Change:
<del> // ignore-tidy-filelength // FIXME: This file seems to have too much functionality wrapped into it, // leading to it being too long. // Splitting this file may involve abstracting functionality into other files. use super::callee::{self, DeferredCallResolution}; use super::coercion::{CoerceMany, DynamicCoerceMany}; use super::method::{self, MethodCallee, SelfSource}; use super::Expectation::*; use super::TupleArgumentsFlag::*; use super::{ potentially_plural_count, struct_span_err, BreakableCtxt, Diverges, EnclosingBreakables, Expectation, FallbackMode, Inherited, LocalTy, Needs, TupleArgumentsFlag, UnsafetyState, }; use crate::astconv::{ AstConv, ExplicitLateBound, GenericArgCountMismatch, GenericArgCountResult, PathSeg, }; use rustc_ast as ast; use rustc_ast::util::parser::ExprPrecedence; use rustc_data_structures::captures::Captures; use rustc_data_structures::fx::FxHashSet; use rustc_errors::ErrorReported; use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId}; use rustc_hir as hir; use rustc_hir::def::{CtorOf, DefKind, Res}; use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; use rustc_hir::{ExprKind, GenericArg, ItemKind, Node, QPath}; use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse}; use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282; use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; use rustc_infer::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind}; use rustc_infer::infer::{self, InferOk, InferResult}; use rustc_middle::hir::map::blocks::FnLikeNode; use rustc_middle::ty::adjustment::{ Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, }; use rustc_middle::ty::fold::TypeFoldable; use rustc_middle::ty::subst::{ self, GenericArgKind, InternalSubsts, Subst, SubstsRef, UserSelfTy, UserSubsts, }; use rustc_middle::ty::{ self, AdtKind, CanonicalUserType, Const, DefIdTree, GenericParamDefKind, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, UserType, }; use rustc_session::{lint, Session}; use rustc_span::hygiene::DesugaringKind; use rustc_span::source_map::{original_sp, DUMMY_SP}; use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::{self, BytePos, MultiSpan, Span}; use rustc_trait_selection::infer::InferCtxtExt as _; use rustc_trait_selection::opaque_types::InferCtxtExt as _; use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _; use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; use rustc_trait_selection::traits::{ self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt, }; use std::cell::{Cell, RefCell}; use std::collections::hash_map::Entry; use std::iter; use std::mem::replace; use std::ops::Deref; use std::slice; pub struct FnCtxt<'a, 'tcx> { pub(super) body_id: hir::HirId, /// The parameter environment used for proving trait obligations /// in this function. This can change when we descend into /// closures (as they bring new things into scope), hence it is /// not part of `Inherited` (as of the time of this writing, /// closures do not yet change the environment, but they will /// eventually). pub(super) param_env: ty::ParamEnv<'tcx>, /// Number of errors that had been reported when we started /// checking this function. On exit, if we find that *more* errors /// have been reported, we will skip regionck and other work that /// expects the types within the function to be consistent. // FIXME(matthewjasper) This should not exist, and it's not correct // if type checking is run in parallel. err_count_on_creation: usize, /// If `Some`, this stores coercion information for returned /// expressions. If `None`, this is in a context where return is /// inappropriate, such as a const expression. /// /// This is a `RefCell<DynamicCoerceMany>`, which means that we /// can track all the return expressions and then use them to /// compute a useful coercion from the set, similar to a match /// expression or other branching context. You can use methods /// like `expected_ty` to access the declared return type (if /// any). pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>, pub(super) ret_coercion_impl_trait: Option<Ty<'tcx>>, pub(super) ret_type_span: Option<Span>, /// Used exclusively to reduce cost of advanced evaluation used for /// more helpful diagnostics. pub(super) in_tail_expr: bool, /// First span of a return site that we find. Used in error messages. pub(super) ret_coercion_span: RefCell<Option<Span>>, pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>, pub(super) ps: RefCell<UnsafetyState>, /// Whether the last checked node generates a divergence (e.g., /// `return` will set this to `Always`). In general, when entering /// an expression or other node in the tree, the initial value /// indicates whether prior parts of the containing expression may /// have diverged. It is then typically set to `Maybe` (and the /// old value remembered) for processing the subparts of the /// current expression. As each subpart is processed, they may set /// the flag to `Always`, etc. Finally, at the end, we take the /// result and "union" it with the original value, so that when we /// return the flag indicates if any subpart of the parent /// expression (up to and including this part) has diverged. So, /// if you read it after evaluating a subexpression `X`, the value /// you get indicates whether any subexpression that was /// evaluating up to and including `X` diverged. /// /// We currently use this flag only for diagnostic purposes: /// /// - To warn about unreachable code: if, after processing a ///   sub-expression but before we have applied the effects of the ///   current node, we see that the flag is set to `Always`, we ///   can issue a warning. This corresponds to something like ///   `foo(return)`; we warn on the `foo()` expression. (We then ///   update the flag to `WarnedAlways` to suppress duplicate ///   reports.) Similarly, if we traverse to a fresh statement (or ///   tail expression) from a `Always` setting, we will issue a ///   warning. This corresponds to something like `{return; ///   foo();}` or `{return; 22}`, where we would warn on the ///   `foo()` or `22`. /// /// An expression represents dead code if, after checking it, /// the diverges flag is set to something other than `Maybe`. pub(super) diverges: Cell<Diverges>, /// Whether any child nodes have any type errors. pub(super) has_errors: Cell<bool>, pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>, pub(super) inh: &'a Inherited<'a, 'tcx>, } impl<'a, 'tcx> FnCtxt<'a, 'tcx> { pub fn new( inh: &'a Inherited<'a, 'tcx>, param_env: ty::ParamEnv<'tcx>, body_id: hir::HirId, ) -> FnCtxt<'a, 'tcx> { FnCtxt { body_id, param_env, err_count_on_creation: inh.tcx.sess.err_count(), ret_coercion: None, ret_coercion_impl_trait: None, ret_type_span: None, in_tail_expr: false, ret_coercion_span: RefCell::new(None), resume_yield_tys: None, ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)), diverges: Cell::new(Diverges::Maybe), has_errors: Cell::new(false), enclosing_breakables: RefCell::new(EnclosingBreakables { stack: Vec::new(), by_id: Default::default(), }), inh, } } pub fn sess(&self) -> &Session { &self.tcx.sess } pub fn errors_reported_since_creation(&self) -> bool { self.tcx.sess.err_count() > self.err_count_on_creation } /// Produces warning on the given node, if the current point in the /// function is unreachable, and there hasn't been another warning. pub(super) fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) { // FIXME: Combine these two 'if' expressions into one once // let chains are implemented if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() { // If span arose from a desugaring of `if` or `while`, then it is the condition itself, // which diverges, that we are about to lint on. This gives suboptimal diagnostics. // Instead, stop here so that the `if`- or `while`-expression's block is linted instead. if !span.is_desugaring(DesugaringKind::CondTemporary) && !span.is_desugaring(DesugaringKind::Async) && !orig_span.is_desugaring(DesugaringKind::Await) { self.diverges.set(Diverges::WarnedAlways); debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind); self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, |lint| { let msg = format!("unreachable {}", kind); lint.build(&msg) .span_label(span, &msg) .span_label( orig_span, custom_note .unwrap_or("any code following this expression is unreachable"), ) .emit(); }) } } } pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> { ObligationCause::new(span, self.body_id, code) } pub fn misc(&self, span: Span) -> ObligationCause<'tcx> { self.cause(span, ObligationCauseCode::MiscObligation) } /// Resolves type and const variables in `ty` if possible. Unlike the infcx /// version (resolve_vars_if_possible), this version will /// also select obligations if it seems useful, in an effort /// to get more type information. pub(super) fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> { debug!("resolve_vars_with_obligations(ty={:?})", ty); // No Infer()? Nothing needs doing. if !ty.has_infer_types_or_consts() { debug!("resolve_vars_with_obligations: ty={:?}", ty); return ty; } // If `ty` is a type variable, see whether we already know what it is. ty = self.resolve_vars_if_possible(&ty); if !ty.has_infer_types_or_consts() { debug!("resolve_vars_with_obligations: ty={:?}", ty); return ty; } // If not, try resolving pending obligations as much as // possible. This can help substantially when there are // indirect dependencies that don't seem worth tracking // precisely. self.select_obligations_where_possible(false, |_| {}); ty = self.resolve_vars_if_possible(&ty); debug!("resolve_vars_with_obligations: ty={:?}", ty); ty } pub(super) fn record_deferred_call_resolution( &self, closure_def_id: DefId, r: DeferredCallResolution<'tcx>, ) { let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut(); deferred_call_resolutions.entry(closure_def_id).or_default().push(r); } pub(super) fn remove_deferred_call_resolutions( &self, closure_def_id: DefId, ) -> Vec<DeferredCallResolution<'tcx>> { let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut(); deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![]) } pub fn tag(&self) -> String { format!("{:p}", self) } pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> { self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| { span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid)) }) } #[inline] pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) { debug!( "write_ty({:?}, {:?}) in fcx {}", id, self.resolve_vars_if_possible(&ty), self.tag() ); self.typeck_results.borrow_mut().node_types_mut().insert(id, ty); if ty.references_error() { self.has_errors.set(true); self.set_tainted_by_errors(); } } pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) { self.typeck_results.borrow_mut().field_indices_mut().insert(hir_id, index); } fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) { self.typeck_results.borrow_mut().type_dependent_defs_mut().insert(hir_id, r); } pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) { debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method); self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id))); self.write_substs(hir_id, method.substs); // When the method is confirmed, the `method.substs` includes // parameters from not just the method, but also the impl of // the method -- in particular, the `Self` type will be fully // resolved. However, those are not something that the "user // specified" -- i.e., those types come from the inferred type // of the receiver, not something the user wrote. So when we // create the user-substs, we want to replace those earlier // types with just the types that the user actually wrote -- // that is, those that appear on the *method itself*. // // As an example, if the user wrote something like // `foo.bar::<u32>(...)