//! Type inference for expressions. use std::iter::{repeat, repeat_with}; use std::sync::Arc; use hir_def::{ builtin_type::Signedness, expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp}, generics::GenericParams, path::{GenericArg, GenericArgs}, resolver::resolver_for_expr, AdtId, ContainerId, Lookup, StructFieldId, }; use hir_expand::name::{self, Name}; use ra_syntax::ast::RangeOp; use crate::{ autoderef, db::HirDatabase, method_resolution, op, traits::InEnvironment, utils::variant_data, CallableDef, InferTy, IntTy, Mutability, Obligation, ProjectionPredicate, ProjectionTy, Substs, TraitRef, Ty, TypeCtor, TypeWalk, Uncertain, }; use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch}; impl<'a, D: HirDatabase> InferenceContext<'a, D> { pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty { let ty = self.infer_expr_inner(tgt_expr, expected); let could_unify = self.unify(&ty, &expected.ty); if !could_unify { self.result.type_mismatches.insert( tgt_expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() }, ); } let ty = self.resolve_ty_as_possible(ty); ty } /// Infer type of expression with possibly implicit coerce to the expected type. /// Return the type after possible coercion. fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty { let ty = self.infer_expr_inner(expr, &expected); let ty = if !self.coerce(&ty, &expected.ty) { self.result .type_mismatches .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() }); // Return actual type when type mismatch. // This is needed for diagnostic when return type mismatch. ty } else if expected.ty == Ty::Unknown { ty } else { expected.ty.clone() }; self.resolve_ty_as_possible(ty) } fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty { let body = Arc::clone(&self.body); // avoid borrow checker problem let ty = match &body[tgt_expr] { Expr::Missing => Ty::Unknown, Expr::If { condition, then_branch, else_branch } => { // if let is desugared to match, so this is always simple if self.infer_expr(*condition, &Expectation::has_type(Ty::simple(TypeCtor::Bool))); let then_ty = self.infer_expr_inner(*then_branch, &expected); let else_ty = match else_branch { Some(else_branch) => self.infer_expr_inner(*else_branch, &expected), None => Ty::unit(), }; self.coerce_merge_branch(&then_ty, &else_ty) } Expr::Block { statements, tail } => self.infer_block(statements, *tail, expected), Expr::TryBlock { body } => { let _inner = self.infer_expr(*body, expected); // FIXME should be std::result::Result<{inner}, _> Ty::Unknown } Expr::Loop { body } => { self.infer_expr(*body, &Expectation::has_type(Ty::unit())); // FIXME handle break with value Ty::simple(TypeCtor::Never) } Expr::While { condition, body } => { // while let is desugared to a match loop, so this is always simple while self.infer_expr(*condition, &Expectation::has_type(Ty::simple(TypeCtor::Bool))); self.infer_expr(*body, &Expectation::has_type(Ty::unit())); Ty::unit() } Expr::For { iterable, body, pat } => { let iterable_ty = self.infer_expr(*iterable, &Expectation::none()); let pat_ty = match self.resolve_into_iter_item() { Some(into_iter_item_alias) => { let pat_ty = self.table.new_type_var(); let projection = ProjectionPredicate { ty: pat_ty.clone(), projection_ty: ProjectionTy { associated_ty: into_iter_item_alias, parameters: Substs::single(iterable_ty), }, }; self.obligations.push(Obligation::Projection(projection)); self.resolve_ty_as_possible(pat_ty) } None => Ty::Unknown, }; self.infer_pat(*pat, &pat_ty, BindingMode::default()); self.infer_expr(*body, &Expectation::has_type(Ty::unit())); Ty::unit() } Expr::Lambda { body, args, arg_types } => { assert_eq!