rustc_typeck to rustc_hir_analysis
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lcnr
parent
de0b511daa
commit
1fc86a63f4
140 changed files with 101 additions and 102 deletions
915
compiler/rustc_hir_analysis/src/expr_use_visitor.rs
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915
compiler/rustc_hir_analysis/src/expr_use_visitor.rs
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//! A different sort of visitor for walking fn bodies. Unlike the
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//! normal visitor, which just walks the entire body in one shot, the
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//! `ExprUseVisitor` determines how expressions are being used.
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use std::slice::from_ref;
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use hir::def::DefKind;
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use hir::Expr;
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// Export these here so that Clippy can use them.
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pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
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use rustc_data_structures::fx::FxIndexMap;
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use rustc_hir as hir;
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use rustc_hir::def::Res;
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use rustc_hir::def_id::LocalDefId;
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use rustc_hir::PatKind;
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use rustc_index::vec::Idx;
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use rustc_infer::infer::InferCtxt;
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use rustc_middle::hir::place::ProjectionKind;
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use rustc_middle::mir::FakeReadCause;
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use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
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use rustc_target::abi::VariantIdx;
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use ty::BorrowKind::ImmBorrow;
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use crate::mem_categorization as mc;
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/// This trait defines the callbacks you can expect to receive when
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/// employing the ExprUseVisitor.
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pub trait Delegate<'tcx> {
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/// The value found at `place` is moved, depending
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/// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
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///
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/// Use of a `Copy` type in a ByValue context is considered a use
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/// by `ImmBorrow` and `borrow` is called instead. This is because
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/// a shared borrow is the "minimum access" that would be needed
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/// to perform a copy.
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///
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///
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/// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
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/// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
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/// id will be the id of the expression `expr` but the place itself will have
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/// the id of the binding in the pattern `pat`.
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fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
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/// The value found at `place` is being borrowed with kind `bk`.
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/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
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fn borrow(
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&mut self,
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place_with_id: &PlaceWithHirId<'tcx>,
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diag_expr_id: hir::HirId,
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bk: ty::BorrowKind,
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);
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/// The value found at `place` is being copied.
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/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
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fn copy(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
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// In most cases, copying data from `x` is equivalent to doing `*&x`, so by default
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// we treat a copy of `x` as a borrow of `x`.
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self.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
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}
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/// The path at `assignee_place` is being assigned to.
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/// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
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fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
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/// The path at `binding_place` is a binding that is being initialized.
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///
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/// This covers cases such as `let x = 42;`
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fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
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// Bindings can normally be treated as a regular assignment, so by default we
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// forward this to the mutate callback.
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self.mutate(binding_place, diag_expr_id)
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}
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/// The `place` should be a fake read because of specified `cause`.
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fn fake_read(
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&mut self,
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place_with_id: &PlaceWithHirId<'tcx>,
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cause: FakeReadCause,
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diag_expr_id: hir::HirId,
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);
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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enum ConsumeMode {
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/// reference to x where x has a type that copies
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Copy,
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/// reference to x where x has a type that moves
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Move,
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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pub enum MutateMode {
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Init,
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/// Example: `x = y`
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JustWrite,
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/// Example: `x += y`
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WriteAndRead,
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}
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/// The ExprUseVisitor type
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///
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/// This is the code that actually walks the tree.
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pub struct ExprUseVisitor<'a, 'tcx> {
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mc: mc::MemCategorizationContext<'a, 'tcx>,
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body_owner: LocalDefId,
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delegate: &'a mut dyn Delegate<'tcx>,
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}
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/// If the MC results in an error, it's because the type check
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/// failed (or will fail, when the error is uncovered and reported
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/// during writeback). In this case, we just ignore this part of the
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/// code.
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///
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/// Note that this macro appears similar to try!(), but, unlike try!(),
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/// it does not propagate the error.
