Auto merge of #76906 - Nicholas-Baron:shorten_typeck_check, r=oli-obk

Split rustc_typeck::check into separate files

Contributing to #60302.

compiler/rustc_typeck/src/check/diverges.rs

@@ -0,0 +1,78 @@
+use rustc_span::source_map::DUMMY_SP;
+use rustc_span::{self, Span};
+use std::{cmp, ops};
+
+/// Tracks whether executing a node may exit normally (versus
+/// return/break/panic, which "diverge", leaving dead code in their
+/// wake). Tracked semi-automatically (through type variables marked
+/// as diverging), with some manual adjustments for control-flow
+/// primitives (approximating a CFG).
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Diverges {
+    /// Potentially unknown, some cases converge,
+    /// others require a CFG to determine them.
+    Maybe,
+
+    /// Definitely known to diverge and therefore
+    /// not reach the next sibling or its parent.
+    Always {
+        /// The `Span` points to the expression
+        /// that caused us to diverge
+        /// (e.g. `return`, `break`, etc).
+        span: Span,
+        /// In some cases (e.g. a `match` expression
+        /// where all arms diverge), we may be
+        /// able to provide a more informative
+        /// message to the user.
+        /// If this is `None`, a default message
+        /// will be generated, which is suitable
+        /// for most cases.
+        custom_note: Option<&'static str>,
+    },
+
+    /// Same as `Always` but with a reachability
+    /// warning already emitted.
+    WarnedAlways,
+}
+
+// Convenience impls for combining `Diverges`.
+
+impl ops::BitAnd for Diverges {
+    type Output = Self;
+    fn bitand(self, other: Self) -> Self {
+        cmp::min(self, other)
+    }
+}
+
+impl ops::BitOr for Diverges {
+    type Output = Self;
+    fn bitor(self, other: Self) -> Self {
+        cmp::max(self, other)
+    }
+}
+
+impl ops::BitAndAssign for Diverges {
+    fn bitand_assign(&mut self, other: Self) {
+        *self = *self & other;
+    }
+}
+
+impl ops::BitOrAssign for Diverges {
+    fn bitor_assign(&mut self, other: Self) {
+        *self = *self | other;
+    }
+}
+
+impl Diverges {
+    /// Creates a `Diverges::Always` with the provided `span` and the default note message.
+    pub(super) fn always(span: Span) -> Diverges {
+        Diverges::Always { span, custom_note: None }
+    }
+
+    pub(super) fn is_always(self) -> bool {
+        // Enum comparison ignores the
+        // contents of fields, so we just
+        // fill them in with garbage here.
+        self >= Diverges::Always { span: DUMMY_SP, custom_note: None }
+    }
+}