(args.len(), arg_types.len()); let mut sig_tys = Vec::new(); for (arg_pat, arg_type) in args.iter().zip(arg_types.iter()) { let expected = if let Some(type_ref) = arg_type { self.make_ty(type_ref) } else { Ty::Unknown }; let arg_ty = self.infer_pat(*arg_pat, &expected, BindingMode::default()); sig_tys.push(arg_ty); } // add return type let ret_ty = self.table.new_type_var(); sig_tys.push(ret_ty.clone()); let sig_ty = Ty::apply( TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1 }, Substs(sig_tys.into()), ); let closure_ty = Ty::apply_one( TypeCtor::Closure { def: self.owner.into(), expr: tgt_expr }, sig_ty, ); // Eagerly try to relate the closure type with the expected // type, otherwise we often won't have enough information to // infer the body. self.coerce(&closure_ty, &expected.ty); self.infer_expr(*body, &Expectation::has_type(ret_ty)); closure_ty } Expr::Call { callee, args } => { let callee_ty = self.infer_expr(*callee, &Expectation::none()); let (param_tys, ret_ty) = match callee_ty.callable_sig(self.db) { Some(sig) => (sig.params().to_vec(), sig.ret().clone()), None => { // Not callable // FIXME: report an error (Vec::new(), Ty::Unknown) } }; self.register_obligations_for_call(&callee_ty); self.check_call_arguments(args, ¶m_tys); let ret_ty = self.normalize_associated_types_in(ret_ty); ret_ty } Expr::MethodCall { receiver, args, method_name, generic_args } => self .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()), Expr::Match { expr, arms } => { let input_ty = self.infer_expr(*expr, &Expectation::none()); let mut result_ty = self.table.new_maybe_never_type_var(); for arm in arms { for &pat in &arm.pats { let _pat_ty = self.infer_pat(pat, &input_ty, BindingMode::default()); } if let Some(guard_expr) = arm.guard { self.infer_expr( guard_expr, &Expectation::has_type(Ty::simple(TypeCtor::Bool)), ); } let arm_ty = self.infer_expr_inner(arm.expr, &expected); result_ty = self.coerce_merge_branch(&result_ty, &arm_ty); } result_ty } Expr::Path(p) => { // FIXME this could be more efficient... let resolver = resolver_for_expr(self.db, self.owner.into(), tgt_expr); self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(Ty::Unknown) } Expr::Continue => Ty::simple(TypeCtor::Never), Expr::Break { expr } => { if let Some(expr) = expr { // FIXME handle break with value self.infer_expr(*expr, &Expectation::none()); } Ty::simple(TypeCtor::Never) } Expr::Return { expr } => { if let Some(expr) = expr { self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone())); } Ty::simple(TypeCtor::Never) } Expr::RecordLit { path, fields, spread } => { let (ty, def_id) = self.resolve_variant(path.as_ref()); if let Some(variant) = def_id { self.write_variant_resolution(tgt_expr.into(), variant); } self.unify(&ty, &expected.ty); let substs = ty.substs().unwrap_or_else(Substs::empty); let field_types = def_id.map(|it| self.db.field_types(it.into())).unwrap_or_default(); let variant_data = def_id.map(|it| variant_data(self.db, it)); for (field_idx, field) in fields.iter().enumerate() { let field_def = variant_data.as_ref().and_then(|it| match it.field(&field.name) { Some(local_id) => { Some(StructFieldId { parent: def_id.unwrap(), local_id }) } None => { self.push_diagnostic(InferenceDiagnostic::NoSuchField { expr: tgt_expr, field: field_idx, }); None } }); if let Some(field_def) = field_def { self.result.record_field_resolutions.insert(field.expr, field_def); } let field_ty = field_def .map_or(Ty::Unknown, |it| field_types[it.local_id].clone()) .subst(&substs); self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty)); } if let Some(expr) = spread { self.infer_expr(*expr, &Expectation::has_type(ty.clone())); } ty } Expr::Field { expr, name } => { let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none()); let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty); let ty = autoderef::autoderef( self.db, self.resolver.krate(), InEnvironment { value: canonicalized.value.clone(), environment: self.trait_env.clone(), }, ) .find_map(|derefed_ty| match canonicalized.decanonicalize_ty(derefed_ty.value) { Ty::Apply(a_ty) => match a_ty.ctor { TypeCtor::Tuple { .. } => name .as_tuple_index() .and_then(|idx| a_ty.parameters.0.get(idx).cloned()), TypeCtor::Adt(AdtId::StructId(s)) => { self.db.struct_data(s).variant_data.field(name).map(|local_id| { let field = StructFieldId { parent: s.into(), local_id }.into(); self.write_field_resolution(tgt_expr, field); self.db.field_types(s.into())[field.local_id] .clone() .subst(&a_ty.parameters) }) } // FIXME: TypeCtor::Adt(AdtId::UnionId(_)) => None, _ => None, }, _ => None, }) .unwrap_or(Ty::Unknown); let ty = self.insert_type_vars(ty); self.normalize_associated_types_in(ty) } Expr::Await { expr } => { let inner_ty = self.infer_expr_inner(*expr, &Expectation::none()); let ty = match self.resolve_future_future_output() { Some(future_future_output_alias) => { let ty = self.table.new_type_var(); let projection = ProjectionPredicate { ty: ty.clone(), projection_ty: ProjectionTy { associated_ty: future_future_output_alias, parameters: Substs::single(inner_ty), }, }; self.obligations.push(Obligation::Projection(projection)); self.resolve_ty_as_possible(ty) } None => Ty::Unknown, }; ty } Expr::Try { expr } => { let inner_ty = self.infer_expr_inner(*expr, &Expectation::none()); let ty = match self.resolve_ops_try_ok() { Some(ops_try_ok_alias) => { let ty = self.table.new_type_var(); let projection = ProjectionPredicate { ty: ty.clone(), projection_ty: ProjectionTy { associated_ty: ops_try_ok_alias, parameters: Substs::single(inner_ty), }, }; self.obligations.push(Obligation::Projection(projection)); self.resolve_ty_as_possible(ty) } None => Ty::Unknown, }; ty } Expr::Cast { expr, type_ref } => { let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none()); let cast_ty = self.make_ty(type_ref); // FIXME check the cast... cast_ty } Expr::Ref { expr, mutability } => { let expectation = if let Some((exp_inner, exp_mutability)) = &expected.ty.as_reference() { if *exp_mutability == Mutability::Mut && *mutability == Mutability::Shared { // FIXME: throw type error - expected mut reference but found shared ref, // which cannot be coerced } Expectation::has_type(Ty::clone(exp_inner)) } else { Expectation::none() }; let inner_ty = self.infer_expr_inner(*expr, &expectation); Ty::apply_one(TypeCtor::Ref(*mutability), inner_ty) } Expr::Box { expr } => { let inner_ty = self.infer_expr_inner(*expr, &Expectation::none()); if let Some(box_) = self.resolve_boxed_box() { Ty::apply_one(TypeCtor::Adt(box_), inner_ty) } else { Ty::Unknown } } Expr::UnaryOp { expr, op } => { let inner_ty = self.infer_expr_inner(*expr, &Expectation::none()); match op { UnaryOp::Deref => match self.resolver.krate() { Some(krate) => { let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty); match autoderef::deref( self.db, krate, InEnvironment { value: &canonicalized.value, environment: self.trait_env.clone(), }, ) { Some(derefed_ty) => { canonicalized.decanonicalize_ty(derefed_ty.value) } None => Ty::Unknown, } } None => Ty::Unknown, }, UnaryOp::Neg => { match &inner_ty { Ty::Apply(a_ty) => match a_ty.ctor { TypeCtor::Int(Uncertain::Unknown) | TypeCtor::Int(Uncertain::Known(IntTy { signedness: Signedness::Signed, .. })) | TypeCtor::Float(..) => inner_ty, _ => Ty::Unknown, }, Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => { inner_ty } // FIXME: resolve ops::Neg trait _ => Ty::Unknown, } } UnaryOp::Not => { match &inner_ty { Ty::Apply(a_ty) => match a_ty.ctor { TypeCtor::Bool | TypeCtor::Int(_) => inner_ty, _ => Ty::Unknown, }, Ty::Infer(InferTy::IntVar(..)) => inner_ty, // FIXME: resolve ops::Not trait for inner_ty _ => Ty::Unknown, } } } } Expr::BinaryOp { lhs, rhs, op } => match op { Some(op) => { let lhs_expectation = match op { BinaryOp::LogicOp(..) => Expectation::has_type(Ty::simple(TypeCtor::Bool)), _ => Expectation::none(), }; let lhs_ty = self.infer_expr(*lhs, &lhs_expectation); // FIXME: find implementation of trait corresponding to operation // symbol and resolve associated `Output` type let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty); let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation)); // FIXME: similar as above, return ty is often associated trait type op::binary_op_return_ty(*op, rhs_ty) } _ => Ty::Unknown, }, Expr::Range { lhs, rhs, range_type } => { let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none())); let rhs_expect = lhs_ty .as_ref() .