--- /dev/null
+//! # Categorization
+//!
+//! The job of the categorization module is to analyze an expression to
+//! determine what kind of memory is used in evaluating it (for example,
+//! where dereferences occur and what kind of pointer is dereferenced;
+//! whether the memory is mutable, etc.).
+//!
+//! Categorization effectively transforms all of our expressions into
+//! expressions of the following forms (the actual enum has many more
+//! possibilities, naturally, but they are all variants of these base
+//! forms):
+//! ```ignore (not-rust)
+//! E = rvalue // some computed rvalue
+//! | x // address of a local variable or argument
+//! | *E // deref of a ptr
+//! | E.comp // access to an interior component
+//! ```
+//! Imagine a routine ToAddr(Expr) that evaluates an expression and returns an
+//! address where the result is to be found. If Expr is a place, then this
+//! is the address of the place. If `Expr` is an rvalue, this is the address of
+//! some temporary spot in memory where the result is stored.
+//!
+//! Now, `cat_expr()` classifies the expression `Expr` and the address `A = ToAddr(Expr)`
+//! as follows:
+//!
+//! - `cat`: what kind of expression was this? This is a subset of the
+//! full expression forms which only includes those that we care about
+//! for the purpose of the analysis.
+//! - `mutbl`: mutability of the address `A`.
+//! - `ty`: the type of data found at the address `A`.
+//!
+//! The resulting categorization tree differs somewhat from the expressions
+//! themselves. For example, auto-derefs are explicit. Also, an index `a[b]` is
+//! decomposed into two operations: a dereference to reach the array data and
+//! then an index to jump forward to the relevant item.
+//!
+//! ## By-reference upvars
+//!
+//! One part of the codegen which may be non-obvious is that we translate
+//! closure upvars into the dereference of a borrowed pointer; this more closely
+//! resembles the runtime codegen. So, for example, if we had:
+//!
+//! let mut x = 3;
+//! let y = 5;
+//! let inc = || x += y;
+//!
+//! Then when we categorize `x` (*within* the closure) we would yield a
+//! result of `*x'`, effectively, where `x'` is a `Categorization::Upvar` reference
+//! tied to `x`. The type of `x'` will be a borrowed pointer.
+
+use rustc_middle::hir::place::*;
+use rustc_middle::ty::adjustment;
+use rustc_middle::ty::fold::TypeFoldable;
+use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind, Res};
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::pat_util::EnumerateAndAdjustIterator;
+use rustc_hir::PatKind;
+use rustc_index::vec::Idx;
+use rustc_infer::infer::InferCtxt;
+use rustc_span::Span;
+use rustc_target::abi::VariantIdx;
+use rustc_trait_selection::infer::InferCtxtExt;
+
+pub(crate) trait HirNode {
+ fn hir_id(&self) -> hir::HirId;
+ fn span(&self) -> Span;
+}
+
+impl HirNode for hir::Expr<'_> {
+ fn hir_id(&self) -> hir::HirId {
+ self.hir_id
+ }
+ fn span(&self) -> Span {
+ self.span
+ }
+}
+
+impl HirNode for hir::Pat<'_> {
+ fn hir_id(&self) -> hir::HirId {
+ self.hir_id
+ }
+ fn span(&self) -> Span {
+ self.span
+ }
+}
+
+#[derive(Clone)]
+pub(crate) struct MemCategorizationContext<'a, 'tcx> {
+ pub(crate) typeck_results: &'a ty::TypeckResults<'tcx>,
+ infcx: &'a InferCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ body_owner: LocalDefId,
+ upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
+}
+
+pub(crate) type McResult<T> = Result<T, ()>;
+
+impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
+ /// Creates a `MemCategorizationContext`.
