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-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs1540
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs383
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs2236
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs312
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs1250
5 files changed, 5721 insertions, 0 deletions
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
new file mode 100644
index 000000000..6a1cffe3e
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -0,0 +1,1540 @@
+use crate::callee::{self, DeferredCallResolution};
+use crate::method::{self, MethodCallee, SelfSource};
+use crate::rvalue_scopes;
+use crate::{BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy};
+use rustc_data_structures::captures::Captures;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
+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, Node, QPath};
+use rustc_hir_analysis::astconv::{
+ AstConv, CreateSubstsForGenericArgsCtxt, ExplicitLateBound, GenericArgCountMismatch,
+ GenericArgCountResult, IsMethodCall, PathSeg,
+};
+use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
+use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
+use rustc_infer::infer::{InferOk, InferResult};
+use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
+use rustc_middle::ty::fold::TypeFoldable;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{
+ self, AdtKind, CanonicalUserType, DefIdTree, EarlyBinder, GenericParamDefKind, ToPolyTraitRef,
+ ToPredicate, Ty, UserType,
+};
+use rustc_middle::ty::{GenericArgKind, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts};
+use rustc_session::lint;
+use rustc_span::def_id::LocalDefId;
+use rustc_span::hygiene::DesugaringKind;
+use rustc_span::symbol::{kw, sym, Ident};
+use rustc_span::{Span, DUMMY_SP};
+use rustc_trait_selection::infer::InferCtxtExt as _;
+use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
+use rustc_trait_selection::traits::{
+ self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt,
+};
+
+use std::collections::hash_map::Entry;
+use std::slice;
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ /// Produces warning on the given node, if the current point in the
+ /// function is unreachable, and there hasn't been another warning.
+ pub(in super::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);
+
+ let msg = format!("unreachable {}", kind);
+ self.tcx().struct_span_lint_hir(
+ lint::builtin::UNREACHABLE_CODE,
+ id,
+ span,
+ &msg,
+ |lint| {
+ lint.span_label(span, &msg).span_label(
+ orig_span,
+ custom_note
+ .unwrap_or("any code following this expression is unreachable"),
+ )
+ },
+ )
+ }
+ }
+ }
+
+ /// 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(in super::super) fn resolve_vars_with_obligations(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
+ self.resolve_vars_with_obligations_and_mutate_fulfillment(ty, |_| {})
+ }
+
+ #[instrument(skip(self, mutate_fulfillment_errors), level = "debug", ret)]
+ pub(in super::super) fn resolve_vars_with_obligations_and_mutate_fulfillment(
+ &self,
+ mut ty: Ty<'tcx>,
+ mutate_fulfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
+ ) -> Ty<'tcx> {
+ // No Infer()? Nothing needs doing.
+ if !ty.has_non_region_infer() {
+ debug!("no inference var, nothing needs doing");
+ 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_non_region_infer() {
+ debug!(?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, mutate_fulfillment_errors);
+ self.resolve_vars_if_possible(ty)
+ }
+
+ pub(in super::super) fn record_deferred_call_resolution(
+ &self,
+ closure_def_id: LocalDefId,
+ 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(in super::super) fn remove_deferred_call_resolutions(
+ &self,
+ closure_def_id: LocalDefId,
+ ) -> Vec<DeferredCallResolution<'tcx>> {
+ let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
+ deferred_call_resolutions.remove(&closure_def_id).unwrap_or_default()
+ }
+
+ 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);
+ }
+
+ #[instrument(level = "debug", skip(self))]
+ pub(in super::super) fn write_resolution(
+ &self,
+ hir_id: hir::HirId,
+ r: Result<(DefKind, DefId), ErrorGuaranteed>,
+ ) {
+ self.typeck_results.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
+ }
+
+ #[instrument(level = "debug", skip(self))]
+ pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
+ 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_empty() {
+ let method_generics = self.tcx.generics_of(method.def_id);
+ if !method_generics.params.is_empty() {
+ let user_type_annotation = self.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.var_for_def(DUMMY_SP, param)
+ } else {
+ method.substs[i]
+ }
+ }),
+ user_self_ty: None, // not relevant here
+ };
+
+ self.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_empty() {
+ 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.
+ #[instrument(skip(self), level = "debug")]
+ 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!("fcx {}", self.tag());
+
+ if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
+ let canonicalized = self.canonicalize_user_type_annotation(UserType::TypeOf(
+ def_id,
+ UserSubsts { substs, user_self_ty },
+ ));
+ debug!(?canonicalized);
+ self.write_user_type_annotation(hir_id, canonicalized);
+ }
+ }
+
+ #[instrument(skip(self), level = "debug")]
+ pub fn write_user_type_annotation(
+ &self,
+ hir_id: hir::HirId,
+ canonical_user_type_annotation: CanonicalUserType<'tcx>,
+ ) {
+ debug!("fcx {}", 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!("skipping identity substs");
+ }
+ }
+
+ #[instrument(skip(self, expr), level = "debug")]
+ pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
+ debug!("expr = {:#?}", expr);
+
+ if adj.is_empty() {
+ return;
+ }
+
+ for a in &adj {
+ if let Adjust::NeverToAny = a.kind {
+ if a.target.is_ty_var() {
+ self.diverging_type_vars.borrow_mut().insert(a.target);
+ debug!("apply_adjustments: adding `{:?}` as diverging type var", a.target);
+ }
+ }
+ }
+
+ 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.
+ _ => {
+ self.tcx.sess.delay_span_bug(
+ expr.span,
+ &format!(
+ "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>,
+ {
+ debug!("instantiate_type_scheme(value={:?}, substs={:?})", value, substs);
+ let value = EarlyBinder(value).subst(self.tcx, substs);
+ let result = self.normalize_associated_types_in(span, value);
+ debug!("instantiate_type_scheme = {:?}", result);
+ result
+ }
+
+ /// As `instantiate_type_scheme`, but for the bounds found in a
+ /// generic type scheme.
+ pub(in super::super) 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)
+ }
+
+ pub(in super::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(in super::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(
+ ObligationCause::misc(span, self.body_id),
+ self.param_env,
+ value,
+ )
+ }
+
+ pub(in super::super) fn normalize_op_associated_types_in_as_infer_ok<T>(
+ &self,
+ span: Span,
+ value: T,
+ opt_input_expr: Option<&hir::Expr<'_>>,
+ ) -> InferOk<'tcx, T>
+ where
+ T: TypeFoldable<'tcx>,
+ {
+ self.inh.partially_normalize_associated_types_in(
+ ObligationCause::new(
+ span,
+ self.body_id,
+ traits::BinOp {
+ rhs_span: opt_input_expr.map(|expr| expr.span),
+ is_lit: opt_input_expr
+ .map_or(false, |expr| matches!(expr.kind, ExprKind::Lit(_))),
+ output_ty: None,
+ },
+ ),
+ 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 = <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_t);
+ self.register_wf_obligation(t.into(), ast_t.span, traits::WellFormed(None));
+ 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.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 array_length_to_const(&self, length: &hir::ArrayLen) -> ty::Const<'tcx> {
+ match length {
+ &hir::ArrayLen::Infer(_, span) => self.ct_infer(self.tcx.types.usize, None, span),
+ hir::ArrayLen::Body(anon_const) => {
+ let const_def_id = self.tcx.hir().local_def_id(anon_const.hir_id);
+ let span = self.tcx.hir().span(anon_const.hir_id);
+ let c = ty::Const::from_anon_const(self.tcx, const_def_id);
+ self.register_wf_obligation(c.into(), span, ObligationCauseCode::WellFormed(None));
+ self.normalize_associated_types_in(span, c)
+ }
+ }
+ }
+
+ pub fn const_arg_to_const(
+ &self,
+ ast_c: &hir::AnonConst,
+ param_def_id: DefId,
+ ) -> 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::WellFormed(None),
+ );
+ 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: TypeVisitable<'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()
+ );
+ }
+ }
+ }
+
+ pub fn node_ty_opt(&self, id: hir::HirId) -> Option<Ty<'tcx>> {
+ match self.typeck_results.borrow().node_types().get(id) {
+ Some(&t) => Some(t),
+ None if self.is_tainted_by_errors() => Some(self.tcx.ty_error()),
+ None => None,
+ }
+ }
+
+ /// Registers an obligation for checking later, during regionck, that `arg` is well-formed.
+ pub fn register_wf_obligation(
+ &self,
+ arg: ty::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::Binder::dummy(ty::PredicateKind::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::WellFormed(None));
+ }
+ }
+
+ // 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(in super::super) fn resolve_rvalue_scopes(&self, def_id: DefId) {
+ let scope_tree = self.tcx.region_scope_tree(def_id);
+ let rvalue_scopes = { rvalue_scopes::resolve_rvalue_scopes(self, &scope_tree, def_id) };
+ let mut typeck_results = self.inh.typeck_results.borrow_mut();
+ typeck_results.rvalue_scopes = rvalue_scopes;
+ }
+
+ pub(in super::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, |_| {});
+ crate::generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
+ }
+ }
+
+ #[instrument(skip(self), level = "debug")]
+ pub(in super::super) fn select_all_obligations_or_error(&self) {
+ let mut errors = self.fulfillment_cx.borrow_mut().select_all_or_error(&self);
+
+ if !errors.is_empty() {
+ self.adjust_fulfillment_errors_for_expr_obligation(&mut errors);
+ self.err_ctxt().report_fulfillment_errors(&errors, self.inh.body_id, false);
+ }
+ }
+
+ /// Select as many obligations as we can at present.
+ pub(in super::super) fn select_obligations_where_possible(
+ &self,
+ fallback_has_occurred: bool,
+ mutate_fulfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
+ ) {
+ let mut result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
+ if !result.is_empty() {
+ mutate_fulfillment_errors(&mut result);
+ self.adjust_fulfillment_errors_for_expr_obligation(&mut result);
+ self.err_ctxt().report_fulfillment_errors(
+ &result,
+ 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(in super::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()
+ }
+
+ #[instrument(skip(self), level = "debug")]
+ 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_ty);
+
+ 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,
+ }
+ }
+
+ #[instrument(skip(self), level = "debug")]
+ pub(in super::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);
+ trace!("pending_obligations = {:#?}", self.fulfillment_cx.borrow().pending_obligations());
+
+ self.fulfillment_cx
+ .borrow()
+ .pending_obligations()
+ .into_iter()
+ .filter_map(move |obligation| {
+ let bound_predicate = obligation.predicate.kind();
+ match bound_predicate.skip_binder() {
+ ty::PredicateKind::Projection(data) => Some((
+ bound_predicate.rebind(data).required_poly_trait_ref(self.tcx),
+ obligation,
+ )),
+ ty::PredicateKind::Trait(data) => {
+ Some((bound_predicate.rebind(data).to_poly_trait_ref(), obligation))
+ }
+ ty::PredicateKind::Subtype(..) => None,
+ ty::PredicateKind::Coerce(..) => None,
+ ty::PredicateKind::RegionOutlives(..) => None,
+ ty::PredicateKind::TypeOutlives(..) => None,
+ ty::PredicateKind::WellFormed(..) => None,
+ ty::PredicateKind::ObjectSafe(..) => None,
+ ty::PredicateKind::ConstEvaluatable(..) => None,
+ ty::PredicateKind::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 an unresolved
+ // inference variable.
+ ty::PredicateKind::ClosureKind(..) => None,
+ ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
+ }
+ })
+ .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
+ }
+
+ pub(in super::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())
+ }
+
+ pub(in super::super) fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
+ vec![self.tcx.ty_error(); len]
+ }
+
+ /// Unifies the output type with the expected type early, for more coercions
+ /// and forward type information on the input expressions.
+ #[instrument(skip(self, call_span), level = "debug")]
+ pub(in super::super) fn expected_inputs_for_expected_output(
+ &self,
+ call_span: Span,
+ expected_ret: Expectation<'tcx>,
+ formal_ret: Ty<'tcx>,
+ formal_args: &[Ty<'tcx>],
+ ) -> Option<Vec<Ty<'tcx>>> {
+ let formal_ret = self.resolve_vars_with_obligations(formal_ret);
+ let ret_ty = expected_ret.only_has_type(self)?;
+
+ // HACK(oli-obk): This is a hack to keep RPIT and TAIT in sync wrt their behaviour.
+ // Without it, the inference
+ // variable will get instantiated with the opaque type. The inference variable often
+ // has various helpful obligations registered for it that help closures figure out their
+ // signature. If we infer the inference var to the opaque type, the closure won't be able
+ // to find those obligations anymore, and it can't necessarily find them from the opaque
+ // type itself. We could be more powerful with inference if we *combined* the obligations
+ // so that we got both the obligations from the opaque type and the ones from the inference
+ // variable. That will accept more code than we do right now, so we need to carefully consider
+ // the implications.
+ // Note: this check is pessimistic, as the inference type could be matched with something other
+ // than the opaque type, but then we need a new `TypeRelation` just for this specific case and
+ // can't re-use `sup` below.
+ // See src/test/ui/impl-trait/hidden-type-is-opaque.rs and
+ // src/test/ui/impl-trait/hidden-type-is-opaque-2.rs for examples that hit this path.
+ if formal_ret.has_infer_types() {
+ for ty in ret_ty.walk() {
+ if let ty::subst::GenericArgKind::Type(ty) = ty.unpack()
+ && let ty::Opaque(def_id, _) = *ty.kind()
+ && let Some(def_id) = def_id.as_local()
+ && self.opaque_type_origin(def_id, DUMMY_SP).is_some() {
+ return None;
+ }
+ }
+ }
+
+ 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.
+ let errors = self.save_and_restore_in_snapshot_flag(|_| {
+ let mut fulfill = <dyn TraitEngine<'_>>::new(self.tcx);
+ for obligation in ok.obligations {
+ fulfill.register_predicate_obligation(self, obligation);
+ }
+ fulfill.select_where_possible(self)
+ });
+
+ if !errors.is_empty() {
+ return Err(());
+ }
+ }
+ Err(_) => return Err(()),
+ }
+
+ // Record all the argument types, with the substitutions
+ // produced from the above subtyping unification.
+ Ok(Some(formal_args.iter().map(|&ty| self.resolve_vars_if_possible(ty)).collect()))
+ })
+ .unwrap_or_default();
+ debug!(?formal_args, ?formal_ret, ?expect_args, ?expected_ret);
+ expect_args
+ }
+
+ pub(in super::super) fn resolve_lang_item_path(
+ &self,
+ lang_item: hir::LangItem,
+ span: Span,
+ hir_id: hir::HirId,
+ expr_hir_id: Option<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.bound_type_of(self.tcx.parent(def_id))
+ } else {
+ self.tcx.bound_type_of(def_id)
+ };
+ let substs = self.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)));
+
+ let code = match lang_item {
+ hir::LangItem::IntoFutureIntoFuture => {
+ Some(ObligationCauseCode::AwaitableExpr(expr_hir_id))
+ }
+ hir::LangItem::IteratorNext | hir::LangItem::IntoIterIntoIter => {
+ Some(ObligationCauseCode::ForLoopIterator)
+ }
+ hir::LangItem::TryTraitFromOutput
+ | hir::LangItem::TryTraitFromResidual
+ | hir::LangItem::TryTraitBranch => Some(ObligationCauseCode::QuestionMark),
+ _ => None,
+ };
+ if let Some(code) = code {
+ self.add_required_obligations_with_code(span, def_id, substs, move |_, _| code.clone());
+ } else {
+ self.add_required_obligations_for_hir(span, def_id, substs, hir_id);
+ }
+
+ (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_fully_qualified_call(
+ &self,
+ qpath: &'tcx QPath<'tcx>,
+ hir_id: hir::HirId,
+ span: Span,
+ ) -> (Res, Option<Ty<'tcx>>, &'tcx [hir::PathSegment<'tcx>]) {
+ debug!(
+ "resolve_ty_and_res_fully_qualified_call: 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) => {
+ // Don't use `self.to_ty`, since this will register a WF obligation.
+ // If we're trying to call a non-existent method on a trait
+ // (e.g. `MyTrait::missing_method`), then resolution will
+ // give us a `QPath::TypeRelative` with a trait object as
+ // `qself`. In that case, we want to avoid registering a WF obligation
+ // for `dyn MyTrait`, since we don't actually need the trait
+ // to be object-safe.
+ // We manually call `register_wf_obligation` in the success path
+ // below.
+ (<dyn AstConv<'_>>::ast_ty_to_ty_in_path(self, qself), qself, segment)
+ }
+ QPath::LangItem(..) => {
+ bug!("`resolve_ty_and_res_fully_qualified_call` called on `LangItem`")
+ }
+ };
+ if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
+ {
+ self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
+ // 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_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
+ return (def, Some(ty), slice::from_ref(&**item_segment));
+ }
+ let item_name = item_segment.ident;
+ let result = self
+ .resolve_fully_qualified_call(span, item_name, ty, qself.span, hir_id)
+ .or_else(|error| {
+ let result = match error {
+ method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
+ _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
+ };
+
+ // If we have a path like `MyTrait::missing_method`, then don't register
+ // a WF obligation for `dyn MyTrait` when method lookup fails. Otherwise,
+ // register a WF obligation so that we can detect any additional
+ // errors in the self type.
+ if !(matches!(error, method::MethodError::NoMatch(_)) && ty.is_trait()) {
+ self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
+ }
+ if item_name.name != kw::Empty {
+ if let Some(mut e) = self.report_method_error(
+ span,
+ ty,
+ item_name,
+ SelfSource::QPath(qself),
+ error,
+ None,
+ ) {
+ e.emit();
+ }
+ }
+ result
+ });
+
+ if result.is_ok() {
+ self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
+ }
+
+ // Write back the new resolution.
+ self.write_resolution(hir_id, result);
+ (
+ result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
+ Some(ty),
+ slice::from_ref(&**item_segment),
+ )
+ }
+
+ /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
+ pub(in super::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))
+ })
+ }
+
+ pub(in super::super) fn note_internal_mutation_in_method(
+ &self,
+ err: &mut Diagnostic,
+ 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...",
+ );
+ 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));
+ }
+ }
+
+ pub(in super::super) fn note_need_for_fn_pointer(
+ &self,
+ err: &mut Diagnostic,
+ 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.bound_fn_sig(*did1).subst(self.tcx, substs1);
+ let sig2 = self.tcx.bound_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.bound_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
+ ));
+ }
+
+ // Instantiates the given path, which must refer to an item with the given
+ // number of type parameters and type.
+ #[instrument(skip(self, span), level = "debug")]
+ 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) {
+ let tcx = self.tcx;
+
+ let path_segs = match res {
+ Res::Local(_) | Res::SelfCtor(_) => vec![],
+ Res::Def(kind, def_id) => <dyn 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 assoc_item = tcx.associated_item(def_id);
+ let container = assoc_item.container;
+ let container_id = assoc_item.container_id(tcx);
+ debug!(?def_id, ?container, ?container_id);
+ match container {
+ ty::TraitContainer => {
+ callee::check_legal_trait_for_method_call(tcx, span, None, span, container_id)
+ }
+ ty::ImplContainer => {
+ 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: container_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 = <dyn 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();
+
+ let mut explicit_late_bound = ExplicitLateBound::No;
+ 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.
