Auto merge of #102306 - lcnr:rustc_hir_analysis, r=compiler-errors

rename rustc_typeck to rustc_hir_analysis

first part of https://github.com/rust-lang/compiler-team/issues/529

r? `@compiler-errors`

1 files changed, 625 insertions, 0 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/method/mod.rs b/compiler/rustc_hir_analysis/src/check/method/mod.rs
new file mode 100644
index 00000000000..3fe9bea2299
--- /dev/null
+++ b/compiler/rustc_hir_analysis/src/check/method/mod.rs
@@ -0,0 +1,625 @@
+//! Method lookup: the secret sauce of Rust. See the [rustc dev guide] for more information.
+//!
+//! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/method-lookup.html
+
+mod confirm;
+mod prelude2021;
+pub mod probe;
+mod suggest;
+
+pub use self::suggest::SelfSource;
+pub use self::MethodError::*;
+
+use crate::check::{Expectation, FnCtxt};
+use crate::ObligationCause;
+use rustc_data_structures::sync::Lrc;
+use rustc_errors::{Applicability, Diagnostic};
+use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind, Namespace};
+use rustc_hir::def_id::DefId;
+use rustc_infer::infer::{self, InferOk};
+use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{self, DefIdTree, GenericParamDefKind, ToPredicate, Ty, TypeVisitable};
+use rustc_span::symbol::Ident;
+use rustc_span::Span;
+use rustc_trait_selection::traits;
+use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
+
+use self::probe::{IsSuggestion, ProbeScope};
+
+pub fn provide(providers: &mut ty::query::Providers) {
+    probe::provide(providers);
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct MethodCallee<'tcx> {
+    /// Impl method ID, for inherent methods, or trait method ID, otherwise.
+    pub def_id: DefId,
+    pub substs: SubstsRef<'tcx>,
+
+    /// Instantiated method signature, i.e., it has been
+    /// substituted, normalized, and has had late-bound
+    /// lifetimes replaced with inference variables.
+    pub sig: ty::FnSig<'tcx>,
+}
+
+#[derive(Debug)]
+pub enum MethodError<'tcx> {
+    // Did not find an applicable method, but we did find various near-misses that may work.
+    NoMatch(NoMatchData<'tcx>),
+
+    // Multiple methods might apply.
+    Ambiguity(Vec<CandidateSource>),
+
+    // Found an applicable method, but it is not visible. The third argument contains a list of
+    // not-in-scope traits which may work.
+    PrivateMatch(DefKind, DefId, Vec<DefId>),
+
+    // Found a `Self: Sized` bound where `Self` is a trait object, also the caller may have
+    // forgotten to import a trait.
+    IllegalSizedBound(Vec<DefId>, bool, Span),
+
+    // Found a match, but the return type is wrong
+    BadReturnType,
+}
+
+// Contains a list of static methods that may apply, a list of unsatisfied trait predicates which
+// could lead to matches if satisfied, and a list of not-in-scope traits which may work.
+#[derive(Debug)]
+pub struct NoMatchData<'tcx> {
+    pub static_candidates: Vec<CandidateSource>,
+    pub unsatisfied_predicates:
+        Vec<(ty::Predicate<'tcx>, Option<ty::Predicate<'tcx>>, Option<ObligationCause<'tcx>>)>,
+    pub out_of_scope_traits: Vec<DefId>,
+    pub lev_candidate: Option<ty::AssocItem>,
+    pub mode: probe::Mode,
+}
+
+// A pared down enum describing just the places from which a method
+// candidate can arise. Used for error reporting only.
+#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub enum CandidateSource {
+    Impl(DefId),
+    Trait(DefId /* trait id */),
+}
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+    /// Determines whether the type `self_ty` supports a method name `method_name` or not.