+ pub(crate) fn new(
+ infcx: &'a InferCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ body_owner: LocalDefId,
+ typeck_results: &'a ty::TypeckResults<'tcx>,
+ ) -> MemCategorizationContext<'a, 'tcx> {
+ MemCategorizationContext {
+ typeck_results,
+ infcx,
+ param_env,
+ body_owner,
+ upvars: infcx.tcx.upvars_mentioned(body_owner),
+ }
+ }
+
+ pub(crate) fn tcx(&self) -> TyCtxt<'tcx> {
+ self.infcx.tcx
+ }
+
+ pub(crate) fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>, span: Span) -> bool {
+ self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span)
+ }
+
+ fn resolve_vars_if_possible<T>(&self, value: T) -> T
+ where
+ T: TypeFoldable<'tcx>,
+ {
+ self.infcx.resolve_vars_if_possible(value)
+ }
+
+ fn is_tainted_by_errors(&self) -> bool {
+ self.infcx.is_tainted_by_errors()
+ }
+
+ fn resolve_type_vars_or_error(
+ &self,
+ id: hir::HirId,
+ ty: Option<Ty<'tcx>>,
+ ) -> McResult<Ty<'tcx>> {
+ match ty {
+ Some(ty) => {
+ let ty = self.resolve_vars_if_possible(ty);
+ if ty.references_error() || ty.is_ty_var() {
+ debug!("resolve_type_vars_or_error: error from {:?}", ty);
+ Err(())
+ } else {
+ Ok(ty)
+ }
+ }
+ // FIXME
+ None if self.is_tainted_by_errors() => Err(()),
+ None => {
+ bug!(
+ "no type for node {}: {} in mem_categorization",
+ id,
+ self.tcx().hir().node_to_string(id)
+ );
+ }
+ }
+ }
+
+ pub(crate) fn node_ty(&self, hir_id: hir::HirId) -> McResult<Ty<'tcx>> {
+ self.resolve_type_vars_or_error(hir_id, self.typeck_results.node_type_opt(hir_id))
+ }
+
+ fn expr_ty(&self, expr: &hir::Expr<'_>) -> McResult<Ty<'tcx>> {
+ self.resolve_type_vars_or_error(expr.hir_id, self.typeck_results.expr_ty_opt(expr))
+ }
+
+ pub(crate) fn expr_ty_adjusted(&self, expr: &hir::Expr<'_>) -> McResult<Ty<'tcx>> {
+ self.resolve_type_vars_or_error(expr.hir_id, self.typeck_results.expr_ty_adjusted_opt(expr))
+ }
+
+ /// Returns the type of value that this pattern matches against.
+ /// Some non-obvious cases:
+ ///
+ /// - a `ref x` binding matches against a value of type `T` and gives
+ /// `x` the type `&T`; we return `T`.
+ /// - a pattern with implicit derefs (thanks to default binding
+ /// modes #42640) may look like `Some(x)` but in fact have
+ /// implicit deref patterns attached (e.g., it is really
+ /// `&Some(x)`). In that case, we return the "outermost" type
+ /// (e.g., `&Option<T>`).
+ pub(crate) fn pat_ty_adjusted(&self, pat: &hir::Pat<'_>) -> McResult<Ty<'tcx>> {
+ // Check for implicit `&` types wrapping the pattern; note
+ // that these are never attached to binding patterns, so
+ // actually this is somewhat "disjoint" from the code below
+ // that aims to account for `ref x`.
+ if let Some(vec) = self.typeck_results.pat_adjustments().get(pat.hir_id) {
+ if let Some(first_ty) = vec.first() {
+ debug!("pat_ty(pat={:?}) found adjusted ty `{:?}`", pat, first_ty);
+ return Ok(*first_ty);
+ }
+ }
+
+ self.pat_ty_unadjusted(pat)
+ }
+
+ /// Like `pat_ty`, but ignores implicit `&` patterns.