+ let arg_count = <dyn AstConv<'_>>::check_generic_arg_count_for_call(
+ tcx,
+ span,
+ def_id,
+ &generics,
+ seg,
+ IsMethodCall::No,
+ );
+
+ if let ExplicitLateBound::Yes = arg_count.explicit_late_bound {
+ explicit_late_bound = ExplicitLateBound::Yes;
+ }
+
+ if let Err(GenericArgCountMismatch { reported: Some(_), .. }) = arg_count.correct {
+ 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",
+ "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,
+ correct: if infer_args_for_err.is_empty() {
+ Ok(())
+ } else {
+ Err(GenericArgCountMismatch::default())
+ },
+ };
+
+ struct CreateCtorSubstsContext<'a, 'tcx> {
+ fcx: &'a FnCtxt<'a, 'tcx>,
+ span: Span,
+ path_segs: &'a [PathSeg],
+ infer_args_for_err: &'a FxHashSet<usize>,
+ segments: &'a [hir::PathSegment<'a>],
+ }
+ impl<'tcx, 'a> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for CreateCtorSubstsContext<'a, 'tcx> {
+ fn args_for_def_id(
+ &mut self,
+ def_id: DefId,
+ ) -> (Option<&'a hir::GenericArgs<'a>>, bool) {
+ if let Some(&PathSeg(_, index)) =
+ self.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 !self.infer_args_for_err.contains(&index) {
+ // Check whether the user has provided generic arguments.
+ if let Some(ref data) = self.segments[index].args {
+ return (Some(data), self.segments[index].infer_args);
+ }
+ }
+ return (None, self.segments[index].infer_args);
+ }
+
+ (None, true)
+ }
+
+ fn provided_kind(
+ &mut self,
+ param: &ty::GenericParamDef,
+ arg: &GenericArg<'_>,
+ ) -> ty::GenericArg<'tcx> {
+ match (&param.kind, arg) {
+ (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
+ <dyn AstConv<'_>>::ast_region_to_region(self.fcx, lt, Some(param)).into()
+ }
+ (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
+ self.fcx.to_ty(ty).into()
+ }
+ (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
+ self.fcx.const_arg_to_const(&ct.value, param.def_id).into()
+ }
+ (GenericParamDefKind::Type { .. }, GenericArg::Infer(inf)) => {
+ self.fcx.ty_infer(Some(param), inf.span).into()
+ }
+ (GenericParamDefKind::Const { .. }, GenericArg::Infer(inf)) => {
+ let tcx = self.fcx.tcx();
+ self.fcx.ct_infer(tcx.type_of(param.def_id), Some(param), inf.span).into()
+ }
+ _ => unreachable!(),
+ }
+ }
+
+ fn inferred_kind(
+ &mut self,
+ substs: Option<&[ty::GenericArg<'tcx>]>,
+ param: &ty::GenericParamDef,
+ infer_args: bool,
+ ) -> ty::GenericArg<'tcx> {
+ let tcx = self.fcx.tcx();
+ match param.kind {
+ GenericParamDefKind::Lifetime => {
+ self.fcx.re_infer(Some(param), self.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.bound_type_of(param.def_id);
+ self.fcx
+ .normalize_ty(self.span, default.subst(tcx, substs.unwrap()))
+ .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.fcx.var_for_def(self.span, param)
+ }
+ }
+ GenericParamDefKind::Const { has_default } => {
+ if !infer_args && has_default {
+ tcx.bound_const_param_default(param.def_id)
+ .subst(tcx, substs.unwrap())
+ .into()
+ } else {
+ self.fcx.var_for_def(self.span, param)
+ }
+ }
+ }
+ }
+ }
+
+ let substs = self_ctor_substs.unwrap_or_else(|| {
+ <dyn AstConv<'_>>::create_substs_for_generic_args(
+ tcx,
+ def_id,
+ &[],
+ has_self,
+ self_ty,
+ &arg_count,
+ &mut CreateCtorSubstsContext {
+ fcx: self,
+ span,
+ path_segs: &path_segs,
+ infer_args_for_err: &infer_args_for_err,
+ segments,
+ },
+ )
+ });
+ 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_for_hir(span, def_id, &substs, hir_id);
+
+ // 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).eq(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,
+ ),
+ );
+ }
+ }
+ }
+
+ 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.
+ pub(crate) fn add_required_obligations_for_hir(
+ &self,
+ span: Span,
+ def_id: DefId,
+ substs: SubstsRef<'tcx>,
+ hir_id: hir::HirId,
+ ) {
+ self.add_required_obligations_with_code(span, def_id, substs, |idx, span| {
+ if span.is_dummy() {
+ ObligationCauseCode::ExprItemObligation(def_id, hir_id, idx)
+ } else {
+ ObligationCauseCode::ExprBindingObligation(def_id, span, hir_id, idx)
+ }
+ })
+ }
+
+ #[instrument(level = "debug", skip(self, code, span, substs))]
+ fn add_required_obligations_with_code(
+ &self,
+ span: Span,
+ def_id: DefId,
+ substs: SubstsRef<'tcx>,
+ code: impl Fn(usize, Span) -> ObligationCauseCode<'tcx>,
+ ) {
+ let param_env = self.param_env;
+
+ let remap = match self.tcx.def_kind(def_id) {
+ // Associated consts have `Self: ~const Trait` bounds that should be satisfiable when
+ // `Self: Trait` is satisfied because it does not matter whether the impl is `const`.
+ // Therefore we have to remap the param env here to be non-const.
+ hir::def::DefKind::AssocConst => true,
+ hir::def::DefKind::AssocFn
+ if self.tcx.def_kind(self.tcx.parent(def_id)) == hir::def::DefKind::Trait =>
+ {
+ // N.B.: All callsites to this function involve checking a path expression.
+ //
+ // When instantiating a trait method as a function item, it does not actually matter whether
+ // the trait is `const` or not, or whether `where T: ~const Tr` needs to be satisfied as
+ // `const`. If we were to introduce instantiating trait methods as `const fn`s, we would
+ // check that after this, either via a bound `where F: ~const FnOnce` or when coercing to a
+ // `const fn` pointer.
+ //
+ // FIXME(fee1-dead) FIXME(const_trait_impl): update this doc when trait methods can satisfy
+ // `~const FnOnce` or can be coerced to `const fn` pointer.
+ true
+ }
+ _ => false,
+ };
+ let (bounds, _) = self.instantiate_bounds(span, def_id, &substs);
+
+ for mut obligation in traits::predicates_for_generics(
+ |idx, predicate_span| {
+ traits::ObligationCause::new(span, self.body_id, code(idx, predicate_span))
+ },
+ param_env,
+ bounds,
+ ) {
+ if remap {
+ obligation = obligation.without_const(self.tcx);
+ }
+ self.register_predicate(obligation);
+ }
+ }
+
+ /// 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.err_ctxt()
+ .emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282, true)
+ .emit();
+ }
+ let err = self.tcx.ty_error();
+ self.demand_suptype(sp, err, ty);
+ err
+ }
+ }
+
+ pub(in super::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(in super::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(in super::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
+ }
+}
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs
new file mode 100644
index 000000000..fc83994ca
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs
@@ -0,0 +1,383 @@
+use std::cmp;
+
+use rustc_index::vec::IndexVec;
+use rustc_middle::ty::error::TypeError;
+
+rustc_index::newtype_index! {
+ pub(crate) struct ExpectedIdx {
+ DEBUG_FORMAT = "ExpectedIdx({})",
+ }
+}
+
+rustc_index::newtype_index! {
+ pub(crate) struct ProvidedIdx {
+ DEBUG_FORMAT = "ProvidedIdx({})",
+ }
+}
+
+impl ExpectedIdx {
+ pub fn to_provided_idx(self) -> ProvidedIdx {
+ ProvidedIdx::from_usize(self.as_usize())
+ }
+}
+
+// An issue that might be found in the compatibility matrix
+#[derive(Debug)]
+enum Issue {
+ /// The given argument is the invalid type for the input
+ Invalid(usize),
+ /// There is a missing input
+ Missing(usize),
+ /// There's a superfluous argument
+ Extra(usize),
+ /// Two arguments should be swapped
+ Swap(usize, usize),
+ /// Several arguments should be reordered
+ Permutation(Vec<Option<usize>>),
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum Compatibility<'tcx> {
+ Compatible,
+ Incompatible(Option<TypeError<'tcx>>),
+}
+
+/// Similar to `Issue`, but contains some extra information
+#[derive(Debug)]
+pub(crate) enum Error<'tcx> {
+ /// The provided argument is the invalid type for the expected input
+ Invalid(ProvidedIdx, ExpectedIdx, Compatibility<'tcx>),
+ /// There is a missing input
+ Missing(ExpectedIdx),
+ /// There's a superfluous argument
+ Extra(ProvidedIdx),
+ /// Two arguments should be swapped
+ Swap(ProvidedIdx, ProvidedIdx, ExpectedIdx, ExpectedIdx),
+ /// Several arguments should be reordered
+ Permutation(Vec<(ExpectedIdx, ProvidedIdx)>),
+}
+
+pub(crate) struct ArgMatrix<'tcx> {
+ /// Maps the indices in the `compatibility_matrix` rows to the indices of
+ /// the *user provided* inputs
+ provided_indices: Vec<ProvidedIdx>,
+ /// Maps the indices in the `compatibility_matrix` columns to the indices
+ /// of the *expected* args
+ expected_indices: Vec<ExpectedIdx>,
+ /// The first dimension (rows) are the remaining user provided inputs to
+ /// match and the second dimension (cols) are the remaining expected args
+ /// to match
+ compatibility_matrix: Vec<Vec<Compatibility<'tcx>>>,
+}
+
+impl<'tcx> ArgMatrix<'tcx> {
+ pub(crate) fn new<F: FnMut(ProvidedIdx, ExpectedIdx) -> Compatibility<'tcx>>(
+ provided_count: usize,
+ expected_input_count: usize,
+ mut is_compatible: F,
+ ) -> Self {
+ let compatibility_matrix = (0..provided_count)
+ .map(|i| {
+ (0..expected_input_count)
+ .map(|j| is_compatible(ProvidedIdx::from_usize(i), ExpectedIdx::from_usize(j)))
+ .collect()
+ })
+ .collect();
+ ArgMatrix {
+ provided_indices: (0..provided_count).map(ProvidedIdx::from_usize).collect(),
+ expected_indices: (0..expected_input_count).map(ExpectedIdx::from_usize).collect(),
+ compatibility_matrix,
+ }
+ }
+
+ /// Remove a given input from consideration
+ fn eliminate_provided(&mut self, idx: usize) {
+ self.provided_indices.remove(idx);
+ self.compatibility_matrix.remove(idx);
+ }
+
+ /// Remove a given argument from consideration
+ fn eliminate_expected(&mut self, idx: usize) {
+ self.expected_indices.remove(idx);
+ for row in &mut self.compatibility_matrix {
+ row.remove(idx);
+ }
+ }
+
+ /// "satisfy" an input with a given arg, removing both from consideration
+ fn satisfy_input(&mut self, provided_idx: usize, expected_idx: usize) {
+ self.eliminate_provided(provided_idx);
+ self.eliminate_expected(expected_idx);
+ }
+
+ // Returns a `Vec` of (user input, expected arg) of matched arguments. These
+ // are inputs on the remaining diagonal that match.
+ fn eliminate_satisfied(&mut self) -> Vec<(ProvidedIdx, ExpectedIdx)> {
+ let num_args = cmp::min(self.provided_indices.len(), self.expected_indices.len());
+ let mut eliminated = vec![];
+ for i in (0..num_args).rev() {
+ if matches!(self.compatibility_matrix[i][i], Compatibility::Compatible) {
+ eliminated.push((self.provided_indices[i], self.expected_indices[i]));
+ self.satisfy_input(i, i);
+ }
+ }
+ eliminated
+ }
+
+ // Find some issue in the compatibility matrix
+ fn find_issue(&self) -> Option<Issue> {
+ let mat = &self.compatibility_matrix;
+ let ai = &self.expected_indices;
+ let ii = &self.provided_indices;
+
+ // Issue: 100478, when we end the iteration,
+ // `next_unmatched_idx` will point to the index of the first unmatched
+ let mut next_unmatched_idx = 0;
+ for i in 0..cmp::max(ai.len(), ii.len()) {
+ // If we eliminate the last row, any left-over arguments are considered missing
+ if i >= mat.len() {
+ return Some(Issue::Missing(next_unmatched_idx));
+ }
+ // If we eliminate the last column, any left-over inputs are extra
+ if mat[i].len() == 0 {
+ return Some(Issue::Extra(next_unmatched_idx));
+ }
+
+ // Make sure we don't pass the bounds of our matrix
+ let is_arg = i < ai.len();
+ let is_input = i < ii.len();
+ if is_arg && is_input && matches!(mat[i][i], Compatibility::Compatible) {
+ // This is a satisfied input, so move along
+ next_unmatched_idx += 1;
+ continue;
+ }
+
+ let mut useless = true;
+ let mut unsatisfiable = true;
+ if is_arg {
+ for j in 0..ii.len() {
+ // If we find at least one input this argument could satisfy
+ // this argument isn't unsatisfiable
+ if matches!(mat[j][i], Compatibility::Compatible) {
+ unsatisfiable = false;
+ break;
+ }
+ }
+ }
+ if is_input {
+ for j in 0..ai.len() {
+ // If we find at least one argument that could satisfy this input
+ // this input isn't useless
+ if matches!(mat[i][j], Compatibility::Compatible) {
+ useless = false;
+ break;
+ }
+ }
+ }
+
+ match (is_input, is_arg, useless, unsatisfiable) {
+ // If an argument is unsatisfied, and the input in its position is useless
+ // then the most likely explanation is that we just got the types wrong
+ (true, true, true, true) => return Some(Issue::Invalid(i)),
+ // Otherwise, if an input is useless, then indicate that this is an extra argument
+ (true, _, true, _) => return Some(Issue::Extra(i)),
+ // Otherwise, if an argument is unsatisfiable, indicate that it's missing
+ (_, true, _, true) => return Some(Issue::Missing(i)),
+ (true, true, _, _) => {
+ // The argument isn't useless, and the input isn't unsatisfied,
+ // so look for a parameter we might swap it with
+ // We look for swaps explicitly, instead of just falling back on permutations
+ // so that cases like (A,B,C,D) given (B,A,D,C) show up as two swaps,
+ // instead of a large permutation of 4 elements.
+ for j in 0..cmp::min(ai.len(), ii.len()) {
+ if i == j || matches!(mat[j][j], Compatibility::Compatible) {
+ continue;
+ }
+ if matches!(mat[i][j], Compatibility::Compatible)
+ && matches!(mat[j][i], Compatibility::Compatible)
+ {
+ return Some(Issue::Swap(i, j));
+ }
+ }
+ }
+ _ => {
+ continue;
+ }
+ }
+ }
+
+ // We didn't find any of the individual issues above, but
+ // there might be a larger permutation of parameters, so we now check for that
+ // by checking for cycles
+ // We use a double option at position i in this vec to represent:
+ // - None: We haven't computed anything about this argument yet
+ // - Some(None): This argument definitely doesn't participate in a cycle
+ // - Some(Some(x)): the i-th argument could permute to the x-th position
+ let mut permutation: Vec<Option<Option<usize>>> = vec![None; mat.len()];
+ let mut permutation_found = false;
+ for i in 0..mat.len() {
+ if permutation[i].is_some() {
+ // We've already decided whether this argument is or is not in a loop
+ continue;
+ }
+
+ let mut stack = vec![];
+ let mut j = i;
+ let mut last = i;
+ let mut is_cycle = true;
+ loop {
+ stack.push(j);
+ // Look for params this one could slot into
+ let compat: Vec<_> =
+ mat[j]
+ .iter()
+ .enumerate()
+ .filter_map(|(i, c)| {
+ if matches!(c, Compatibility::Compatible) { Some(i) } else { None }
+ })
+ .collect();
+ if compat.len() < 1 {
+ // try to find a cycle even when this could go into multiple slots, see #101097
+ is_cycle = false;
+ break;
+ }
+ j = compat[0];
+ if stack.contains(&j) {
+ last = j;
+ break;
+ }
+ }
+ if stack.len() <= 2 {
+ // If we encounter a cycle of 1 or 2 elements, we'll let the
+ // "satisfy" and "swap" code above handle those
+ is_cycle = false;
+ }
+ // We've built up some chain, some of which might be a cycle
+ // ex: [1,2,3,4]; last = 2; j = 2;
+ // So, we want to mark 4, 3, and 2 as part of a permutation
+ permutation_found = is_cycle;
+ while let Some(x) = stack.pop() {
+ if is_cycle {
+ permutation[x] = Some(Some(j));
+ j = x;
+ if j == last {
+ // From here on out, we're a tail leading into a cycle,
+ // not the cycle itself
+ is_cycle = false;
+ }
+ } else {
+ // Some(None) ensures we save time by skipping this argument again
+ permutation[x] = Some(None);
+ }
+ }
+ }
+
+ if permutation_found {
+ // Map unwrap to remove the first layer of Some
+ let final_permutation: Vec<Option<usize>> =
+ permutation.into_iter().map(|x| x.unwrap()).collect();
+ return Some(Issue::Permutation(final_permutation));
+ }
+ return None;
+ }
+
+ // Obviously, detecting exact user intention is impossible, so the goal here is to
+ // come up with as likely of a story as we can to be helpful.
+ //
+ // We'll iteratively removed "satisfied" input/argument pairs,
+ // then check for the cases above, until we've eliminated the entire grid
+ //
+ // We'll want to know which arguments and inputs these rows and columns correspond to
+ // even after we delete them.
+ pub(crate) fn find_errors(
+ mut self,
+ ) -> (Vec<Error<'tcx>>, IndexVec<ExpectedIdx, Option<ProvidedIdx>>) {
+ let provided_arg_count = self.provided_indices.len();
+
+ let mut errors: Vec<Error<'tcx>> = vec![];
+ // For each expected argument, the matched *actual* input
+ let mut matched_inputs: IndexVec<ExpectedIdx, Option<ProvidedIdx>> =
+ IndexVec::from_elem_n(None, self.expected_indices.len());
+
+ // Before we start looking for issues, eliminate any arguments that are already satisfied,
+ // so that an argument which is already spoken for by the input it's in doesn't
+ // spill over into another similarly typed input
+ // ex:
+ // fn some_func(_a: i32, _b: i32) {}
+ // some_func(1, "");
+ // Without this elimination, the first argument causes the second argument
+ // to show up as both a missing input and extra argument, rather than
+ // just an invalid type.
