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, 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,
21 method_resolution, op,
22 primitive::{self, UintTy},
23 static_lifetime, to_chalk_trait_id,
25 utils::{generics, Generics},
26 AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
27 ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
31 find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
32 InferenceDiagnostic, TypeMismatch,
35 impl<'a> InferenceContext<'a> {
36 pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
37 let ty = self.infer_expr_inner(tgt_expr, expected);
38 if self.resolve_ty_shallow(&ty).is_never() {
39 // Any expression that produces a value of type `!` must have diverged
40 self.diverges = Diverges::Always;
42 if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
43 let could_unify = self.unify(&ty, &expected_ty);
45 self.result.type_mismatches.insert(
47 TypeMismatch { expected: expected_ty.clone(), actual: ty.clone() },
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 let Some(target) = expected.only_has_type(&mut self.table) {
59 if !self.coerce(&ty, &target) {
60 self.result.type_mismatches.insert(
62 TypeMismatch { expected: target.clone(), actual: ty.clone() },
64 // Return actual type when type mismatch.
65 // This is needed for diagnostic when return type mismatch.
77 fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
78 let krate = self.resolver.krate()?;
79 let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
80 let output_assoc_type =
81 self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
83 let mut arg_tys = vec![];
84 let arg_ty = TyBuilder::tuple(num_args)
85 .fill(repeat_with(|| {
86 let arg = self.table.new_type_var();
87 arg_tys.push(arg.clone());
93 let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
94 if b.remaining() != 2 {
97 b.push(ty.clone()).push(arg_ty).build()
100 let trait_env = self.trait_env.env.clone();
101 let obligation = InEnvironment {
102 goal: projection.trait_ref(self.db).cast(&Interner),
103 environment: trait_env,
105 let canonical = self.canonicalize(obligation.clone());
106 if self.db.trait_solve(krate, canonical.value.cast(&Interner)).is_some() {
107 self.push_obligation(obligation.goal);
108 let return_ty = self.table.normalize_projection_ty(projection);
109 Some((arg_tys, return_ty))
115 pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
116 match ty.callable_sig(self.db) {
117 Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
118 None => self.callable_sig_from_fn_trait(ty, num_args),
122 fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
123 self.db.check_canceled();
125 let body = Arc::clone(&self.body); // avoid borrow checker problem
126 let ty = match &body[tgt_expr] {
127 Expr::Missing => self.err_ty(),
128 Expr::If { condition, then_branch, else_branch } => {
129 // if let is desugared to match, so this is always simple if
132 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
135 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
136 let mut both_arms_diverge = Diverges::Always;
138 let mut result_ty = self.table.new_type_var();
139 let then_ty = self.infer_expr_inner(*then_branch, &expected);
140 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
141 result_ty = self.coerce_merge_branch(Some(*then_branch), &result_ty, &then_ty);
142 let else_ty = match else_branch {
143 Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
144 None => TyBuilder::unit(),
146 both_arms_diverge &= self.diverges;
147 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
148 result_ty = self.coerce_merge_branch(*else_branch, &result_ty, &else_ty);
150 self.diverges = condition_diverges | both_arms_diverge;
154 Expr::Block { statements, tail, label, id: _ } => {
155 let old_resolver = mem::replace(
157 resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
159 let ty = match label {
161 let break_ty = self.table.new_type_var();
162 self.breakables.push(BreakableContext {
164 break_ty: break_ty.clone(),
165 label: label.map(|label| self.body[label].name.clone()),
168 self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
169 let ctxt = self.breakables.pop().expect("breakable stack broken");
176 None => self.infer_block(statements, *tail, expected),
178 self.resolver = old_resolver;
181 Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
182 Expr::TryBlock { body } => {
183 let _inner = self.infer_expr(*body, expected);
184 // FIXME should be std::result::Result<{inner}, _>
187 Expr::Async { body } => {
188 // Use the first type parameter as the output type of future.