+ fn pat_ty_unadjusted(&self, pat: &hir::Pat<'_>) -> McResult<Ty<'tcx>> {
+ let base_ty = self.node_ty(pat.hir_id)?;
+ debug!("pat_ty(pat={:?}) base_ty={:?}", pat, base_ty);
+
+ // This code detects whether we are looking at a `ref x`,
+ // and if so, figures out what the type *being borrowed* is.
+ let ret_ty = match pat.kind {
+ PatKind::Binding(..) => {
+ let bm = *self
+ .typeck_results
+ .pat_binding_modes()
+ .get(pat.hir_id)
+ .expect("missing binding mode");
+
+ if let ty::BindByReference(_) = bm {
+ // a bind-by-ref means that the base_ty will be the type of the ident itself,
+ // but what we want here is the type of the underlying value being borrowed.
+ // So peel off one-level, turning the &T into T.
+ match base_ty.builtin_deref(false) {
+ Some(t) => t.ty,
+ None => {
+ debug!("By-ref binding of non-derefable type {:?}", base_ty);
+ return Err(());
+ }
+ }
+ } else {
+ base_ty
+ }
+ }
+ _ => base_ty,
+ };
+ debug!("pat_ty(pat={:?}) ret_ty={:?}", pat, ret_ty);
+
+ Ok(ret_ty)
+ }
+
+ pub(crate) fn cat_expr(&self, expr: &hir::Expr<'_>) -> McResult<PlaceWithHirId<'tcx>> {
+ // This recursion helper avoids going through *too many*
+ // adjustments, since *only* non-overloaded deref recurses.
+ fn helper<'a, 'tcx>(
+ mc: &MemCategorizationContext<'a, 'tcx>,
+ expr: &hir::Expr<'_>,
+ adjustments: &[adjustment::Adjustment<'tcx>],
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ match adjustments.split_last() {
+ None => mc.cat_expr_unadjusted(expr),
+ Some((adjustment, previous)) => {
+ mc.cat_expr_adjusted_with(expr, || helper(mc, expr, previous), adjustment)
+ }
+ }
+ }
+
+ helper(self, expr, self.typeck_results.expr_adjustments(expr))
+ }
+
+ pub(crate) fn cat_expr_adjusted(
+ &self,
+ expr: &hir::Expr<'_>,
+ previous: PlaceWithHirId<'tcx>,
+ adjustment: &adjustment::Adjustment<'tcx>,
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ self.cat_expr_adjusted_with(expr, || Ok(previous), adjustment)
+ }
+
+ #[instrument(level = "debug", skip(self, previous))]
+ fn cat_expr_adjusted_with<F>(
+ &self,
+ expr: &hir::Expr<'_>,
+ previous: F,
+ adjustment: &adjustment::Adjustment<'tcx>,
+ ) -> McResult<PlaceWithHirId<'tcx>>
+ where
+ F: FnOnce() -> McResult<PlaceWithHirId<'tcx>>,
+ {
+ let target = self.resolve_vars_if_possible(adjustment.target);
+ match adjustment.kind {
+ adjustment::Adjust::Deref(overloaded) => {
+ // Equivalent to *expr or something similar.
+ let base = if let Some(deref) = overloaded {
+ let ref_ty = self
+ .tcx()
+ .mk_ref(deref.region, ty::TypeAndMut { ty: target, mutbl: deref.mutbl });
+ self.cat_rvalue(expr.hir_id, expr.span, ref_ty)
+ } else {
+ previous()?
+ };
+ self.cat_deref(expr, base)
+ }
+
+ adjustment::Adjust::NeverToAny
+ | adjustment::Adjust::Pointer(_)
+ | adjustment::Adjust::Borrow(_)
+ | adjustment::Adjust::DynStar => {
+ // Result is an rvalue.