+ for (provided, expected) in self.eliminate_satisfied() {
+ matched_inputs[expected] = Some(provided);
+ }
+
+ while !self.provided_indices.is_empty() || !self.expected_indices.is_empty() {
+ let res = self.find_issue();
+ match res {
+ Some(Issue::Invalid(idx)) => {
+ let compatibility = self.compatibility_matrix[idx][idx].clone();
+ let input_idx = self.provided_indices[idx];
+ let arg_idx = self.expected_indices[idx];
+ self.satisfy_input(idx, idx);
+ errors.push(Error::Invalid(input_idx, arg_idx, compatibility));
+ }
+ Some(Issue::Extra(idx)) => {
+ let input_idx = self.provided_indices[idx];
+ self.eliminate_provided(idx);
+ errors.push(Error::Extra(input_idx));
+ }
+ Some(Issue::Missing(idx)) => {
+ let arg_idx = self.expected_indices[idx];
+ self.eliminate_expected(idx);
+ errors.push(Error::Missing(arg_idx));
+ }
+ Some(Issue::Swap(idx, other)) => {
+ let input_idx = self.provided_indices[idx];
+ let other_input_idx = self.provided_indices[other];
+ let arg_idx = self.expected_indices[idx];
+ let other_arg_idx = self.expected_indices[other];
+ let (min, max) = (cmp::min(idx, other), cmp::max(idx, other));
+ self.satisfy_input(min, max);
+ // Subtract 1 because we already removed the "min" row
+ self.satisfy_input(max - 1, min);
+ errors.push(Error::Swap(input_idx, other_input_idx, arg_idx, other_arg_idx));
+ matched_inputs[other_arg_idx] = Some(input_idx);
+ matched_inputs[arg_idx] = Some(other_input_idx);
+ }
+ Some(Issue::Permutation(args)) => {
+ let mut idxs: Vec<usize> = args.iter().filter_map(|&a| a).collect();
+
+ let mut real_idxs: IndexVec<ProvidedIdx, Option<(ExpectedIdx, ProvidedIdx)>> =
+ IndexVec::from_elem_n(None, provided_arg_count);
+ for (src, dst) in
+ args.iter().enumerate().filter_map(|(src, dst)| dst.map(|dst| (src, dst)))
+ {
+ let src_input_idx = self.provided_indices[src];
+ let dst_input_idx = self.provided_indices[dst];
+ let dest_arg_idx = self.expected_indices[dst];
+ real_idxs[src_input_idx] = Some((dest_arg_idx, dst_input_idx));
+ matched_inputs[dest_arg_idx] = Some(src_input_idx);
+ }
+ idxs.sort();
+ idxs.reverse();
+ for i in idxs {
+ self.satisfy_input(i, i);
+ }
+ errors.push(Error::Permutation(real_idxs.into_iter().flatten().collect()));
+ }
+ None => {
+ // We didn't find any issues, so we need to push the algorithm forward
+ // First, eliminate any arguments that currently satisfy their inputs
+ let eliminated = self.eliminate_satisfied();
+ assert!(!eliminated.is_empty(), "didn't eliminated any indice in this round");
+ for (inp, arg) in eliminated {
+ matched_inputs[arg] = Some(inp);
+ }
+ }
+ };
+ }
+
+ return (errors, matched_inputs);
+ }
+}
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
new file mode 100644
index 000000000..8e0fcb56c
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -0,0 +1,2236 @@
+use crate::coercion::CoerceMany;
+use crate::fn_ctxt::arg_matrix::{ArgMatrix, Compatibility, Error, ExpectedIdx, ProvidedIdx};
+use crate::gather_locals::Declaration;
+use crate::method::MethodCallee;
+use crate::Expectation::*;
+use crate::TupleArgumentsFlag::*;
+use crate::{
+ struct_span_err, BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy, Needs,
+ TupleArgumentsFlag,
+};
+use rustc_ast as ast;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{pluralize, Applicability, Diagnostic, DiagnosticId, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::{ExprKind, Node, QPath};
+use rustc_hir_analysis::astconv::AstConv;
+use rustc_hir_analysis::check::intrinsicck::InlineAsmCtxt;
+use rustc_hir_analysis::check::potentially_plural_count;
+use rustc_hir_analysis::structured_errors::StructuredDiagnostic;
+use rustc_index::vec::IndexVec;
+use rustc_infer::infer::error_reporting::{FailureCode, ObligationCauseExt};
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_infer::infer::InferOk;
+use rustc_infer::infer::TypeTrace;
+use rustc_middle::ty::adjustment::AllowTwoPhase;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty, TypeSuperVisitable, TypeVisitor};
+use rustc_session::Session;
+use rustc_span::symbol::Ident;
+use rustc_span::{self, sym, Span};
+use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext};
+
+use std::iter;
+use std::mem;
+use std::ops::ControlFlow;
+use std::slice;
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ pub(in super::super) fn check_casts(&mut self) {
+ // don't hold the borrow to deferred_cast_checks while checking to avoid borrow checker errors
+ // when writing to `self.param_env`.
+ let mut deferred_cast_checks = mem::take(&mut *self.deferred_cast_checks.borrow_mut());
+
+ debug!("FnCtxt::check_casts: {} deferred checks", deferred_cast_checks.len());
+ for cast in deferred_cast_checks.drain(..) {
+ let prev_env = self.param_env;
+ self.param_env = self.param_env.with_constness(cast.constness);
+
+ cast.check(self);
+
+ self.param_env = prev_env;
+ }
+
+ *self.deferred_cast_checks.borrow_mut() = deferred_cast_checks;
+ }
+
+ pub(in super::super) fn check_transmutes(&self) {
+ let mut deferred_transmute_checks = self.deferred_transmute_checks.borrow_mut();
+ debug!("FnCtxt::check_transmutes: {} deferred checks", deferred_transmute_checks.len());
+ for (from, to, hir_id) in deferred_transmute_checks.drain(..) {
+ self.check_transmute(from, to, hir_id);
+ }
+ }
+
+ pub(in super::super) fn check_asms(&self) {
+ let mut deferred_asm_checks = self.deferred_asm_checks.borrow_mut();
+ debug!("FnCtxt::check_asm: {} deferred checks", deferred_asm_checks.len());
+ for (asm, hir_id) in deferred_asm_checks.drain(..) {
+ let enclosing_id = self.tcx.hir().enclosing_body_owner(hir_id);
+ let get_operand_ty = |expr| {
+ let ty = self.typeck_results.borrow().expr_ty_adjusted(expr);
+ let ty = self.resolve_vars_if_possible(ty);
+ if ty.has_non_region_infer() {
+ assert!(self.is_tainted_by_errors());
+ self.tcx.ty_error()
+ } else {
+ self.tcx.erase_regions(ty)
+ }
+ };
+ InlineAsmCtxt::new_in_fn(self.tcx, self.param_env, get_operand_ty)
+ .check_asm(asm, self.tcx.hir().local_def_id_to_hir_id(enclosing_id));
+ }
+ }
+
+ pub(in super::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,
+ None,
+ args_no_rcvr,
+ false,
+ tuple_arguments,
+ method.ok().map(|method| method.def_id),
+ );
+ return self.tcx.ty_error();
+ }
+
+ let method = method.unwrap();
+ // HACK(eddyb) ignore self in the definition (see above).
+ let expected_input_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_input_tys,
+ args_no_rcvr,
+ method.sig.c_variadic,
+ tuple_arguments,
+ Some(method.def_id),
+ );
+ method.sig.output()
+ }
+
+ /// Generic function that factors out common logic from function calls,
+ /// method calls and overloaded operators.
+ pub(in super::super) fn check_argument_types(
+ &self,
+ // Span enclosing the call site
+ call_span: Span,
+ // Expression of the call site
+ call_expr: &'tcx hir::Expr<'tcx>,
+ // Types (as defined in the *signature* of the target function)
+ formal_input_tys: &[Ty<'tcx>],
+ // More specific expected types, after unifying with caller output types
+ expected_input_tys: Option<Vec<Ty<'tcx>>>,
+ // The expressions for each provided argument
+ provided_args: &'tcx [hir::Expr<'tcx>],
+ // Whether the function is variadic, for example when imported from C
+ c_variadic: bool,
+ // Whether the arguments have been bundled in a tuple (ex: closures)
+ tuple_arguments: TupleArgumentsFlag,
+ // The DefId for the function being called, for better error messages
+ fn_def_id: Option<DefId>,
+ ) {
+ let tcx = self.tcx;
+
+ // Conceptually, we've got some number of expected inputs, and some number of provided arguments
+ // and we can form a grid of whether each argument could satisfy a given input:
+ // in1 | in2 | in3 | ...
+ // arg1 ? | | |
+ // arg2 | ? | |
+ // arg3 | | ? |
+ // ...
+ // Initially, we just check the diagonal, because in the case of correct code
+ // these are the only checks that matter
+ // However, in the unhappy path, we'll fill in this whole grid to attempt to provide
+ // better error messages about invalid method calls.
+
+ // 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 iter::zip(formal_input_tys, provided_args) {
+ self.register_wf_obligation(fn_input_ty.into(), arg_expr.span, traits::MiscObligation);
+ }
+
+ let mut err_code = "E0061";
+
+ // If the arguments should be wrapped in a tuple (ex: closures), unwrap them here
+ let (formal_input_tys, expected_input_tys) = if tuple_arguments == TupleArguments {
+ let tuple_type = self.structurally_resolved_type(call_span, formal_input_tys[0]);
+ match tuple_type.kind() {
+ // We expected a tuple and got a tuple
+ ty::Tuple(arg_types) => {
+ // Argument length differs
+ if arg_types.len() != provided_args.len() {
+ err_code = "E0057";
+ }
+ let expected_input_tys = match expected_input_tys {
+ Some(expected_input_tys) => match expected_input_tys.get(0) {
+ Some(ty) => match ty.kind() {
+ ty::Tuple(tys) => Some(tys.iter().collect()),
+ _ => None,
+ },
+ None => None,
+ },
+ None => None,
+ };
+ (arg_types.iter().collect(), expected_input_tys)
+ }
+ _ => {
+ // Otherwise, there's a mismatch, so clear out what we're expecting, and set
+ // our input types to err_args so we don't blow up the error messages
+ struct_span_err!(
+ tcx.sess,
+ call_span,
+ E0059,
+ "cannot use call notation; the first type parameter \
+ for the function trait is neither a tuple nor unit"
+ )
+ .emit();
+ (self.err_args(provided_args.len()), None)
+ }
+ }
+ } else {
+ (formal_input_tys.to_vec(), expected_input_tys)
+ };
+
+ // If there are no external expectations at the call site, just use the types from the function defn
+ let expected_input_tys = if let Some(expected_input_tys) = expected_input_tys {
+ assert_eq!(expected_input_tys.len(), formal_input_tys.len());
+ expected_input_tys
+ } else {
+ formal_input_tys.clone()
+ };
+
+ let minimum_input_count = expected_input_tys.len();
+ let provided_arg_count = provided_args.len();
+
+ let is_const_eval_select = matches!(fn_def_id, Some(def_id) if
+ self.tcx.def_kind(def_id) == hir::def::DefKind::Fn
+ && self.tcx.is_intrinsic(def_id)
+ && self.tcx.item_name(def_id) == sym::const_eval_select);
+
+ // We introduce a helper function to demand that a given argument satisfy a given input
+ // This is more complicated than just checking type equality, as arguments could be coerced
+ // This version writes those types back so further type checking uses the narrowed types
+ let demand_compatible = |idx| {
+ let formal_input_ty: Ty<'tcx> = formal_input_tys[idx];
+ let expected_input_ty: Ty<'tcx> = expected_input_tys[idx];
+ let provided_arg = &provided_args[idx];
+
+ debug!("checking argument {}: {:?} = {:?}", idx, provided_arg, formal_input_ty);
+
+ // We're on the happy path here, so we'll do a more involved check and write back types
+ // To check compatibility, we'll do 3 things:
+ // 1. Unify the provided argument with the expected type
+ let expectation = Expectation::rvalue_hint(self, expected_input_ty);
+
+ let checked_ty = self.check_expr_with_expectation(provided_arg, expectation);
+
+ // 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 coerced_ty = expectation.only_has_type(self).unwrap_or(formal_input_ty);
+
+ // Cause selection errors caused by resolving a single argument to point at the
+ // argument and not the call. This lets us customize the span pointed to in the
+ // fulfillment error to be more accurate.
+ let coerced_ty = self.resolve_vars_with_obligations(coerced_ty);
+
+ let coerce_error = self
+ .try_coerce(provided_arg, checked_ty, coerced_ty, AllowTwoPhase::Yes, None)
+ .err();
+
+ if coerce_error.is_some() {
+ return Compatibility::Incompatible(coerce_error);
+ }
+
+ // Check that second and third argument of `const_eval_select` must be `FnDef`, and additionally that
+ // the second argument must be `const fn`. The first argument must be a tuple, but this is already expressed
+ // in the function signature (`F: FnOnce<ARG>`), so I did not bother to add another check here.
+ //
+ // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
+ if is_const_eval_select && (1..=2).contains(&idx) {
+ if let ty::FnDef(def_id, _) = checked_ty.kind() {
+ if idx == 1 && !self.tcx.is_const_fn_raw(*def_id) {
+ self.tcx
+ .sess
+ .struct_span_err(provided_arg.span, "this argument must be a `const fn`")
+ .help("consult the documentation on `const_eval_select` for more information")
+ .emit();
+ }
+ } else {
+ self.tcx
+ .sess
+ .struct_span_err(provided_arg.span, "this argument must be a function item")
+ .note(format!("expected a function item, found {checked_ty}"))
+ .help(
+ "consult the documentation on `const_eval_select` for more information",
+ )
+ .emit();
+ }
+ }
+
+ // 3. Check if the formal type is a supertype of the checked one
+ // and register any such obligations for future type checks
+ let supertype_error = self
+ .at(&self.misc(provided_arg.span), self.param_env)
+ .sup(formal_input_ty, coerced_ty);
+ let subtyping_error = match supertype_error {
+ Ok(InferOk { obligations, value: () }) => {
+ self.register_predicates(obligations);
+ None
+ }
+ Err(err) => Some(err),
+ };
+
+ // If neither check failed, the types are compatible
+ match subtyping_error {
+ None => Compatibility::Compatible,
+ Some(_) => Compatibility::Incompatible(subtyping_error),
+ }
+ };
+
+ // To start, we only care "along the diagonal", where we expect every
+ // provided arg to be in the right spot
+ let mut compatibility_diagonal =
+ vec![Compatibility::Incompatible(None); provided_args.len()];
+
+ // Keep track of whether we *could possibly* be satisfied, i.e. whether we're on the happy path
+ // if the wrong number of arguments were supplied, we CAN'T be satisfied,
+ // and if we're c_variadic, the supplied arguments must be >= the minimum count from the function
+ // otherwise, they need to be identical, because rust doesn't currently support variadic functions
+ let mut call_appears_satisfied = if c_variadic {
+ provided_arg_count >= minimum_input_count
+ } else {
+ provided_arg_count == minimum_input_count
+ };
+
+ // 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] {
+ // 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, |_| {})
+ }
+
+ // Check each argument, to satisfy the input it was provided for
+ // Visually, we're traveling down the diagonal of the compatibility matrix
+ for (idx, arg) in provided_args.iter().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");
+ }
+
+ // 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. However, we *can* check
+ // for unreachable expressions (see above).
+ // FIXME: unreachable warning current isn't emitted
+ if idx >= minimum_input_count {
+ continue;
+ }
+
+ let is_closure = matches!(arg.kind, ExprKind::Closure { .. });
+ if is_closure != check_closures {
+ continue;
+ }
+
+ let compatible = demand_compatible(idx);
+ let is_compatible = matches!(compatible, Compatibility::Compatible);
+ compatibility_diagonal[idx] = compatible;
+
+ if !is_compatible {
+ call_appears_satisfied = false;
+ }
+ }
+ }
+
+ if c_variadic && provided_arg_count < minimum_input_count {
+ err_code = "E0060";
+ }
+
+ for arg in provided_args.iter().skip(minimum_input_count) {
+ // Make sure we've checked this expr at least once.
+ let arg_ty = self.check_expr(&arg);
+
+ // If the function is c-style variadic, we skipped a bunch of arguments
+ // so we need to check those, and write out the types
+ // Ideally this would be folded into the above, for uniform style
+ // but c-variadic is already a corner case
+ if c_variadic {
+ fn variadic_error<'tcx>(
+ sess: &'tcx Session,
+ span: Span,
+ ty: Ty<'tcx>,
+ cast_ty: &str,
+ ) {
+ use rustc_hir_analysis::structured_errors::MissingCastForVariadicArg;
+
+ MissingCastForVariadicArg { sess, span, ty, cast_ty }.diagnostic().emit();
+ }
+
+ // 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(ty::FloatTy::F32) => {
+ variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
+ }
+ ty::Int(ty::IntTy::I8 | ty::IntTy::I16) | ty::Bool => {
+ variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
+ }
+ ty::Uint(ty::UintTy::U8 | ty::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());
+ }
+ _ => {}
+ }
+ }
+ }
+
+ if !call_appears_satisfied {
+ let compatibility_diagonal = IndexVec::from_raw(compatibility_diagonal);
+ let provided_args = IndexVec::from_iter(provided_args.iter().take(if c_variadic {
+ minimum_input_count
+ } else {
+ provided_arg_count
+ }));
+ debug_assert_eq!(
+ formal_input_tys.len(),
+ expected_input_tys.len(),
+ "expected formal_input_tys to be the same size as expected_input_tys"
+ );
+ let formal_and_expected_inputs = IndexVec::from_iter(
+ formal_input_tys
+ .iter()
+ .copied()
+ .zip(expected_input_tys.iter().copied())
+ .map(|vars| self.resolve_vars_if_possible(vars)),
+ );
+
+ self.report_arg_errors(
+ compatibility_diagonal,
+ formal_and_expected_inputs,
+ provided_args,
+ c_variadic,
+ err_code,
+ fn_def_id,
+ call_span,
+ call_expr,
+ );
+ }
+ }
+
+ fn report_arg_errors(
+ &self,
+ compatibility_diagonal: IndexVec<ProvidedIdx, Compatibility<'tcx>>,
+ formal_and_expected_inputs: IndexVec<ExpectedIdx, (Ty<'tcx>, Ty<'tcx>)>,
+ provided_args: IndexVec<ProvidedIdx, &'tcx hir::Expr<'tcx>>,
+ c_variadic: bool,
+ err_code: &str,
+ fn_def_id: Option<DefId>,
+ call_span: Span,
+ call_expr: &hir::Expr<'tcx>,
+ ) {
+ // Next, let's construct the error
+ let (error_span, full_call_span, ctor_of, is_method) = match &call_expr.kind {
+ hir::ExprKind::Call(
+ hir::Expr { hir_id, span, kind: hir::ExprKind::Path(qpath), .. },
+ _,
+ ) => {
+ if let Res::Def(DefKind::Ctor(of, _), _) =
+ self.typeck_results.borrow().qpath_res(qpath, *hir_id)
+ {
+ (call_span, *span, Some(of), false)
+ } else {
+ (call_span, *span, None, false)
+ }
+ }
+ hir::ExprKind::Call(hir::Expr { span, .. }, _) => (call_span, *span, None, false),
+ hir::ExprKind::MethodCall(path_segment, _, _, span) => {
+ let ident_span = path_segment.ident.span;
+ let ident_span = if let Some(args) = path_segment.args {
+ ident_span.with_hi(args.span_ext.hi())
+ } else {
+ ident_span
+ };
+ // methods are never ctors
+ (*span, ident_span, None, true)
+ }
+ k => span_bug!(call_span, "checking argument types on a non-call: `{:?}`", k),
+ };
+ let args_span = error_span.trim_start(full_call_span).unwrap_or(error_span);
+ let call_name = match ctor_of {
+ Some(CtorOf::Struct) => "struct",
+ Some(CtorOf::Variant) => "enum variant",
+ None => "function",
+ };
+
+ // Don't print if it has error types or is just plain `_`
+ fn has_error_or_infer<'tcx>(tys: impl IntoIterator<Item = Ty<'tcx>>) -> bool {
+ tys.into_iter().any(|ty| ty.references_error() || ty.is_ty_var())
+ }
+
+ self.set_tainted_by_errors();
+ let tcx = self.tcx;
+
+ // Get the argument span in the context of the call span so that
+ // suggestions and labels are (more) correct when an arg is a
+ // macro invocation.
