module();
458 let is_visible = |field_id: &FieldId| {
461 self.db.field_visibilities(field_id.parent)[field_id.local_id]
462 .is_visible_from(def_db, mod_id)
466 match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
467 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
471 .map(|a| a.assert_ty_ref(&Interner))
474 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
475 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
476 let field = FieldId { parent: (*s).into(), local_id };
477 if is_visible(&field) {
478 self.write_field_resolution(tgt_expr, field);
480 self.db.field_types((*s).into())[field.local_id]
482 .substitute(&Interner, ¶meters),
488 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
489 let local_id = self.db.union_data(*u).variant_data.field(name)?;
490 let field = FieldId { parent: (*u).into(), local_id };
491 if is_visible(&field) {
492 self.write_field_resolution(tgt_expr, field);
494 self.db.field_types((*u).into())[field.local_id]
496 .substitute(&Interner, ¶meters),
505 .unwrap_or(self.err_ty());
506 let ty = self.insert_type_vars(ty);
507 self.normalize_associated_types_in(ty)
509 Expr::Await { expr } => {
510 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
511 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
513 Expr::Try { expr } => {
514 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
515 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
517 Expr::Cast { expr, type_ref } => {
518 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
519 let cast_ty = self.make_ty(type_ref);
520 // FIXME check the cast...
523 Expr::Ref { expr, rawness, mutability } => {
524 let mutability = lower_to_chalk_mutability(*mutability);
525 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
526 &expected.ty.as_reference_or_ptr()
528 if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
529 // FIXME: throw type error - expected mut reference but found shared ref,
530 // which cannot be coerced
532 if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
533 // FIXME: throw type error - expected reference but found ptr,
534 // which cannot be coerced
536 Expectation::rvalue_hint(Ty::clone(exp_inner))
540 let inner_ty = self.infer_expr_inner(*expr, &expectation);
542 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
543 Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
547 Expr::Box { expr } => {
548 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
549 if let Some(box_) = self.resolve_boxed_box() {
550 TyBuilder::adt(self.db, box_)
552 .fill_with_defaults(self.db, || self.table.new_type_var())
558 Expr::UnaryOp { expr, op } => {
559 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
561 UnaryOp::Deref => match self.resolver.krate() {
563 let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
564 match autoderef::deref(
568 goal: &canonicalized.value,
569 environment: self.trait_env.env.clone(),
572 Some(derefed_ty) => {
573 canonicalized.decanonicalize_ty(derefed_ty.value)
575 None => self.err_ty(),
578 None => self.err_ty(),
581 match inner_ty.kind(&Interner) {
582 // Fast path for builtins
583 TyKind::Scalar(Scalar::Int(_))
584 | TyKind::Scalar(Scalar::Uint(_))
585 | TyKind::Scalar(Scalar::Float(_))
586 | TyKind::InferenceVar(_, TyVariableKind::Integer)
587 | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
588 // Otherwise we resolve via the std::ops::Neg trait
590 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
594 match inner_ty.kind(&Interner) {
595 // Fast path for builtins
596 TyKind::Scalar(Scalar::Bool)
597 | TyKind::Scalar(Scalar::Int(_))
598 | TyKind::Scalar(Scalar::Uint(_))
599 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
600 // Otherwise we resolve via the std::ops::Not trait
602 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
607 Expr::BinaryOp { lhs, rhs, op } => match op {
609 let lhs_expectation = match op {
610 BinaryOp::LogicOp(..) => {
611 Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
613 _ => Expectation::none(),
615 let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
616 let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
617 let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
619 let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
621 if ret.is_unknown() {
622 cov_mark::hit!(infer_expr_inner_binary_operator_overload);
624 self.resolve_associated_type_with_params(
626 self.resolve_binary_op_output(op),
635 Expr::Range { lhs, rhs, range_type } => {
636 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
637 let rhs_expect = lhs_ty
639 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
640 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
641 match (range_type, lhs_ty, rhs_ty) {
642 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
643 Some(adt) => TyBuilder::adt(self.db, adt).build(),
644 None => self.err_ty(),
646 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
647 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
648 None => self.err_ty(),
650 (RangeOp::Inclusive, None, Some(ty)) => {