+ Ok(self.cat_rvalue(expr.hir_id, expr.span, target))
+ }
+ }
+ }
+
+ #[instrument(level = "debug", skip(self))]
+ pub(crate) fn cat_expr_unadjusted(
+ &self,
+ expr: &hir::Expr<'_>,
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ debug!("cat_expr: id={} expr={:?}", expr.hir_id, expr);
+
+ let expr_ty = self.expr_ty(expr)?;
+ match expr.kind {
+ hir::ExprKind::Unary(hir::UnOp::Deref, ref e_base) => {
+ if self.typeck_results.is_method_call(expr) {
+ self.cat_overloaded_place(expr, e_base)
+ } else {
+ let base = self.cat_expr(e_base)?;
+ self.cat_deref(expr, base)
+ }
+ }
+
+ hir::ExprKind::Field(ref base, _) => {
+ let base = self.cat_expr(base)?;
+ debug!("cat_expr(cat_field): id={} expr={:?} base={:?}", expr.hir_id, expr, base);
+
+ let field_idx = self
+ .typeck_results
+ .field_indices()
+ .get(expr.hir_id)
+ .cloned()
+ .expect("Field index not found");
+
+ Ok(self.cat_projection(
+ expr,
+ base,
+ expr_ty,
+ ProjectionKind::Field(field_idx as u32, VariantIdx::new(0)),
+ ))
+ }
+
+ hir::ExprKind::Index(ref base, _) => {
+ if self.typeck_results.is_method_call(expr) {
+ // If this is an index implemented by a method call, then it
+ // will include an implicit deref of the result.
+ // The call to index() returns a `&T` value, which
+ // is an rvalue. That is what we will be
+ // dereferencing.
+ self.cat_overloaded_place(expr, base)
+ } else {
+ let base = self.cat_expr(base)?;
+ Ok(self.cat_projection(expr, base, expr_ty, ProjectionKind::Index))
+ }
+ }
+
+ hir::ExprKind::Path(ref qpath) => {
+ let res = self.typeck_results.qpath_res(qpath, expr.hir_id);
+ self.cat_res(expr.hir_id, expr.span, expr_ty, res)
+ }
+
+ hir::ExprKind::Type(ref e, _) => self.cat_expr(e),
+
+ hir::ExprKind::AddrOf(..)
+ | hir::ExprKind::Call(..)
+ | hir::ExprKind::Assign(..)
+ | hir::ExprKind::AssignOp(..)
+ | hir::ExprKind::Closure { .. }
+ | hir::ExprKind::Ret(..)
+ | hir::ExprKind::Unary(..)
+ | hir::ExprKind::Yield(..)
+ | hir::ExprKind::MethodCall(..)
+ | hir::ExprKind::Cast(..)
+ | hir::ExprKind::DropTemps(..)
+ | hir::ExprKind::Array(..)
+ | hir::ExprKind::If(..)
+ | hir::ExprKind::Tup(..)
+ | hir::ExprKind::Binary(..)
+ | hir::ExprKind::Block(..)
+ | hir::ExprKind::Let(..)
+ | hir::ExprKind::Loop(..)
+ | hir::ExprKind::Match(..)
+ | hir::ExprKind::Lit(..)
+ | hir::ExprKind::ConstBlock(..)
+ | hir::ExprKind::Break(..)
+ | hir::ExprKind::Continue(..)
+ | hir::ExprKind::Struct(..)
+ | hir::ExprKind::Repeat(..)
+ | hir::ExprKind::InlineAsm(..)
+ | hir::ExprKind::Box(..)
+ | hir::ExprKind::Err => Ok(self.cat_rvalue(expr.hir_id, expr.span, expr_ty)),
+ }
+ }
+
+ #[instrument(level = "debug", skip(self, span))]
+ pub(crate) fn cat_res(
+ &self,
+ hir_id: hir::HirId,
+ span: Span,
+ expr_ty: Ty<'tcx>,
+ res: Res,
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ match res {
+ Res::Def(
+ DefKind::Ctor(..)