+ let normalize_span = |span: Span| -> Span {
+ let normalized_span = span.find_ancestor_inside(error_span).unwrap_or(span);
+ // Sometimes macros mess up the spans, so do not normalize the
+ // arg span to equal the error span, because that's less useful
+ // than pointing out the arg expr in the wrong context.
+ if normalized_span.source_equal(error_span) { span } else { normalized_span }
+ };
+
+ // Precompute the provided types and spans, since that's all we typically need for below
+ let provided_arg_tys: IndexVec<ProvidedIdx, (Ty<'tcx>, Span)> = provided_args
+ .iter()
+ .map(|expr| {
+ let ty = self
+ .typeck_results
+ .borrow()
+ .expr_ty_adjusted_opt(*expr)
+ .unwrap_or_else(|| tcx.ty_error());
+ (self.resolve_vars_if_possible(ty), normalize_span(expr.span))
+ })
+ .collect();
+ let callee_expr = match &call_expr.peel_blocks().kind {
+ hir::ExprKind::Call(callee, _) => Some(*callee),
+ hir::ExprKind::MethodCall(_, receiver, ..) => {
+ if let Some((DefKind::AssocFn, def_id)) =
+ self.typeck_results.borrow().type_dependent_def(call_expr.hir_id)
+ && let Some(assoc) = tcx.opt_associated_item(def_id)
+ && assoc.fn_has_self_parameter
+ {
+ Some(*receiver)
+ } else {
+ None
+ }
+ }
+ _ => None,
+ };
+ let callee_ty = callee_expr
+ .and_then(|callee_expr| self.typeck_results.borrow().expr_ty_adjusted_opt(callee_expr));
+
+ // A "softer" version of the `demand_compatible`, which checks types without persisting them,
+ // and treats error types differently
+ // This will allow us to "probe" for other argument orders that would likely have been correct
+ let check_compatible = |provided_idx: ProvidedIdx, expected_idx: ExpectedIdx| {
+ if provided_idx.as_usize() == expected_idx.as_usize() {
+ return compatibility_diagonal[provided_idx].clone();
+ }
+
+ let (formal_input_ty, expected_input_ty) = formal_and_expected_inputs[expected_idx];
+ // If either is an error type, we defy the usual convention and consider them to *not* be
+ // coercible. This prevents our error message heuristic from trying to pass errors into
+ // every argument.
+ if (formal_input_ty, expected_input_ty).references_error() {
+ return Compatibility::Incompatible(None);
+ }
+
+ let (arg_ty, arg_span) = provided_arg_tys[provided_idx];
+
+ let expectation = Expectation::rvalue_hint(self, expected_input_ty);
+ let coerced_ty = expectation.only_has_type(self).unwrap_or(formal_input_ty);
+ let can_coerce = self.can_coerce(arg_ty, coerced_ty);
+ if !can_coerce {
+ return Compatibility::Incompatible(Some(ty::error::TypeError::Sorts(
+ ty::error::ExpectedFound::new(true, coerced_ty, arg_ty),
+ )));
+ }
+
+ // Using probe here, since we don't want this subtyping to affect inference.
+ let subtyping_error = self.probe(|_| {
+ self.at(&self.misc(arg_span), self.param_env).sup(formal_input_ty, coerced_ty).err()
+ });
+
+ // Same as above: if either the coerce type or the checked type is an error type,
+ // consider them *not* compatible.
+ let references_error = (coerced_ty, arg_ty).references_error();
+ match (references_error, subtyping_error) {
+ (false, None) => Compatibility::Compatible,
+ (_, subtyping_error) => Compatibility::Incompatible(subtyping_error),
+ }
+ };
+
+ // The algorithm here is inspired by levenshtein distance and longest common subsequence.
+ // We'll try to detect 4 different types of mistakes:
+ // - An extra parameter has been provided that doesn't satisfy *any* of the other inputs
+ // - An input is missing, which isn't satisfied by *any* of the other arguments
+ // - Some number of arguments have been provided in the wrong order
+ // - A type is straight up invalid
+
+ // First, let's find the errors
+ let (mut errors, matched_inputs) =
+ ArgMatrix::new(provided_args.len(), formal_and_expected_inputs.len(), check_compatible)
+ .find_errors();
+
+ // First, check if we just need to wrap some arguments in a tuple.
+ if let Some((mismatch_idx, terr)) =
+ compatibility_diagonal.iter().enumerate().find_map(|(i, c)| {
+ if let Compatibility::Incompatible(Some(terr)) = c {
+ Some((i, *terr))
+ } else {
+ None
+ }
+ })
+ {
+ // Is the first bad expected argument a tuple?
+ // Do we have as many extra provided arguments as the tuple's length?
+ // If so, we might have just forgotten to wrap some args in a tuple.
+ if let Some(ty::Tuple(tys)) =
+ formal_and_expected_inputs.get(mismatch_idx.into()).map(|tys| tys.1.kind())
+ // If the tuple is unit, we're not actually wrapping any arguments.
+ && !tys.is_empty()
+ && provided_arg_tys.len() == formal_and_expected_inputs.len() - 1 + tys.len()
+ {
+ // Wrap up the N provided arguments starting at this position in a tuple.
+ let provided_as_tuple = tcx.mk_tup(
+ provided_arg_tys.iter().map(|(ty, _)| *ty).skip(mismatch_idx).take(tys.len()),
+ );
+
+ let mut satisfied = true;
+ // Check if the newly wrapped tuple + rest of the arguments are compatible.
+ for ((_, expected_ty), provided_ty) in std::iter::zip(
+ formal_and_expected_inputs.iter().skip(mismatch_idx),
+ [provided_as_tuple].into_iter().chain(
+ provided_arg_tys.iter().map(|(ty, _)| *ty).skip(mismatch_idx + tys.len()),
+ ),
+ ) {
+ if !self.can_coerce(provided_ty, *expected_ty) {
+ satisfied = false;
+ break;
+ }
+ }
+
+ // If they're compatible, suggest wrapping in an arg, and we're done!
+ // Take some care with spans, so we don't suggest wrapping a macro's
+ // innards in parenthesis, for example.
+ if satisfied
+ && let Some((_, lo)) =
+ provided_arg_tys.get(ProvidedIdx::from_usize(mismatch_idx))
+ && let Some((_, hi)) =
+ provided_arg_tys.get(ProvidedIdx::from_usize(mismatch_idx + tys.len() - 1))
+ {
+ let mut err;
+ if tys.len() == 1 {
+ // A tuple wrap suggestion actually occurs within,
+ // so don't do anything special here.
+ err = self.err_ctxt().report_and_explain_type_error(
+ TypeTrace::types(
+ &self.misc(*lo),
+ true,
+ formal_and_expected_inputs[mismatch_idx.into()].1,
+ provided_arg_tys[mismatch_idx.into()].0,
+ ),
+ terr,
+ );
+ err.span_label(
+ full_call_span,
+ format!("arguments to this {} are incorrect", call_name),
+ );
+ } else {
+ err = tcx.sess.struct_span_err_with_code(
+ full_call_span,
+ &format!(
+ "this {} takes {}{} but {} {} supplied",
+ call_name,
+ if c_variadic { "at least " } else { "" },
+ potentially_plural_count(
+ formal_and_expected_inputs.len(),
+ "argument"
+ ),
+ potentially_plural_count(provided_args.len(), "argument"),
+ pluralize!("was", provided_args.len())
+ ),
+ DiagnosticId::Error(err_code.to_owned()),
+ );
+ err.multipart_suggestion_verbose(
+ "wrap these arguments in parentheses to construct a tuple",
+ vec![
+ (lo.shrink_to_lo(), "(".to_string()),
+ (hi.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MachineApplicable,
+ );
+ };
+ self.label_fn_like(
+ &mut err,
+ fn_def_id,
+ callee_ty,
+ Some(mismatch_idx),
+ is_method,
+ );
+ err.emit();
+ return;
+ }
+ }
+ }
+
+ // Okay, so here's where it gets complicated in regards to what errors
+ // we emit and how.
+ // There are 3 different "types" of errors we might encounter.
+ // 1) Missing/extra/swapped arguments
+ // 2) Valid but incorrect arguments
+ // 3) Invalid arguments
+ // - Currently I think this only comes up with `CyclicTy`
+ //
+ // We first need to go through, remove those from (3) and emit those
+ // as their own error, particularly since they're error code and
+ // message is special. From what I can tell, we *must* emit these
+ // here (vs somewhere prior to this function) since the arguments
+ // become invalid *because* of how they get used in the function.
+ // It is what it is.
+
+ if errors.is_empty() {
+ if cfg!(debug_assertions) {
+ span_bug!(error_span, "expected errors from argument matrix");
+ } else {
+ tcx.sess
+ .struct_span_err(
+ error_span,
+ "argument type mismatch was detected, \
+ but rustc had trouble determining where",
+ )
+ .note(
+ "we would appreciate a bug report: \
+ https://github.com/rust-lang/rust/issues/new",
+ )
+ .emit();
+ }
+ return;
+ }
+
+ errors.drain_filter(|error| {
+ let Error::Invalid(provided_idx, expected_idx, Compatibility::Incompatible(Some(e))) = error else { return false };
+ let (provided_ty, provided_span) = provided_arg_tys[*provided_idx];
+ let (expected_ty, _) = formal_and_expected_inputs[*expected_idx];
+ let cause = &self.misc(provided_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308(_)) {
+ self.err_ctxt().report_and_explain_type_error(trace, *e).emit();
+ return true;
+ }
+ false
+ });
+
+ // We're done if we found errors, but we already emitted them.
+ if errors.is_empty() {
+ return;
+ }
+
+ // Okay, now that we've emitted the special errors separately, we
+ // are only left missing/extra/swapped and mismatched arguments, both
+ // can be collated pretty easily if needed.
+
+ // Next special case: if there is only one "Incompatible" error, just emit that
+ if let [
+ Error::Invalid(provided_idx, expected_idx, Compatibility::Incompatible(Some(err))),
+ ] = &errors[..]
+ {
+ let (formal_ty, expected_ty) = formal_and_expected_inputs[*expected_idx];
+ let (provided_ty, provided_arg_span) = provided_arg_tys[*provided_idx];
+ let cause = &self.misc(provided_arg_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ let mut err = self.err_ctxt().report_and_explain_type_error(trace, *err);
+ self.emit_coerce_suggestions(
+ &mut err,
+ &provided_args[*provided_idx],
+ provided_ty,
+ Expectation::rvalue_hint(self, expected_ty)
+ .only_has_type(self)
+ .unwrap_or(formal_ty),
+ None,
+ None,
+ );
+ err.span_label(
+ full_call_span,
+ format!("arguments to this {} are incorrect", call_name),
+ );
+ // Call out where the function is defined
+ self.label_fn_like(
+ &mut err,
+ fn_def_id,
+ callee_ty,
+ Some(expected_idx.as_usize()),
+ is_method,
+ );
+ err.emit();
+ return;
+ }
+
+ let mut err = if formal_and_expected_inputs.len() == provided_args.len() {
+ struct_span_err!(
+ tcx.sess,
+ full_call_span,
+ E0308,
+ "arguments to this {} are incorrect",
+ call_name,
+ )
+ } else {
+ tcx.sess.struct_span_err_with_code(
+ full_call_span,
+ &format!(
+ "this {} takes {}{} but {} {} supplied",
+ call_name,
+ if c_variadic { "at least " } else { "" },
+ potentially_plural_count(formal_and_expected_inputs.len(), "argument"),
+ potentially_plural_count(provided_args.len(), "argument"),
+ pluralize!("was", provided_args.len())
+ ),
+ DiagnosticId::Error(err_code.to_owned()),
+ )
+ };
+
+ // As we encounter issues, keep track of what we want to provide for the suggestion
+ let mut labels = vec![];
+ // If there is a single error, we give a specific suggestion; otherwise, we change to
+ // "did you mean" with the suggested function call
+ enum SuggestionText {
+ None,
+ Provide(bool),
+ Remove(bool),
+ Swap,
+ Reorder,
+ DidYouMean,
+ }
+ let mut suggestion_text = SuggestionText::None;
+
+ let mut errors = errors.into_iter().peekable();
+ while let Some(error) = errors.next() {
+ match error {
+ Error::Invalid(provided_idx, expected_idx, compatibility) => {
+ let (formal_ty, expected_ty) = formal_and_expected_inputs[expected_idx];
+ let (provided_ty, provided_span) = provided_arg_tys[provided_idx];
+ if let Compatibility::Incompatible(error) = compatibility {
+ let cause = &self.misc(provided_span);
+ let trace = TypeTrace::types(cause, true, expected_ty, provided_ty);
+ if let Some(e) = error {
+ self.err_ctxt().note_type_err(
+ &mut err,
+ &trace.cause,
+ None,
+ Some(trace.values),
+ e,
+ false,
+ true,
+ );
+ }
+ }
+
+ self.emit_coerce_suggestions(
+ &mut err,
+ &provided_args[provided_idx],
+ provided_ty,
+ Expectation::rvalue_hint(self, expected_ty)
+ .only_has_type(self)
+ .unwrap_or(formal_ty),
+ None,
+ None,
+ );
+ }
+ Error::Extra(arg_idx) => {
+ let (provided_ty, provided_span) = provided_arg_tys[arg_idx];
+ let provided_ty_name = if !has_error_or_infer([provided_ty]) {
+ // FIXME: not suggestable, use something else
+ format!(" of type `{}`", provided_ty)
+ } else {
+ "".to_string()
+ };
+ labels
+ .push((provided_span, format!("argument{} unexpected", provided_ty_name)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Remove(false),
+ SuggestionText::Remove(_) => SuggestionText::Remove(true),
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ Error::Missing(expected_idx) => {
+ // If there are multiple missing arguments adjacent to each other,
+ // then we can provide a single error.
+
+ let mut missing_idxs = vec![expected_idx];
+ while let Some(e) = errors.next_if(|e| {
+ matches!(e, Error::Missing(next_expected_idx)
+ if *next_expected_idx == *missing_idxs.last().unwrap() + 1)
+ }) {
+ match e {
+ Error::Missing(expected_idx) => missing_idxs.push(expected_idx),
+ _ => unreachable!(),
+ }
+ }
+
+ // NOTE: Because we might be re-arranging arguments, might have extra
+ // arguments, etc. it's hard to *really* know where we should provide
+ // this error label, so as a heuristic, we point to the provided arg, or
+ // to the call if the missing inputs pass the provided args.
+ match &missing_idxs[..] {
+ &[expected_idx] => {
+ let (_, input_ty) = formal_and_expected_inputs[expected_idx];
+ let span = if let Some((_, arg_span)) =
+ provided_arg_tys.get(expected_idx.to_provided_idx())
+ {
+ *arg_span
+ } else {
+ args_span
+ };
+ let rendered = if !has_error_or_infer([input_ty]) {
+ format!(" of type `{}`", input_ty)
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("an argument{} is missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Provide(false),
+ SuggestionText::Provide(_) => SuggestionText::Provide(true),
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ &[first_idx, second_idx] => {
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_idx];
+ let span = if let (Some((_, first_span)), Some((_, second_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(second_idx.to_provided_idx()),
+ ) {
+ first_span.to(*second_span)
+ } else {
+ args_span
+ };
+ let rendered =
+ if !has_error_or_infer([first_expected_ty, second_expected_ty]) {
+ format!(
+ " of type `{}` and `{}`",
+ first_expected_ty, second_expected_ty
+ )
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("two arguments{} are missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ &[first_idx, second_idx, third_idx] => {
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_idx];
+ let (_, third_expected_ty) = formal_and_expected_inputs[third_idx];
+ let span = if let (Some((_, first_span)), Some((_, third_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(third_idx.to_provided_idx()),
+ ) {
+ first_span.to(*third_span)
+ } else {
+ args_span
+ };
+ let rendered = if !has_error_or_infer([
+ first_expected_ty,
+ second_expected_ty,
+ third_expected_ty,
+ ]) {
+ format!(
+ " of type `{}`, `{}`, and `{}`",
+ first_expected_ty, second_expected_ty, third_expected_ty
+ )
+ } else {
+ "".to_string()
+ };
+ labels.push((span, format!("three arguments{} are missing", rendered)));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ missing_idxs => {
+ let first_idx = *missing_idxs.first().unwrap();
+ let last_idx = *missing_idxs.last().unwrap();
+ // NOTE: Because we might be re-arranging arguments, might have extra arguments, etc.