` -- the `Self` type here will be the // type of `foo` (possibly adjusted), but we don't want to // include that. We want just the `[_, u32]` part. if !method.substs.is_noop() { let method_generics = self.tcx.generics_of(method.def_id); if !method_generics.params.is_empty() { let user_type_annotation = self.infcx.probe(|_| { let user_substs = UserSubsts { substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| { let i = param.index as usize; if i < method_generics.parent_count { self.infcx.var_for_def(DUMMY_SP, param) } else { method.substs[i] } }), user_self_ty: None, // not relevant here }; self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf( method.def_id, user_substs, )) }); debug!("write_method_call: user_type_annotation={:?}", user_type_annotation); self.write_user_type_annotation(hir_id, user_type_annotation); } } } pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) { if !substs.is_noop() { debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag()); self.typeck_results.borrow_mut().node_substs_mut().insert(node_id, substs); } } /// Given the substs that we just converted from the HIR, try to /// canonicalize them and store them as user-given substitutions /// (i.e., substitutions that must be respected by the NLL check). /// /// This should be invoked **before any unifications have /// occurred**, so that annotations like `Vec<_>` are preserved /// properly. pub fn write_user_type_annotation_from_substs( &self, hir_id: hir::HirId, def_id: DefId, substs: SubstsRef<'tcx>, user_self_ty: Option<UserSelfTy<'tcx>>, ) { debug!( "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?}  user_self_ty={:?} in fcx {}", hir_id, def_id, substs, user_self_ty, self.tag(), ); if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) { let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf( def_id, UserSubsts { substs, user_self_ty }, )); debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized); self.write_user_type_annotation(hir_id, canonicalized); } } pub fn write_user_type_annotation( &self, hir_id: hir::HirId, canonical_user_type_annotation: CanonicalUserType<'tcx>, ) { debug!( "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}", hir_id, canonical_user_type_annotation, self.tag(), ); if !canonical_user_type_annotation.is_identity() { self.typeck_results .borrow_mut() .user_provided_types_mut() .insert(hir_id, canonical_user_type_annotation); } else { debug!("write_user_type_annotation: skipping identity substs"); } } pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) { debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj); if adj.is_empty() { return; } let autoborrow_mut = adj.iter().any(|adj| { matches!(adj, &Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Mut { .. })), .. }) }); match self.typeck_results.borrow_mut().adjustments_mut().entry(expr.hir_id) { Entry::Vacant(entry) => { entry.insert(adj); } Entry::Occupied(mut entry) => { debug!(" - composing on top of {:?}", entry.get()); match (&entry.get()[..], &adj[..]) { // Applying any adjustment on top of a NeverToAny // is a valid NeverToAny adjustment, because it can't // be reached. (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return, (&[ Adjustment { kind: Adjust::Deref(_), .. }, Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. }, ], &[ Adjustment { kind: Adjust::Deref(_), .. }, .. // Any following adjustments are allowed. ]) => { // A reborrow has no effect before a dereference. } // FIXME: currently we never try to compose autoderefs // and ReifyFnPointer/UnsafeFnPointer, but we could. _ => bug!("while adjusting {:?}, can't compose {:?} and {:?}", expr, entry.get(), adj) }; *entry.get_mut() = adj; } } // If there is an mutable auto-borrow, it is equivalent to `&mut <expr>`. // In this case implicit use of `Deref` and `Index` within `<expr>` should // instead be `DerefMut` and `IndexMut`, so fix those up. if autoborrow_mut { self.convert_place_derefs_to_mutable(expr); } } /// Basically whenever we are converting from a type scheme into /// the fn body space, we always want to normalize associated /// types as well. This function combines the two. fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T where T: TypeFoldable<'tcx>, { let value = value.subst(self.tcx, substs); let result = self.normalize_associated_types_in(span, &value); debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result); result } /// As `instantiate_type_scheme`, but for the bounds found in a /// generic type scheme. fn instantiate_bounds( &self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>, ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) { let bounds = self.tcx.predicates_of(def_id); let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect(); let result = bounds.instantiate(self.tcx, substs); let result = self.normalize_associated_types_in(span, &result); debug!( "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}", bounds, substs, result, spans, ); (result, spans) } /// Replaces the opaque types from the given value with type variables, /// and records the `OpaqueTypeMap` for later use during writeback. See /// `InferCtxt::instantiate_opaque_types` for more details. pub(super) fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>( &self, parent_id: hir::HirId, value: &T, value_span: Span, ) -> T { let parent_def_id = self.tcx.hir().local_def_id(parent_id); debug!( "instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})", parent_def_id, value ); let (value, opaque_type_map) = self.register_infer_ok_obligations(self.instantiate_opaque_types( parent_def_id, self.body_id, self.param_env, value, value_span, )); let mut opaque_types = self.opaque_types.borrow_mut(); let mut opaque_types_vars = self.opaque_types_vars.borrow_mut(); for (ty, decl) in opaque_type_map { let _ = opaque_types.insert(ty, decl); let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type); } value } pub(super) fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T where T: TypeFoldable<'tcx>, { self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value) } pub(super) fn normalize_associated_types_in_as_infer_ok<T>( &self, span: Span, value: &T, ) -> InferOk<'tcx, T> where T: TypeFoldable<'tcx>, { self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value) } pub fn require_type_meets( &self, ty: Ty<'tcx>, span: Span, code: traits::ObligationCauseCode<'tcx>, def_id: DefId, ) { self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code)); } pub fn require_type_is_sized( &self, ty: Ty<'tcx>, span: Span, code: traits::ObligationCauseCode<'tcx>, ) { if !ty.references_error() { let lang_item = self.tcx.require_lang_item(LangItem::Sized, None); self.require_type_meets(ty, span, code, lang_item); } } pub fn require_type_is_sized_deferred( &self, ty: Ty<'tcx>, span: Span, code: traits::ObligationCauseCode<'tcx>, ) { if !ty.references_error() { self.deferred_sized_obligations.borrow_mut().push((ty, span, code)); } } pub fn register_bound( &self, ty: Ty<'tcx>, def_id: DefId, cause: traits::ObligationCause<'tcx>, ) { if !ty.references_error() { self.fulfillment_cx.borrow_mut().register_bound( self, self.param_env, ty, def_id, cause, ); } } pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> { let t = AstConv::ast_ty_to_ty(self, ast_t); self.register_wf_obligation(t.into(), ast_t.span, traits::MiscObligation); t } pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> { let ty = self.to_ty(ast_ty); debug!("to_ty_saving_user_provided_ty: ty={:?}", ty); if Self::can_contain_user_lifetime_bounds(ty) { let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty)); debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty); self.typeck_results.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty); } ty } pub fn to_const(&self, ast_c: &hir::AnonConst) -> &'tcx ty::Const<'tcx> { let const_def_id = self.tcx.hir().local_def_id(ast_c.hir_id); let c = ty::Const::from_anon_const(self.tcx, const_def_id); self.register_wf_obligation( c.into(), self.tcx.hir().span(ast_c.hir_id), ObligationCauseCode::MiscObligation, ); c } pub fn const_arg_to_const( &self, ast_c: &hir::AnonConst, param_def_id: DefId, ) -> &'tcx ty::Const<'tcx> { let const_def = ty::WithOptConstParam { did: self.tcx.hir().local_def_id(ast_c.hir_id), const_param_did: Some(param_def_id), }; let c = ty::Const::from_opt_const_arg_anon_const(self.tcx, const_def); self.register_wf_obligation( c.into(), self.tcx.hir().span(ast_c.hir_id), ObligationCauseCode::MiscObligation, ); c } // If the type given by the user has free regions, save it for later, since // NLL would like to enforce those. Also pass in types that involve // projections, since those can resolve to `'static` bounds (modulo #54940, // which hopefully will be fixed by the time you see this comment, dear // reader, although I have my doubts). Also pass in types with inference // types, because they may be repeated. Other sorts of things are already // sufficiently enforced with erased regions. =) fn can_contain_user_lifetime_bounds<T>(t: T) -> bool where T: TypeFoldable<'tcx>, { t.has_free_regions() || t.has_projections() || t.has_infer_types() } pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> { match self.typeck_results.borrow().node_types().get(id) { Some(&t) => t, None if self.is_tainted_by_errors() => self.tcx.ty_error(), None => { bug!( "no type for node {}: {} in fcx {}", id, self.tcx.hir().node_to_string(id), self.tag() ); } } } /// Registers an obligation for checking later, during regionck, that `arg` is well-formed. pub fn register_wf_obligation( &self, arg: subst::GenericArg<'tcx>, span: Span, code: traits::ObligationCauseCode<'tcx>, ) { // WF obligations never themselves fail, so no real need to give a detailed cause: let cause = traits::ObligationCause::new(span, self.body_id, code); self.register_predicate(traits::Obligation::new( cause, self.param_env, ty::PredicateAtom::WellFormed(arg).to_predicate(self.tcx), )); } /// Registers obligations that all `substs` are well-formed. pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) { for arg in substs.iter().filter(|arg| { matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..)) }) { self.register_wf_obligation(arg, expr.span, traits::MiscObligation); } } /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each /// type/region parameter was instantiated (`substs`), creates and registers suitable /// trait/region obligations. /// /// For example, if there is a function: /// /// ``` /// fn foo<'a,T:'a>(...) /// ``` /// /// and a reference: /// /// ``` /// let f = foo; /// ``` /// /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a` /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally. pub fn add_obligations_for_parameters( &self, cause: traits::ObligationCause<'tcx>, predicates: ty::InstantiatedPredicates<'tcx>, ) { assert!(!predicates.has_escaping_bound_vars()); debug!("add_obligations_for_parameters(predicates={:?