compiler/rustc_typeck/src/check/expectation.rs

@@ -0,0 +1,117 @@
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_middle::ty::{self, Ty};
+use rustc_span::{self, Span};
+
+use super::Expectation::*;
+use super::FnCtxt;
+
+/// When type-checking an expression, we propagate downward
+/// whatever type hint we are able in the form of an `Expectation`.
+#[derive(Copy, Clone, Debug)]
+pub enum Expectation<'tcx> {
+    /// We know nothing about what type this expression should have.
+    NoExpectation,
+
+    /// This expression should have the type given (or some subtype).
+    ExpectHasType(Ty<'tcx>),
+
+    /// This expression will be cast to the `Ty`.
+    ExpectCastableToType(Ty<'tcx>),
+
+    /// This rvalue expression will be wrapped in `&` or `Box` and coerced
+    /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
+    ExpectRvalueLikeUnsized(Ty<'tcx>),
+}
+
+impl<'a, 'tcx> Expectation<'tcx> {
+    // Disregard "castable to" expectations because they
+    // can lead us astray. Consider for example `if cond
+    // {22} else {c} as u8` -- if we propagate the
+    // "castable to u8" constraint to 22, it will pick the
+    // type 22u8, which is overly constrained (c might not
+    // be a u8). In effect, the problem is that the
+    // "castable to" expectation is not the tightest thing
+    // we can say, so we want to drop it in this case.
+    // The tightest thing we can say is "must unify with
+    // else branch". Note that in the case of a "has type"
+    // constraint, this limitation does not hold.
+
+    // If the expected type is just a type variable, then don't use
+    // an expected type. Otherwise, we might write parts of the type
+    // when checking the 'then' block which are incompatible with the
+    // 'else' branch.
+    pub(super) fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
+        match *self {
+            ExpectHasType(ety) => {
+                let ety = fcx.shallow_resolve(ety);
+                if !ety.is_ty_var() { ExpectHasType(ety) } else { NoExpectation }
+            }
+            ExpectRvalueLikeUnsized(ety) => ExpectRvalueLikeUnsized(ety),
+            _ => NoExpectation,
+        }
+    }
+
+    /// Provides an expectation for an rvalue expression given an *optional*
+    /// hint, which is not required for type safety (the resulting type might
+    /// be checked higher up, as is the case with `&expr` and `box expr`), but
+    /// is useful in determining the concrete type.
+    ///
+    /// The primary use case is where the expected type is a fat pointer,
+    /// like `&[isize]`. For example, consider the following statement:
+    ///
+    ///    let x: &[isize] = &[1, 2, 3];
+    ///
+    /// In this case, the expected type for the `&[1, 2, 3]` expression is
+    /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
+    /// expectation `ExpectHasType([isize])`, that would be too strong --
+    /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
+    /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
+    /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
+    /// which still is useful, because it informs integer literals and the like.
+    /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
+    /// for examples of where this comes up,.
+    pub(super) fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
+        match fcx.tcx.struct_tail_without_normalization(ty).kind() {
+            ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
+            _ => ExpectHasType(ty),
+        }
+    }
+
+    // Resolves `expected` by a single level if it is a variable. If
+    // there is no expected type or resolution is not possible (e.g.,
+    // no constraints yet present), just returns `None`.
+    fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
+        match self {
+            NoExpectation => NoExpectation,
+            ExpectCastableToType(t) => ExpectCastableToType(fcx.resolve_vars_if_possible(&t)),
+            ExpectHasType(t) => ExpectHasType(fcx.resolve_vars_if_possible(&t)),
+            ExpectRvalueLikeUnsized(t) => ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t)),
+        }
+    }
+
+    pub(super) fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
+        match self.resolve(fcx) {
+            NoExpectation => None,
+            ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => Some(ty),
+        }
+    }
+
+    /// It sometimes happens that we want to turn an expectation into
+    /// a **hard constraint** (i.e., something that must be satisfied
+    /// for the program to type-check). `only_has_type` will return
+    /// such a constraint, if it exists.
+    pub(super) fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
+        match self.resolve(fcx) {
+            ExpectHasType(ty) => Some(ty),
+            NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
+        }
+    }
+
+    /// Like `only_has_type`, but instead of returning `None` if no
+    /// hard constraint exists, creates a fresh type variable.
+    pub(super) fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
+        self.only_has_type(fcx).unwrap_or_else(|| {
+            fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span })
+        })
+    }
+}