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macro_rules! return_if_err {
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($inp: expr) => {
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match $inp {
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Ok(v) => v,
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Err(()) => {
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debug!("mc reported err");
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return;
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}
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}
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};
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}
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impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
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/// Creates the ExprUseVisitor, configuring it with the various options provided:
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///
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/// - `delegate` -- who receives the callbacks
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/// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
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/// - `typeck_results` --- typeck results for the code being analyzed
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pub fn new(
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delegate: &'a mut (dyn Delegate<'tcx> + 'a),
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infcx: &'a InferCtxt<'a, 'tcx>,
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body_owner: LocalDefId,
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param_env: ty::ParamEnv<'tcx>,
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typeck_results: &'a ty::TypeckResults<'tcx>,
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) -> Self {
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ExprUseVisitor {
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mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
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body_owner,
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delegate,
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}
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}
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#[instrument(skip(self), level = "debug")]
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pub fn consume_body(&mut self, body: &hir::Body<'_>) {
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for param in body.params {
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let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
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debug!("consume_body: param_ty = {:?}", param_ty);
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let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
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self.walk_irrefutable_pat(¶m_place, param.pat);
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}
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self.consume_expr(&body.value);
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}
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fn tcx(&self) -> TyCtxt<'tcx> {
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self.mc.tcx()
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}
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fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
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delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
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}
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fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
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for expr in exprs {
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self.consume_expr(expr);
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}
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}
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pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
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debug!("consume_expr(expr={:?})", expr);
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let place_with_id = return_if_err!(self.mc.cat_expr(expr));
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self.delegate_consume(&place_with_id, place_with_id.hir_id);
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self.walk_expr(expr);
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}
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fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
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let place_with_id = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.mutate(&place_with_id, place_with_id.hir_id);
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self.walk_expr(expr);
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}
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fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
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debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
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let place_with_id = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
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self.walk_expr(expr)
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}
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fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
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self.walk_expr(expr)
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}
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pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
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debug!("walk_expr(expr={:?})", expr);
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self.walk_adjustment(expr);
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match expr.kind {
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hir::ExprKind::Path(_) => {}
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hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
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hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
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// *base
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self.select_from_expr(base);
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}
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hir::ExprKind::Field(base, _) => {
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// base.f
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self.select_from_expr(base);
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}
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hir::ExprKind::Index(lhs, rhs) => {
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// lhs[rhs]
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self.select_from_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Call(callee, args) => {
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// callee(args)
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self.consume_expr(callee);
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self.consume_exprs(args);
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}
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hir::ExprKind::MethodCall(.., receiver, args, _) => {
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// callee.m(args)
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self.consume_expr(receiver);
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self.consume_exprs(args);
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}
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hir::ExprKind::Struct(_, fields, ref opt_with) => {
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self.walk_struct_expr(fields, opt_with);
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}
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hir::ExprKind::Tup(exprs) => {
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self.consume_exprs(exprs);
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}
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hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
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self.consume_expr(cond_expr);
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self.consume_expr(then_expr);
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if let Some(ref else_expr) = *opt_else_expr {
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self.consume_expr(else_expr);
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}
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}
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hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
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self.walk_local(init, pat, None, |t| t.borrow_expr(init, ty::ImmBorrow))
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}
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hir::ExprKind::Match(ref discr, arms, _) => {
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let discr_place = return_if_err!(self.mc.cat_expr(discr));
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self.maybe_read_scrutinee(
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discr,
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discr_place.clone(),
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arms.iter().map(|arm| arm.pat),
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);
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// treatment of the discriminant is handled while walking the arms.