189 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
190 let inner_ty = self.infer_expr(*body, &Expectation::none());
191 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
192 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
193 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
196 Expr::Loop { body, label } => {
197 self.breakables.push(BreakableContext {
199 break_ty: self.table.new_type_var(),
200 label: label.map(|label| self.body[label].name.clone()),
202 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
204 let ctxt = self.breakables.pop().expect("breakable stack broken");
206 self.diverges = Diverges::Maybe;
212 TyKind::Never.intern(&Interner)
215 Expr::While { condition, body, label } => {
216 self.breakables.push(BreakableContext {
218 break_ty: self.err_ty(),
219 label: label.map(|label| self.body[label].name.clone()),
221 // while let is desugared to a match loop, so this is always simple while
224 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
226 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
227 let _ctxt = self.breakables.pop().expect("breakable stack broken");
228 // the body may not run, so it diverging doesn't mean we diverge
229 self.diverges = Diverges::Maybe;
232 Expr::For { iterable, body, pat, label } => {
233 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
235 self.breakables.push(BreakableContext {
237 break_ty: self.err_ty(),
238 label: label.map(|label| self.body[label].name.clone()),
241 self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
243 self.infer_pat(*pat, &pat_ty, BindingMode::default());
245 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
246 let _ctxt = self.breakables.pop().expect("breakable stack broken");
247 // the body may not run, so it diverging doesn't mean we diverge
248 self.diverges = Diverges::Maybe;
251 Expr::Lambda { body, args, ret_type, arg_types } => {
252 assert_eq!(args.len(), arg_types.len());
254 let mut sig_tys = Vec::new();
256 // collect explicitly written argument types
257 for arg_type in arg_types.iter() {
258 let arg_ty = if let Some(type_ref) = arg_type {
259 self.make_ty(type_ref)
261 self.table.new_type_var()
263 sig_tys.push(arg_ty);
267 let ret_ty = match ret_type {
268 Some(type_ref) => self.make_ty(type_ref),
269 None => self.table.new_type_var(),
271 sig_tys.push(ret_ty.clone());
272 let sig_ty = TyKind::Function(FnPointer {
274 sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
275 substitution: FnSubst(
276 Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
280 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
282 TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty))
285 // Eagerly try to relate the closure type with the expected
286 // type, otherwise we often won't have enough information to
288 if let Some(t) = expected.only_has_type(&mut self.table) {
289 self.coerce(&closure_ty, &t);
292 // Now go through the argument patterns
293 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
294 self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
297 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
298 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
300 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
302 self.diverges = prev_diverges;
303 self.return_ty = prev_ret_ty;
307 Expr::Call { callee, args } => {
308 let callee_ty = self.infer_expr(*callee, &Expectation::none());
309 let canonicalized = self.canonicalize(callee_ty.clone());
310 let mut derefs = autoderef(
312 self.resolver.krate(),
314 goal: canonicalized.value.clone(),
315 environment: self.table.trait_env.env.clone(),
318 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
319 .find_map(|callee_deref_ty| {
321 &canonicalized.decanonicalize_ty(callee_deref_ty.value),
325 .unwrap_or((Vec::new(), self.err_ty()));
326 self.register_obligations_for_call(&callee_ty);
327 self.check_call_arguments(args, ¶m_tys);
328 self.normalize_associated_types_in(ret_ty)
330 Expr::MethodCall { receiver, args, method_name, generic_args } => self
336 generic_args.as_deref(),
338 Expr::Match { expr, arms } => {
339 let input_ty = self.infer_expr(*expr, &Expectation::none());
341 let mut result_ty = if arms.is_empty() {
342 TyKind::Never.intern(&Interner)
344 self.table.new_type_var()
347 let matchee_diverges = self.diverges;
348 let mut all_arms_diverge = Diverges::Always;
351 self.diverges = Diverges::Maybe;
352 let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
353 if let Some(guard_expr) = arm.guard {
356 &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
360 let arm_ty = self.infer_expr_inner(arm.expr, &expected);
361 all_arms_diverge &= self.diverges;
362 result_ty = self.coerce_merge_branch(Some(arm.expr), &result_ty, &arm_ty);
365 self.diverges = matchee_diverges | all_arms_diverge;
370 // FIXME this could be more efficient...