})", predicates); for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) { self.register_predicate(obligation); } } // FIXME(arielb1): use this instead of field.ty everywhere // Only for fields! Returns <none> for methods> // Indifferent to privacy flags pub fn field_ty( &self, span: Span, field: &'tcx ty::FieldDef, substs: SubstsRef<'tcx>, ) -> Ty<'tcx> { self.normalize_associated_types_in(span, &field.ty(self.tcx, substs)) } pub(super) fn check_casts(&self) { let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut(); for cast in deferred_cast_checks.drain(..) { cast.check(self); } } pub(super) fn resolve_generator_interiors(&self, def_id: DefId) { let mut generators = self.deferred_generator_interiors.borrow_mut(); for (body_id, interior, kind) in generators.drain(..) { self.select_obligations_where_possible(false, |_| {}); super::generator_interior::resolve_interior(self, def_id, body_id, interior, kind); } } // Tries to apply a fallback to `ty` if it is an unsolved variable. // // - Unconstrained ints are replaced with `i32`. // // - Unconstrained floats are replaced with with `f64`. // // - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]` //   is enabled. Otherwise, they are replaced with `()`. // // Fallback becomes very dubious if we have encountered type-checking errors. // In that case, fallback to Error. // The return value indicates whether fallback has occurred. pub(super) fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool { use rustc_middle::ty::error::UnconstrainedNumeric::Neither; use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt}; assert!(ty.is_ty_infer()); let fallback = match self.type_is_unconstrained_numeric(ty) { _ if self.is_tainted_by_errors() => self.tcx().ty_error(), UnconstrainedInt => self.tcx.types.i32, UnconstrainedFloat => self.tcx.types.f64, Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(), Neither => { // This type variable was created from the instantiation of an opaque // type. The fact that we're attempting to perform fallback for it // means that the function neither constrained it to a concrete // type, nor to the opaque type itself. // // For example, in this code: // //``` // type MyType = impl Copy; // fn defining_use() -> MyType { true } // fn other_use() -> MyType { defining_use() } // ``` // // `defining_use` will constrain the instantiated inference // variable to `bool`, while `other_use` will constrain // the instantiated inference variable to `MyType`. // // When we process opaque types during writeback, we // will handle cases like `other_use`, and not count // them as defining usages // // However, we also need to handle cases like this: // // ```rust // pub type Foo = impl Copy; // fn produce() -> Option<Foo> { //     None //  } //  ``` // // In the above snippet, the inference variable created by // instantiating `Option<Foo>` will be completely unconstrained. // We treat this as a non-defining use by making the inference // variable fall back to the opaque type itself. if let FallbackMode::All = mode { if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) { debug!( "fallback_if_possible: falling back opaque type var {:?} to {:?}", ty, opaque_ty ); *opaque_ty } else { return false; } } else { return false; } } }; debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback); self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback); true } pub(super) fn select_all_obligations_or_error(&self) { debug!("select_all_obligations_or_error"); if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) { self.report_fulfillment_errors(&errors, self.inh.body_id, false); } } /// Select as many obligations as we can at present. pub(super) fn select_obligations_where_possible( &self, fallback_has_occurred: bool, mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>), ) { let result = self.fulfillment_cx.borrow_mut().select_where_possible(self); if let Err(mut errors) = result { mutate_fullfillment_errors(&mut errors); self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred); } } /// For the overloaded place expressions (`*x`, `x[3]`), the trait /// returns a type of `&T`, but the actual type we assign to the /// *expression* is `T`. So this function just peels off the return /// type by one layer to yield `T`. pub(super) fn make_overloaded_place_return_type( &self, method: MethodCallee<'tcx>, ) -> ty::TypeAndMut<'tcx> { // extract method return type, which will be &T; let ret_ty = method.sig.output(); // method returns &T, but the type as visible to user is T, so deref ret_ty.builtin_deref(true).unwrap() } pub(super) fn check_method_argument_types( &self, sp: Span, expr: &'tcx hir::Expr<'tcx>, method: Result<MethodCallee<'tcx>, ()>, args_no_rcvr: &'tcx [hir::Expr<'tcx>], tuple_arguments: TupleArgumentsFlag, expected: Expectation<'tcx>, ) -> Ty<'tcx> { let has_error = match method { Ok(method) => method.substs.references_error() || method.sig.references_error(), Err(_) => true, }; if has_error { let err_inputs = self.err_args(args_no_rcvr.len()); let err_inputs = match tuple_arguments { DontTupleArguments => err_inputs, TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])], }; self.check_argument_types( sp, expr, &err_inputs[..], &[], args_no_rcvr, false, tuple_arguments, None, ); return self.tcx.ty_error(); } let method = method.unwrap(); // HACK(eddyb) ignore self in the definition (see above). let expected_arg_tys = self.expected_inputs_for_expected_output( sp, expected, method.sig.output(), &method.sig.inputs()[1..], ); self.check_argument_types( sp, expr, &method.sig.inputs()[1..], &expected_arg_tys[..], args_no_rcvr, method.sig.c_variadic, tuple_arguments, self.tcx.hir().span_if_local(method.def_id), ); method.sig.output() } fn self_type_matches_expected_vid( &self, trait_ref: ty::PolyTraitRef<'tcx>, expected_vid: ty::TyVid, ) -> bool { let self_ty = self.shallow_resolve(trait_ref.skip_binder().self_ty()); debug!( "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})", trait_ref, self_ty, expected_vid ); match *self_ty.kind() { ty::Infer(ty::TyVar(found_vid)) => { // FIXME: consider using `sub_root_var` here so we // can see through subtyping. let found_vid = self.root_var(found_vid); debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid); expected_vid == found_vid } _ => false, } } pub(super) fn obligations_for_self_ty<'b>( &'b self, self_ty: ty::TyVid, ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)> + Captures<'tcx> + 'b { // FIXME: consider using `sub_root_var` here so we // can see through subtyping. let ty_var_root = self.root_var(self_ty); debug!( "obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}", self_ty, ty_var_root, self.fulfillment_cx.borrow().pending_obligations() ); self.fulfillment_cx .borrow() .pending_obligations() .into_iter() .filter_map(move |obligation| { match obligation.predicate.skip_binders() { ty::PredicateAtom::Projection(data) => { Some((ty::Binder::bind(data).to_poly_trait_ref(self.tcx), obligation)) } ty::PredicateAtom::Trait(data, _) => { Some((ty::Binder::bind(data).to_poly_trait_ref(), obligation)) } ty::PredicateAtom::Subtype(..) => None, ty::PredicateAtom::RegionOutlives(..) => None, ty::PredicateAtom::TypeOutlives(..) => None, ty::PredicateAtom::WellFormed(..) => None, ty::PredicateAtom::ObjectSafe(..) => None, ty::PredicateAtom::ConstEvaluatable(..) => None, ty::PredicateAtom::ConstEquate(..) => None, // N.B., this predicate is created by breaking down a // `ClosureType: FnFoo()` predicate, where // `ClosureType` represents some `Closure`. It can't // possibly be referring to the current closure, // because we haven't produced the `Closure` for // this closure yet; this is exactly why the other // code is looking for a self type of a unresolved // inference variable. ty::PredicateAtom::ClosureKind(..) => None, ty::PredicateAtom::TypeWellFormedFromEnv(..) => None, } }) .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root)) } pub(super) fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool { self.obligations_for_self_ty(self_ty) .any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait()) } /// Generic function that factors out common logic from function calls, /// method calls and overloaded operators. pub(super) fn check_argument_types( &self, sp: Span, expr: &'tcx hir::Expr<'tcx>, fn_inputs: &[Ty<'tcx>], expected_arg_tys: &[Ty<'tcx>], args: &'tcx [hir::Expr<'tcx>], c_variadic: bool, tuple_arguments: TupleArgumentsFlag, def_span: Option<Span>, ) { let tcx = self.tcx; // Grab the argument types, supplying fresh type variables // if the wrong number of arguments were supplied let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 }; // All the input types from the fn signature must outlive the call // so as to validate implied bounds. for (&fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) { self.register_wf_obligation(fn_input_ty.into(), arg_expr.span, traits::MiscObligation); } let expected_arg_count = fn_inputs.len(); let param_count_error = |expected_count: usize, arg_count: usize, error_code: &str, c_variadic: bool, sugg_unit: bool| { let (span, start_span, args) = match &expr.kind { hir::ExprKind::Call(hir::Expr { span, .. }, args) => (*span, *span, &args[..]), hir::ExprKind::MethodCall(path_segment, span, args, _) => ( *span, // `sp` doesn't point at the whole `foo.bar()`, only at `bar`. path_segment .args .and_then(|args| args.args.iter().last()) // Account for `foo.bar::<T>()`. .map(|arg| { // Skip the closing `>`. tcx.sess .source_map() .next_point(tcx.sess.source_map().next_point(arg.span())) }) .unwrap_or(*span), &args[1..], // Skip the receiver. ), k => span_bug!(sp, "checking argument types on a non-call: `{:?}`", k), }; let arg_spans = if args.is_empty() { // foo() // ^^^-- supplied 0 arguments // | // expected 2 arguments vec![tcx.sess.source_map().next_point(start_span).with_hi(sp.hi())] } else { // foo(1, 2, 3) // ^^^ -  -  - supplied 3 arguments // | // expected 2 arguments args.iter().map(|arg| arg.span).collect::<Vec<Span>>() }; let mut err = tcx.sess.struct_span_err_with_code( span, &format!( "this function takes {}{} but {} {} supplied", if c_variadic { "at least " } else { "" }, potentially_plural_count(expected_count, "argument"), potentially_plural_count(arg_count, "argument"), if arg_count == 1 { "was" } else { "were" } ), DiagnosticId::Error(error_code.to_owned()), ); let label = format!("supplied {}", potentially_plural_count(arg_count, "argument")); for (i, span) in arg_spans.into_iter().enumerate() { err.span_label( span, if arg_count == 0 || i + 1 == arg_count { &label } else { "" }, ); } if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().guess_head_span(sp)) { err.span_label(def_s, "defined here"); } if sugg_unit { let sugg_span = tcx.sess.source_map().end_point(expr.span); // remove closing `)` from the span let sugg_span = sugg_span.shrink_to_lo(); err.span_suggestion( sugg_span, "expected the unit value `()`; create it with empty parentheses", String::from("()"), Applicability::MachineApplicable, ); } else { err.span_label( span, format!( "expected {}{}", if c_variadic { "at least " } else { "" }, potentially_plural_count(expected_count, "argument") ), ); } err.emit(); }; let mut expected_arg_tys = expected_arg_tys.to_vec(); let formal_tys = if tuple_arguments == TupleArguments { let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]); match tuple_type.kind() { ty::Tuple(arg_types) if arg_types.len() != args.len() => { param_count_error(arg_types.len(), args.len(), "E0057", false, false); expected_arg_tys = vec![]; self.err_args(args.len()) } ty::Tuple(arg_types) => { expected_arg_tys = match expected_arg_tys.get(0) { Some(&ty) => match ty.kind() { ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(), _ => vec![], }, None => vec![], }; arg_types.iter().map(|k| k.expect_ty()).collect() } _ => { struct_span_err!