+    #[instrument(level = "debug", skip(self))]
+    pub fn method_exists(
+        &self,
+        method_name: Ident,
+        self_ty: Ty<'tcx>,
+        call_expr_id: hir::HirId,
+        allow_private: bool,
+    ) -> bool {
+        let mode = probe::Mode::MethodCall;
+        match self.probe_for_name(
+            method_name.span,
+            mode,
+            method_name,
+            IsSuggestion(false),
+            self_ty,
+            call_expr_id,
+            ProbeScope::TraitsInScope,
+        ) {
+            Ok(..) => true,
+            Err(NoMatch(..)) => false,
+            Err(Ambiguity(..)) => true,
+            Err(PrivateMatch(..)) => allow_private,
+            Err(IllegalSizedBound(..)) => true,
+            Err(BadReturnType) => bug!("no return type expectations but got BadReturnType"),
+        }
+    }
+
+    /// Adds a suggestion to call the given method to the provided diagnostic.
+    #[instrument(level = "debug", skip(self, err, call_expr))]
+    pub(crate) fn suggest_method_call(
+        &self,
+        err: &mut Diagnostic,
+        msg: &str,
+        method_name: Ident,
+        self_ty: Ty<'tcx>,
+        call_expr: &hir::Expr<'_>,
+        span: Option<Span>,
+    ) {
+        let params = self
+            .probe_for_name(
+                method_name.span,
+                probe::Mode::MethodCall,
+                method_name,
+                IsSuggestion(false),
+                self_ty,
+                call_expr.hir_id,
+                ProbeScope::TraitsInScope,
+            )
+            .map(|pick| {
+                let sig = self.tcx.fn_sig(pick.item.def_id);
+                sig.inputs().skip_binder().len().saturating_sub(1)
+            })
+            .unwrap_or(0);
+
+        // Account for `foo.bar<T>`;
+        let sugg_span = span.unwrap_or(call_expr.span).shrink_to_hi();
+        let (suggestion, applicability) = (
+            format!("({})", (0..params).map(|_| "_").collect::<Vec<_>>().join(", ")),
+            if params > 0 { Applicability::HasPlaceholders } else { Applicability::MaybeIncorrect },
+        );
+
+        err.span_suggestion_verbose(sugg_span, msg, suggestion, applicability);
+    }
+
+    /// Performs method lookup. If lookup is successful, it will return the callee
+    /// and store an appropriate adjustment for the self-expr. In some cases it may
+    /// report an error (e.g., invoking the `drop` method).
+    ///
+    /// # Arguments
+    ///
+    /// Given a method call like `foo.bar::<T1,...Tn>(a, b + 1, ...)`:
+    ///
+    /// * `self`:                  the surrounding `FnCtxt` (!)
+    /// * `self_ty`:               the (unadjusted) type of the self expression (`foo`)
+    /// * `segment`:               the name and generic arguments of the method (`bar::<T1, ...Tn>`)
+    /// * `span`:                  the span for the method call
+    /// * `call_expr`:             the complete method call: (`foo.bar::<T1,...Tn>(...)`)
+    /// * `self_expr`:             the self expression (`foo`)
+    /// * `args`:                  the expressions of the arguments (`a, b + 1, ...`)
+    #[instrument(level = "debug", skip(self))]
+    pub fn lookup_method(
+        &self,
+        self_ty: Ty<'tcx>,
+        segment: &hir::PathSegment<'_>,
+        span: Span,
+        call_expr: &'tcx hir::Expr<'tcx>,
+        self_expr: &'tcx hir::Expr<'tcx>,
+        args: &'tcx [hir::Expr<'tcx>],
+    ) -> Result<MethodCallee<'tcx>, MethodError<'tcx>> {
+        let pick =
+            self.lookup_probe(span, segment.ident, self_ty, call_expr, ProbeScope::TraitsInScope)?;
+
+        self.lint_dot_call_from_2018(self_ty, segment, span, call_expr, self_expr, &pick, args);
+
+        for import_id in &pick.import_ids {
+            debug!("used_trait_import: {:?}", import_id);
+            Lrc::get_mut(&mut self.typeck_results.borrow_mut().used_trait_imports)
+                .unwrap()
+                .insert(*import_id);
+        }
+
+        self.tcx.check_stability(pick.item.def_id, Some(call_expr.hir_id), span, None);
+
+        let result =
+            self.confirm_method(span, self_expr, call_expr, self_ty, pick.clone(), segment);
+        debug!("result = {:?}", result);
+
+        if let Some(span) = result.illegal_sized_bound {
+            let mut needs_mut = false;
+            if let ty::Ref(region, t_type, mutability) = self_ty.kind() {
+                let trait_type = self
+                    .tcx
+                    .mk_ref(*region, ty::TypeAndMut { ty: *t_type, mutbl: mutability.invert() });
+                // We probe again to see if there might be a borrow mutability discrepancy.