+ | DefKind::Const
+ | DefKind::ConstParam
+ | DefKind::AssocConst
+ | DefKind::Fn
+ | DefKind::AssocFn,
+ _,
+ )
+ | Res::SelfCtor(..) => Ok(self.cat_rvalue(hir_id, span, expr_ty)),
+
+ Res::Def(DefKind::Static(_), _) => {
+ Ok(PlaceWithHirId::new(hir_id, expr_ty, PlaceBase::StaticItem, Vec::new()))
+ }
+
+ Res::Local(var_id) => {
+ if self.upvars.map_or(false, |upvars| upvars.contains_key(&var_id)) {
+ self.cat_upvar(hir_id, var_id)
+ } else {
+ Ok(PlaceWithHirId::new(hir_id, expr_ty, PlaceBase::Local(var_id), Vec::new()))
+ }
+ }
+
+ def => span_bug!(span, "unexpected definition in memory categorization: {:?}", def),
+ }
+ }
+
+ /// Categorize an upvar.
+ ///
+ /// Note: the actual upvar access contains invisible derefs of closure
+ /// environment and upvar reference as appropriate. Only regionck cares
+ /// about these dereferences, so we let it compute them as needed.
+ fn cat_upvar(&self, hir_id: hir::HirId, var_id: hir::HirId) -> McResult<PlaceWithHirId<'tcx>> {
+ let closure_expr_def_id = self.body_owner;
+
+ let upvar_id = ty::UpvarId {
+ var_path: ty::UpvarPath { hir_id: var_id },
+ closure_expr_id: closure_expr_def_id,
+ };
+ let var_ty = self.node_ty(var_id)?;
+
+ let ret = PlaceWithHirId::new(hir_id, var_ty, PlaceBase::Upvar(upvar_id), Vec::new());
+
+ debug!("cat_upvar ret={:?}", ret);
+ Ok(ret)
+ }
+
+ pub(crate) fn cat_rvalue(
+ &self,
+ hir_id: hir::HirId,
+ span: Span,
+ expr_ty: Ty<'tcx>,
+ ) -> PlaceWithHirId<'tcx> {
+ debug!("cat_rvalue hir_id={:?}, expr_ty={:?}, span={:?}", hir_id, expr_ty, span);
+ let ret = PlaceWithHirId::new(hir_id, expr_ty, PlaceBase::Rvalue, Vec::new());
+ debug!("cat_rvalue ret={:?}", ret);
+ ret
+ }
+
+ pub(crate) fn cat_projection<N: HirNode>(
+ &self,
+ node: &N,
+ base_place: PlaceWithHirId<'tcx>,
+ ty: Ty<'tcx>,
+ kind: ProjectionKind,
+ ) -> PlaceWithHirId<'tcx> {
+ let mut projections = base_place.place.projections;
+ projections.push(Projection { kind, ty });
+ let ret = PlaceWithHirId::new(
+ node.hir_id(),
+ base_place.place.base_ty,
+ base_place.place.base,
+ projections,
+ );
+ debug!("cat_field ret {:?}", ret);
+ ret
+ }
+
+ #[instrument(level = "debug", skip(self))]
+ fn cat_overloaded_place(
+ &self,
+ expr: &hir::Expr<'_>,
+ base: &hir::Expr<'_>,
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ // Reconstruct the output assuming it's a reference with the
+ // same region and mutability as the receiver. This holds for
+ // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
+ let place_ty = self.expr_ty(expr)?;
+ let base_ty = self.expr_ty_adjusted(base)?;
+
+ let ty::Ref(region, _, mutbl) = *base_ty.kind() else {
+ span_bug!(expr.span, "cat_overloaded_place: base is not a reference");
+ };
+ let ref_ty = self.tcx().mk_ref(region, ty::TypeAndMut { ty: place_ty, mutbl });
+
+ let base = self.cat_rvalue(expr.hir_id, expr.span, ref_ty);