( tcx.sess, sp, E0059, "cannot use call notation; the first type parameter  for the function trait is neither a tuple nor unit" ) .emit(); expected_arg_tys = vec![]; self.err_args(args.len()) } } } else if expected_arg_count == supplied_arg_count { fn_inputs.to_vec() } else if c_variadic { if supplied_arg_count >= expected_arg_count { fn_inputs.to_vec() } else { param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false); expected_arg_tys = vec![]; self.err_args(supplied_arg_count) } } else { // is the missing argument of type `()`? let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 { self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit() } else if fn_inputs.len() == 1 && supplied_arg_count == 0 { self.resolve_vars_if_possible(&fn_inputs[0]).is_unit() } else { false }; param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit); expected_arg_tys = vec![]; self.err_args(supplied_arg_count) }; debug!( "check_argument_types: formal_tys={:?}", formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>() ); // If there is no expectation, expect formal_tys. let expected_arg_tys = if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() }; let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![]; // Check the arguments. // 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] { debug!("check_closures={}", check_closures); // More awful hacks: before we check argument types, try to do // an "opportunistic" trait resolution of any trait bounds on // the call. This helps coercions. if check_closures { self.select_obligations_where_possible(false, |errors| { self.point_at_type_arg_instead_of_call_if_possible(errors, expr); self.point_at_arg_instead_of_call_if_possible( errors, &final_arg_types[..], sp, &args, ); }) } // For C-variadic functions, we don't have a declared type for all of // the arguments hence we only do our usual type checking with // the arguments who's types we do know. let t = if c_variadic { expected_arg_count } else if tuple_arguments == TupleArguments { args.len() } else { supplied_arg_count }; for (i, arg) in args.iter().take(t).enumerate() { // Warn only for the first loop (the "no closures" one). // Closure arguments themselves can't be diverging, but // a previous argument can, e.g., `foo(panic!(), || {})`. if !check_closures { self.warn_if_unreachable(arg.hir_id, arg.span, "expression"); } let is_closure = match arg.kind { ExprKind::Closure(..) => true, _ => false, }; if is_closure != check_closures { continue; } debug!("checking the argument"); let formal_ty = formal_tys[i]; // The special-cased logic below has three functions: // 1. Provide as good of an expected type as possible. let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]); let checked_ty = self.check_expr_with_expectation(&arg, expected); // 2. Coerce to the most detailed type that could be coerced //    to, which is `expected_ty` if `rvalue_hint` returns an //    `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise. let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty); // We're processing function arguments so we definitely want to use // two-phase borrows. self.demand_coerce(&arg, checked_ty, coerce_ty, None, AllowTwoPhase::Yes); final_arg_types.push((i, checked_ty, coerce_ty)); // 3. Relate the expected type and the formal one, //    if the expected type was used for the coercion. self.demand_suptype(arg.span, formal_ty, coerce_ty); } } // We also need to make sure we at least write the ty of the other // arguments which we skipped above. if c_variadic { fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) { use crate::structured_errors::{StructuredDiagnostic, VariadicError}; VariadicError::new(s, span, t, cast_ty).diagnostic().emit(); } for arg in args.iter().skip(expected_arg_count) { let arg_ty = self.check_expr(&arg); // There are a few types which get autopromoted when passed via varargs // in C but we just error out instead and require explicit casts. let arg_ty = self.structurally_resolved_type(arg.span, arg_ty); match arg_ty.kind() { ty::Float(ast::FloatTy::F32) => { variadic_error(tcx.sess, arg.span, arg_ty, "c_double"); } ty::Int(ast::IntTy::I8 | ast::IntTy::I16) | ty::Bool => { variadic_error(tcx.sess, arg.span, arg_ty, "c_int"); } ty::Uint(ast::UintTy::U8 | ast::UintTy::U16) => { variadic_error(tcx.sess, arg.span, arg_ty, "c_uint"); } ty::FnDef(..) => { let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx)); let ptr_ty = self.resolve_vars_if_possible(&ptr_ty); variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string()); } _ => {} } } } } pub(super) fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> { vec![self.tcx.ty_error(); len] } /// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s /// reference a type argument. The reason to walk also the checked type is that the coerced type /// can be not easily comparable with predicate type (because of coercion). If the types match /// for either checked or coerced type, and there's only *one* argument that does, we point at /// the corresponding argument's expression span instead of the `fn` call path span. fn point_at_arg_instead_of_call_if_possible( &self, errors: &mut Vec<traits::FulfillmentError<'tcx>>, final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)], call_sp: Span, args: &'tcx [hir::Expr<'tcx>], ) { // We *do not* do this for desugared call spans to keep good diagnostics when involving // the `?` operator. if call_sp.desugaring_kind().is_some() { return; } for error in errors { // Only if the cause is somewhere inside the expression we want try to point at arg. // Otherwise, it means that the cause is somewhere else and we should not change // anything because we can break the correct span. if !call_sp.contains(error.obligation.cause.span) { continue; } if let ty::PredicateAtom::Trait(predicate, _) = error.obligation.predicate.skip_binders() { // Collect the argument position for all arguments that could have caused this // `FulfillmentError`. let mut referenced_in = final_arg_types .iter() .map(|&(i, checked_ty, _)| (i, checked_ty)) .chain(final_arg_types.iter().map(|&(i, _, coerced_ty)| (i, coerced_ty))) .flat_map(|(i, ty)| { let ty = self.resolve_vars_if_possible(&ty); // We walk the argument type because the argument's type could have // been `Option<T>`, but the `FulfillmentError` references `T`. if ty.walk().any(|arg| arg == predicate.self_ty().into()) { Some(i) } else { None } }) .collect::<Vec<usize>>(); // Both checked and coerced types could have matched, thus we need to remove // duplicates. // We sort primitive type usize here and can use unstable sort referenced_in.sort_unstable(); referenced_in.dedup(); if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) { // We make sure that only *one* argument matches the obligation failure // and we assign the obligation's span to its expression's. error.obligation.cause.make_mut().span = args[ref_in].span; error.points_at_arg_span = true; } } } } /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s /// were caused by them. If they were, we point at the corresponding type argument's span /// instead of the `fn` call path span. fn point_at_type_arg_instead_of_call_if_possible( &self, errors: &mut Vec<traits::FulfillmentError<'tcx>>, call_expr: &'tcx hir::Expr<'tcx>, ) { if let hir::ExprKind::Call(path, _) = &call_expr.kind { if let hir::ExprKind::Path(qpath) = &path.kind { if let hir::QPath::Resolved(_, path) = &qpath { for error in errors { if let ty::PredicateAtom::Trait(predicate, _) = error.obligation.predicate.skip_binders() { // If any of the type arguments in this path segment caused the // `FullfillmentError`, point at its span (#61860). for arg in path .segments .iter() .filter_map(|seg| seg.args.as_ref()) .flat_map(|a| a.args.iter()) { if let hir::GenericArg::Type(hir_ty) = &arg { if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) = &hir_ty.kind { // Avoid ICE with associated types. As this is best // effort only, it's ok to ignore the case. It // would trigger in `is_send::<T::AssocType>();` // from `typeck-default-trait-impl-assoc-type.rs`. } else { let ty = AstConv::ast_ty_to_ty(self, hir_ty); let ty = self.resolve_vars_if_possible(&ty); if ty == predicate.self_ty() { error.obligation.cause.make_mut().span = hir_ty.span; } } } } } } } } } } // AST fragment checking pub(super) fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> { let tcx = self.tcx; match lit.node { ast::LitKind::Str(..) => tcx.mk_static_str(), ast::LitKind::ByteStr(ref v) => { tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64)) } ast::LitKind::Byte(_) => tcx.types.u8, ast::LitKind::Char(_) => tcx.types.char, ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t), ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t), ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => { let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() { ty::Int(_) | ty::Uint(_) => Some(ty), ty::Char => Some(tcx.types.u8), ty::RawPtr(..) => Some(tcx.types.usize), ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize), _ => None, }); opt_ty.unwrap_or_else(|| self.next_int_var()) } ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t), ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => { let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() { ty::Float(_) => Some(ty), _ => None, }); opt_ty.unwrap_or_else(|| self.next_float_var()) } ast::LitKind::Bool(_) => tcx.types.bool, ast::LitKind::Err(_) => tcx.ty_error(), } } /// Unifies the output type with the expected type early, for more coercions /// and forward type information on the input expressions. pub(super) fn expected_inputs_for_expected_output( &self, call_span: Span, expected_ret: Expectation<'tcx>, formal_ret: Ty<'tcx>, formal_args: &[Ty<'tcx>], ) -> Vec<Ty<'tcx>> { let formal_ret = self.resolve_vars_with_obligations(formal_ret); let ret_ty = match expected_ret.only_has_type(self) { Some(ret) => ret, None => return Vec::new(), }; let expect_args = self .fudge_inference_if_ok(|| { // Attempt to apply a subtyping relationship between the formal // return type (likely containing type variables if the function // is polymorphic) and the expected return type. // No argument expectations are produced if unification fails. let origin = self.misc(call_span); let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret); // FIXME(#27336) can't use ? here, Try::from_error doesn't default // to identity so the resulting type is not constrained. match ures { Ok(ok) => { // Process any obligations locally as much as // we can.  We don't care if some things turn // out unconstrained or ambiguous, as we're // just trying to get hints here. self.save_and_restore_in_snapshot_flag(|_| { let mut fulfill = TraitEngine::new(self.tcx); for obligation in ok.obligations { fulfill.register_predicate_obligation(self, obligation); } fulfill.select_where_possible(self) }) .map_err(|_| ())?; } Err(_) => return Err(()), } // Record all the argument types, with the substitutions // produced from the above subtyping unification. Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect()) }) .unwrap_or_default(); debug!( "expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})", formal_args, formal_ret, expect_args, expected_ret ); expect_args } pub fn check_struct_path( &self, qpath: &QPath<'_>, hir_id: hir::HirId, ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> { let path_span = qpath.qself_span(); let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id); let variant = match def { Res::Err => { self.set_tainted_by_errors(); return None; } Res::Def(DefKind::Variant, _) => match ty.kind() { ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)), _ => bug!("unexpected type: {:?}", ty), }, Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _) | Res::SelfTy(..) => match ty.kind() { ty::Adt(adt, substs) if !adt.is_enum() => { Some((adt.non_enum_variant(), adt.did, substs)) } _ => None, }, _ => bug!("unexpected definition: {:?