+ // It's hard to *really* know where we should provide this error label, so this is a
+ // decent heuristic
+ let span = if let (Some((_, first_span)), Some((_, last_span))) = (
+ provided_arg_tys.get(first_idx.to_provided_idx()),
+ provided_arg_tys.get(last_idx.to_provided_idx()),
+ ) {
+ first_span.to(*last_span)
+ } else {
+ args_span
+ };
+ labels.push((span, format!("multiple arguments are missing")));
+ suggestion_text = match suggestion_text {
+ SuggestionText::None | SuggestionText::Provide(_) => {
+ SuggestionText::Provide(true)
+ }
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ }
+ }
+ Error::Swap(
+ first_provided_idx,
+ second_provided_idx,
+ first_expected_idx,
+ second_expected_idx,
+ ) => {
+ let (first_provided_ty, first_span) = provided_arg_tys[first_provided_idx];
+ let (_, first_expected_ty) = formal_and_expected_inputs[first_expected_idx];
+ let first_provided_ty_name = if !has_error_or_infer([first_provided_ty]) {
+ format!(", found `{}`", first_provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ first_span,
+ format!("expected `{}`{}", first_expected_ty, first_provided_ty_name),
+ ));
+
+ let (second_provided_ty, second_span) = provided_arg_tys[second_provided_idx];
+ let (_, second_expected_ty) = formal_and_expected_inputs[second_expected_idx];
+ let second_provided_ty_name = if !has_error_or_infer([second_provided_ty]) {
+ format!(", found `{}`", second_provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ second_span,
+ format!("expected `{}`{}", second_expected_ty, second_provided_ty_name),
+ ));
+
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Swap,
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ Error::Permutation(args) => {
+ for (dst_arg, dest_input) in args {
+ let (_, expected_ty) = formal_and_expected_inputs[dst_arg];
+ let (provided_ty, provided_span) = provided_arg_tys[dest_input];
+ let provided_ty_name = if !has_error_or_infer([provided_ty]) {
+ format!(", found `{}`", provided_ty)
+ } else {
+ String::new()
+ };
+ labels.push((
+ provided_span,
+ format!("expected `{}`{}", expected_ty, provided_ty_name),
+ ));
+ }
+
+ suggestion_text = match suggestion_text {
+ SuggestionText::None => SuggestionText::Reorder,
+ _ => SuggestionText::DidYouMean,
+ };
+ }
+ }
+ }
+
+ // If we have less than 5 things to say, it would be useful to call out exactly what's wrong
+ if labels.len() <= 5 {
+ for (span, label) in labels {
+ err.span_label(span, label);
+ }
+ }
+
+ // Call out where the function is defined
+ self.label_fn_like(&mut err, fn_def_id, callee_ty, None, is_method);
+
+ // And add a suggestion block for all of the parameters
+ let suggestion_text = match suggestion_text {
+ SuggestionText::None => None,
+ SuggestionText::Provide(plural) => {
+ Some(format!("provide the argument{}", if plural { "s" } else { "" }))
+ }
+ SuggestionText::Remove(plural) => {
+ Some(format!("remove the extra argument{}", if plural { "s" } else { "" }))
+ }
+ SuggestionText::Swap => Some("swap these arguments".to_string()),
+ SuggestionText::Reorder => Some("reorder these arguments".to_string()),
+ SuggestionText::DidYouMean => Some("did you mean".to_string()),
+ };
+ if let Some(suggestion_text) = suggestion_text {
+ let source_map = self.sess().source_map();
+ let (mut suggestion, suggestion_span) =
+ if let Some(call_span) = full_call_span.find_ancestor_inside(error_span) {
+ ("(".to_string(), call_span.shrink_to_hi().to(error_span.shrink_to_hi()))
+ } else {
+ (
+ format!(
+ "{}(",
+ source_map.span_to_snippet(full_call_span).unwrap_or_else(|_| {
+ fn_def_id.map_or("".to_string(), |fn_def_id| {
+ tcx.item_name(fn_def_id).to_string()
+ })
+ })
+ ),
+ error_span,
+ )
+ };
+ let mut needs_comma = false;
+ for (expected_idx, provided_idx) in matched_inputs.iter_enumerated() {
+ if needs_comma {
+ suggestion += ", ";
+ } else {
+ needs_comma = true;
+ }
+ let suggestion_text = if let Some(provided_idx) = provided_idx
+ && let (_, provided_span) = provided_arg_tys[*provided_idx]
+ && let Ok(arg_text) = source_map.span_to_snippet(provided_span)
+ {
+ arg_text
+ } else {
+ // Propose a placeholder of the correct type
+ let (_, expected_ty) = formal_and_expected_inputs[expected_idx];
+ if expected_ty.is_unit() {
+ "()".to_string()
+ } else if expected_ty.is_suggestable(tcx, false) {
+ format!("/* {} */", expected_ty)
+ } else {
+ "/* value */".to_string()
+ }
+ };
+ suggestion += &suggestion_text;
+ }
+ suggestion += ")";
+ err.span_suggestion_verbose(
+ suggestion_span,
+ &suggestion_text,
+ suggestion,
+ Applicability::HasPlaceholders,
+ );
+ }
+
+ err.emit();
+ }
+
+ // AST fragment checking
+ pub(in super::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(ty::int_ty(t)),
+ ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(ty::uint_ty(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(ty::float_ty(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(),
+ }
+ }
+
+ pub fn check_struct_path(
+ &self,
+ qpath: &QPath<'_>,
+ hir_id: hir::HirId,
+ ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
+ let path_span = qpath.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::SelfTyParam { .. }
+ | Res::SelfTyAlias { .. } => 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.
+ self.add_required_obligations_for_hir(path_span, did, substs, hir_id);
+
+ Some((variant, ty))
+ } else {
+ match ty.kind() {
+ ty::Error(_) => {
+ // E0071 might be caused by a spelling error, which will have
+ // already caused an error message and probably a suggestion
+ // elsewhere. Refrain from emitting more unhelpful errors here
+ // (issue #88844).
+ }
+ _ => {
+ 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
+ }
+ }
+
+ pub fn check_decl_initializer(
+ &self,
+ hir_id: hir::HirId,
+ pat: &'tcx hir::Pat<'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 = pat.contains_explicit_ref_binding();
+
+ let local_ty = self.local_ty(init.span, 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)
+ }
+ }
+
+ pub(in super::super) fn check_decl(&self, decl: Declaration<'tcx>) {
+ // Determine and write the type which we'll check the pattern against.
+ let decl_ty = self.local_ty(decl.span, decl.hir_id).decl_ty;
+ self.write_ty(decl.hir_id, decl_ty);
+
+ // Type check the initializer.
+ if let Some(ref init) = decl.init {
+ let init_ty = self.check_decl_initializer(decl.hir_id, decl.pat, &init);
+ self.overwrite_local_ty_if_err(decl.hir_id, decl.pat, decl_ty, init_ty);
+ }
+
+ // Does the expected pattern type originate from an expression and what is the span?
+ let (origin_expr, ty_span) = match (decl.ty, decl.init) {
+ (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
+ (_, Some(init)) => {
+ (true, Some(init.span.find_ancestor_inside(decl.span).unwrap_or(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(&decl.pat, decl_ty, ty_span, origin_expr);
+ let pat_ty = self.node_ty(decl.pat.hir_id);
+ self.overwrite_local_ty_if_err(decl.hir_id, decl.pat, decl_ty, pat_ty);
+
+ if let Some(blk) = decl.els {
+ let previous_diverges = self.diverges.get();
+ let else_ty = self.check_block_with_expected(blk, NoExpectation);
+ let cause = self.cause(blk.span, ObligationCauseCode::LetElse);
+ if let Some(mut err) =
+ self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
+ {
+ err.emit();
+ }
+ self.diverges.set(previous_diverges);
+ }
+ }
+
+ /// Type check a `let` statement.
+ pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
+ self.check_decl(local.into());
+ }
+
+ pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>, is_last: bool) {
+ // 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(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| {
+ if expr.can_have_side_effects() {
+ self.suggest_semicolon_at_end(expr.span, err);
+ }
+ });
+ }
+ hir::StmtKind::Semi(ref expr) => {
+ // All of this is equivalent to calling `check_expr`, but it is inlined out here
+ // in order to capture the fact that this `match` is the last statement in its
+ // function. This is done for better suggestions to remove the `;`.
+ let expectation = match expr.kind {
+ hir::ExprKind::Match(..) if is_last => IsLast(stmt.span),
+ _ => NoExpectation,
+ };
+ self.check_expr_with_expectation(expr, expectation);
+ }
+ }
+
+ // 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);
+ }
+ }
+
+ pub(in super::super) fn check_block_with_expected(
+ &self,
+ blk: &'tcx hir::Block<'tcx>,
+ expected: Expectation<'tcx>,
+ ) -> Ty<'tcx> {
+ let prev = self.ps.replace(self.ps.get().recurse(blk));
+
+ // 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 (pos, s) in blk.stmts.iter().enumerate() {
+ self.check_stmt(s, blk.stmts.len() - 1 == pos);
+ }
+
+ // 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));
+ let ty_for_diagnostic = coerce.merged_ty();
+ // We use coerce_inner here because we want to augment the error
+ // suggesting to wrap the block in square brackets if it might've
+ // been mistaken array syntax
+ coerce.coerce_inner(
+ self,
+ &cause,
+ Some(tail_expr),
+ tail_expr_ty,
+ Some(&mut |diag: &mut Diagnostic| {
+ self.suggest_block_to_brackets(diag, blk, tail_expr_ty, ty_for_diagnostic);
+ }),
+ false,
+ );
+ } 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) {
+ if !self.consider_removing_semicolon(blk, expected_ty, err) {
+ self.err_ctxt().consider_returning_binding(
+ blk,
+ expected_ty,
+ err,
+ );
+ }
+ if expected_ty == self.tcx.types.bool {
+ // If this is caused by a missing `let` in a `while let`,
+ // silence this redundant error, as we already emit E0070.
+
+ // Our block must be a `assign desugar local; assignment`
+ if let Some(hir::Node::Block(hir::Block {
+ stmts:
+ [
+ hir::Stmt {
+ kind:
+ hir::StmtKind::Local(hir::Local {
+ source:
+ hir::LocalSource::AssignDesugar(_),
+ ..
+ }),
+ ..
+ },
+ hir::Stmt {
+ kind:
+ hir::StmtKind::Expr(hir::Expr {
+ kind: hir::ExprKind::Assign(..),
+ ..
+ }),
+ ..
+ },
+ ],
+ ..
+ })) = self.tcx.hir().find(blk.hir_id)
+ {
+ self.comes_from_while_condition(blk.hir_id, |_| {
+ err.downgrade_to_delayed_bug();
+ })
+ }
+ }
+ }
+ 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.set(prev);
+ ty
+ }
+
+ fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
+ let node = self.tcx.hir().get_by_def_id(self.tcx.hir().get_parent_item(id).def_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_by_def_id(self.tcx.hir().get_parent_item(blk_id).def_id);
+ self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
+ }
+
+ /// 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 {
+ let check_in_progress = |elem: &hir::Expr<'_>| {
+ self.typeck_results.borrow().node_type_opt(elem.hir_id).filter(|ty| !ty.is_never()).map(
+ |_| match elem.kind {
+ // Point at the tail expression when possible.
+ hir::ExprKind::Block(block, _) => block.expr.map_or(block.span, |e| e.span),
+ _ => elem.span,
+ },
+ )
+ };
+
+ if let hir::ExprKind::If(_, _, Some(el)) = expr.kind {
+ if let Some(rslt) = check_in_progress(el) {
+ return rslt;
+ }
+ }
+
+ if let hir::ExprKind::Match(_, arms, _) = expr.kind {
+ let mut iter = arms.iter().filter_map(|arm| check_in_progress(arm.body));
+ if let Some(span) = iter.next() {
+ if iter.next().is_none() {
+ return span;
+ }
+ }
+ }
+
+ expr.span
+ }
+
+ fn overwrite_local_ty_if_err(
+ &self,
+ hir_id: hir::HirId,
+ pat: &'tcx hir::Pat<'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(hir_id, ty);
+ self.write_ty(pat.hir_id, ty);
+ let local_ty = LocalTy { decl_ty, revealed_ty: ty };
+ self.locals.borrow_mut().insert(hir_id, local_ty);
+ self.locals.borrow_mut().insert(pat.hir_id, local_ty);
+ }
+ }
+
+ // 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 = <dyn 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 result = <dyn AstConv<'_>>::associated_path_to_ty(
+ self, hir_id, path_span, ty, qself, 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_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)), ty)
+ }
+ QPath::LangItem(lang_item, span, id) => {
+ self.resolve_lang_item_path(lang_item, span, hir_id, id)
+ }
+ }
+ }
+
+ /// Given a vector of fulfillment errors, try to adjust the spans of the
+ /// errors to more accurately point at the cause of the failure.
+ ///
+ /// This applies to calls, methods, and struct expressions. This will also
+ /// try to deduplicate errors that are due to the same cause but might
+ /// have been created with different [`ObligationCause`][traits::ObligationCause]s.
+ pub(super) fn adjust_fulfillment_errors_for_expr_obligation(
+ &self,
+ errors: &mut Vec<traits::FulfillmentError<'tcx>>,
+ ) {
+ // Store a mapping from `(Span, Predicate) -> ObligationCause`, so that
+ // other errors that have the same span and predicate can also get fixed,
+ // even if their `ObligationCauseCode` isn't an `Expr*Obligation` kind.
+ // This is important since if we adjust one span but not the other, then
+ // we will have "duplicated" the error on the UI side.
+ let mut remap_cause = FxHashSet::default();
+ let mut not_adjusted = vec![];
+
+ for error in errors {
+ let before_span = error.obligation.cause.span;
+ if self.adjust_fulfillment_error_for_expr_obligation(error)
+ || before_span != error.obligation.cause.span
+ {
+ // Store both the predicate and the predicate *without constness*
+ // since sometimes we instantiate and check both of these in a
+ // method call, for example.
+ remap_cause.insert((
+ before_span,
+ error.obligation.predicate,
+ error.obligation.cause.clone(),
+ ));
+ remap_cause.insert((
+ before_span,
+ error.obligation.predicate.without_const(self.tcx),
+ error.obligation.cause.clone(),
+ ));
+ } else {
+ // If it failed to be adjusted once around, it may be adjusted
+ // via the "remap cause" mapping the second time...
+ not_adjusted.push(error);
+ }
+ }
+
+ for error in not_adjusted {
+ for (span, predicate, cause) in &remap_cause {
+ if *predicate == error.obligation.predicate
+ && span.contains(error.obligation.cause.span)
+ {
+ error.obligation.cause = cause.clone();
+ continue;
+ }
+ }
+ }
+ }
+
+ fn adjust_fulfillment_error_for_expr_obligation(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ ) -> bool {
+ let (traits::ExprItemObligation(def_id, hir_id, idx) | traits::ExprBindingObligation(def_id, _, hir_id, idx))
+ = *error.obligation.cause.code().peel_derives() else { return false; };
+ let hir = self.tcx.hir();
+ let hir::Node::Expr(expr) = hir.get(hir_id) else { return false; };
+
+ // Skip over mentioning async lang item
+ if Some(def_id) == self.tcx.lang_items().from_generator_fn()
+ && error.obligation.cause.span.desugaring_kind()
+ == Some(rustc_span::DesugaringKind::Async)
+ {
+ return false;
+ }
+
+ let Some(unsubstituted_pred) =
+ self.tcx.predicates_of(def_id).instantiate_identity(self.tcx).predicates.into_iter().nth(idx)
+ else { return false; };
+
+ let generics = self.tcx.generics_of(def_id);
+ let predicate_substs = match unsubstituted_pred.kind().skip_binder() {
+ ty::PredicateKind::Trait(pred) => pred.trait_ref.substs,
+ ty::PredicateKind::Projection(pred) => pred.projection_ty.substs,
+ _ => ty::List::empty(),
+ };
+
+ let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| {
+ predicate_substs.types().find_map(|ty| {
+ ty.walk().find_map(|arg| {
+ if let ty::GenericArgKind::Type(ty) = arg.unpack()
+ && let ty::Param(param_ty) = ty.kind()
+ && matches(param_ty)
+ {
+ Some(arg)
+ } else {
+ None
+ }
+ })
+ })
+ };
+
+ // Prefer generics that are local to the fn item, since these are likely
+ // to be the cause of the unsatisfied predicate.
+ let mut param_to_point_at = find_param_matching(&|param_ty| {
+ self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id
+ });
+ // Fall back to generic that isn't local to the fn item. This will come
+ // from a trait or impl, for example.
+ let mut fallback_param_to_point_at = find_param_matching(&|param_ty| {
+ self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id
+ && param_ty.name != rustc_span::symbol::kw::SelfUpper
+ });
+ // Finally, the `Self` parameter is possibly the reason that the predicate
+ // is unsatisfied. This is less likely to be true for methods, because
+ // method probe means that we already kinda check that the predicates due
+ // to the `Self` type are true.
+ let mut self_param_to_point_at =
+ find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper);
+
+ // Finally, for ambiguity-related errors, we actually want to look
+ // for a parameter that is the source of the inference type left
+ // over in this predicate.
+ if let traits::FulfillmentErrorCode::CodeAmbiguity = error.code {
+ fallback_param_to_point_at = None;
+ self_param_to_point_at = None;
+ param_to_point_at =
+ self.find_ambiguous_parameter_in(def_id, error.root_obligation.predicate);
+ }
+
+ if self.closure_span_overlaps_error(error, expr.span) {
+ return false;
+ }
+
+ match &expr.kind {
+ hir::ExprKind::Path(qpath) => {
+ if let hir::Node::Expr(hir::Expr {
+ kind: hir::ExprKind::Call(callee, args),
+ hir_id: call_hir_id,
+ span: call_span,
+ ..
+ }) = hir.get(hir.get_parent_node(expr.hir_id))
+ && callee.hir_id == expr.hir_id
+ {
+ if self.closure_span_overlaps_error(error, *call_span) {
+ return false;
+ }
+
+ for param in
+ [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ .into_iter()
+ .flatten()
+ {
+ if self.point_at_arg_if_possible(
+ error,
+ def_id,
+ param,
+ *call_hir_id,
+ callee.span,
+ None,
+ args,
+ )
+ {
+ return true;
+ }
+ }
+ }
+ // Notably, we only point to params that are local to the
+ // item we're checking, since those are the ones we are able
+ // to look in the final `hir::PathSegment` for. Everything else
+ // would require a deeper search into the `qpath` than I think
+ // is worthwhile.
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath)
+ {
+ return true;
+ }
+ }
+ hir::ExprKind::MethodCall(segment, receiver, args, ..) => {
+ for param in [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ .into_iter()
+ .flatten()
+ {
+ if self.point_at_arg_if_possible(
+ error,
+ def_id,
+ param,
+ hir_id,
+ segment.ident.span,
+ Some(receiver),
+ args,
+ ) {
+ return true;
+ }
+ }
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_generic_if_possible(error, def_id, param_to_point_at, segment)
+ {
+ return true;
+ }
+ }
+ hir::ExprKind::Struct(qpath, fields, ..) => {
+ if let Res::Def(DefKind::Struct | DefKind::Variant, variant_def_id) =
+ self.typeck_results.borrow().qpath_res(qpath, hir_id)
+ {
+ for param in
+ [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+ {
+ if let Some(param) = param
+ && self.point_at_field_if_possible(
+ error,
+ def_id,
+ param,
+ variant_def_id,
+ fields,
+ )
+ {
+ return true;
+ }
+ }
+ }
+ if let Some(param_to_point_at) = param_to_point_at
+ && self.point_at_path_if_possible(error, def_id, param_to_point_at, qpath)
+ {
+ return true;
+ }
+ }
+ _ => {}
+ }
+
+ false
+ }
+
+ fn closure_span_overlaps_error(
+ &self,
+ error: &traits::FulfillmentError<'tcx>,
+ span: Span,
+ ) -> bool {
+ if let traits::FulfillmentErrorCode::CodeSelectionError(
+ traits::SelectionError::OutputTypeParameterMismatch(_, expected, _),
+ ) = error.code
+ && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected.skip_binder().self_ty().kind()
+ && span.overlaps(self.tcx.def_span(*def_id))
+ {
+ true
+ } else {
+ false
+ }
+ }
+
+ fn point_at_arg_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ call_hir_id: hir::HirId,
+ callee_span: Span,
+ receiver: Option<&'tcx hir::Expr<'tcx>>,
+ args: &'tcx [hir::Expr<'tcx>],
+ ) -> bool {
+ let sig = self.tcx.fn_sig(def_id).skip_binder();
+ let args_referencing_param: Vec<_> = sig
+ .inputs()
+ .iter()
+ .enumerate()
+ .filter(|(_, ty)| find_param_in_ty(**ty, param_to_point_at))
+ .collect();
+ // If there's one field that references the given generic, great!