+ self.cat_deref(expr, base)
+ }
+
+ #[instrument(level = "debug", skip(self, node))]
+ fn cat_deref(
+ &self,
+ node: &impl HirNode,
+ base_place: PlaceWithHirId<'tcx>,
+ ) -> McResult<PlaceWithHirId<'tcx>> {
+ let base_curr_ty = base_place.place.ty();
+ let deref_ty = match base_curr_ty.builtin_deref(true) {
+ Some(mt) => mt.ty,
+ None => {
+ debug!("explicit deref of non-derefable type: {:?}", base_curr_ty);
+ return Err(());
+ }
+ };
+ let mut projections = base_place.place.projections;
+ projections.push(Projection { kind: ProjectionKind::Deref, ty: deref_ty });
+
+ let ret = PlaceWithHirId::new(
+ node.hir_id(),
+ base_place.place.base_ty,
+ base_place.place.base,
+ projections,
+ );
+ debug!("cat_deref ret {:?}", ret);
+ Ok(ret)
+ }
+
+ pub(crate) fn cat_pattern<F>(
+ &self,
+ place: PlaceWithHirId<'tcx>,
+ pat: &hir::Pat<'_>,
+ mut op: F,
+ ) -> McResult<()>
+ where
+ F: FnMut(&PlaceWithHirId<'tcx>, &hir::Pat<'_>),
+ {
+ self.cat_pattern_(place, pat, &mut op)
+ }
+
+ /// Returns the variant index for an ADT used within a Struct or TupleStruct pattern
+ /// Here `pat_hir_id` is the HirId of the pattern itself.
+ fn variant_index_for_adt(
+ &self,
+ qpath: &hir::QPath<'_>,
+ pat_hir_id: hir::HirId,
+ span: Span,
+ ) -> McResult<VariantIdx> {
+ let res = self.typeck_results.qpath_res(qpath, pat_hir_id);
+ let ty = self.typeck_results.node_type(pat_hir_id);
+ let ty::Adt(adt_def, _) = ty.kind() else {
+ self.tcx()
+ .sess
+ .delay_span_bug(span, "struct or tuple struct pattern not applied to an ADT");
+ return Err(());
+ };
+
+ match res {
+ Res::Def(DefKind::Variant, variant_id) => Ok(adt_def.variant_index_with_id(variant_id)),
+ Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_id) => {
+ Ok(adt_def.variant_index_with_ctor_id(variant_ctor_id))
+ }
+ Res::Def(DefKind::Ctor(CtorOf::Struct, ..), _)
+ | Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _)
+ | Res::SelfCtor(..)
+ | Res::SelfTyParam { .. }
+ | Res::SelfTyAlias { .. } => {
+ // Structs and Unions have only have one variant.
+ Ok(VariantIdx::new(0))
+ }
+ _ => bug!("expected ADT path, found={:?}", res),
+ }
+ }
+
+ /// Returns the total number of fields in an ADT variant used within a pattern.
+ /// Here `pat_hir_id` is the HirId of the pattern itself.
+ fn total_fields_in_adt_variant(
+ &self,
+ pat_hir_id: hir::HirId,
+ variant_index: VariantIdx,
+ span: Span,
+ ) -> McResult<usize> {
+ let ty = self.typeck_results.node_type(pat_hir_id);
+ match ty.kind() {
+ ty::Adt(adt_def, _) => Ok(adt_def.variant(variant_index).fields.len()),
+ _ => {
+ self.tcx()
+ .sess
+ .delay_span_bug(span, "struct or tuple struct pattern not applied to an ADT");
+ Err(())
+ }
+ }
+ }
+
+ /// Returns the total number of fields in a tuple used within a Tuple pattern.
+ /// Here `pat_hir_id` is the HirId of the pattern itself.