}", def), }; if let Some((variant, did, substs)) = variant { debug!("check_struct_path: did={:?} substs={:?}", did, substs); self.write_user_type_annotation_from_substs(hir_id, did, substs, None); // Check bounds on type arguments used in the path. let (bounds, _) = self.instantiate_bounds(path_span, did, substs); let cause = traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did)); self.add_obligations_for_parameters(cause, bounds); Some((variant, ty)) } else { struct_span_err!( self.tcx.sess, path_span, E0071, "expected struct, variant or union type, found {}", ty.sort_string(self.tcx) ) .span_label(path_span, "not a struct") .emit(); None } } // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary. // The newly resolved definition is written into `type_dependent_defs`. fn finish_resolving_struct_path( &self, qpath: &QPath<'_>, path_span: Span, hir_id: hir::HirId, ) -> (Res, Ty<'tcx>) { match *qpath { QPath::Resolved(ref maybe_qself, ref path) => { let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself)); let ty = AstConv::res_to_ty(self, self_ty, path, true); (path.res, ty) } QPath::TypeRelative(ref qself, ref segment) => { let ty = self.to_ty(qself); let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind { path.res } else { Res::Err }; let result = AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true); let ty = result.map(|(ty, _, _)| ty).unwrap_or_else(|_| self.tcx().ty_error()); let result = result.map(|(_, kind, def_id)| (kind, def_id)); // Write back the new resolution. self.write_resolution(hir_id, result); (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty) } QPath::LangItem(lang_item, span) => { self.resolve_lang_item_path(lang_item, span, hir_id) } } } pub(super) fn resolve_lang_item_path( &self, lang_item: hir::LangItem, span: Span, hir_id: hir::HirId, ) -> (Res, Ty<'tcx>) { let def_id = self.tcx.require_lang_item(lang_item, Some(span)); let def_kind = self.tcx.def_kind(def_id); let item_ty = if let DefKind::Variant = def_kind { self.tcx.type_of(self.tcx.parent(def_id).expect("variant w/out parent")) } else { self.tcx.type_of(def_id) }; let substs = self.infcx.fresh_substs_for_item(span, def_id); let ty = item_ty.subst(self.tcx, substs); self.write_resolution(hir_id, Ok((def_kind, def_id))); self.add_required_obligations(span, def_id, &substs); (Res::Def(def_kind, def_id), ty) } /// Resolves an associated value path into a base type and associated constant, or method /// resolution. The newly resolved definition is written into `type_dependent_defs`. pub fn resolve_ty_and_res_ufcs<'b>( &self, qpath: &'b QPath<'b>, hir_id: hir::HirId, span: Span, ) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) { debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span); let (ty, qself, item_segment) = match *qpath { QPath::Resolved(ref opt_qself, ref path) => { return ( path.res, opt_qself.as_ref().map(|qself| self.to_ty(qself)), &path.segments[..], ); } QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment), QPath::LangItem(..) => bug!("`resolve_ty_and_res_ufcs` called on `LangItem`"), }; if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id) { // Return directly on cache hit. This is useful to avoid doubly reporting // errors with default match binding modes. See #44614. let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err); return (def, Some(ty), slice::from_ref(&**item_segment)); } let item_name = item_segment.ident; let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| { let result = match error { method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)), _ => Err(ErrorReported), }; if item_name.name != kw::Invalid { if let Some(mut e) = self.report_method_error( span, ty, item_name, SelfSource::QPath(qself), error, None, ) { e.emit(); } } result }); // Write back the new resolution. self.write_resolution(hir_id, result); ( result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), Some(ty), slice::from_ref(&**item_segment), ) } pub fn check_decl_initializer( &self, local: &'tcx hir::Local<'tcx>, init: &'tcx hir::Expr<'tcx>, ) -> Ty<'tcx> { // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed // for #42640 (default match binding modes). // // See #44848. let ref_bindings = local.pat.contains_explicit_ref_binding(); let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty; if let Some(m) = ref_bindings { // Somewhat subtle: if we have a `ref` binding in the pattern, // we want to avoid introducing coercions for the RHS. This is // both because it helps preserve sanity and, in the case of // ref mut, for soundness (issue #23116). In particular, in // the latter case, we need to be clear that the type of the // referent for the reference that results is *equal to* the // type of the place it is referencing, and not some // supertype thereof. let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m)); self.demand_eqtype(init.span, local_ty, init_ty); init_ty } else { self.check_expr_coercable_to_type(init, local_ty, None) } } /// Type check a `let` statement. pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) { // Determine and write the type which we'll check the pattern against. let ty = self.local_ty(local.span, local.hir_id).decl_ty; self.write_ty(local.hir_id, ty); // Type check the initializer. if let Some(ref init) = local.init { let init_ty = self.check_decl_initializer(local, &init); self.overwrite_local_ty_if_err(local, ty, init_ty); } // Does the expected pattern type originate from an expression and what is the span? let (origin_expr, ty_span) = match (local.ty, local.init) { (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type. (_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee. _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained. }; // Type check the pattern. Override if necessary to avoid knock-on errors. self.check_pat_top(&local.pat, ty, ty_span, origin_expr); let pat_ty = self.node_ty(local.pat.hir_id); self.overwrite_local_ty_if_err(local, ty, pat_ty); } fn overwrite_local_ty_if_err( &self, local: &'tcx hir::Local<'tcx>, decl_ty: Ty<'tcx>, ty: Ty<'tcx>, ) { if ty.references_error() { // Override the types everywhere with `err()` to avoid knock on errors. self.write_ty(local.hir_id, ty); self.write_ty(local.pat.hir_id, ty); let local_ty = LocalTy { decl_ty, revealed_ty: ty }; self.locals.borrow_mut().insert(local.hir_id, local_ty); self.locals.borrow_mut().insert(local.pat.hir_id, local_ty); } } pub(super) fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) { err.span_suggestion_short( span.shrink_to_hi(), "consider using a semicolon here", ";".to_string(), Applicability::MachineApplicable, ); } pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) { // Don't do all the complex logic below for `DeclItem`. match stmt.kind { hir::StmtKind::Item(..) => return, hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {} } self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement"); // Hide the outer diverging and `has_errors` flags. let old_diverges = self.diverges.replace(Diverges::Maybe); let old_has_errors = self.has_errors.replace(false); match stmt.kind { hir::StmtKind::Local(ref l) => { self.check_decl_local(&l); } // Ignore for now. hir::StmtKind::Item(_) => {} hir::StmtKind::Expr(ref expr) => { // Check with expected type of `()`. self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| { self.suggest_semicolon_at_end(expr.span, err); }); } hir::StmtKind::Semi(ref expr) => { self.check_expr(&expr); } } // Combine the diverging and `has_error` flags. self.diverges.set(self.diverges.get() | old_diverges); self.has_errors.set(self.has_errors.get() | old_has_errors); } pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) { let unit = self.tcx.mk_unit(); let ty = self.check_block_with_expected(blk, ExpectHasType(unit)); // if the block produces a `!` value, that can always be // (effectively) coerced to unit. if !ty.is_never() { self.demand_suptype(blk.span, unit, ty); } } /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors /// when given code like the following: /// ```text /// if false { return 0i32; } else { 1u32 } /// //                               ^^^^ point at this instead of the whole `if` expression /// ``` fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span { if let hir::ExprKind::Match(_, arms, _) = &expr.kind { let arm_spans: Vec<Span> = arms .iter() .filter_map(|arm| { self.in_progress_typeck_results .and_then(|typeck_results| { typeck_results.borrow().node_type_opt(arm.body.hir_id) }) .and_then(|arm_ty| { if arm_ty.is_never() { None } else { Some(match &arm.body.kind { // Point at the tail expression when possible. hir::ExprKind::Block(block, _) => { block.expr.as_ref().map(|e| e.span).unwrap_or(block.span) } _ => arm.body.span, }) } }) }) .collect(); if arm_spans.len() == 1 { return arm_spans[0]; } } expr.span } pub(super) fn check_block_with_expected( &self, blk: &'tcx hir::Block<'tcx>, expected: Expectation<'tcx>, ) -> Ty<'tcx> { let prev = { let mut fcx_ps = self.ps.borrow_mut(); let unsafety_state = fcx_ps.recurse(blk); replace(&mut *fcx_ps, unsafety_state) }; // In some cases, blocks have just one exit, but other blocks // can be targeted by multiple breaks. This can happen both // with labeled blocks as well as when we desugar // a `try { ... }` expression. // // Example 1: // //    'a: { if true { break 'a Err(()); } Ok(()) } // // Here we would wind up with two coercions, one from // `Err(())` and the other from the tail expression // `Ok(())`. If the tail expression is omitted, that's a // "forced unit" -- unless the block diverges, in which // case we can ignore the tail expression (e.g., `'a: { // break 'a 22; }` would not force the type of the block // to be `()`). let tail_expr = blk.expr.as_ref(); let coerce_to_ty = expected.coercion_target_type(self, blk.span); let coerce = if blk.targeted_by_break { CoerceMany::new(coerce_to_ty) } else { let tail_expr: &[&hir::Expr<'_>] = match tail_expr { Some(e) => slice::from_ref(e), None => &[], }; CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr) }; let prev_diverges = self.diverges.get(); let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false }; let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || { for s in blk.stmts { self.check_stmt(s); } // check the tail expression **without** holding the // `enclosing_breakables` lock below. let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected)); let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); let ctxt = enclosing_breakables.find_breakable(blk.hir_id); let coerce = ctxt.coerce.as_mut().unwrap(); if let Some(tail_expr_ty) = tail_expr_ty { let tail_expr = tail_expr.unwrap(); let span = self.get_expr_coercion_span(tail_expr); let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id)); coerce.coerce(self, &cause, tail_expr, tail_expr_ty); } else { // Subtle: if there is no explicit tail expression, // that is typically equivalent to a tail expression // of `()` -- except if the block diverges. In that // case, there is no value supplied from the tail // expression (assuming there are no other breaks, // this implies that the type of the block will be // `!