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone())); let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect)); match (range_type, lhs_ty, rhs_ty) { (RangeOp::Exclusive, None, None) => match self.resolve_range_full() { Some(adt) => Ty::simple(TypeCtor::Adt(adt)), None => Ty::Unknown, }, (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() { Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty), None => Ty::Unknown, }, (RangeOp::Inclusive, None, Some(ty)) => { match self.resolve_range_to_inclusive() { Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty), None => Ty::Unknown, } } (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() { Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty), None => Ty::Unknown, }, (RangeOp::Inclusive, Some(_), Some(ty)) => { match self.resolve_range_inclusive() { Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty), None => Ty::Unknown, } } (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() { Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty), None => Ty::Unknown, }, (RangeOp::Inclusive, _, None) => Ty::Unknown, } } Expr::Index { base, index } => { let _base_ty = self.infer_expr_inner(*base, &Expectation::none()); let _index_ty = self.infer_expr(*index, &Expectation::none()); // FIXME: use `std::ops::Index::Output` to figure out the real return type Ty::Unknown } Expr::Tuple { exprs } => { let mut tys = match &expected.ty { ty_app!(TypeCtor::Tuple { .. }, st) => st .iter() .cloned() .chain(repeat_with(|| self.table.new_type_var())) .take(exprs.len()) .collect::>(), _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(), }; for (expr, ty) in exprs.iter().zip(tys.iter_mut()) { self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone())); } Ty::apply(TypeCtor::Tuple { cardinality: tys.len() as u16 }, Substs(tys.into())) } Expr::Array(array) => { let elem_ty = match &expected.ty { ty_app!(TypeCtor::Array, st) | ty_app!(TypeCtor::Slice, st) => { st.as_single().clone() } _ => self.table.new_type_var(), }; match array { Array::ElementList(items) => { for expr in items.iter() { self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone())); } } Array::Repeat { initializer, repeat } => { self.infer_expr_coerce( *initializer, &Expectation::has_type(elem_ty.clone()), ); self.infer_expr( *repeat, &Expectation::has_type(Ty::simple(TypeCtor::Int(Uncertain::Known( IntTy::usize(), )))), ); } } Ty::apply_one(TypeCtor::Array, elem_ty) } Expr::Literal(lit) => match lit { Literal::Bool(..) => Ty::simple(TypeCtor::Bool), Literal::String(..) => { Ty::apply_one(TypeCtor::Ref(Mutability::Shared), Ty::simple(TypeCtor::Str)) } Literal::ByteString(..) => { let byte_type = Ty::simple(TypeCtor::Int(Uncertain::Known(IntTy::u8()))); let slice_type = Ty::apply_one(TypeCtor::Slice, byte_type); Ty::apply_one(TypeCtor::Ref(Mutability::Shared), slice_type) } Literal::Char(..) => Ty::simple(TypeCtor::Char), Literal::Int(_v, ty) => Ty::simple(TypeCtor::Int((*ty).into())), Literal::Float(_v, ty) => Ty::simple(TypeCtor::Float((*ty).into())), }, }; // use a new type variable if we got Ty::Unknown here let ty = self.insert_type_vars_shallow(ty); let ty = self.resolve_ty_as_possible(ty); self.write_expr_ty(tgt_expr, ty.clone()); ty } fn infer_block( &mut self, statements: &[Statement], tail: Option, expected: &Expectation, ) -> Ty { let mut diverges = false; for stmt in statements { match stmt { Statement::Let { pat, type_ref, initializer } => { let decl_ty = type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(Ty::Unknown); // Always use the declared type when specified let mut ty = decl_ty.clone(); if let Some(expr) = initializer { let actual_ty = self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone())); if decl_ty == Ty::Unknown { ty = actual_ty; } } let ty = self.resolve_ty_as_possible(ty); self.infer_pat(*pat, &ty, BindingMode::default()); } Statement::Expr(expr) => { if let ty_app!(TypeCtor::Never) = self.infer_expr(*expr, &Expectation::none()) { diverges = true; } } } } let ty = if let Some(expr) = tail { self.infer_expr_coerce(expr, expected) } else { self.coerce(&Ty::unit(), &expected.ty); Ty::unit() }; if diverges { Ty::simple(TypeCtor::Never) } else { ty } } fn infer_method_call( &mut self, tgt_expr: ExprId, receiver: ExprId, args: &[ExprId], method_name: &Name, generic_args: Option<&GenericArgs>, ) -> Ty { let receiver_ty = self.infer_expr(receiver, &Expectation::none()); let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone()); let resolved = method_resolution::lookup_method( &canonicalized_receiver.value, self.db, method_name, &self.resolver, ); let (derefed_receiver_ty, method_ty, def_generics) = match resolved { Some((ty, func)) => { let ty = canonicalized_receiver.decanonicalize_ty(ty); self.write_method_resolution(tgt_expr, func); (ty, self.db.value_ty(func.into()), Some(self.db.generic_params(func.into()))) } None => (receiver_ty, Ty::Unknown, None), }; let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty); let method_ty = method_ty.apply_substs(substs); let method_ty = self.insert_type_vars(method_ty); self.register_obligations_for_call(&method_ty); let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) { Some(sig) => { if !sig.params().is_empty() { (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone()) } else { (Ty::Unknown, Vec::new(), sig.ret().clone()) } } None => (Ty::Unknown, Vec::new(), Ty::Unknown), }; // Apply autoref so the below unification works correctly // FIXME: return correct autorefs from lookup_method let actual_receiver_ty = match expected_receiver_ty.as_reference() { Some((_, mutability)) => Ty::apply_one(TypeCtor::Ref(mutability), derefed_receiver_ty), _ => derefed_receiver_ty, }; self.unify(&expected_receiver_ty, &actual_receiver_ty); self.check_call_arguments(args, ¶m_tys); let ret_ty = self.normalize_associated_types_in(ret_ty); ret_ty } fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) { // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 -- // We do this in a pretty awful way: first we type-check any arguments // that are not closures, then we type-check the closures. This is so // that we have more information about the types of arguments when we // type-check the functions. This isn't really the right way to do this. for &check_closures in &[false, true] { let param_iter = param_tys.iter().cloned().chain(repeat(Ty::Unknown)); for (&arg, param_ty) in args.iter().zip(param_iter) { let is_closure = match &self.body[arg] { Expr::Lambda { .. } => true, _ => false, }; if is_closure != check_closures { continue; } let param_ty = self.normalize_associated_types_in(param_ty); self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone())); } } } fn substs_for_method_call( &mut self, def_generics: Option>, generic_args: Option<&GenericArgs>, receiver_ty: &Ty, ) -> Substs { let (parent_param_count, param_count) = def_generics.as_ref().map_or((0, 0), |g| (g.count_parent_params(), g.params.len())); let mut substs = Vec::with_capacity(parent_param_count + param_count); // Parent arguments are unknown, except for the receiver type if let Some(parent_generics) = def_generics.and_then(|p| p.parent_params.clone()) { for (_id, param) in parent_generics.params.iter() { if param.name == name::SELF_TYPE { substs.push(receiver_ty.clone()); } else { substs.push(Ty::Unknown); } } } // handle provided type arguments if let Some(generic_args) = generic_args { // if args are provided, it should be all of them, but we can't rely on that for arg in generic_args.args.iter().take(param_count) { match arg { GenericArg::Type(type_ref) => { let ty = self.make_ty(type_ref); substs.push(ty); } } } }; let supplied_params = substs.len(); for _ in supplied_params..parent_param_count + param_count { substs.push(Ty::Unknown); } assert_eq!(substs.len(), parent_param_count + param_count); Substs(substs.into()) } fn register_obligations_for_call(&mut self, callable_ty: &Ty) { if let Ty::Apply(a_ty) = callable_ty { if let TypeCtor::FnDef(def) = a_ty.ctor { let generic_predicates = self.db.generic_predicates(def.into()); for predicate in generic_predicates.iter() { let predicate = predicate.clone().subst(&a_ty.parameters); if let Some(obligation) = Obligation::from_predicate(predicate) { self.obligations.push(obligation); } } // add obligation for trait implementation, if this is a trait method match def { CallableDef::FunctionId(f) => { if let ContainerId::TraitId(trait_) = f.lookup(self.db).container { // construct a TraitDef let substs = a_ty.parameters.prefix( self.db .generic_params(trait_.into()) .count_params_including_parent(), ); self.obligations.push(Obligation::Trait(TraitRef { trait_: trait_.into(), substs, })); } } CallableDef::StructId(_) | CallableDef::EnumVariantId(_) => {} } } } } }