+ fn total_fields_in_tuple(&self, pat_hir_id: hir::HirId, span: Span) -> McResult<usize> {
+ let ty = self.typeck_results.node_type(pat_hir_id);
+ match ty.kind() {
+ ty::Tuple(substs) => Ok(substs.len()),
+ _ => {
+ self.tcx().sess.delay_span_bug(span, "tuple pattern not applied to a tuple");
+ Err(())
+ }
+ }
+ }
+
+ // FIXME(#19596) This is a workaround, but there should be a better way to do this
+ fn cat_pattern_<F>(
+ &self,
+ mut place_with_id: PlaceWithHirId<'tcx>,
+ pat: &hir::Pat<'_>,
+ op: &mut F,
+ ) -> McResult<()>
+ where
+ F: FnMut(&PlaceWithHirId<'tcx>, &hir::Pat<'_>),
+ {
+ // Here, `place` is the `PlaceWithHirId` being matched and pat is the pattern it
+ // is being matched against.
+ //
+ // In general, the way that this works is that we walk down the pattern,
+ // constructing a `PlaceWithHirId` that represents the path that will be taken
+ // to reach the value being matched.
+
+ debug!("cat_pattern(pat={:?}, place_with_id={:?})", pat, place_with_id);
+
+ // If (pattern) adjustments are active for this pattern, adjust the `PlaceWithHirId` correspondingly.
+ // `PlaceWithHirId`s are constructed differently from patterns. For example, in
+ //
+ // ```
+ // match foo {
+ // &&Some(x, ) => { ... },
+ // _ => { ... },
+ // }
+ // ```
+ //
+ // the pattern `&&Some(x,)` is represented as `Ref { Ref { TupleStruct }}`. To build the
+ // corresponding `PlaceWithHirId` we start with the `PlaceWithHirId` for `foo`, and then, by traversing the
+ // pattern, try to answer the question: given the address of `foo`, how is `x` reached?
+ //
+ // `&&Some(x,)` `place_foo`
+ // `&Some(x,)` `deref { place_foo}`
+ // `Some(x,)` `deref { deref { place_foo }}`
+ // (x,)` `field0 { deref { deref { place_foo }}}` <- resulting place
+ //
+ // The above example has no adjustments. If the code were instead the (after adjustments,
+ // equivalent) version
+ //
+ // ```
+ // match foo {
+ // Some(x, ) => { ... },
+ // _ => { ... },
+ // }
+ // ```
+ //
+ // Then we see that to get the same result, we must start with
+ // `deref { deref { place_foo }}` instead of `place_foo` since the pattern is now `Some(x,)`
+ // and not `&&Some(x,)`, even though its assigned type is that of `&&Some(x,)`.
+ for _ in 0..self.typeck_results.pat_adjustments().get(pat.hir_id).map_or(0, |v| v.len()) {
+ debug!("cat_pattern: applying adjustment to place_with_id={:?}", place_with_id);
+ place_with_id = self.cat_deref(pat, place_with_id)?;
+ }
+ let place_with_id = place_with_id; // lose mutability
+ debug!("cat_pattern: applied adjustment derefs to get place_with_id={:?}", place_with_id);
+
+ // Invoke the callback, but only now, after the `place_with_id` has adjusted.
+ //
+ // To see that this makes sense, consider `match &Some(3) { Some(x) => { ... }}`. In that
+ // case, the initial `place_with_id` will be that for `&Some(3)` and the pattern is `Some(x)`. We
+ // don't want to call `op` with these incompatible values. As written, what happens instead
+ // is that `op` is called with the adjusted place (that for `*&Some(3)`) and the pattern
+ // `Some(x)` (which matches). Recursing once more, `*&Some(3)` and the pattern `Some(x)`
+ // result in the place `Downcast<Some>(*&Some(3)).0` associated to `x` and invoke `op` with
+ // that (where the `ref` on `x` is implied).