`). // // #41425 -- label the implicit `()` as being the // "found type" here, rather than the "expected type". if !self.diverges.get().is_always() { // #50009 -- Do not point at the entire fn block span, point at the return type // span, as it is the cause of the requirement, and // `consider_hint_about_removing_semicolon` will point at the last expression // if it were a relevant part of the error. This improves usability in editors // that highlight errors inline. let mut sp = blk.span; let mut fn_span = None; if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) { let ret_sp = decl.output.span(); if let Some(block_sp) = self.parent_item_span(blk.hir_id) { // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the // output would otherwise be incorrect and even misleading. Make sure // the span we're aiming at correspond to a `fn` body. if block_sp == blk.span { sp = ret_sp; fn_span = Some(ident.span); } } } coerce.coerce_forced_unit( self, &self.misc(sp), &mut |err| { if let Some(expected_ty) = expected.only_has_type(self) { self.consider_hint_about_removing_semicolon(blk, expected_ty, err); } if let Some(fn_span) = fn_span { err.span_label( fn_span, "implicitly returns `()` as its body has no tail or `return`  expression", ); } }, false, ); } } }); if ctxt.may_break { // If we can break from the block, then the block's exit is always reachable // (... as long as the entry is reachable) - regardless of the tail of the block. self.diverges.set(prev_diverges); } let mut ty = ctxt.coerce.unwrap().complete(self); if self.has_errors.get() || ty.references_error() { ty = self.tcx.ty_error() } self.write_ty(blk.hir_id, ty); *self.ps.borrow_mut() = prev; ty } fn parent_item_span(&self, id: hir::HirId) -> Option<Span> { let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id)); match node { Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => { let body = self.tcx.hir().body(body_id); if let ExprKind::Block(block, _) = &body.value.kind { return Some(block.span); } } _ => {} } None } /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise. fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident)> { let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id)); self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident)) } /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise. pub(super) fn get_node_fn_decl( &self, node: Node<'tcx>, ) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident, bool)> { match node { Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => { // This is less than ideal, it will not suggest a return type span on any // method called `main`, regardless of whether it is actually the entry point, // but it will still present it as the reason for the expected type. Some((&sig.decl, ident, ident.name != sym::main)) } Node::TraitItem(&hir::TraitItem { ident, kind: hir::TraitItemKind::Fn(ref sig, ..), .. }) => Some((&sig.decl, ident, true)), Node::ImplItem(&hir::ImplItem { ident, kind: hir::ImplItemKind::Fn(ref sig, ..), .. }) => Some((&sig.decl, ident, false)), _ => None, } } /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a /// suggestion can be made, `None` otherwise. pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> { // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or // `while` before reaching it, as block tail returns are not available in them. self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| { let parent = self.tcx.hir().get(blk_id); self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main)) }) } /// On implicit return expressions with mismatched types, provides the following suggestions: /// /// - Points out the method's return type as the reason for the expected type. /// - Possible missing semicolon. /// - Possible missing return type if the return type is the default, and not `fn main()`. pub fn suggest_mismatched_types_on_tail( &self, err: &mut DiagnosticBuilder<'_>, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>, found: Ty<'tcx>, cause_span: Span, blk_id: hir::HirId, ) -> bool { let expr = expr.peel_drop_temps(); self.suggest_missing_semicolon(err, expr, expected, cause_span); let mut pointing_at_return_type = false; if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) { pointing_at_return_type = self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest); } pointing_at_return_type } /// When encountering an fn-like ctor that needs to unify with a value, check whether calling /// the ctor would successfully solve the type mismatch and if so, suggest it: /// ``` /// fn foo(x: usize) -> usize { x } /// let x: usize = foo;  // suggest calling the `foo` function: `foo(42)` /// ``` fn suggest_fn_call( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) -> bool { let hir = self.tcx.hir(); let (def_id, sig) = match *found.kind() { ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)), ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()), _ => return false, }; let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0; let sig = self.normalize_associated_types_in(expr.span, &sig); if self.can_coerce(sig.output(), expected) { let (mut sugg_call, applicability) = if sig.inputs().is_empty() { (String::new(), Applicability::MachineApplicable) } else { ("...".to_string(), Applicability::HasPlaceholders) }; let mut msg = "call this function"; match hir.get_if_local(def_id) { Some( Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }) | Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) | Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)), .. }), ) => { let body = hir.body(*body_id); sugg_call = body .params .iter() .map(|param| match &param.pat.kind { hir::PatKind::Binding(_, _, ident, None) if ident.name != kw::SelfLower => { ident.to_string() } _ => "_".to_string(), }) .collect::<Vec<_>>() .join(", "); } Some(Node::Expr(hir::Expr { kind: ExprKind::Closure(_, _, body_id, _, _), span: full_closure_span, .. })) => { if *full_closure_span == expr.span { return false; } msg = "call this closure"; let body = hir.body(*body_id); sugg_call = body .params .iter() .map(|param| match &param.pat.kind { hir::PatKind::Binding(_, _, ident, None) if ident.name != kw::SelfLower => { ident.to_string() } _ => "_".to_string(), }) .collect::<Vec<_>>() .join(", "); } Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => { sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", "); match def_id.as_local().map(|def_id| hir.def_kind(def_id)) { Some(DefKind::Ctor(hir::def::CtorOf::Variant, _)) => { msg = "instantiate this tuple variant"; } Some(DefKind::Ctor(CtorOf::Struct, _)) => { msg = "instantiate this tuple struct"; } _ => {} } } Some(Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(_, idents, _), .. })) => { sugg_call = idents .iter() .map(|ident| { if ident.name != kw::SelfLower { ident.to_string() } else { "_".to_string() } }) .collect::<Vec<_>>() .join(", ") } Some(Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)), .. })) => { sugg_call = idents .iter() .map(|ident| { if ident.name != kw::SelfLower { ident.to_string() } else { "_".to_string() } }) .collect::<Vec<_>>() .join(", ") } _ => {} } err.span_suggestion_verbose( expr.span.shrink_to_hi(), &format!("use parentheses to {}", msg), format!("({})", sugg_call), applicability, ); return true; } false } pub fn suggest_deref_ref_or_into( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, ) { if let Some((sp, msg, suggestion, applicability)) = self.check_ref(expr, found, expected) { err.span_suggestion(sp, msg, suggestion, applicability); } else if let (ty::FnDef(def_id, ..), true) = (&found.kind(), self.suggest_fn_call(err, expr, expected, found)) { if let Some(sp) = self.tcx.hir().span_if_local(*def_id) { let sp = self.sess().source_map().guess_head_span(sp); err.span_label(sp, &format!("{} defined here", found)); } } else if !self.check_for_cast(err, expr, found, expected, expected_ty_expr) { let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span); let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id); if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) { let mut suggestions = iter::repeat(&expr_text) .zip(methods.iter()) .filter_map(|(receiver, method)| { let method_call = format!(".{}()", method.ident); if receiver.ends_with(&method_call) { None // do not suggest code that is already there (#53348) } else { let method_call_list = [".to_vec()", ".to_string()"]; let sugg = if receiver.ends_with(".clone()") && method_call_list.contains(&method_call.as_str()) { let max_len = receiver.rfind('.').unwrap(); format!("{}{}", &receiver[..max_len], method_call) } else { if expr.precedence().order() < ExprPrecedence::MethodCall.order() { format!("({}){}", receiver, method_call) } else { format!("{}{}", receiver, method_call) } }; Some(if is_struct_pat_shorthand_field { format!("{}: {}", receiver, sugg) } else { sugg }) } }) .peekable(); if suggestions.peek().is_some() { err.span_suggestions( expr.span, "try using a conversion method", suggestions, Applicability::MaybeIncorrect, ); } } } } /// When encountering the expected boxed value allocated in the stack, suggest allocating it /// in the heap by calling `Box::new()`. pub(super) fn suggest_boxing_when_appropriate( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) { if self.tcx.hir().is_inside_const_context(expr.hir_id) { // Do not suggest `Box::new` in const context. return; } if !expected.is_box() || found.is_box() { return; } let boxed_found = self.tcx.mk_box(found); if let (true, Ok(snippet)) = ( self.can_coerce(boxed_found, expected), self.sess().source_map().span_to_snippet(expr.span), ) { err.span_suggestion( expr.span, "store this in the heap by calling `Box::new`", format!("Box::new({})", snippet), Applicability::MachineApplicable, ); err.note( "for more on the distinction between the stack and the heap, read  https://doc.rust-lang.org/book/ch15-01-box.html,  https://doc.rust-lang.org/rust-by-example/std/box.html, and  https://doc.rust-lang.org/std/boxed/index.html", ); } } pub(super) fn note_internal_mutation_in_method( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) { if found != self.tcx.types.unit { return; } if let ExprKind::MethodCall(path_segment, _, [rcvr, ..], _) = expr.kind { if self .typeck_results .borrow() .expr_ty_adjusted_opt(rcvr) .map_or(true, |ty| expected.peel_refs() != ty.peel_refs()) { return; } let mut sp = MultiSpan::from_span(path_segment.ident.span); sp.push_span_label( path_segment.ident.span, format!( "this call modifies {} in-place", match rcvr.kind { ExprKind::Path(QPath::Resolved( None, hir::Path { segments: [segment], .. }, )) => format!("`{}`", segment.ident), _ => "its receiver".to_string(), } ), ); sp.push_span_label( rcvr.span, "you probably want to use this value after calling the method...".to_string(), ); err.span_note( sp, &format!("method `{}` modifies its receiver in-place", path_segment.ident), ); err.note(&format!("...instead of the `()` output of method `{}`", path_segment.ident)); } } /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`. pub(super) fn suggest_calling_boxed_future_when_appropriate( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) -> bool { // Handle #68197. if self.tcx.hir().is_inside_const_context(expr.hir_id) { // Do not suggest `Box::new` in const context. return false; } let pin_did = self.tcx.lang_items().pin_type(); match expected.kind() { ty::Adt(def, _) if Some(def.did) != pin_did => return false, // This guards the `unwrap` and `mk_box` below. _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false, _ => {} } let boxed_found = self.tcx.mk_box(found); let new_found = self.tcx.mk_lang_item(boxed_found, LangItem::Pin).unwrap(); if let (true, Ok(snippet)) = ( self.can_coerce(new_found, expected), self.sess().source_map().span_to_snippet(expr.span), ) { match found.kind() { ty::Adt(def, _) if def.is_box() => { err.help("use `Box::pin`"); } _ => { err.span_suggestion( expr.span, "you need to pin and box this expression", format!