+                match self.lookup_probe(
+                    span,
+                    segment.ident,
+                    trait_type,
+                    call_expr,
+                    ProbeScope::TraitsInScope,
+                ) {
+                    Ok(ref new_pick) if *new_pick != pick => {
+                        needs_mut = true;
+                    }
+                    _ => {}
+                }
+            }
+
+            // We probe again, taking all traits into account (not only those in scope).
+            let mut candidates = match self.lookup_probe(
+                span,
+                segment.ident,
+                self_ty,
+                call_expr,
+                ProbeScope::AllTraits,
+            ) {
+                // If we find a different result the caller probably forgot to import a trait.
+                Ok(ref new_pick) if *new_pick != pick => vec![new_pick.item.container_id(self.tcx)],
+                Err(Ambiguity(ref sources)) => sources
+                    .iter()
+                    .filter_map(|source| {
+                        match *source {
+                            // Note: this cannot come from an inherent impl,
+                            // because the first probing succeeded.
+                            CandidateSource::Impl(def) => self.tcx.trait_id_of_impl(def),
+                            CandidateSource::Trait(_) => None,
+                        }
+                    })
+                    .collect(),
+                _ => Vec::new(),
+            };
+            candidates.retain(|candidate| *candidate != self.tcx.parent(result.callee.def_id));
+
+            return Err(IllegalSizedBound(candidates, needs_mut, span));
+        }
+
+        Ok(result.callee)
+    }
+
+    #[instrument(level = "debug", skip(self, call_expr))]
+    pub fn lookup_probe(
+        &self,
+        span: Span,
+        method_name: Ident,
+        self_ty: Ty<'tcx>,
+        call_expr: &'tcx hir::Expr<'tcx>,
+        scope: ProbeScope,
+    ) -> probe::PickResult<'tcx> {
+        let mode = probe::Mode::MethodCall;
+        let self_ty = self.resolve_vars_if_possible(self_ty);
+        self.probe_for_name(
+            span,
+            mode,
+            method_name,
+            IsSuggestion(false),
+            self_ty,
+            call_expr.hir_id,
+            scope,
+        )
+    }
+
+    pub(super) fn obligation_for_method(
+        &self,
+        span: Span,
+        trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        opt_input_types: Option<&[Ty<'tcx>]>,
+    ) -> (traits::Obligation<'tcx, ty::Predicate<'tcx>>, &'tcx ty::List<ty::subst::GenericArg<'tcx>>)
+    {
+        // Construct a trait-reference `self_ty : Trait<input_tys>`
+        let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
+            match param.kind {
+                GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => {}
+                GenericParamDefKind::Type { .. } => {
+                    if param.index == 0 {
+                        return self_ty.into();
+                    } else if let Some(input_types) = opt_input_types {
+                        return input_types[param.index as usize - 1].into();
+                    }
+                }
+            }
+            self.var_for_def(span, param)
+        });
+
+        let trait_ref = ty::TraitRef::new(trait_def_id, substs);
+
+        // Construct an obligation
+        let poly_trait_ref = ty::Binder::dummy(trait_ref);
+        (
+            traits::Obligation::misc(
+                span,
+                self.body_id,
+                self.param_env,
+                poly_trait_ref.without_const().to_predicate(self.tcx),
+            ),
+            substs,