371 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
372 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
374 Expr::Continue { .. } => TyKind::Never.intern(&Interner),
375 Expr::Break { expr, label } => {
377 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
378 ctxt.break_ty.clone()
383 let val_ty = if let Some(expr) = expr {
384 self.infer_expr(*expr, &Expectation::none())
389 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
390 let merged_type = self.coerce_merge_branch(*expr, &last_ty, &val_ty);
392 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
393 ctxt.break_ty = merged_type;
394 ctxt.may_break = true;
396 self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
400 TyKind::Never.intern(&Interner)
402 Expr::Return { expr } => {
403 if let Some(expr) = expr {
404 self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
406 let unit = TyBuilder::unit();
407 self.coerce(&unit, &self.return_ty.clone());
409 TyKind::Never.intern(&Interner)
411 Expr::Yield { expr } => {
412 // FIXME: track yield type for coercion
413 if let Some(expr) = expr {
414 self.infer_expr(*expr, &Expectation::none());
416 TyKind::Never.intern(&Interner)
418 Expr::RecordLit { path, fields, spread } => {
419 let (ty, def_id) = self.resolve_variant(path.as_deref());
420 if let Some(variant) = def_id {
421 self.write_variant_resolution(tgt_expr.into(), variant);
424 if let Some(t) = expected.only_has_type(&mut self.table) {
430 .map(|(_, s)| s.clone())
431 .unwrap_or_else(|| Substitution::empty(&Interner));
432 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
433 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
434 for field in fields.iter() {
436 variant_data.as_ref().and_then(|it| match it.field(&field.name) {
437 Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
439 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
445 let field_ty = field_def.map_or(self.err_ty(), |it| {
446 field_types[it.local_id].clone().substitute(&Interner, &substs)
448 self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
450 if let Some(expr) = spread {
451 self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
455 Expr::Field { expr, name } => {
456 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
457 let canonicalized = self.canonicalize(receiver_ty);
458 let ty = autoderef::autoderef(
460 self.resolver.krate(),
462 goal: canonicalized.value.clone(),
463 environment: self.trait_env.env.clone(),
466 .find_map(|derefed_ty| {
467 let def_db = self.db.upcast();
468 let module = self.resolver.module();
469 let is_visible = |field_id: &FieldId| {
472 self.db.field_visibilities(field_id.parent)[field_id.local_id]
473 .is_visible_from(def_db, mod_id)
477 match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
478 TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
482 .map(|a| a.assert_ty_ref(&Interner))
485 TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
486 let local_id = self.db.struct_data(*s).variant_data.field(name)?;
487 let field = FieldId { parent: (*s).into(), local_id };
488 if is_visible(&field) {
489 self.write_field_resolution(tgt_expr, field);
491 self.db.field_types((*s).into())[field.local_id]
493 .substitute(&Interner, ¶meters),
499 TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
500 let local_id = self.db.union_data(*u).variant_data.field(name)?;
501 let field = FieldId { parent: (*u).into(), local_id };
502 if is_visible(&field) {
503 self.write_field_resolution(tgt_expr, field);
505 self.db.field_types((*u).into())[field.local_id]
507 .substitute(&Interner, ¶meters),
516 .unwrap_or(self.err_ty());
517 let ty = self.insert_type_vars(ty);
518 self.normalize_associated_types_in(ty)
520 Expr::Await { expr } => {
521 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
522 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
524 Expr::Try { expr } => {
525 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
526 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
528 Expr::Cast { expr, type_ref } => {
529 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
530 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
531 let cast_ty = self.make_ty(type_ref);
532 // FIXME check the cast...
