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-rw-r--r--compiler/rustc_typeck/src/mem_categorization.rs786
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diff --git a/compiler/rustc_typeck/src/mem_categorization.rs b/compiler/rustc_typeck/src/mem_categorization.rs
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--- a/compiler/rustc_typeck/src/mem_categorization.rs
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@@ -1,786 +0,0 @@
-//! # 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<'a, '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<'a, '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)
- }
-
- 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>>,
- {
- debug!("cat_expr_adjusted_with({:?}): {:?}", adjustment, expr);
- 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(_) => {
- // Result is an rvalue.
- Ok(self.cat_rvalue(expr.hir_id, expr.span, target))
- }
- }
- }
-
- 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)),
- }
- }
-
- pub(crate) fn cat_res(
- &self,
- hir_id: hir::HirId,
- span: Span,
- expr_ty: Ty<'tcx>,
- res: Res,
- ) -> McResult<PlaceWithHirId<'tcx>> {
- debug!("cat_res: id={:?} expr={:?} def={:?}", hir_id, expr_ty, res);
-
- 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
- }
-
- fn cat_overloaded_place(
- &self,
- expr: &hir::Expr<'_>,
- base: &hir::Expr<'_>,
- ) -> McResult<PlaceWithHirId<'tcx>> {
- debug!("cat_overloaded_place(expr={:?}, base={:?})", expr, base);
-
- // 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)
- }
-
- fn cat_deref(
- &self,
- node: &impl HirNode,
- base_place: PlaceWithHirId<'tcx>,
- ) -> McResult<PlaceWithHirId<'tcx>> {
- debug!("cat_deref: base_place={:?}", base_place);
-
- 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::SelfTy { .. } => {
- // 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(())
- }
-}
generated by cgit v1.2.3 (git 2.39.1) at 2024-09-07 04:07:44 +0000