+        )
+    }
+
+    pub(super) fn obligation_for_op_method(
+        &self,
+        span: Span,
+        trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        opt_input_type: Option<Ty<'tcx>>,
+        opt_input_expr: Option<&'tcx hir::Expr<'tcx>>,
+        expected: Expectation<'tcx>,
+    ) -> (traits::Obligation<'tcx, ty::Predicate<'tcx>>, &'tcx ty::List<ty::subst::GenericArg<'tcx>>)
+    {
+        // Construct a trait-reference `self_ty : Trait<input_tys>`
+        let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
+            match param.kind {
+                GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => {}
+                GenericParamDefKind::Type { .. } => {
+                    if param.index == 0 {
+                        return self_ty.into();
+                    } else if let Some(input_type) = opt_input_type {
+                        return input_type.into();
+                    }
+                }
+            }
+            self.var_for_def(span, param)
+        });
+
+        let trait_ref = ty::TraitRef::new(trait_def_id, substs);
+
+        // Construct an obligation
+        let poly_trait_ref = ty::Binder::dummy(trait_ref);
+        let output_ty = expected.only_has_type(self).and_then(|ty| (!ty.needs_infer()).then(|| ty));
+
+        (
+            traits::Obligation::new(
+                traits::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, hir::ExprKind::Lit(_))),
+                        output_ty,
+                    },
+                ),
+                self.param_env,
+                poly_trait_ref.without_const().to_predicate(self.tcx),
+            ),
+            substs,
+        )
+    }
+
+    /// `lookup_method_in_trait` is used for overloaded operators.
+    /// It does a very narrow slice of what the normal probe/confirm path does.
+    /// In particular, it doesn't really do any probing: it simply constructs
+    /// an obligation for a particular trait with the given self type and checks
+    /// whether that trait is implemented.
+    #[instrument(level = "debug", skip(self, span))]
+    pub(super) fn lookup_method_in_trait(
+        &self,
+        span: Span,
+        m_name: Ident,
+        trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        opt_input_types: Option<&[Ty<'tcx>]>,
+    ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
+        let (obligation, substs) =
+            self.obligation_for_method(span, trait_def_id, self_ty, opt_input_types);
+        self.construct_obligation_for_trait(
+            span,
+            m_name,
+            trait_def_id,
+            obligation,
+            substs,
+            None,
+            false,
+        )
+    }
+
+    pub(super) fn lookup_op_method_in_trait(
+        &self,
+        span: Span,
+        m_name: Ident,
+        trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        opt_input_type: Option<Ty<'tcx>>,
+        opt_input_expr: Option<&'tcx hir::Expr<'tcx>>,
+        expected: Expectation<'tcx>,
+    ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
+        let (obligation, substs) = self.obligation_for_op_method(
+            span,
+            trait_def_id,
+            self_ty,
+            opt_input_type,
+            opt_input_expr,
+            expected,
+        );
+        self.construct_obligation_for_trait(
+            span,
+            m_name,
+            trait_def_id,
+            obligation,
+            substs,
+            opt_input_expr,
+            true,
+        )
+    }
+
+    // FIXME(#18741): it seems likely that we can consolidate some of this
+    // code with the other method-lookup code. In particular, the second half
+    // of this method is basically the same as confirmation.