compiler/rustc_typeck/src/check/gather_locals.rs

@@ -0,0 +1,120 @@
+use crate::check::{FnCtxt, LocalTy, UserType};
+use rustc_hir as hir;
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_hir::PatKind;
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_middle::ty::Ty;
+use rustc_span::Span;
+use rustc_trait_selection::traits;
+
+pub(super) struct GatherLocalsVisitor<'a, 'tcx> {
+    fcx: &'a FnCtxt<'a, 'tcx>,
+    parent_id: hir::HirId,
+}
+
+impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
+    pub(super) fn new(fcx: &'a FnCtxt<'a, 'tcx>, parent_id: hir::HirId) -> Self {
+        Self { fcx, parent_id }
+    }
+
+    fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
+        match ty_opt {
+            None => {
+                // Infer the variable's type.
+                let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
+                    kind: TypeVariableOriginKind::TypeInference,
+                    span,
+                });
+                self.fcx
+                    .locals
+                    .borrow_mut()
+                    .insert(nid, LocalTy { decl_ty: var_ty, revealed_ty: var_ty });
+                var_ty
+            }
+            Some(typ) => {
+                // Take type that the user specified.
+                self.fcx.locals.borrow_mut().insert(nid, typ);
+                typ.revealed_ty
+            }
+        }
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
+    type Map = intravisit::ErasedMap<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+        NestedVisitorMap::None
+    }
+
+    // Add explicitly-declared locals.
+    fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
+        let local_ty = match local.ty {
+            Some(ref ty) => {
+                let o_ty = self.fcx.to_ty(&ty);
+
+                let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
+                    self.fcx.instantiate_opaque_types_from_value(self.parent_id, &o_ty, ty.span)
+                } else {
+                    o_ty
+                };
+
+                let c_ty = self
+                    .fcx
+                    .inh
+                    .infcx
+                    .canonicalize_user_type_annotation(&UserType::Ty(revealed_ty));
+                debug!(
+                    "visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
+                    ty.hir_id, o_ty, revealed_ty, c_ty
+                );
+                self.fcx
+                    .typeck_results
+                    .borrow_mut()
+                    .user_provided_types_mut()
+                    .insert(ty.hir_id, c_ty);
+
+                Some(LocalTy { decl_ty: o_ty, revealed_ty })
+            }
+            None => None,
+        };
+        self.assign(local.span, local.hir_id, local_ty);
+
+        debug!(
+            "local variable {:?} is assigned type {}",
+            local.pat,
+            self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&local.hir_id).unwrap().decl_ty)
+        );
+        intravisit::walk_local(self, local);
+    }
+
+    // Add pattern bindings.
+    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
+        if let PatKind::Binding(_, _, ident, _) = p.kind {
+            let var_ty = self.assign(p.span, p.hir_id, None);
+
+            if !self.fcx.tcx.features().unsized_locals {
+                self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
+            }
+
+            debug!(
+                "pattern binding {} is assigned to {} with type {:?}",
+                ident,
+                self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&p.hir_id).unwrap().decl_ty),
+                var_ty
+            );
+        }
+        intravisit::walk_pat(self, p);
+    }
+
+    // Don't descend into the bodies of nested closures.
+    fn visit_fn(
+        &mut self,
+        _: intravisit::FnKind<'tcx>,
+        _: &'tcx hir::FnDecl<'tcx>,
+        _: hir::BodyId,
+        _: Span,
+        _: hir::HirId,
+    ) {
+    }
+}