+ op(&place_with_id, pat);
+
+ match pat.kind {
+ PatKind::Tuple(subpats, dots_pos) => {
+ // (p1, ..., pN)
+ let total_fields = self.total_fields_in_tuple(pat.hir_id, pat.span)?;
+
+ for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
+ let subpat_ty = self.pat_ty_adjusted(subpat)?;
+ let projection_kind = ProjectionKind::Field(i as u32, VariantIdx::new(0));
+ let sub_place =
+ self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
+ self.cat_pattern_(sub_place, subpat, op)?;
+ }
+ }
+
+ PatKind::TupleStruct(ref qpath, subpats, dots_pos) => {
+ // S(p1, ..., pN)
+ let variant_index = self.variant_index_for_adt(qpath, pat.hir_id, pat.span)?;
+ let total_fields =
+ self.total_fields_in_adt_variant(pat.hir_id, variant_index, pat.span)?;
+
+ for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
+ let subpat_ty = self.pat_ty_adjusted(subpat)?;
+ let projection_kind = ProjectionKind::Field(i as u32, variant_index);
+ let sub_place =
+ self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
+ self.cat_pattern_(sub_place, subpat, op)?;
+ }
+ }
+
+ PatKind::Struct(ref qpath, field_pats, _) => {
+ // S { f1: p1, ..., fN: pN }
+
+ let variant_index = self.variant_index_for_adt(qpath, pat.hir_id, pat.span)?;
+
+ for fp in field_pats {
+ let field_ty = self.pat_ty_adjusted(fp.pat)?;
+ let field_index = self
+ .typeck_results
+ .field_indices()
+ .get(fp.hir_id)
+ .cloned()
+ .expect("no index for a field");
+
+ let field_place = self.cat_projection(
+ pat,
+ place_with_id.clone(),
+ field_ty,
+ ProjectionKind::Field(field_index as u32, variant_index),
+ );
+ self.cat_pattern_(field_place, fp.pat, op)?;
+ }
+ }
+
+ PatKind::Or(pats) => {
+ for pat in pats {
+ self.cat_pattern_(place_with_id.clone(), pat, op)?;
+ }
+ }
+
+ PatKind::Binding(.., Some(ref subpat)) => {
+ self.cat_pattern_(place_with_id, subpat, op)?;
+ }
+
+ PatKind::Box(ref subpat) | PatKind::Ref(ref subpat, _) => {
+ // box p1, &p1, &mut p1. we can ignore the mutability of
+ // PatKind::Ref since that information is already contained
+ // in the type.
+ let subplace = self.cat_deref(pat, place_with_id)?;
+ self.cat_pattern_(subplace, subpat, op)?;
+ }
+
+ PatKind::Slice(before, ref slice, after) => {
+ let Some(element_ty) = place_with_id.place.ty().builtin_index() else {
+ debug!("explicit index of non-indexable type {:?}", place_with_id);
+ return Err(());
+ };
+ let elt_place = self.cat_projection(
+ pat,
+ place_with_id.clone(),
+ element_ty,
+ ProjectionKind::Index,
+ );
+ for before_pat in before {
+ self.cat_pattern_(elt_place.clone(), before_pat, op)?;
+ }
+ if let Some(ref slice_pat) = *slice {
+ let slice_pat_ty = self.pat_ty_adjusted(slice_pat)?;
+ let slice_place = self.cat_projection(
+ pat,
+ place_with_id,
+ slice_pat_ty,
+ ProjectionKind::Subslice,
+ );
+ self.cat_pattern_(slice_place, slice_pat, op)?;
+ }
+ for after_pat in after {
+ self.cat_pattern_(elt_place.clone(), after_pat, op)?;
+ }
+ }
+
+ PatKind::Path(_)
+ | PatKind::Binding(.., None)
+ | PatKind::Lit(..)
+ | PatKind::Range(..)
+ | PatKind::Wild => {
+ // always ok
+ }
+ }
+
+ Ok(())
+ }
+}
projects / rustc.git / blobdiff