+    fn construct_obligation_for_trait(
+        &self,
+        span: Span,
+        m_name: Ident,
+        trait_def_id: DefId,
+        obligation: traits::PredicateObligation<'tcx>,
+        substs: &'tcx ty::List<ty::subst::GenericArg<'tcx>>,
+        opt_input_expr: Option<&'tcx hir::Expr<'tcx>>,
+        is_op: bool,
+    ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
+        debug!(?obligation);
+
+        // Now we want to know if this can be matched
+        if !self.predicate_may_hold(&obligation) {
+            debug!("--> Cannot match obligation");
+            // Cannot be matched, no such method resolution is possible.
+            return None;
+        }
+
+        // Trait must have a method named `m_name` and it should not have
+        // type parameters or early-bound regions.
+        let tcx = self.tcx;
+        let Some(method_item) = self.associated_value(trait_def_id, m_name) else {
+            tcx.sess.delay_span_bug(
+                span,
+                "operator trait does not have corresponding operator method",
+            );
+            return None;
+        };
+        let def_id = method_item.def_id;
+        let generics = tcx.generics_of(def_id);
+        assert_eq!(generics.params.len(), 0);
+
+        debug!("lookup_in_trait_adjusted: method_item={:?}", method_item);
+        let mut obligations = vec![];
+
+        // Instantiate late-bound regions and substitute the trait
+        // parameters into the method type to get the actual method type.
+        //
+        // N.B., instantiate late-bound regions first so that
+        // `instantiate_type_scheme` can normalize associated types that
+        // may reference those regions.
+        let fn_sig = tcx.bound_fn_sig(def_id);
+        let fn_sig = fn_sig.subst(self.tcx, substs);
+        let fn_sig = self.replace_bound_vars_with_fresh_vars(span, infer::FnCall, fn_sig);
+
+        let InferOk { value, obligations: o } = if is_op {
+            self.normalize_op_associated_types_in_as_infer_ok(span, fn_sig, opt_input_expr)
+        } else {
+            self.normalize_associated_types_in_as_infer_ok(span, fn_sig)
+        };
+        let fn_sig = {
+            obligations.extend(o);
+            value
+        };
+
+        // Register obligations for the parameters. This will include the
+        // `Self` parameter, which in turn has a bound of the main trait,
+        // so this also effectively registers `obligation` as well.  (We
+        // used to register `obligation` explicitly, but that resulted in
+        // double error messages being reported.)
+        //
+        // Note that as the method comes from a trait, it should not have
+        // any late-bound regions appearing in its bounds.
+        let bounds = self.tcx.predicates_of(def_id).instantiate(self.tcx, substs);
+
+        let InferOk { value, obligations: o } = if is_op {
+            self.normalize_op_associated_types_in_as_infer_ok(span, bounds, opt_input_expr)
+        } else {
+            self.normalize_associated_types_in_as_infer_ok(span, bounds)
+        };
+        let bounds = {
+            obligations.extend(o);
+            value
+        };
+
+        assert!(!bounds.has_escaping_bound_vars());
+
+        let cause = if is_op {
+            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, hir::ExprKind::Lit(_))),
+                    output_ty: None,
+                },
+            )
+        } else {
+            traits::ObligationCause::misc(span, self.body_id)
+        };
+        let predicates_cause = cause.clone();
+        obligations.extend(traits::predicates_for_generics(
+            move |_, _| predicates_cause.clone(),
+            self.param_env,
+            bounds,
+        ));
+
+        // Also add an obligation for the method type being well-formed.
+        let method_ty = tcx.mk_fn_ptr(ty::Binder::dummy(fn_sig));
+        debug!(
+            "lookup_in_trait_adjusted: matched method method_ty={:?} obligation={:?}",
+            method_ty, obligation
+        );
+        obligations.push(traits::Obligation::new(
+            cause,
+            self.param_env,
+            ty::Binder::dummy(ty::PredicateKind::WellFormed(method_ty.into())).to_predicate(tcx),
+        ));
+
+        let callee = MethodCallee { def_id, substs, sig: fn_sig };
+
+        debug!("callee = {:?}", callee);
+
+        Some(InferOk { obligations, value: callee })
+    }
+
+    /// Performs a [full-qualified function call] (formerly "universal function call") lookup. If
+    /// lookup is successful, it will return the type of definition and the [`DefId`] of the found
+    /// function definition.