535 Expr::Ref { expr, rawness, mutability } => {
536 let mutability = lower_to_chalk_mutability(*mutability);
537 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
538 .only_has_type(&mut self.table)
540 .and_then(|t| t.as_reference_or_ptr())
542 if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
543 // FIXME: record type error - expected mut reference but found shared ref,
544 // which cannot be coerced
546 if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
547 // FIXME: record type error - expected reference but found ptr,
548 // which cannot be coerced
550 Expectation::rvalue_hint(Ty::clone(exp_inner))
554 let inner_ty = self.infer_expr_inner(*expr, &expectation);
556 Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
557 Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
561 Expr::Box { expr } => {
562 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
563 if let Some(box_) = self.resolve_boxed_box() {
564 TyBuilder::adt(self.db, box_)
566 .fill_with_defaults(self.db, || self.table.new_type_var())
572 Expr::UnaryOp { expr, op } => {
573 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
574 let inner_ty = self.resolve_ty_shallow(&inner_ty);
576 UnaryOp::Deref => match self.resolver.krate() {
578 let canonicalized = self.canonicalize(inner_ty);
579 match autoderef::deref(
583 goal: &canonicalized.value,
584 environment: self.trait_env.env.clone(),
587 Some(derefed_ty) => {
588 canonicalized.decanonicalize_ty(derefed_ty.value)
590 None => self.err_ty(),
593 None => self.err_ty(),
596 match inner_ty.kind(&Interner) {
597 // Fast path for builtins
598 TyKind::Scalar(Scalar::Int(_))
599 | TyKind::Scalar(Scalar::Uint(_))
600 | TyKind::Scalar(Scalar::Float(_))
601 | TyKind::InferenceVar(_, TyVariableKind::Integer)
602 | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
603 // Otherwise we resolve via the std::ops::Neg trait
605 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
609 match inner_ty.kind(&Interner) {
610 // Fast path for builtins
611 TyKind::Scalar(Scalar::Bool)
612 | TyKind::Scalar(Scalar::Int(_))
613 | TyKind::Scalar(Scalar::Uint(_))
614 | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
615 // Otherwise we resolve via the std::ops::Not trait
617 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
622 Expr::BinaryOp { lhs, rhs, op } => match op {
624 let lhs_expectation = match op {
625 BinaryOp::LogicOp(..) => {
626 Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
628 _ => Expectation::none(),
630 let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
631 let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
632 let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
633 let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
634 let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
636 let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
638 if ret.is_unknown() {
639 cov_mark::hit!(infer_expr_inner_binary_operator_overload);
641 self.resolve_associated_type_with_params(
643 self.resolve_binary_op_output(op),
652 Expr::Range { lhs, rhs, range_type } => {
653 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
654 let rhs_expect = lhs_ty
656 .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
657 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
658 match (range_type, lhs_ty, rhs_ty) {
659 (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
660 Some(adt) => TyBuilder::adt(self.db, adt).build(),
661 None => self.err_ty(),
663 (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
664 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
665 None => self.err_ty(),
667 (RangeOp::Inclusive, None, Some(ty)) => {
668 match self.resolve_range_to_inclusive() {
669 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
670 None => self.err_ty(),
673 (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
674 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
675 None => self.err_ty(),
677 (RangeOp::Inclusive, Some(_), Some(ty)) => {
678 match self.resolve_range_inclusive() {
679 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
680 None => self.err_ty(),
683 (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
684 Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
685 None => self.err_ty(),
687 (RangeOp::Inclusive, _, None) => self.err_ty(),
690 Expr::Index { base, index } => {
691 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
692 let index_ty = self.infer_expr(*index, &Expectation::none());
694 if let (Some(index_trait), Some(krate)) =