+ if let [(idx, _)] = args_referencing_param.as_slice()
+ && let Some(arg) = receiver
+ .map_or(args.get(*idx), |rcvr| if *idx == 0 { Some(rcvr) } else { args.get(*idx - 1) }) {
+ error.obligation.cause.span = arg.span.find_ancestor_in_same_ctxt(error.obligation.cause.span).unwrap_or(arg.span);
+ error.obligation.cause.map_code(|parent_code| {
+ ObligationCauseCode::FunctionArgumentObligation {
+ arg_hir_id: arg.hir_id,
+ call_hir_id,
+ parent_code,
+ }
+ });
+ return true;
+ } else if args_referencing_param.len() > 0 {
+ // If more than one argument applies, then point to the callee span at least...
+ // We have chance to fix this up further in `point_at_generics_if_possible`
+ error.obligation.cause.span = callee_span;
+ }
+
+ false
+ }
+
+ fn point_at_field_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ variant_def_id: DefId,
+ expr_fields: &[hir::ExprField<'tcx>],
+ ) -> bool {
+ let def = self.tcx.adt_def(def_id);
+
+ let identity_substs = ty::InternalSubsts::identity_for_item(self.tcx, def_id);
+ let fields_referencing_param: Vec<_> = def
+ .variant_with_id(variant_def_id)
+ .fields
+ .iter()
+ .filter(|field| {
+ let field_ty = field.ty(self.tcx, identity_substs);
+ find_param_in_ty(field_ty, param_to_point_at)
+ })
+ .collect();
+
+ if let [field] = fields_referencing_param.as_slice() {
+ for expr_field in expr_fields {
+ // Look for the ExprField that matches the field, using the
+ // same rules that check_expr_struct uses for macro hygiene.
+ if self.tcx.adjust_ident(expr_field.ident, variant_def_id) == field.ident(self.tcx)
+ {
+ error.obligation.cause.span = expr_field
+ .expr
+ .span
+ .find_ancestor_in_same_ctxt(error.obligation.cause.span)
+ .unwrap_or(expr_field.span);
+ return true;
+ }
+ }
+ }
+
+ false
+ }
+
+ fn point_at_path_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param: ty::GenericArg<'tcx>,
+ qpath: &QPath<'tcx>,
+ ) -> bool {
+ match qpath {
+ hir::QPath::Resolved(_, path) => {
+ if let Some(segment) = path.segments.last()
+ && self.point_at_generic_if_possible(error, def_id, param, segment)
+ {
+ return true;
+ }
+ }
+ hir::QPath::TypeRelative(_, segment) => {
+ if self.point_at_generic_if_possible(error, def_id, param, segment) {
+ return true;
+ }
+ }
+ _ => {}
+ }
+
+ false
+ }
+
+ fn point_at_generic_if_possible(
+ &self,
+ error: &mut traits::FulfillmentError<'tcx>,
+ def_id: DefId,
+ param_to_point_at: ty::GenericArg<'tcx>,
+ segment: &hir::PathSegment<'tcx>,
+ ) -> bool {
+ let own_substs = self
+ .tcx
+ .generics_of(def_id)
+ .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id));
+ let Some((index, _)) = own_substs
+ .iter()
+ .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
+ .enumerate()
+ .find(|(_, arg)| **arg == param_to_point_at) else { return false };
+ let Some(arg) = segment
+ .args()
+ .args
+ .iter()
+ .filter(|arg| matches!(arg, hir::GenericArg::Type(_)))
+ .nth(index) else { return false; };
+ error.obligation.cause.span = arg
+ .span()
+ .find_ancestor_in_same_ctxt(error.obligation.cause.span)
+ .unwrap_or(arg.span());
+ true
+ }
+
+ fn find_ambiguous_parameter_in<T: TypeVisitable<'tcx>>(
+ &self,
+ item_def_id: DefId,
+ t: T,
+ ) -> Option<ty::GenericArg<'tcx>> {
+ struct FindAmbiguousParameter<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, DefId);
+ impl<'tcx> TypeVisitor<'tcx> for FindAmbiguousParameter<'_, 'tcx> {
+ type BreakTy = ty::GenericArg<'tcx>;
+ fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow<Self::BreakTy> {
+ if let Some(origin) = self.0.type_var_origin(ty)
+ && let TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) =
+ origin.kind
+ && let generics = self.0.tcx.generics_of(self.1)
+ && let Some(index) = generics.param_def_id_to_index(self.0.tcx, def_id)
+ && let Some(subst) = ty::InternalSubsts::identity_for_item(self.0.tcx, self.1)
+ .get(index as usize)
+ {
+ ControlFlow::Break(*subst)
+ } else {
+ ty.super_visit_with(self)
+ }
+ }
+ }
+ t.visit_with(&mut FindAmbiguousParameter(self, item_def_id)).break_value()
+ }
+
+ fn label_fn_like(
+ &self,
+ err: &mut Diagnostic,
+ callable_def_id: Option<DefId>,
+ callee_ty: Option<Ty<'tcx>>,
+ // A specific argument should be labeled, instead of all of them
+ expected_idx: Option<usize>,
+ is_method: bool,
+ ) {
+ let Some(mut def_id) = callable_def_id else {
+ return;
+ };
+
+ if let Some(assoc_item) = self.tcx.opt_associated_item(def_id)
+ // Possibly points at either impl or trait item, so try to get it
+ // to point to trait item, then get the parent.
+ // This parent might be an impl in the case of an inherent function,
+ // but the next check will fail.
+ && let maybe_trait_item_def_id = assoc_item.trait_item_def_id.unwrap_or(def_id)
+ && let maybe_trait_def_id = self.tcx.parent(maybe_trait_item_def_id)
+ // Just an easy way to check "trait_def_id == Fn/FnMut/FnOnce"
+ && let Some(call_kind) = ty::ClosureKind::from_def_id(self.tcx, maybe_trait_def_id)
+ && let Some(callee_ty) = callee_ty
+ {
+ let callee_ty = callee_ty.peel_refs();
+ match *callee_ty.kind() {
+ ty::Param(param) => {
+ let param =
+ self.tcx.generics_of(self.body_id.owner).type_param(&param, self.tcx);
+ if param.kind.is_synthetic() {
+ // if it's `impl Fn() -> ..` then just fall down to the def-id based logic
+ def_id = param.def_id;
+ } else {
+ // Otherwise, find the predicate that makes this generic callable,
+ // and point at that.
+ let instantiated = self
+ .tcx
+ .explicit_predicates_of(self.body_id.owner)
+ .instantiate_identity(self.tcx);
+ // FIXME(compiler-errors): This could be problematic if something has two
+ // fn-like predicates with different args, but callable types really never
+ // do that, so it's OK.
+ for (predicate, span) in
+ std::iter::zip(instantiated.predicates, instantiated.spans)
+ {
+ if let ty::PredicateKind::Trait(pred) = predicate.kind().skip_binder()
+ && pred.self_ty().peel_refs() == callee_ty
+ && ty::ClosureKind::from_def_id(self.tcx, pred.def_id()).is_some()
+ {
+ err.span_note(span, "callable defined here");
+ return;
+ }
+ }
+ }
+ }
+ ty::Opaque(new_def_id, _)
+ | ty::Closure(new_def_id, _)
+ | ty::FnDef(new_def_id, _) => {
+ def_id = new_def_id;
+ }
+ _ => {
+ // Look for a user-provided impl of a `Fn` trait, and point to it.
+ let new_def_id = self.probe(|_| {
+ let trait_ref = ty::TraitRef::new(
+ call_kind.to_def_id(self.tcx),
+ self.tcx.mk_substs(
+ [
+ ty::GenericArg::from(callee_ty),
+ self.next_ty_var(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::MiscVariable,
+ span: rustc_span::DUMMY_SP,
+ })
+ .into(),
+ ]
+ .into_iter(),
+ ),
+ );
+ let obligation = traits::Obligation::new(
+ traits::ObligationCause::dummy(),
+ self.param_env,
+ ty::Binder::dummy(ty::TraitPredicate {
+ trait_ref,
+ constness: ty::BoundConstness::NotConst,
+ polarity: ty::ImplPolarity::Positive,
+ }),
+ );
+ match SelectionContext::new(&self).select(&obligation) {
+ Ok(Some(traits::ImplSource::UserDefined(impl_source))) => {
+ Some(impl_source.impl_def_id)
+ }
+ _ => None,
+ }
+ });
+ if let Some(new_def_id) = new_def_id {
+ def_id = new_def_id;
+ } else {
+ return;
+ }
+ }
+ }
+ }
+
+ if let Some(def_span) = self.tcx.def_ident_span(def_id) && !def_span.is_dummy() {
+ let mut spans: MultiSpan = def_span.into();
+
+ let params = self
+ .tcx
+ .hir()
+ .get_if_local(def_id)
+ .and_then(|node| node.body_id())
+ .into_iter()
+ .flat_map(|id| self.tcx.hir().body(id).params)
+ .skip(if is_method { 1 } else { 0 });
+
+ for (_, param) in params
+ .into_iter()
+ .enumerate()
+ .filter(|(idx, _)| expected_idx.map_or(true, |expected_idx| expected_idx == *idx))
+ {
+ spans.push_span_label(param.span, "");
+ }
+
+ let def_kind = self.tcx.def_kind(def_id);
+ err.span_note(spans, &format!("{} defined here", def_kind.descr(def_id)));
+ } else if let Some(hir::Node::Expr(e)) = self.tcx.hir().get_if_local(def_id)
+ && let hir::ExprKind::Closure(hir::Closure { body, .. }) = &e.kind
+ {
+ let param = expected_idx
+ .and_then(|expected_idx| self.tcx.hir().body(*body).params.get(expected_idx));
+ let (kind, span) = if let Some(param) = param {
+ ("closure parameter", param.span)
+ } else {
+ ("closure", self.tcx.def_span(def_id))
+ };
+ err.span_note(span, &format!("{} defined here", kind));
+ } else {
+ let def_kind = self.tcx.def_kind(def_id);
+ err.span_note(
+ self.tcx.def_span(def_id),
+ &format!("{} defined here", def_kind.descr(def_id)),
+ );
+ }
+ }
+}
+
+fn find_param_in_ty<'tcx>(ty: Ty<'tcx>, param_to_point_at: ty::GenericArg<'tcx>) -> bool {
+ let mut walk = ty.walk();
+ while let Some(arg) = walk.next() {
+ if arg == param_to_point_at {
+ return true;
+ } else if let ty::GenericArgKind::Type(ty) = arg.unpack()
+ && let ty::Projection(..) = ty.kind()
+ {
+ // This logic may seem a bit strange, but typically when
+ // we have a projection type in a function signature, the
+ // argument that's being passed into that signature is
+ // not actually constraining that projection's substs in
+ // a meaningful way. So we skip it, and see improvements
+ // in some UI tests.
+ walk.skip_current_subtree();
+ }
+ }
+ false
+}
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
new file mode 100644
index 000000000..0c600daf4
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -0,0 +1,312 @@
+mod _impl;
+mod arg_matrix;
+mod checks;
+mod suggestions;
+
+pub use _impl::*;
+pub use suggestions::*;
+
+use crate::coercion::DynamicCoerceMany;
+use crate::{Diverges, EnclosingBreakables, Inherited, UnsafetyState};
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+use rustc_hir_analysis::astconv::AstConv;
+use rustc_infer::infer;
+use rustc_infer::infer::error_reporting::TypeErrCtxt;
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
+use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{self, Const, Ty, TyCtxt};
+use rustc_session::Session;
+use rustc_span::symbol::Ident;
+use rustc_span::{self, Span};
+use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
+
+use std::cell::{Cell, RefCell};
+use std::ops::Deref;
+
+/// The `FnCtxt` stores type-checking context needed to type-check bodies of
+/// functions, closures, and `const`s, including performing type inference
+/// with [`InferCtxt`].
+///
+/// This is in contrast to [`ItemCtxt`], which is used to type-check item *signatures*
+/// and thus does not perform type inference.
+///
+/// See [`ItemCtxt`]'s docs for more.
+///
+/// [`ItemCtxt`]: rustc_hir_analysis::collect::ItemCtxt
+/// [`InferCtxt`]: infer::InferCtxt
+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>>>,
+
+ /// 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: Cell<Option<Span>>,
+
+ pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
+
+ pub(super) ps: Cell<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 an `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<'tcx>,
+
+ /// True if the function or closure's return type is known before
+ /// entering the function/closure, i.e. if the return type is
+ /// either given explicitly or inferred from, say, an `Fn*` trait
+ /// bound. Used for diagnostic purposes only.
+ pub(super) return_type_pre_known: bool,
+
+ /// True if the return type has an Opaque type
+ pub(super) return_type_has_opaque: bool,
+}
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ pub fn new(
+ inh: &'a Inherited<'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,
+ in_tail_expr: false,
+ ret_coercion_span: Cell::new(None),
+ resume_yield_tys: None,
+ ps: Cell::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,
+ return_type_pre_known: true,
+ return_type_has_opaque: false,
+ }
+ }
+
+ 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)
+ }
+
+ pub fn sess(&self) -> &Session {
+ &self.tcx.sess
+ }
+
+ /// Creates an `TypeErrCtxt` with a reference to the in-progress
+ /// `TypeckResults` which is used for diagnostics.
+ /// Use [`InferCtxt::err_ctxt`] to start one without a `TypeckResults`.
+ ///
+ /// [`InferCtxt::err_ctxt`]: infer::InferCtxt::err_ctxt
+ pub fn err_ctxt(&'a self) -> TypeErrCtxt<'a, 'tcx> {
+ TypeErrCtxt { infcx: &self.infcx, typeck_results: Some(self.typeck_results.borrow()) }
+ }
+
+ pub fn errors_reported_since_creation(&self) -> bool {
+ self.tcx.sess.err_count() > self.err_count_on_creation
+ }
+}
+
+impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
+ type Target = Inherited<'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 get_type_parameter_bounds(
+ &self,
+ _: Span,
+ def_id: DefId,
+ _: Ident,
+ ) -> ty::GenericPredicates<'tcx> {
+ let tcx = self.tcx;
+ let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
+ 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.kind().skip_binder() {
+ ty::PredicateKind::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,
+ ) -> 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,
+ 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)
+ }
+}
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
new file mode 100644
index 000000000..4db9c56f9
--- /dev/null
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -0,0 +1,1250 @@
+use super::FnCtxt;
+
+use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel};
+use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX};
+use rustc_errors::{Applicability, Diagnostic, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind};
+use rustc_hir::lang_items::LangItem;
+use rustc_hir::{
+ Expr, ExprKind, GenericBound, Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicate,
+};
+use rustc_hir_analysis::astconv::AstConv;
+use rustc_infer::infer::{self, TyCtxtInferExt};
+use rustc_infer::traits::{self, StatementAsExpression};
+use rustc_middle::lint::in_external_macro;
+use rustc_middle::ty::{self, Binder, IsSuggestable, ToPredicate, Ty};
+use rustc_session::errors::ExprParenthesesNeeded;
+use rustc_span::symbol::sym;
+use rustc_span::Span;
+use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::error_reporting::DefIdOrName;
+use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ pub(in super::super) fn suggest_semicolon_at_end(&self, span: Span, err: &mut Diagnostic) {
+ err.span_suggestion_short(
+ span.shrink_to_hi(),
+ "consider using a semicolon here",
+ ";",
+ Applicability::MachineApplicable,
+ );
+ }
+
+ /// 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 Diagnostic,
+ expr: &'tcx hir::Expr<'tcx>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ blk_id: hir::HirId,
+ ) -> bool {
+ let expr = expr.peel_drop_temps();
+ self.suggest_missing_semicolon(err, expr, expected, false);
+ let mut pointing_at_return_type = false;
+ if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
+ let fn_id = self.tcx.hir().get_return_block(blk_id).unwrap();
+ pointing_at_return_type = self.suggest_missing_return_type(
+ err,
+ &fn_decl,
+ expected,
+ found,
+ can_suggest,
+ fn_id,
+ );
+ self.suggest_missing_break_or_return_expr(
+ err, expr, &fn_decl, expected, found, blk_id, fn_id,
+ );
+ }
+ pointing_at_return_type
+ }
+
+ /// When encountering an fn-like type, try accessing the output of the type
+ /// and suggesting calling it if it satisfies a predicate (i.e. if the
+ /// output has a method or a field):
+ /// ```compile_fail,E0308
+ /// fn foo(x: usize) -> usize { x }
+ /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
+ /// ```
+ pub(crate) fn suggest_fn_call(
+ &self,
+ err: &mut Diagnostic,
+ expr: &hir::Expr<'_>,
+ found: Ty<'tcx>,
+ can_satisfy: impl FnOnce(Ty<'tcx>) -> bool,
+ ) -> bool {
+ let Some((def_id_or_name, output, inputs)) = self.extract_callable_info(expr, found)
+ else { return false; };
+ if can_satisfy(output) {
+ let (sugg_call, mut applicability) = match inputs.len() {
+ 0 => ("".to_string(), Applicability::MachineApplicable),
+ 1..=4 => (
+ inputs
+ .iter()
+ .map(|ty| {
+ if ty.is_suggestable(self.tcx, false) {
+ format!("/* {ty} */")
+ } else {
+ "/* value */".to_string()
+ }
+ })
+ .collect::<Vec<_>>()
+ .join(", "),
+ Applicability::HasPlaceholders,
+ ),
+ _ => ("/* ... */".to_string(), Applicability::HasPlaceholders),
+ };
+
+ let msg = match def_id_or_name {
+ DefIdOrName::DefId(def_id) => match self.tcx.def_kind(def_id) {
+ DefKind::Ctor(CtorOf::Struct, _) => "construct this tuple struct".to_string(),
+ DefKind::Ctor(CtorOf::Variant, _) => "construct this tuple variant".to_string(),
+ kind => format!("call this {}", kind.descr(def_id)),
+ },
+ DefIdOrName::Name(name) => format!("call this {name}"),
+ };
+
+ let sugg = match expr.kind {
+ hir::ExprKind::Call(..)