+    ///
+    /// [full-qualified function call]: https://doc.rust-lang.org/reference/expressions/call-expr.html#disambiguating-function-calls
+    ///
+    /// # Arguments
+    ///
+    /// Given a function call like `Foo::bar::<T1,...Tn>(...)`:
+    ///
+    /// * `self`:                  the surrounding `FnCtxt` (!)
+    /// * `span`:                  the span of the call, excluding arguments (`Foo::bar::<T1, ...Tn>`)
+    /// * `method_name`:           the identifier of the function within the container type (`bar`)
+    /// * `self_ty`:               the type to search within (`Foo`)
+    /// * `self_ty_span`           the span for the type being searched within (span of `Foo`)
+    /// * `expr_id`:               the [`hir::HirId`] of the expression composing the entire call
+    #[instrument(level = "debug", skip(self), ret)]
+    pub fn resolve_fully_qualified_call(
+        &self,
+        span: Span,
+        method_name: Ident,
+        self_ty: Ty<'tcx>,
+        self_ty_span: Span,
+        expr_id: hir::HirId,
+    ) -> Result<(DefKind, DefId), MethodError<'tcx>> {
+        let tcx = self.tcx;
+
+        // Check if we have an enum variant.
+        if let ty::Adt(adt_def, _) = self_ty.kind() {
+            if adt_def.is_enum() {
+                let variant_def = adt_def
+                    .variants()
+                    .iter()
+                    .find(|vd| tcx.hygienic_eq(method_name, vd.ident(tcx), adt_def.did()));
+                if let Some(variant_def) = variant_def {
+                    // Braced variants generate unusable names in value namespace (reserved for
+                    // possible future use), so variants resolved as associated items may refer to
+                    // them as well. It's ok to use the variant's id as a ctor id since an
+                    // error will be reported on any use of such resolution anyway.
+                    let ctor_def_id = variant_def.ctor_def_id.unwrap_or(variant_def.def_id);
+                    tcx.check_stability(ctor_def_id, Some(expr_id), span, Some(method_name.span));
+                    return Ok((
+                        DefKind::Ctor(CtorOf::Variant, variant_def.ctor_kind),
+                        ctor_def_id,
+                    ));
+                }
+            }
+        }
+
+        let pick = self.probe_for_name(
+            span,
+            probe::Mode::Path,
+            method_name,
+            IsSuggestion(false),
+            self_ty,
+            expr_id,
+            ProbeScope::TraitsInScope,
+        )?;
+
+        self.lint_fully_qualified_call_from_2018(
+            span,
+            method_name,
+            self_ty,
+            self_ty_span,
+            expr_id,
+            &pick,
+        );
+
+        debug!(?pick);
+        {
+            let mut typeck_results = self.typeck_results.borrow_mut();
+            let used_trait_imports = Lrc::get_mut(&mut typeck_results.used_trait_imports).unwrap();
+            for import_id in pick.import_ids {
+                debug!(used_trait_import=?import_id);
+                used_trait_imports.insert(import_id);
+            }
+        }
+
+        let def_kind = pick.item.kind.as_def_kind();
+        tcx.check_stability(pick.item.def_id, Some(expr_id), span, Some(method_name.span));
+        Ok((def_kind, pick.item.def_id))
+    }
+
+    /// Finds item with name `item_name` defined in impl/trait `def_id`
+    /// and return it, or `None`, if no such item was defined there.
+    pub fn associated_value(&self, def_id: DefId, item_name: Ident) -> Option<ty::AssocItem> {
+        self.tcx
+            .associated_items(def_id)
+            .find_by_name_and_namespace(self.tcx, item_name, Namespace::ValueNS, def_id)
+            .copied()
+    }
+}