695 (self.resolve_ops_index(), self.resolver.krate())
697 let canonicalized = self.canonicalize(base_ty);
698 let self_ty = method_resolution::resolve_indexing_op(
700 &canonicalized.value,
701 self.trait_env.clone(),
706 self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
707 self.resolve_associated_type_with_params(
709 self.resolve_ops_index_output(),
716 Expr::Tuple { exprs } => {
717 let mut tys = match expected
718 .only_has_type(&mut self.table)
720 .map(|t| t.kind(&Interner))
722 Some(TyKind::Tuple(_, substs)) => substs
724 .map(|a| a.assert_ty_ref(&Interner).clone())
725 .chain(repeat_with(|| self.table.new_type_var()))
727 .collect::<Vec<_>>(),
728 _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
731 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
732 self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
735 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
737 Expr::Array(array) => {
739 match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(&Interner)) {
740 Some(TyKind::Array(st, _)) | Some(TyKind::Slice(st)) => st.clone(),
741 _ => self.table.new_type_var(),
744 let len = match array {
745 Array::ElementList(items) => {
746 for expr in items.iter() {
747 // FIXME: use CoerceMany (coerce_merge_branch)
748 self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
750 Some(items.len() as u64)
752 Array::Repeat { initializer, repeat } => {
753 self.infer_expr_coerce(
755 &Expectation::has_type(elem_ty.clone()),
759 &Expectation::has_type(
760 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
764 let repeat_expr = &self.body.exprs[*repeat];
765 consteval::eval_usize(repeat_expr)
769 TyKind::Array(elem_ty, consteval::usize_const(len)).intern(&Interner)
771 Expr::Literal(lit) => match lit {
772 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
773 Literal::String(..) => {
774 TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
777 Literal::ByteString(bs) => {
778 let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
780 let len = consteval::usize_const(Some(bs.len() as u64));
782 let array_type = TyKind::Array(byte_type, len).intern(&Interner);
783 TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
785 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
786 Literal::Int(_v, ty) => match ty {
788 TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
791 None => self.table.new_integer_var(),
793 Literal::Uint(_v, ty) => match ty {
795 TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
798 None => self.table.new_integer_var(),
800 Literal::Float(_v, ty) => match ty {
802 TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
805 None => self.table.new_float_var(),
808 Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
810 // use a new type variable if we got unknown here
811 let ty = self.insert_type_vars_shallow(ty);
812 self.write_expr_ty(tgt_expr, ty.clone());
818 statements: &[Statement],
819 tail: Option<ExprId>,
820 expected: &Expectation,
822 for stmt in statements {
824 Statement::Let { pat, type_ref, initializer } => {
826 type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
828 // Always use the declared type when specified
829 let mut ty = decl_ty.clone();
831 if let Some(expr) = initializer {
833 self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
834 if decl_ty.is_unknown() {
839 self.infer_pat(*pat, &ty, BindingMode::default());
841 Statement::Expr { expr, .. } => {
842 self.infer_expr(*expr, &Expectation::none());
847 let ty = if let Some(expr) = tail {
848 self.infer_expr_coerce(expr, expected)
850 // Citing rustc: if there is no explicit tail expression,
851 // that is typically equivalent to a tail expression
852 // of `()` -- except if the block diverges. In that
853 // case, there is no value supplied from the tail
854 // expression (assuming there are no other breaks,
855 // this implies that the type of the block will be
857 if self.diverges.is_always() {
858 // we don't even make an attempt at coercion
859 self.table.new_maybe_never_var()
861 if let Some(t) = expected.only_has_type(&mut self.table) {
862 self.coerce(&TyBuilder::unit(), &t);
870 fn infer_method_call(
876 generic_args: Option<&GenericArgs>,
878 let receiver_ty = self.infer_expr(receiver, &Expectation::none());
879 let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
881 let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
883 let resolved = self.resolver.krate().and_then(|krate| {
884 method_resolution::lookup_method(
885 &canonicalized_receiver.value,