("Box::pin({})", snippet), Applicability::MachineApplicable, ); } } true } else { false } } /// A common error is to forget to add a semicolon at the end of a block, e.g., /// /// ``` /// fn foo() { ///     bar_that_returns_u32() /// } /// ``` /// /// This routine checks if the return expression in a block would make sense on its own as a /// statement and the return type has been left as default or has been specified as `()`. If so, /// it suggests adding a semicolon. fn suggest_missing_semicolon( &self, err: &mut DiagnosticBuilder<'_>, expression: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>, cause_span: Span, ) { if expected.is_unit() { // `BlockTailExpression` only relevant if the tail expr would be // useful on its own. match expression.kind { ExprKind::Call(..) | ExprKind::MethodCall(..) | ExprKind::Loop(..) | ExprKind::Match(..) | ExprKind::Block(..) => { err.span_suggestion( cause_span.shrink_to_hi(), "try adding a semicolon", ";".to_string(), Applicability::MachineApplicable, ); } _ => (), } } } /// A possible error is to forget to add a return type that is needed: /// /// ``` /// fn foo() { ///     bar_that_returns_u32() /// } /// ``` /// /// This routine checks if the return type is left as default, the method is not part of an /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return /// type. pub(super) fn suggest_missing_return_type( &self, err: &mut DiagnosticBuilder<'_>, fn_decl: &hir::FnDecl<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, can_suggest: bool, ) -> bool { // Only suggest changing the return type for methods that // haven't set a return type at all (and aren't `fn main()` or an impl). match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) { (&hir::FnRetTy::DefaultReturn(span), true, true, true) => { err.span_suggestion( span, "try adding a return type", format!("-> {} ", self.resolve_vars_with_obligations(found)), Applicability::MachineApplicable, ); true } (&hir::FnRetTy::DefaultReturn(span), false, true, true) => { err.span_label(span, "possibly return type missing here?"); true } (&hir::FnRetTy::DefaultReturn(span), _, false, true) => { // `fn main()` must return `()`, do not suggest changing return type err.span_label(span, "expected `()` because of default return type"); true } // expectation was caused by something else, not the default return (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false, (&hir::FnRetTy::Return(ref ty), _, _, _) => { // Only point to return type if the expected type is the return type, as if they // are not, the expectation must have been caused by something else. debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind); let sp = ty.span; let ty = AstConv::ast_ty_to_ty(self, ty); debug!("suggest_missing_return_type: return type {:?}", ty); debug!("suggest_missing_return_type: expected type {:?}", ty); if ty.kind() == expected.kind() { err.span_label(sp, format!("expected `{}` because of return type", expected)); return true; } false } } } /// A possible error is to forget to add `.await` when using futures: /// /// ``` /// async fn make_u32() -> u32 { ///     22 /// } /// /// fn take_u32(x: u32) {} /// /// async fn foo() { ///     let x = make_u32(); ///     take_u32(x); /// } /// ``` /// /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the /// expected type. If this is the case, and we are inside of an async body, it suggests adding /// `.await` to the tail of the expression. pub(super) fn suggest_missing_await( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) { debug!("suggest_missing_await: expr={:?} expected={:?}, found={:?}", expr, expected, found); // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the // body isn't `async`. let item_id = self.tcx().hir().get_parent_node(self.body_id); if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) { let body = self.tcx().hir().body(body_id); if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind { let sp = expr.span; // Check for `Future` implementations by constructing a predicate to // prove: `<T as Future>::Output == U` let future_trait = self.tcx.require_lang_item(LangItem::Future, Some(sp)); let item_def_id = self .tcx .associated_items(future_trait) .in_definition_order() .next() .unwrap() .def_id; // `<T as Future>::Output` let projection_ty = ty::ProjectionTy { // `T` substs: self .tcx .mk_substs_trait(found, self.fresh_substs_for_item(sp, item_def_id)), // `Future::Output` item_def_id, }; let predicate = ty::PredicateAtom::Projection(ty::ProjectionPredicate { projection_ty, ty: expected, }) .potentially_quantified(self.tcx, ty::PredicateKind::ForAll); let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate); debug!("suggest_missing_await: trying obligation {:?}", obligation); if self.infcx.predicate_may_hold(&obligation) { debug!("suggest_missing_await: obligation held: {:?}", obligation); if let Ok(code) = self.sess().source_map().span_to_snippet(sp) { err.span_suggestion( sp, "consider using `.await` here", format!("{}.await", code), Applicability::MaybeIncorrect, ); } else { debug!("suggest_missing_await: no snippet for {:?}", sp); } } else { debug!("suggest_missing_await: obligation did not hold: {:?}", obligation) } } } } pub(super) fn suggest_missing_parentheses( &self, err: &mut DiagnosticBuilder<'_>, expr: &hir::Expr<'_>, ) { let sp = self.tcx.sess.source_map().start_point(expr.span); if let Some(sp) = self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp) { // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }` self.tcx.sess.parse_sess.expr_parentheses_needed(err, *sp, None); } } pub(super) fn note_need_for_fn_pointer( &self, err: &mut DiagnosticBuilder<'_>, expected: Ty<'tcx>, found: Ty<'tcx>, ) { let (sig, did, substs) = match (&expected.kind(), &found.kind()) { (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => { let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1); let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2); if sig1 != sig2 { return; } err.note( "different `fn` items always have unique types, even if their signatures are  the same", ); (sig1, *did1, substs1) } (ty::FnDef(did, substs), ty::FnPtr(sig2)) => { let sig1 = self.tcx.fn_sig(*did).subst(self.tcx, substs); if sig1 != *sig2 { return; } (sig1, *did, substs) } _ => return, }; err.help(&format!("change the expected type to be function pointer `{}`", sig)); err.help(&format!( "if the expected type is due to type inference, cast the expected `fn` to a function  pointer: `{} as {}`", self.tcx.def_path_str_with_substs(did, substs), sig )); } /// A common error is to add an extra semicolon: /// /// ``` /// fn foo() -> usize { ///     22; /// } /// ``` /// /// This routine checks if the final statement in a block is an /// expression with an explicit semicolon whose type is compatible /// with `expected_ty`. If so, it suggests removing the semicolon. fn consider_hint_about_removing_semicolon( &self, blk: &'tcx hir::Block<'tcx>, expected_ty: Ty<'tcx>, err: &mut DiagnosticBuilder<'_>, ) { if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) { err.span_suggestion( span_semi, "consider removing this semicolon", String::new(), Applicability::MachineApplicable, ); } } pub(super) fn could_remove_semicolon( &self, blk: &'tcx hir::Block<'tcx>, expected_ty: Ty<'tcx>, ) -> Option<Span> { // Be helpful when the user wrote `{... expr;}` and // taking the `;` off is enough to fix the error. let last_stmt = blk.stmts.last()?; let last_expr = match last_stmt.kind { hir::StmtKind::Semi(ref e) => e, _ => return None, }; let last_expr_ty = self.node_ty(last_expr.hir_id); if matches!(last_expr_ty.kind(), ty::Error(_)) || self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() { return None; } let original_span = original_sp(last_stmt.span, blk.span); Some(original_span.with_lo(original_span.hi() - BytePos(1))) } // Instantiates the given path, which must refer to an item with the given // number of type parameters and type. pub fn instantiate_value_path( &self, segments: &[hir::PathSegment<'_>], self_ty: Option<Ty<'tcx>>, res: Res, span: Span, hir_id: hir::HirId, ) -> (Ty<'tcx>, Res) { debug!( "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})", segments, self_ty, res, hir_id, ); let tcx = self.tcx; let path_segs = match res { Res::Local(_) | Res::SelfCtor(_) => vec![], Res::Def(kind, def_id) => { AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id) } _ => bug!("instantiate_value_path on {:?}", res), }; let mut user_self_ty = None; let mut is_alias_variant_ctor = false; match res { Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => { if let Some(self_ty) = self_ty { let adt_def = self_ty.ty_adt_def().unwrap(); user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty }); is_alias_variant_ctor = true; } } Res::Def(DefKind::AssocFn | DefKind::AssocConst, def_id) => { let container = tcx.associated_item(def_id).container; debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container); match container { ty::TraitContainer(trait_did) => { callee::check_legal_trait_for_method_call(tcx, span, None, trait_did) } ty::ImplContainer(impl_def_id) => { if segments.len() == 1 { // `<T>::assoc` will end up here, and so // can `T::assoc`. It this came from an // inherent impl, we need to record the // `T` for posterity (see `UserSelfTy` for // details). let self_ty = self_ty.expect("UFCS sugared assoc missing Self"); user_self_ty = Some(UserSelfTy { impl_def_id, self_ty }); } } } } _ => {} } // Now that we have categorized what space the parameters for each // segment belong to, let's sort out the parameters that the user // provided (if any) into their appropriate spaces. We'll also report // errors if type parameters are provided in an inappropriate place. let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect(); let generics_has_err = AstConv::prohibit_generics( self, segments.iter().enumerate().filter_map(|(index, seg)| { if !generic_segs.contains(&index) || is_alias_variant_ctor { Some(seg) } else { None } }), ); if let Res::Local(hid) = res { let ty = self.local_ty(span, hid).decl_ty; let ty = self.normalize_associated_types_in(span, &ty); self.write_ty(hir_id, ty); return (ty, res); } if generics_has_err { // Don't try to infer type parameters when prohibited generic arguments were given. user_self_ty = None; } // Now we have to compare the types that the user *actually* // provided against the types that were *expected*. If the user // did not provide any types, then we want to substitute inference // variables. If the user provided some types, we may still need // to add defaults. If the user provided *too many* types, that's // a problem. let mut infer_args_for_err = FxHashSet::default(); for &PathSeg(def_id, index) in &path_segs { let seg = &segments[index]; let generics = tcx.generics_of(def_id); // Argument-position `impl Trait` is treated as a normal generic // parameter internally, but we don't allow users to specify the // parameter's value explicitly, so we have to do some error- // checking here. if let GenericArgCountResult { correct: Err(GenericArgCountMismatch { reported: Some(ErrorReported), .. }), .. } = AstConv::check_generic_arg_count_for_call( tcx, span, &generics, &seg, false, // `is_method_call` ) { infer_args_for_err.insert(index); self.set_tainted_by_errors(); // See issue #53251. } } let has_self = path_segs .last() .