651 match self.resolve_range_to_inclusive() {
652 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
653 None => self.err_ty(),
656 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
657 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
658 None => self.err_ty(),
660 (RangeOp::Inclusive, Some(_), Some(ty)) => {
661 match self.resolve_range_inclusive() {
662 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
663 None => self.err_ty(),
666 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
667 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
668 None => self.err_ty(),
670 (RangeOp::Inclusive, _, None) => self.err_ty(),
673 Expr::Index { base, index } => {
674 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
675 let index_ty = self.infer_expr(*index, &Expectation::none());
677 if let (Some(index_trait), Some(krate)) =
678 (self.resolve_ops_index(), self.resolver.krate())
680 let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
681 let self_ty = method_resolution::resolve_indexing_op(
683 &canonicalized.value,
684 self.trait_env.clone(),
689 self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
690 self.resolve_associated_type_with_params(
692 self.resolve_ops_index_output(),
699 Expr::Tuple { exprs } => {
700 let mut tys = match expected.ty.kind(&Interner) {
701 TyKind::Tuple(_, substs) => substs
703 .map(|a| a.assert_ty_ref(&Interner).clone())
704 .chain(repeat_with(|| self.table.new_type_var()))
706 .collect::<Vec<_>>(),
707 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
710 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
711 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
714 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
716 Expr::Array(array) => {
717 let elem_ty = match expected.ty.kind(&Interner) {
718 TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
719 _ => self.table.new_type_var(),
722 let len = match array {
723 Array::ElementList(items) => {
724 for expr in items.iter() {
725 self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
729 Array::Repeat { initializer, repeat } => {
730 self.infer_expr_coerce(
732 &Expectation::has_type(elem_ty.clone()),
736 &Expectation::has_type(
737 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
740 // FIXME: we don't know the length here because hir Exprs don't actually
741 // get the value out of the AST, even though it is there.
747 ty: TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
748 value: ConstValue::Concrete(chalk_ir::ConcreteConst {
750 .map(|len| ConstScalar::Usize(len as u64))
751 .unwrap_or(ConstScalar::Unknown),
754 TyKind::Array(elem_ty, cd.intern(&Interner)).intern(&Interner)
756 Expr::Literal(lit) => match lit {
757 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
758 Literal::String(..) => {
759 TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
762 Literal::ByteString(bs) => {
763 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
765 let len = ConstData {
766 ty: TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
767 value: ConstValue::Concrete(ConcreteConst {
768 interned: ConstScalar::Usize(bs.len() as u64),
773 let array_type = TyKind::Array(byte_type, len).intern(&Interner);
774 TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
776 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
777 Literal::Int(_v, ty) => match ty {
779 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
782 None => self.table.new_integer_var(),
784 Literal::Uint(_v, ty) => match ty {
786 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
789 None => self.table.new_integer_var(),
791 Literal::Float(_v, ty) => match ty {
793 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
796 None => self.table.new_float_var(),
799 Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
801 // use a new type variable if we got unknown here
802 let ty = self.insert_type_vars_shallow(ty);
803 let ty = self.resolve_ty_as_possible(ty);
804 self.write_expr_ty(tgt_expr, ty.clone());
810 statements: &[Statement],
811 tail: Option<ExprId>,
812 expected: &Expectation,
814 for stmt in statements {
816 Statement::Let { pat, type_ref, initializer } => {
818 type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
820 // Always use the declared type when specified
821 let mut ty = decl_ty.clone();
823 if let Some(expr) = initializer {
825 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
826 if decl_ty.is_unknown() {
831 let ty = self.resolve_ty_as_possible(ty);
832 self.infer_pat(*pat, &ty, BindingMode::default());
834 Statement::Expr { expr, .. } => {
835 self.infer_expr(*expr, &Expectation::none());
840 let ty = if let Some(expr) = tail {
841 self.infer_expr_coerce(expr, expected)
843 // Citing rustc: if there is no explicit tail expression,
844 // that is typically equivalent to a tail expression
845 // of `()` -- except if the block diverges. In that
846 // case, there is no value supplied from the tail
847 // expression (assuming there are no other breaks,