887 self.trait_env.clone(),
890 self.resolver.module(),
894 let (derefed_receiver_ty, method_ty, substs) = match resolved {
895 Some((ty, func)) => {
896 let ty = canonicalized_receiver.decanonicalize_ty(ty);
897 let generics = generics(self.db.upcast(), func.into());
898 let substs = self.substs_for_method_call(generics, generic_args, &ty);
899 self.write_method_resolution(tgt_expr, func, substs.clone());
900 (ty, self.db.value_ty(func.into()), substs)
904 Binders::empty(&Interner, self.err_ty()),
905 Substitution::empty(&Interner),
908 let method_ty = method_ty.substitute(&Interner, &substs);
909 self.register_obligations_for_call(&method_ty);
910 let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
912 if !sig.params().is_empty() {
913 (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
915 (self.err_ty(), Vec::new(), sig.ret().clone())
918 None => (self.err_ty(), Vec::new(), self.err_ty()),
920 // Apply autoref so the below unification works correctly
921 // FIXME: return correct autorefs from lookup_method
922 let actual_receiver_ty = match self.resolve_ty_shallow(&expected_receiver_ty).as_reference()
924 Some((_, lifetime, mutability)) => {
925 TyKind::Ref(mutability, lifetime, derefed_receiver_ty).intern(&Interner)
927 _ => derefed_receiver_ty,
929 self.unify(&expected_receiver_ty, &actual_receiver_ty);
931 self.check_call_arguments(args, ¶m_tys);
932 self.normalize_associated_types_in(ret_ty)
935 fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
936 // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
937 // We do this in a pretty awful way: first we type-check any arguments
938 // that are not closures, then we type-check the closures. This is so
939 // that we have more information about the types of arguments when we
940 // type-check the functions. This isn't really the right way to do this.
941 for &check_closures in &[false, true] {
942 let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
943 for (&arg, param_ty) in args.iter().zip(param_iter) {
944 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
945 if is_closure != check_closures {
949 let param_ty = self.normalize_associated_types_in(param_ty);
950 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
955 fn substs_for_method_call(
957 def_generics: Generics,
958 generic_args: Option<&GenericArgs>,
961 let (parent_params, self_params, type_params, impl_trait_params) =
962 def_generics.provenance_split();
963 assert_eq!(self_params, 0); // method shouldn't have another Self param
964 let total_len = parent_params + type_params + impl_trait_params;
965 let mut substs = Vec::with_capacity(total_len);
966 // Parent arguments are unknown, except for the receiver type
967 for (_id, param) in def_generics.iter_parent() {
968 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
969 substs.push(receiver_ty.clone());
971 substs.push(self.table.new_type_var());
974 // handle provided type arguments
975 if let Some(generic_args) = generic_args {
976 // if args are provided, it should be all of them, but we can't rely on that
977 for arg in generic_args
980 .filter(|arg| matches!(arg, GenericArg::Type(_)))
984 GenericArg::Type(type_ref) => {
985 let ty = self.make_ty(type_ref);
988 GenericArg::Lifetime(_) => {}
992 let supplied_params = substs.len();
993 for _ in supplied_params..total_len {
994 substs.push(self.table.new_type_var());
996 assert_eq!(substs.len(), total_len);
997 Substitution::from_iter(&Interner, substs)
1000 fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1001 let callable_ty = self.resolve_ty_shallow(&callable_ty);
1002 if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
1003 let def: CallableDefId = from_chalk(self.db, *fn_def);
1004 let generic_predicates = self.db.generic_predicates(def.into());
1005 for predicate in generic_predicates.iter() {
1006 let (predicate, binders) = predicate
1008 .substitute(&Interner, parameters)
1009 .into_value_and_skipped_binders();
1010 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
1011 self.push_obligation(predicate.cast(&Interner));
1013 // add obligation for trait implementation, if this is a trait method
1015 CallableDefId::FunctionId(f) => {
1016 if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1018 // construct a TraitRef
1019 let substs = crate::subst_prefix(
1021 generics(self.db.upcast(), trait_.into()).len(),
1023 self.push_obligation(
1024 TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1029 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}