+ | hir::ExprKind::Path(..)
+ | hir::ExprKind::Index(..)
+ | hir::ExprKind::Lit(..) => {
+ vec![(expr.span.shrink_to_hi(), format!("({sugg_call})"))]
+ }
+ hir::ExprKind::Closure { .. } => {
+ // Might be `{ expr } || { bool }`
+ applicability = Applicability::MaybeIncorrect;
+ vec![
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), format!(")({sugg_call})")),
+ ]
+ }
+ _ => {
+ vec![
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), format!(")({sugg_call})")),
+ ]
+ }
+ };
+
+ err.multipart_suggestion_verbose(
+ format!("use parentheses to {msg}"),
+ sugg,
+ applicability,
+ );
+ return true;
+ }
+ false
+ }
+
+ /// Extracts information about a callable type for diagnostics. This is a
+ /// heuristic -- it doesn't necessarily mean that a type is always callable,
+ /// because the callable type must also be well-formed to be called.
+ pub(in super::super) fn extract_callable_info(
+ &self,
+ expr: &Expr<'_>,
+ found: Ty<'tcx>,
+ ) -> Option<(DefIdOrName, Ty<'tcx>, Vec<Ty<'tcx>>)> {
+ // Autoderef is useful here because sometimes we box callables, etc.
+ let Some((def_id_or_name, output, inputs)) = self.autoderef(expr.span, found).silence_errors().find_map(|(found, _)| {
+ match *found.kind() {
+ ty::FnPtr(fn_sig) =>
+ Some((DefIdOrName::Name("function pointer"), fn_sig.output(), fn_sig.inputs())),
+ ty::FnDef(def_id, _) => {
+ let fn_sig = found.fn_sig(self.tcx);
+ Some((DefIdOrName::DefId(def_id), fn_sig.output(), fn_sig.inputs()))
+ }
+ ty::Closure(def_id, substs) => {
+ let fn_sig = substs.as_closure().sig();
+ Some((DefIdOrName::DefId(def_id), fn_sig.output(), fn_sig.inputs().map_bound(|inputs| &inputs[1..])))
+ }
+ ty::Opaque(def_id, substs) => {
+ self.tcx.bound_item_bounds(def_id).subst(self.tcx, substs).iter().find_map(|pred| {
+ if let ty::PredicateKind::Projection(proj) = pred.kind().skip_binder()
+ && Some(proj.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output()
+ // args tuple will always be substs[1]
+ && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind()
+ {
+ Some((
+ DefIdOrName::DefId(def_id),
+ pred.kind().rebind(proj.term.ty().unwrap()),
+ pred.kind().rebind(args.as_slice()),
+ ))
+ } else {
+ None
+ }
+ })
+ }
+ ty::Dynamic(data, _, ty::Dyn) => {
+ data.iter().find_map(|pred| {
+ if let ty::ExistentialPredicate::Projection(proj) = pred.skip_binder()
+ && Some(proj.item_def_id) == self.tcx.lang_items().fn_once_output()
+ // for existential projection, substs are shifted over by 1
+ && let ty::Tuple(args) = proj.substs.type_at(0).kind()
+ {
+ Some((
+ DefIdOrName::Name("trait object"),
+ pred.rebind(proj.term.ty().unwrap()),
+ pred.rebind(args.as_slice()),
+ ))
+ } else {
+ None
+ }
+ })
+ }
+ ty::Param(param) => {
+ let def_id = self.tcx.generics_of(self.body_id.owner).type_param(&param, self.tcx).def_id;
+ self.tcx.predicates_of(self.body_id.owner).predicates.iter().find_map(|(pred, _)| {
+ if let ty::PredicateKind::Projection(proj) = pred.kind().skip_binder()
+ && Some(proj.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output()
+ && proj.projection_ty.self_ty() == found
+ // args tuple will always be substs[1]
+ && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind()
+ {
+ Some((
+ DefIdOrName::DefId(def_id),
+ pred.kind().rebind(proj.term.ty().unwrap()),
+ pred.kind().rebind(args.as_slice()),
+ ))
+ } else {
+ None
+ }
+ })
+ }
+ _ => None,
+ }
+ }) else { return None; };
+
+ let output = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, output);
+ let inputs = inputs
+ .skip_binder()
+ .iter()
+ .map(|ty| {
+ self.replace_bound_vars_with_fresh_vars(
+ expr.span,
+ infer::FnCall,
+ inputs.rebind(*ty),
+ )
+ })
+ .collect();
+
+ // We don't want to register any extra obligations, which should be
+ // implied by wf, but also because that would possibly result in
+ // erroneous errors later on.
+ let infer::InferOk { value: output, obligations: _ } =
+ self.normalize_associated_types_in_as_infer_ok(expr.span, output);
+
+ if output.is_ty_var() { None } else { Some((def_id_or_name, output, inputs)) }
+ }
+
+ pub fn suggest_two_fn_call(
+ &self,
+ err: &mut Diagnostic,
+ lhs_expr: &'tcx hir::Expr<'tcx>,
+ lhs_ty: Ty<'tcx>,
+ rhs_expr: &'tcx hir::Expr<'tcx>,
+ rhs_ty: Ty<'tcx>,
+ can_satisfy: impl FnOnce(Ty<'tcx>, Ty<'tcx>) -> bool,
+ ) -> bool {
+ let Some((_, lhs_output_ty, lhs_inputs)) = self.extract_callable_info(lhs_expr, lhs_ty)
+ else { return false; };
+ let Some((_, rhs_output_ty, rhs_inputs)) = self.extract_callable_info(rhs_expr, rhs_ty)
+ else { return false; };
+
+ if can_satisfy(lhs_output_ty, rhs_output_ty) {
+ let mut sugg = vec![];
+ let mut applicability = Applicability::MachineApplicable;
+
+ for (expr, inputs) in [(lhs_expr, lhs_inputs), (rhs_expr, rhs_inputs)] {
+ let (sugg_call, this_applicability) = match inputs.len() {
+ 0 => ("".to_string(), Applicability::MachineApplicable),
+ 1..=4 => (
+ inputs
+ .iter()
+ .map(|ty| {
+ if ty.is_suggestable(self.tcx, false) {
+ format!("/* {ty} */")
+ } else {
+ "/* value */".to_string()
+ }
+ })
+ .collect::<Vec<_>>()
+ .join(", "),
+ Applicability::HasPlaceholders,
+ ),
+ _ => ("/* ... */".to_string(), Applicability::HasPlaceholders),
+ };
+
+ applicability = applicability.max(this_applicability);
+
+ match expr.kind {
+ hir::ExprKind::Call(..)
+ | hir::ExprKind::Path(..)
+ | hir::ExprKind::Index(..)
+ | hir::ExprKind::Lit(..) => {
+ sugg.extend([(expr.span.shrink_to_hi(), format!("({sugg_call})"))]);
+ }
+ hir::ExprKind::Closure { .. } => {
+ // Might be `{ expr } || { bool }`
+ applicability = Applicability::MaybeIncorrect;
+ sugg.extend([
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), format!(")({sugg_call})")),
+ ]);
+ }
+ _ => {
+ sugg.extend([
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), format!(")({sugg_call})")),
+ ]);
+ }
+ }
+ }
+
+ err.multipart_suggestion_verbose(
+ format!("use parentheses to call these"),
+ sugg,
+ applicability,
+ );
+
+ true
+ } else {
+ false
+ }
+ }
+
+ pub fn suggest_deref_ref_or_into(
+ &self,
+ err: &mut Diagnostic,
+ expr: &hir::Expr<'tcx>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
+ ) -> bool {
+ let expr = expr.peel_blocks();
+ if let Some((sp, msg, suggestion, applicability, verbose, annotation)) =
+ self.check_ref(expr, found, expected)
+ {
+ if verbose {
+ err.span_suggestion_verbose(sp, &msg, suggestion, applicability);
+ } else {
+ err.span_suggestion(sp, &msg, suggestion, applicability);
+ }
+ if annotation {
+ let suggest_annotation = match expr.peel_drop_temps().kind {
+ hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, _) => "&",
+ hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, _) => "&mut ",
+ _ => return true,
+ };
+ let mut tuple_indexes = Vec::new();
+ let mut expr_id = expr.hir_id;
+ for (parent_id, node) in self.tcx.hir().parent_iter(expr.hir_id) {
+ match node {
+ Node::Expr(&Expr { kind: ExprKind::Tup(subs), .. }) => {
+ tuple_indexes.push(
+ subs.iter()
+ .enumerate()
+ .find(|(_, sub_expr)| sub_expr.hir_id == expr_id)
+ .unwrap()
+ .0,
+ );
+ expr_id = parent_id;
+ }
+ Node::Local(local) => {
+ if let Some(mut ty) = local.ty {
+ while let Some(index) = tuple_indexes.pop() {
+ match ty.kind {
+ TyKind::Tup(tys) => ty = &tys[index],
+ _ => return true,
+ }
+ }
+ let annotation_span = ty.span;
+ err.span_suggestion(
+ annotation_span.with_hi(annotation_span.lo()),
+ format!("alternatively, consider changing the type annotation"),
+ suggest_annotation,
+ Applicability::MaybeIncorrect,
+ );
+ }
+ break;
+ }
+ _ => break,
+ }
+ }
+ }
+ return true;
+ } else if self.suggest_else_fn_with_closure(err, expr, found, expected) {
+ return true;
+ } else if self.suggest_fn_call(err, expr, found, |output| self.can_coerce(output, expected))
+ && let ty::FnDef(def_id, ..) = &found.kind()
+ && let Some(sp) = self.tcx.hir().span_if_local(*def_id)
+ {
+ err.span_label(sp, format!("{found} defined here"));
+ return true;
+ } else if self.check_for_cast(err, expr, found, expected, expected_ty_expr) {
+ return true;
+ } else {
+ let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
+ if !methods.is_empty() {
+ let mut suggestions = methods.iter()
+ .filter_map(|conversion_method| {
+ let receiver_method_ident = expr.method_ident();
+ if let Some(method_ident) = receiver_method_ident
+ && method_ident.name == conversion_method.name
+ {
+ return None // do not suggest code that is already there (#53348)
+ }
+
+ let method_call_list = [sym::to_vec, sym::to_string];
+ let mut sugg = if let ExprKind::MethodCall(receiver_method, ..) = expr.kind
+ && receiver_method.ident.name == sym::clone
+ && method_call_list.contains(&conversion_method.name)
+ // If receiver is `.clone()` and found type has one of those methods,
+ // we guess that the user wants to convert from a slice type (`&[]` or `&str`)
+ // to an owned type (`Vec` or `String`). These conversions clone internally,
+ // so we remove the user's `clone` call.
+ {
+ vec![(
+ receiver_method.ident.span,
+ conversion_method.name.to_string()
+ )]
+ } else if expr.precedence().order()
+ < ExprPrecedence::MethodCall.order()
+ {
+ vec![
+ (expr.span.shrink_to_lo(), "(".to_string()),
+ (expr.span.shrink_to_hi(), format!(").{}()", conversion_method.name)),
+ ]
+ } else {
+ vec![(expr.span.shrink_to_hi(), format!(".{}()", conversion_method.name))]
+ };
+ let struct_pat_shorthand_field = self.maybe_get_struct_pattern_shorthand_field(expr);
+ if let Some(name) = struct_pat_shorthand_field {
+ sugg.insert(
+ 0,
+ (expr.span.shrink_to_lo(), format!("{}: ", name)),
+ );
+ }
+ Some(sugg)
+ })
+ .peekable();
+ if suggestions.peek().is_some() {
+ err.multipart_suggestions(
+ "try using a conversion method",
+ suggestions,
+ Applicability::MaybeIncorrect,
+ );
+ return true;
+ }
+ } else if let ty::Adt(found_adt, found_substs) = found.kind()
+ && self.tcx.is_diagnostic_item(sym::Option, found_adt.did())
+ && let ty::Adt(expected_adt, expected_substs) = expected.kind()
+ && self.tcx.is_diagnostic_item(sym::Option, expected_adt.did())
+ && let ty::Ref(_, inner_ty, _) = expected_substs.type_at(0).kind()
+ && inner_ty.is_str()
+ {
+ let ty = found_substs.type_at(0);
+ let mut peeled = ty;
+ let mut ref_cnt = 0;
+ while let ty::Ref(_, inner, _) = peeled.kind() {
+ peeled = *inner;
+ ref_cnt += 1;
+ }
+ if let ty::Adt(adt, _) = peeled.kind()
+ && self.tcx.is_diagnostic_item(sym::String, adt.did())
+ {
+ err.span_suggestion_verbose(
+ expr.span.shrink_to_hi(),
+ "try converting the passed type into a `&str`",
+ format!(".map(|x| &*{}x)", "*".repeat(ref_cnt)),
+ Applicability::MaybeIncorrect,
+ );
+ return true;
+ }
+ }
+ }
+
+ false
+ }
+
+ /// When encountering the expected boxed value allocated in the stack, suggest allocating it
+ /// in the heap by calling `Box::new()`.
+ pub(in super::super) fn suggest_boxing_when_appropriate(
+ &self,
+ err: &mut Diagnostic,
+ expr: &hir::Expr<'_>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ ) -> bool {
+ if self.tcx.hir().is_inside_const_context(expr.hir_id) {
+ // Do not suggest `Box::new` in const context.
+ return false;
+ }
+ if !expected.is_box() || found.is_box() {
+ return false;
+ }
+ let boxed_found = self.tcx.mk_box(found);
+ if self.can_coerce(boxed_found, expected) {
+ err.multipart_suggestion(
+ "store this in the heap by calling `Box::new`",
+ vec![
+ (expr.span.shrink_to_lo(), "Box::new(".to_string()),
+ (expr.span.shrink_to_hi(), ")".to_string()),
+ ],
+ 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",
+ );
+ true
+ } else {
+ false
+ }
+ }
+
+ /// When encountering a closure that captures variables, where a FnPtr is expected,
+ /// suggest a non-capturing closure
+ pub(in super::super) fn suggest_no_capture_closure(
+ &self,
+ err: &mut Diagnostic,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ ) -> bool {
+ if let (ty::FnPtr(_), ty::Closure(def_id, _)) = (expected.kind(), found.kind()) {
+ if let Some(upvars) = self.tcx.upvars_mentioned(*def_id) {
+ // Report upto four upvars being captured to reduce the amount error messages
+ // reported back to the user.
+ let spans_and_labels = upvars
+ .iter()
+ .take(4)
+ .map(|(var_hir_id, upvar)| {
+ let var_name = self.tcx.hir().name(*var_hir_id).to_string();
+ let msg = format!("`{}` captured here", var_name);
+ (upvar.span, msg)
+ })
+ .collect::<Vec<_>>();
+
+ let mut multi_span: MultiSpan =
+ spans_and_labels.iter().map(|(sp, _)| *sp).collect::<Vec<_>>().into();
+ for (sp, label) in spans_and_labels {
+ multi_span.push_span_label(sp, label);
+ }
+ err.span_note(
+ multi_span,
+ "closures can only be coerced to `fn` types if they do not capture any variables"
+ );
+ return true;
+ }
+ }
+ false
+ }
+
+ /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`.
+ #[instrument(skip(self, err))]
+ pub(in super::super) fn suggest_calling_boxed_future_when_appropriate(
+ &self,
+ err: &mut Diagnostic,
+ 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();
+ // This guards the `unwrap` and `mk_box` below.
+ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() {
+ return false;
+ }
+ let box_found = self.tcx.mk_box(found);
+ let pin_box_found = self.tcx.mk_lang_item(box_found, LangItem::Pin).unwrap();
+ let pin_found = self.tcx.mk_lang_item(found, LangItem::Pin).unwrap();
+ match expected.kind() {
+ ty::Adt(def, _) if Some(def.did()) == pin_did => {
+ if self.can_coerce(pin_box_found, expected) {
+ debug!("can coerce {:?} to {:?}, suggesting Box::pin", pin_box_found, expected);
+ match found.kind() {
+ ty::Adt(def, _) if def.is_box() => {
+ err.help("use `Box::pin`");
+ }
+ _ => {
+ err.multipart_suggestion(
+ "you need to pin and box this expression",
+ vec![
+ (expr.span.shrink_to_lo(), "Box::pin(".to_string()),
+ (expr.span.shrink_to_hi(), ")".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ true
+ } else if self.can_coerce(pin_found, expected) {
+ match found.kind() {
+ ty::Adt(def, _) if def.is_box() => {
+ err.help("use `Box::pin`");
+ true
+ }
+ _ => false,
+ }
+ } else {
+ false
+ }
+ }
+ ty::Adt(def, _) if def.is_box() && self.can_coerce(box_found, expected) => {
+ // Check if the parent expression is a call to Pin::new. If it
+ // is and we were expecting a Box, ergo Pin<Box<expected>>, we
+ // can suggest Box::pin.
+ let parent = self.tcx.hir().get_parent_node(expr.hir_id);
+ let Some(Node::Expr(Expr { kind: ExprKind::Call(fn_name, _), .. })) = self.tcx.hir().find(parent) else {
+ return false;
+ };
+ match fn_name.kind {
+ ExprKind::Path(QPath::TypeRelative(
+ hir::Ty {
+ kind: TyKind::Path(QPath::Resolved(_, Path { res: recv_ty, .. })),
+ ..
+ },
+ method,
+ )) if recv_ty.opt_def_id() == pin_did && method.ident.name == sym::new => {
+ err.span_suggestion(
+ fn_name.span,
+ "use `Box::pin` to pin and box this expression",
+ "Box::pin",
+ Applicability::MachineApplicable,
+ );
+ true
+ }
+ _ => false,
+ }
+ }
+ _ => false,
+ }
+ }
+
+ /// A common error is to forget to add a semicolon at the end of a block, e.g.,
+ ///
+ /// ```compile_fail,E0308
+ /// # fn bar_that_returns_u32() -> u32 { 4 }
+ /// 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.
+ ///
+ /// If the expression is the expression of a closure without block (`|| expr`), a
+ /// block is needed to be added too (`|| { expr; }`). This is denoted by `needs_block`.
+ pub fn suggest_missing_semicolon(
+ &self,
+ err: &mut Diagnostic,
+ expression: &'tcx hir::Expr<'tcx>,
+ expected: Ty<'tcx>,
+ needs_block: bool,
+ ) {
+ 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::If(..)
+ | ExprKind::Match(..)
+ | ExprKind::Block(..)
+ if expression.can_have_side_effects()
+ // If the expression is from an external macro, then do not suggest
+ // adding a semicolon, because there's nowhere to put it.
+ // See issue #81943.