848 // this implies that the type of the block will be
850 if self.diverges.is_always() {
851 // we don't even make an attempt at coercion
852 self.table.new_maybe_never_var()
854 self.coerce(&TyBuilder::unit(), &expected.coercion_target());
861 fn infer_method_call(
867 generic_args: Option<&GenericArgs>,
869 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
870 let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
872 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
874 let resolved = self.resolver.krate().and_then(|krate| {
875 method_resolution::lookup_method(
876 &canonicalized_receiver.value,
878 self.trait_env.clone(),
881 self.resolver.module(),
885 let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
886 Some((ty, func)) => {
887 let ty = canonicalized_receiver.decanonicalize_ty(ty);
888 self.write_method_resolution(tgt_expr, func);
889 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
891 None => (receiver_ty, Binders::empty(&Interner, self.err_ty()), None),
893 let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
894 let method_ty = method_ty.substitute(&Interner, &substs);
895 let method_ty = self.insert_type_vars(method_ty);
896 self.register_obligations_for_call(&method_ty);
897 let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
899 if !sig.params().is_empty() {
900 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
902 (self.err_ty(), Vec::new(), sig.ret().clone())
905 None => (self.err_ty(), Vec::new(), self.err_ty()),
907 // Apply autoref so the below unification works correctly
908 // FIXME: return correct autorefs from lookup_method
909 let actual_receiver_ty = match expected_receiver_ty.as_reference() {
910 Some((_, lifetime, mutability)) => {
911 TyKind::Ref(mutability, lifetime, derefed_receiver_ty).intern(&Interner)
913 _ => derefed_receiver_ty,
915 self.unify(&expected_receiver_ty, &actual_receiver_ty);
917 self.check_call_arguments(args, ¶m_tys);
918 self.normalize_associated_types_in(ret_ty)
921 fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
922 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
923 // We do this in a pretty awful way: first we type-check any arguments
924 // that are not closures, then we type-check the closures. This is so
925 // that we have more information about the types of arguments when we
926 // type-check the functions. This isn't really the right way to do this.
927 for &check_closures in &[false, true] {
928 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
929 for (&arg, param_ty) in args.iter().zip(param_iter) {
930 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
931 if is_closure != check_closures {
935 let param_ty = self.normalize_associated_types_in(param_ty);
936 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
941 fn substs_for_method_call(
943 def_generics: Option<Generics>,
944 generic_args: Option<&GenericArgs>,
947 let (parent_params, self_params, type_params, impl_trait_params) =
948 def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
949 assert_eq!(self_params, 0); // method shouldn't have another Self param
950 let total_len = parent_params + type_params + impl_trait_params;
951 let mut substs = Vec::with_capacity(total_len);
952 // Parent arguments are unknown, except for the receiver type
953 if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
954 for (_id, param) in parent_generics {
955 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
956 substs.push(receiver_ty.clone());
958 substs.push(self.err_ty());
962 // handle provided type arguments
963 if let Some(generic_args) = generic_args {
964 // if args are provided, it should be all of them, but we can't rely on that
965 for arg in generic_args
968 .filter(|arg| matches!(arg, GenericArg::Type(_)))
972 GenericArg::Type(type_ref) => {
973 let ty = self.make_ty(type_ref);
976 GenericArg::Lifetime(_) => {}
980 let supplied_params = substs.len();
981 for _ in supplied_params..total_len {
982 substs.push(self.err_ty());
984 assert_eq!(substs.len(), total_len);
985 Substitution::from_iter(&Interner, substs)
988 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
989 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
990 let def: CallableDefId = from_chalk(self.db, *fn_def);
991 let generic_predicates = self.db.generic_predicates(def.into());
992 for predicate in generic_predicates.iter() {
993 let (predicate, binders) = predicate
995 .substitute(&Interner, parameters)
996 .into_value_and_skipped_binders();
997 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
998 self.push_obligation(predicate.cast(&Interner));
1000 // add obligation for trait implementation, if this is a trait method
1002 CallableDefId::FunctionId(f) => {
1003 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1005 // construct a TraitRef
1006 let substs = crate::subst_prefix(
1008 generics(self.db.upcast(), trait_.into()).len(),
1010 self.push_obligation(
1011 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1016 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}