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self) .unwrap_or(false); let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res { let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id)); match *ty.kind() { ty::Adt(adt_def, substs) if adt_def.has_ctor() => { let variant = adt_def.non_enum_variant(); let ctor_def_id = variant.ctor_def_id.unwrap(); ( Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id), Some(substs), ) } _ => { let mut err = tcx.sess.struct_span_err( span, "the `Self` constructor can only be used with tuple or unit structs", ); if let Some(adt_def) = ty.ty_adt_def() { match adt_def.adt_kind() { AdtKind::Enum => { err.help("did you mean to use one of the enum's variants?"); } AdtKind::Struct | AdtKind::Union => { err.span_suggestion( span, "use curly brackets", String::from("Self { /* fields */ }"), Applicability::HasPlaceholders, ); } } } err.emit(); return (tcx.ty_error(), res); } } } else { (res, None) }; let def_id = res.def_id(); // The things we are substituting into the type should not contain // escaping late-bound regions, and nor should the base type scheme. let ty = tcx.type_of(def_id); let arg_count = GenericArgCountResult { explicit_late_bound: ExplicitLateBound::No, correct: if infer_args_for_err.is_empty() { Ok(()) } else { Err(GenericArgCountMismatch::default()) }, }; let substs = self_ctor_substs.unwrap_or_else(|| { AstConv::create_substs_for_generic_args( tcx, def_id, &[][..], has_self, self_ty, arg_count, // Provide the generic args, and whether types should be inferred. |def_id| { if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| *did == def_id) { // If we've encountered an `impl Trait`-related error, we're just // going to infer the arguments for better error messages. if !infer_args_for_err.contains(&index) { // Check whether the user has provided generic arguments. if let Some(ref data) = segments[index].args { return (Some(data), segments[index].infer_args); } } return (None, segments[index].infer_args); } (None, true) }, // Provide substitutions for parameters for which (valid) arguments have been provided. |param, arg| match (&param.kind, arg) { (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { AstConv::ast_region_to_region(self, lt, Some(param)).into() } (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => { self.to_ty(ty).into() } (GenericParamDefKind::Const, GenericArg::Const(ct)) => { self.const_arg_to_const(&ct.value, param.def_id).into() } _ => unreachable!(), }, // Provide substitutions for parameters for which arguments are inferred. |substs, param, infer_args| { match param.kind { GenericParamDefKind::Lifetime => { self.re_infer(Some(param), span).unwrap().into() } GenericParamDefKind::Type { has_default, .. } => { if !infer_args && has_default { // If we have a default, then we it doesn't matter that we're not // inferring the type arguments: we provide the default where any // is missing. let default = tcx.type_of(param.def_id); self.normalize_ty( span, default.subst_spanned(tcx, substs.unwrap(), Some(span)), ) .into() } else { // If no type arguments were provided, we have to infer them. // This case also occurs as a result of some malformed input, e.g. // a lifetime argument being given instead of a type parameter. // Using inference instead of `Error` gives better error messages. self.var_for_def(span, param) } } GenericParamDefKind::Const => { // FIXME(const_generics:defaults) // No const parameters were provided, we have to infer them. self.var_for_def(span, param) } } }, ) }); assert!(!substs.has_escaping_bound_vars()); assert!(!ty.has_escaping_bound_vars()); // First, store the "user substs" for later. self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty); self.add_required_obligations(span, def_id, &substs); // Substitute the values for the type parameters into the type of // the referenced item. let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty); if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty { // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method` // is inherent, there is no `Self` parameter; instead, the impl needs // type parameters, which we can infer by unifying the provided `Self` // with the substituted impl type. // This also occurs for an enum variant on a type alias. let ty = tcx.type_of(impl_def_id); let impl_ty = self.instantiate_type_scheme(span, &substs, &ty); match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) { Ok(ok) => self.register_infer_ok_obligations(ok), Err(_) => { self.tcx.sess.delay_span_bug( span, &format!( "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?", self_ty, impl_ty, ), ); } } } self.check_rustc_args_require_const(def_id, hir_id, span); debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted); self.write_substs(hir_id, substs); (ty_substituted, res) } /// Add all the obligations that are required, substituting and normalized appropriately. fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) { let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs); for (i, mut obligation) in traits::predicates_for_generics( traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)), self.param_env, bounds, ) .enumerate() { // This makes the error point at the bound, but we want to point at the argument if let Some(span) = spans.get(i) { obligation.cause.make_mut().code = traits::BindingObligation(def_id, *span); } self.register_predicate(obligation); } } fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) { // We're only interested in functions tagged with // #[rustc_args_required_const], so ignore anything that's not. if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) { return; } // If our calling expression is indeed the function itself, we're good! // If not, generate an error that this can only be called directly. if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) { if let ExprKind::Call(ref callee, ..) = expr.kind { if callee.hir_id == hir_id { return; } } } self.tcx.sess.span_err( span, "this function can only be invoked directly, not through a function pointer", ); } /// Resolves `typ` by a single level if `typ` is a type variable. /// If no resolution is possible, then an error is reported. /// Numeric inference variables may be left unresolved. pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> { let ty = self.resolve_vars_with_obligations(ty); if !ty.is_ty_var() { ty } else { if !self.is_tainted_by_errors() { self.emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282) .note("type must be known at this point") .emit(); } let err = self.tcx.ty_error(); self.demand_suptype(sp, err, ty); err } } pub(super) fn with_breakable_ctxt<F: FnOnce() -> R, R>( &self, id: hir::HirId, ctxt: BreakableCtxt<'tcx>, f: F, ) -> (BreakableCtxt<'tcx>, R) { let index; { let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); index = enclosing_breakables.stack.len(); enclosing_breakables.by_id.insert(id, index); enclosing_breakables.stack.push(ctxt); } let result = f(); let ctxt = { let mut enclosing_breakables = self.enclosing_breakables.borrow_mut(); debug_assert!(enclosing_breakables.stack.len() == index + 1); enclosing_breakables.by_id.remove(&id).expect("missing breakable context"); enclosing_breakables.stack.pop().expect("missing breakable context") }; (ctxt, result) } /// Instantiate a QueryResponse in a probe context, without a /// good ObligationCause. pub(super) fn probe_instantiate_query_response( &self, span: Span, original_values: &OriginalQueryValues<'tcx>, query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>, ) -> InferResult<'tcx, Ty<'tcx>> { self.instantiate_query_response_and_region_obligations( &traits::ObligationCause::misc(span, self.body_id), self.param_env, original_values, query_result, ) } /// Returns `true` if an expression is contained inside the LHS of an assignment expression. pub(super) fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool { let mut contained_in_place = false; while let hir::Node::Expr(parent_expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id)) { match &parent_expr.kind { hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => { if lhs.hir_id == expr_id { contained_in_place = true; break; } } _ => (), } expr_id = parent_expr.hir_id; } contained_in_place } } impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> { type Target = Inherited<'a, 'tcx>; fn deref(&self) -> &Self::Target { &self.inh } } impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> { fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { self.tcx } fn item_def_id(&self) -> Option<DefId> { None } fn default_constness_for_trait_bounds(&self) -> hir::Constness { // FIXME: refactor this into a method let node = self.tcx.hir().get(self.body_id); if let Some(fn_like) = FnLikeNode::from_node(node) { fn_like.constness() } else { hir::Constness::NotConst } } fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> { let tcx = self.tcx; let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); let item_id = tcx.hir().ty_param_owner(hir_id); let item_def_id = tcx.hir().local_def_id(item_id); let generics = tcx.generics_of(item_def_id); let index = generics.param_def_id_to_index[&def_id]; ty::GenericPredicates { parent: None, predicates: tcx.arena.alloc_from_iter( self.param_env.caller_bounds().iter().filter_map(|predicate| { match predicate.skip_binders() { ty::PredicateAtom::Trait(data, _) if data.self_ty().is_param(index) => { // HACK(eddyb) should get the original `Span`. let span = tcx.def_span(def_id); Some((predicate, span)) } _ => None, } }), ), } } fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> { let v = match def { Some(def) => infer::EarlyBoundRegion(span, def.name), None => infer::MiscVariable(span), }; Some(self.next_region_var(v)) } fn allow_ty_infer(&self) -> bool { true } fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> { if let Some(param) = param { if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() { return ty; } unreachable!() } else { self.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span, }) } } fn ct_infer( &self, ty: Ty<'tcx>, param: Option<&ty::GenericParamDef>, span: Span, ) -> &'tcx Const<'tcx> { if let Some(param) = param { if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() { return ct; } unreachable!() } else { self.next_const_var( ty, ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span }, ) } } fn projected_ty_from_poly_trait_ref( &self, span: Span, item_def_id: DefId, item_segment: &hir::PathSegment<'_>, poly_trait_ref: ty::PolyTraitRef<'tcx>, ) -> Ty<'tcx> { let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars( span, infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id), &poly_trait_ref, ); let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item( self, self.tcx, span, item_def_id, item_segment, trait_ref.substs, ); self.tcx().mk_projection(item_def_id, item_substs) } fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> { if ty.has_escaping_bound_vars() { ty // FIXME: normalization and escaping regions } else { self.normalize_associated_types_in(span, &ty) } } fn set_tainted_by_errors(&self) { self.infcx.set_tainted_by_errors() } fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) { self.write_ty(hir_id, ty) } } </del>

Discussion:
Branching this from . Originally, for was over 6,000 lines. I was able to push that to around 1,100 lines (PR ). However, in the process, I found that was rather long, with 13 fields in the struct and some rather long s attached. The sum total is 3,200 lines, which effectively means that the comment was moved from to . The goal of this issue is to smaller, at minimum less than 3,000 lines by some of its functionality into "sub-structs" that will be in separate files Unknowns to solve: [ ] How do the 13 fields group into nice sub-structs [ ] What to name the above mentioned sub-structs [X] How to achieve this refactoring without changing the interface of Solution: Cannot do
modify labels to +T-compiler and +C-cleanup.
The third unknown is probably impossible. All fields (except ) can be accessed from outside the file (). So the interface must change.
modify labels to +E-needs-mentor.