+ && !in_external_macro(self.tcx.sess, expression.span) =>
+ {
+ if needs_block {
+ err.multipart_suggestion(
+ "consider using a semicolon here",
+ vec![
+ (expression.span.shrink_to_lo(), "{ ".to_owned()),
+ (expression.span.shrink_to_hi(), "; }".to_owned()),
+ ],
+ Applicability::MachineApplicable,
+ );
+ } else {
+ err.span_suggestion(
+ expression.span.shrink_to_hi(),
+ "consider using a semicolon here",
+ ";",
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ _ => (),
+ }
+ }
+ }
+
+ /// A possible error is to forget to add a return type that is needed:
+ ///
+ /// ```compile_fail,E0308
+ /// # fn bar_that_returns_u32() -> u32 { 4 }
+ /// 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(in super::super) fn suggest_missing_return_type(
+ &self,
+ err: &mut Diagnostic,
+ fn_decl: &hir::FnDecl<'_>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ can_suggest: bool,
+ fn_id: hir::HirId,
+ ) -> bool {
+ let found =
+ self.resolve_numeric_literals_with_default(self.resolve_vars_if_possible(found));
+ // 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 {
+ &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() && !can_suggest => {
+ // `fn main()` must return `()`, do not suggest changing return type
+ err.subdiagnostic(ExpectedReturnTypeLabel::Unit { span });
+ return true;
+ }
+ &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() => {
+ if found.is_suggestable(self.tcx, false) {
+ err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: found.to_string() });
+ return true;
+ } else if let ty::Closure(_, substs) = found.kind()
+ // FIXME(compiler-errors): Get better at printing binders...
+ && let closure = substs.as_closure()
+ && closure.sig().is_suggestable(self.tcx, false)
+ {
+ err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: closure.print_as_impl_trait().to_string() });
+ return true;
+ } else {
+ // FIXME: if `found` could be `impl Iterator` we should suggest that.
+ err.subdiagnostic(AddReturnTypeSuggestion::MissingHere { span });
+ return true
+ }
+ }
+ &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 span = ty.span;
+ let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, ty);
+ debug!("suggest_missing_return_type: return type {:?}", ty);
+ debug!("suggest_missing_return_type: expected type {:?}", ty);
+ let bound_vars = self.tcx.late_bound_vars(fn_id);
+ let ty = Binder::bind_with_vars(ty, bound_vars);
+ let ty = self.normalize_associated_types_in(span, ty);
+ let ty = self.tcx.erase_late_bound_regions(ty);
+ if self.can_coerce(expected, ty) {
+ err.subdiagnostic(ExpectedReturnTypeLabel::Other { span, expected });
+ self.try_suggest_return_impl_trait(err, expected, ty, fn_id);
+ return true;
+ }
+ }
+ _ => {}
+ }
+ false
+ }
+
+ /// check whether the return type is a generic type with a trait bound
+ /// only suggest this if the generic param is not present in the arguments
+ /// if this is true, hint them towards changing the return type to `impl Trait`
+ /// ```compile_fail,E0308
+ /// fn cant_name_it<T: Fn() -> u32>() -> T {
+ /// || 3
+ /// }
+ /// ```
+ fn try_suggest_return_impl_trait(
+ &self,
+ err: &mut Diagnostic,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ fn_id: hir::HirId,
+ ) {
+ // Only apply the suggestion if:
+ // - the return type is a generic parameter
+ // - the generic param is not used as a fn param
+ // - the generic param has at least one bound
+ // - the generic param doesn't appear in any other bounds where it's not the Self type
+ // Suggest:
+ // - Changing the return type to be `impl <all bounds>`
+
+ debug!("try_suggest_return_impl_trait, expected = {:?}, found = {:?}", expected, found);
+
+ let ty::Param(expected_ty_as_param) = expected.kind() else { return };
+
+ let fn_node = self.tcx.hir().find(fn_id);
+
+ let Some(hir::Node::Item(hir::Item {
+ kind:
+ hir::ItemKind::Fn(
+ hir::FnSig { decl: hir::FnDecl { inputs: fn_parameters, output: fn_return, .. }, .. },
+ hir::Generics { params, predicates, .. },
+ _body_id,
+ ),
+ ..
+ })) = fn_node else { return };
+
+ if params.get(expected_ty_as_param.index as usize).is_none() {
+ return;
+ };
+
+ // get all where BoundPredicates here, because they are used in to cases below
+ let where_predicates = predicates
+ .iter()
+ .filter_map(|p| match p {
+ WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
+ bounds,
+ bounded_ty,
+ ..
+ }) => {
+ // FIXME: Maybe these calls to `ast_ty_to_ty` can be removed (and the ones below)
+ let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, bounded_ty);
+ Some((ty, bounds))
+ }
+ _ => None,
+ })
+ .map(|(ty, bounds)| match ty.kind() {
+ ty::Param(param_ty) if param_ty == expected_ty_as_param => Ok(Some(bounds)),
+ // check whether there is any predicate that contains our `T`, like `Option<T>: Send`
+ _ => match ty.contains(expected) {
+ true => Err(()),
+ false => Ok(None),
+ },
+ })
+ .collect::<Result<Vec<_>, _>>();
+
+ let Ok(where_predicates) = where_predicates else { return };
+
+ // now get all predicates in the same types as the where bounds, so we can chain them
+ let predicates_from_where =
+ where_predicates.iter().flatten().flat_map(|bounds| bounds.iter());
+
+ // extract all bounds from the source code using their spans
+ let all_matching_bounds_strs = predicates_from_where
+ .filter_map(|bound| match bound {
+ GenericBound::Trait(_, _) => {
+ self.tcx.sess.source_map().span_to_snippet(bound.span()).ok()
+ }
+ _ => None,
+ })
+ .collect::<Vec<String>>();
+
+ if all_matching_bounds_strs.len() == 0 {
+ return;
+ }
+
+ let all_bounds_str = all_matching_bounds_strs.join(" + ");
+
+ let ty_param_used_in_fn_params = fn_parameters.iter().any(|param| {
+ let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, param);
+ matches!(ty.kind(), ty::Param(fn_param_ty_param) if expected_ty_as_param == fn_param_ty_param)
+ });
+
+ if ty_param_used_in_fn_params {
+ return;
+ }
+
+ err.span_suggestion(
+ fn_return.span(),
+ "consider using an impl return type",
+ format!("impl {}", all_bounds_str),
+ Applicability::MaybeIncorrect,
+ );
+ }
+
+ pub(in super::super) fn suggest_missing_break_or_return_expr(
+ &self,
+ err: &mut Diagnostic,
+ expr: &'tcx hir::Expr<'tcx>,
+ fn_decl: &hir::FnDecl<'_>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ id: hir::HirId,
+ fn_id: hir::HirId,
+ ) {
+ if !expected.is_unit() {
+ return;
+ }
+ let found = self.resolve_vars_with_obligations(found);
+
+ let in_loop = self.is_loop(id)
+ || self.tcx.hir().parent_iter(id).any(|(parent_id, _)| self.is_loop(parent_id));
+
+ let in_local_statement = self.is_local_statement(id)
+ || self
+ .tcx
+ .hir()
+ .parent_iter(id)
+ .any(|(parent_id, _)| self.is_local_statement(parent_id));
+
+ if in_loop && in_local_statement {
+ err.multipart_suggestion(
+ "you might have meant to break the loop with this value",
+ vec![
+ (expr.span.shrink_to_lo(), "break ".to_string()),
+ (expr.span.shrink_to_hi(), ";".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ return;
+ }
+
+ if let hir::FnRetTy::Return(ty) = fn_decl.output {
+ let ty = <dyn AstConv<'_>>::ast_ty_to_ty(self, ty);
+ let bound_vars = self.tcx.late_bound_vars(fn_id);
+ let ty = self.tcx.erase_late_bound_regions(Binder::bind_with_vars(ty, bound_vars));
+ let ty = self.normalize_associated_types_in(expr.span, ty);
+ let ty = match self.tcx.asyncness(fn_id.owner) {
+ hir::IsAsync::Async => {
+ let infcx = self.tcx.infer_ctxt().build();
+ infcx
+ .get_impl_future_output_ty(ty)
+ .unwrap_or_else(|| {
+ span_bug!(
+ fn_decl.output.span(),
+ "failed to get output type of async function"
+ )
+ })
+ .skip_binder()
+ }
+ hir::IsAsync::NotAsync => ty,
+ };
+ if self.can_coerce(found, ty) {
+ err.multipart_suggestion(
+ "you might have meant to return this value",
+ vec![
+ (expr.span.shrink_to_lo(), "return ".to_string()),
+ (expr.span.shrink_to_hi(), ";".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ }
+
+ pub(in super::super) fn suggest_missing_parentheses(
+ &self,
+ err: &mut Diagnostic,
+ expr: &hir::Expr<'_>,
+ ) -> bool {
+ 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 }`
+ err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
+ true
+ } else {
+ false
+ }
+ }
+
+ /// Given an expression type mismatch, peel any `&` expressions until we get to
+ /// a block expression, and then suggest replacing the braces with square braces
+ /// if it was possibly mistaken array syntax.
+ pub(crate) fn suggest_block_to_brackets_peeling_refs(
+ &self,
+ diag: &mut Diagnostic,
+ mut expr: &hir::Expr<'_>,
+ mut expr_ty: Ty<'tcx>,
+ mut expected_ty: Ty<'tcx>,
+ ) -> bool {
+ loop {
+ match (&expr.kind, expr_ty.kind(), expected_ty.kind()) {
+ (
+ hir::ExprKind::AddrOf(_, _, inner_expr),
+ ty::Ref(_, inner_expr_ty, _),
+ ty::Ref(_, inner_expected_ty, _),
+ ) => {
+ expr = *inner_expr;
+ expr_ty = *inner_expr_ty;
+ expected_ty = *inner_expected_ty;
+ }
+ (hir::ExprKind::Block(blk, _), _, _) => {
+ self.suggest_block_to_brackets(diag, *blk, expr_ty, expected_ty);
+ break true;
+ }
+ _ => break false,
+ }
+ }
+ }
+
+ pub(crate) fn suggest_copied_or_cloned(
+ &self,
+ diag: &mut Diagnostic,
+ expr: &hir::Expr<'_>,
+ expr_ty: Ty<'tcx>,
+ expected_ty: Ty<'tcx>,
+ ) -> bool {
+ let ty::Adt(adt_def, substs) = expr_ty.kind() else { return false; };
+ let ty::Adt(expected_adt_def, expected_substs) = expected_ty.kind() else { return false; };
+ if adt_def != expected_adt_def {
+ return false;
+ }
+
+ let mut suggest_copied_or_cloned = || {
+ let expr_inner_ty = substs.type_at(0);
+ let expected_inner_ty = expected_substs.type_at(0);
+ if let ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
+ && self.can_eq(self.param_env, *ty, expected_inner_ty).is_ok()
+ {
+ let def_path = self.tcx.def_path_str(adt_def.did());
+ if self.type_is_copy_modulo_regions(self.param_env, *ty, expr.span) {
+ diag.span_suggestion_verbose(
+ expr.span.shrink_to_hi(),
+ format!(
+ "use `{def_path}::copied` to copy the value inside the `{def_path}`"
+ ),
+ ".copied()",
+ Applicability::MachineApplicable,
+ );
+ return true;
+ } else if let Some(clone_did) = self.tcx.lang_items().clone_trait()
+ && rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions(
+ self,
+ self.param_env,
+ *ty,
+ clone_did,
+ expr.span
+ )
+ {
+ diag.span_suggestion_verbose(
+ expr.span.shrink_to_hi(),
+ format!(
+ "use `{def_path}::cloned` to clone the value inside the `{def_path}`"
+ ),
+ ".cloned()",
+ Applicability::MachineApplicable,
+ );
+ return true;
+ }
+ }
+ false
+ };
+
+ if let Some(result_did) = self.tcx.get_diagnostic_item(sym::Result)
+ && adt_def.did() == result_did
+ // Check that the error types are equal
+ && self.can_eq(self.param_env, substs.type_at(1), expected_substs.type_at(1)).is_ok()
+ {
+ return suggest_copied_or_cloned();
+ } else if let Some(option_did) = self.tcx.get_diagnostic_item(sym::Option)
+ && adt_def.did() == option_did
+ {
+ return suggest_copied_or_cloned();
+ }
+
+ false
+ }
+
+ pub(crate) fn suggest_into(
+ &self,
+ diag: &mut Diagnostic,
+ expr: &hir::Expr<'_>,
+ expr_ty: Ty<'tcx>,
+ expected_ty: Ty<'tcx>,
+ ) -> bool {
+ let expr = expr.peel_blocks();
+
+ // We have better suggestions for scalar interconversions...
+ if expr_ty.is_scalar() && expected_ty.is_scalar() {
+ return false;
+ }
+
+ // Don't suggest turning a block into another type (e.g. `{}.into()`)
+ if matches!(expr.kind, hir::ExprKind::Block(..)) {
+ return false;
+ }
+
+ // We'll later suggest `.as_ref` when noting the type error,
+ // so skip if we will suggest that instead.
+ if self.err_ctxt().should_suggest_as_ref(expected_ty, expr_ty).is_some() {
+ return false;
+ }
+
+ if let Some(into_def_id) = self.tcx.get_diagnostic_item(sym::Into)
+ && self.predicate_must_hold_modulo_regions(&traits::Obligation::new(
+ self.misc(expr.span),
+ self.param_env,
+ ty::Binder::dummy(ty::TraitRef {
+ def_id: into_def_id,
+ substs: self.tcx.mk_substs_trait(expr_ty, &[expected_ty.into()]),
+ })
+ .to_poly_trait_predicate()
+ .to_predicate(self.tcx),
+ ))
+ {
+ let sugg = if expr.precedence().order() >= PREC_POSTFIX {
+ vec![(expr.span.shrink_to_hi(), ".into()".to_owned())]
+ } else {
+ vec![(expr.span.shrink_to_lo(), "(".to_owned()), (expr.span.shrink_to_hi(), ").into()".to_owned())]
+ };
+ diag.multipart_suggestion(
+ format!("call `Into::into` on this expression to convert `{expr_ty}` into `{expected_ty}`"),
+ sugg,
+ Applicability::MaybeIncorrect
+ );
+ return true;
+ }
+
+ false
+ }
+
+ /// Suggest wrapping the block in square brackets instead of curly braces
+ /// in case the block was mistaken array syntax, e.g. `{ 1 }` -> `[ 1 ]`.
+ pub(crate) fn suggest_block_to_brackets(
+ &self,
+ diag: &mut Diagnostic,
+ blk: &hir::Block<'_>,
+ blk_ty: Ty<'tcx>,
+ expected_ty: Ty<'tcx>,
+ ) {
+ if let ty::Slice(elem_ty) | ty::Array(elem_ty, _) = expected_ty.kind() {
+ if self.can_coerce(blk_ty, *elem_ty)
+ && blk.stmts.is_empty()
+ && blk.rules == hir::BlockCheckMode::DefaultBlock
+ {
+ let source_map = self.tcx.sess.source_map();
+ if let Ok(snippet) = source_map.span_to_snippet(blk.span) {
+ if snippet.starts_with('{') && snippet.ends_with('}') {
+ diag.multipart_suggestion_verbose(
+ "to create an array, use square brackets instead of curly braces",
+ vec![
+ (
+ blk.span
+ .shrink_to_lo()
+ .with_hi(rustc_span::BytePos(blk.span.lo().0 + 1)),
+ "[".to_string(),
+ ),
+ (
+ blk.span
+ .shrink_to_hi()
+ .with_lo(rustc_span::BytePos(blk.span.hi().0 - 1)),
+ "]".to_string(),
+ ),
+ ],
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ }
+ }
+ }
+
+ fn is_loop(&self, id: hir::HirId) -> bool {
+ let node = self.tcx.hir().get(id);
+ matches!(node, Node::Expr(Expr { kind: ExprKind::Loop(..), .. }))
+ }
+
+ fn is_local_statement(&self, id: hir::HirId) -> bool {
+ let node = self.tcx.hir().get(id);
+ matches!(node, Node::Stmt(Stmt { kind: StmtKind::Local(..), .. }))
+ }
+
+ /// Suggest that `&T` was cloned instead of `T` because `T` does not implement `Clone`,
+ /// which is a side-effect of autoref.
+ pub(crate) fn note_type_is_not_clone(
+ &self,
+ diag: &mut Diagnostic,
+ expected_ty: Ty<'tcx>,
+ found_ty: Ty<'tcx>,
+ expr: &hir::Expr<'_>,
+ ) {
+ let hir::ExprKind::MethodCall(segment, callee_expr, &[], _) = expr.kind else { return; };
+ let Some(clone_trait_did) = self.tcx.lang_items().clone_trait() else { return; };
+ let ty::Ref(_, pointee_ty, _) = found_ty.kind() else { return };
+ let results = self.typeck_results.borrow();
+ // First, look for a `Clone::clone` call
+ if segment.ident.name == sym::clone
+ && results.type_dependent_def_id(expr.hir_id).map_or(
+ false,
+ |did| {
+ let assoc_item = self.tcx.associated_item(did);
+ assoc_item.container == ty::AssocItemContainer::TraitContainer
+ && assoc_item.container_id(self.tcx) == clone_trait_did
+ },
+ )
+ // If that clone call hasn't already dereferenced the self type (i.e. don't give this
+ // diagnostic in cases where we have `(&&T).clone()` and we expect `T`).
+ && !results.expr_adjustments(callee_expr).iter().any(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(..)))
+ // Check that we're in fact trying to clone into the expected type
+ && self.can_coerce(*pointee_ty, expected_ty)
+ // And the expected type doesn't implement `Clone`
+ && !self.predicate_must_hold_considering_regions(&traits::Obligation {
+ cause: traits::ObligationCause::dummy(),
+ param_env: self.param_env,
+ recursion_depth: 0,
+ predicate: ty::Binder::dummy(ty::TraitRef {
+ def_id: clone_trait_did,
+ substs: self.tcx.mk_substs([expected_ty.into()].iter()),
+ })
+ .without_const()
+ .to_predicate(self.tcx),
+ })
+ {
+ diag.span_note(
+ callee_expr.span,
+ &format!(
+ "`{expected_ty}` does not implement `Clone`, so `{found_ty}` was cloned instead"
+ ),
+ );
+ }
+ }
+
+ /// A common error is to add an extra semicolon:
+ ///
+ /// ```compile_fail,E0308
+ /// 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.
+ pub(crate) fn consider_removing_semicolon(
+ &self,
+ blk: &'tcx hir::Block<'tcx>,
+ expected_ty: Ty<'tcx>,
+ err: &mut Diagnostic,
+ ) -> bool {
+ if let Some((span_semi, boxed)) = self.err_ctxt().could_remove_semicolon(blk, expected_ty) {
+ if let StatementAsExpression::NeedsBoxing = boxed {
+ err.span_suggestion_verbose(
+ span_semi,
+ "consider removing this semicolon and boxing the expression",
+ "",
+ Applicability::HasPlaceholders,
+ );
+ } else {
+ err.span_suggestion_short(
+ span_semi,
+ "remove this semicolon to return this value",
+ "",
+ Applicability::MachineApplicable,
+ );
+ }
+ true
+ } else {
+ false
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-09 19:40:04 +0000