compiler/rustc_typeck/src/check/inherited.rs

@@ -0,0 +1,167 @@
+use super::callee::DeferredCallResolution;
+use super::MaybeInProgressTables;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir as hir;
+use rustc_hir::def_id::{DefIdMap, LocalDefId};
+use rustc_hir::HirIdMap;
+use rustc_infer::infer;
+use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
+use rustc_middle::ty::fold::TypeFoldable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::{self, Span};
+use rustc_trait_selection::infer::InferCtxtExt as _;
+use rustc_trait_selection::opaque_types::OpaqueTypeDecl;
+use rustc_trait_selection::traits::{self, TraitEngine, TraitEngineExt};
+
+use std::cell::RefCell;
+use std::ops::Deref;
+
+/// Closures defined within the function. For example:
+///
+///     fn foo() {
+///         bar(move|| { ... })
+///     }
+///
+/// Here, the function `foo()` and the closure passed to
+/// `bar()` will each have their own `FnCtxt`, but they will
+/// share the inherited fields.
+pub struct Inherited<'a, 'tcx> {
+    pub(super) infcx: InferCtxt<'a, 'tcx>,
+
+    pub(super) typeck_results: super::MaybeInProgressTables<'a, 'tcx>,
+
+    pub(super) locals: RefCell<HirIdMap<super::LocalTy<'tcx>>>,
+
+    pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
+
+    // Some additional `Sized` obligations badly affect type inference.
+    // These obligations are added in a later stage of typeck.
+    pub(super) deferred_sized_obligations:
+        RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
+
+    // When we process a call like `c()` where `c` is a closure type,
+    // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
+    // `FnOnce` closure. In that case, we defer full resolution of the
+    // call until upvar inference can kick in and make the
+    // decision. We keep these deferred resolutions grouped by the
+    // def-id of the closure, so that once we decide, we can easily go
+    // back and process them.
+    pub(super) deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
+
+    pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,
+
+    pub(super) deferred_generator_interiors:
+        RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
+
+    // Opaque types found in explicit return types and their
+    // associated fresh inference variable. Writeback resolves these
+    // variables to get the concrete type, which can be used to
+    // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
+    pub(super) opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
+
+    /// A map from inference variables created from opaque
+    /// type instantiations (`ty::Infer`) to the actual opaque
+    /// type (`ty::Opaque`). Used during fallback to map unconstrained
+    /// opaque type inference variables to their corresponding
+    /// opaque type.
+    pub(super) opaque_types_vars: RefCell<FxHashMap<Ty<'tcx>, Ty<'tcx>>>,
+
+    pub(super) body_id: Option<hir::BodyId>,
+}
+
+impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
+    type Target = InferCtxt<'a, 'tcx>;
+    fn deref(&self) -> &Self::Target {
+        &self.infcx
+    }
+}
+
+/// Helper type of a temporary returned by `Inherited::build(...)`.
+/// Necessary because we can't write the following bound:
+/// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
+pub struct InheritedBuilder<'tcx> {
+    infcx: infer::InferCtxtBuilder<'tcx>,
+    def_id: LocalDefId,
+}
+
+impl Inherited<'_, 'tcx> {
+    pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
+        let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
+
+        InheritedBuilder {
+            infcx: tcx.infer_ctxt().with_fresh_in_progress_typeck_results(hir_owner),
+            def_id,
+        }
+    }
+}
+
+impl<'tcx> InheritedBuilder<'tcx> {
+    pub fn enter<F, R>(&mut self, f: F) -> R
+    where
+        F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
+    {
+        let def_id = self.def_id;
+        self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
+    }
+}
+
+impl Inherited<'a, 'tcx> {
+    pub(super) fn new(infcx: InferCtxt<'a, 'tcx>, def_id: LocalDefId) -> Self {
+        let tcx = infcx.tcx;
+        let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
+        let body_id = tcx.hir().maybe_body_owned_by(item_id);
+
+        Inherited {
+            typeck_results: MaybeInProgressTables {
+                maybe_typeck_results: infcx.in_progress_typeck_results,
+            },
+            infcx,
+            fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
+            locals: RefCell::new(Default::default()),
+            deferred_sized_obligations: RefCell::new(Vec::new()),
+            deferred_call_resolutions: RefCell::new(Default::default()),
+            deferred_cast_checks: RefCell::new(Vec::new()),
+            deferred_generator_interiors: RefCell::new(Vec::new()),
+            opaque_types: RefCell::new(Default::default()),
+            opaque_types_vars: RefCell::new(Default::default()),
+            body_id,
+        }
+    }
+
+    pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
+        debug!("register_predicate({:?})", obligation);
+        if obligation.has_escaping_bound_vars() {
+            span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
+        }
+        self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
+    }
+
+    pub(super) fn register_predicates<I>(&self, obligations: I)
+    where
+        I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
+    {
+        for obligation in obligations {
+            self.register_predicate(obligation);
+        }
+    }
+
+    pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
+        self.register_predicates(infer_ok.obligations);
+        infer_ok.value
+    }
+
+    pub(super) fn normalize_associated_types_in<T>(
+        &self,
+        span: Span,
+        body_id: hir::HirId,
+        param_env: ty::ParamEnv<'tcx>,
+        value: &T,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
+        self.register_infer_ok_obligations(ok)
+    }
+}