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for arm in arms {
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self.walk_arm(&discr_place, arm);
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}
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}
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hir::ExprKind::Array(exprs) => {
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self.consume_exprs(exprs);
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}
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hir::ExprKind::AddrOf(_, m, ref base) => {
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// &base
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// make sure that the thing we are pointing out stays valid
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// for the lifetime `scope_r` of the resulting ptr:
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let bk = ty::BorrowKind::from_mutbl(m);
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self.borrow_expr(base, bk);
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}
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hir::ExprKind::InlineAsm(asm) => {
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for (op, _op_sp) in asm.operands {
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match op {
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hir::InlineAsmOperand::In { expr, .. } => self.consume_expr(expr),
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hir::InlineAsmOperand::Out { expr: Some(expr), .. }
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| hir::InlineAsmOperand::InOut { expr, .. } => {
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self.mutate_expr(expr);
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}
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hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
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self.consume_expr(in_expr);
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if let Some(out_expr) = out_expr {
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self.mutate_expr(out_expr);
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}
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}
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hir::InlineAsmOperand::Out { expr: None, .. }
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| hir::InlineAsmOperand::Const { .. }
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| hir::InlineAsmOperand::SymFn { .. }
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| hir::InlineAsmOperand::SymStatic { .. } => {}
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}
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}
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}
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hir::ExprKind::Continue(..)
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| hir::ExprKind::Lit(..)
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| hir::ExprKind::ConstBlock(..)
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| hir::ExprKind::Err => {}
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hir::ExprKind::Loop(blk, ..) => {
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self.walk_block(blk);
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}
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hir::ExprKind::Unary(_, lhs) => {
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self.consume_expr(lhs);
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}
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hir::ExprKind::Binary(_, lhs, rhs) => {
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self.consume_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Block(blk, _) => {
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self.walk_block(blk);
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}
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hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
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if let Some(expr) = *opt_expr {
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self.consume_expr(expr);
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}
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}
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hir::ExprKind::Assign(lhs, rhs, _) => {
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self.mutate_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Cast(base, _) => {
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self.consume_expr(base);
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}
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hir::ExprKind::DropTemps(expr) => {
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self.consume_expr(expr);
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}
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hir::ExprKind::AssignOp(_, lhs, rhs) => {
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if self.mc.typeck_results.is_method_call(expr) {
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self.consume_expr(lhs);
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} else {
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self.mutate_expr(lhs);
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}
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self.consume_expr(rhs);
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}
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hir::ExprKind::Repeat(base, _) => {
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self.consume_expr(base);
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}
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hir::ExprKind::Closure { .. } => {
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self.walk_captures(expr);
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}
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hir::ExprKind::Box(ref base) => {
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self.consume_expr(base);
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}
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hir::ExprKind::Yield(value, _) => {
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self.consume_expr(value);
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}
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}
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}
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fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
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match stmt.kind {
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hir::StmtKind::Local(hir::Local { pat, init: Some(expr), els, .. }) => {
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self.walk_local(expr, pat, *els, |_| {})
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}
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hir::StmtKind::Local(_) => {}
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hir::StmtKind::Item(_) => {
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// We don't visit nested items in this visitor,
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// only the fn body we were given.
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}
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hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
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self.consume_expr(expr);
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}
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}
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}
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fn maybe_read_scrutinee<'t>(
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&mut self,
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discr: &Expr<'_>,
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discr_place: PlaceWithHirId<'tcx>,
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pats: impl Iterator<Item = &'t hir::Pat<'t>>,
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) {
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// Matching should not always be considered a use of the place, hence
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// discr does not necessarily need to be borrowed.
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// We only want to borrow discr if the pattern contain something other
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// than wildcards.
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let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
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let mut needs_to_be_read = false;
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for pat in pats {
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return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
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match &pat.kind {
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PatKind::Binding(.., opt_sub_pat) => {
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// If the opt_sub_pat is None, than the binding does not count as
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// a wildcard for the purpose of borrowing discr.
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if opt_sub_pat.is_none() {
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needs_to_be_read = true;
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}
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}
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PatKind::Path(qpath) => {
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// A `Path` pattern is just a name like `Foo`. This is either a
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// named constant or else it refers to an ADT variant
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let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
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match res {
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Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {
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// Named constants have to be equated with the value
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// being matched, so that's a read of the value being matched.
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//
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// FIXME: We don't actually reads for ZSTs.
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needs_to_be_read = true;
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}
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_ => {
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// Otherwise, this is a struct/enum variant, and so it's
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// only a read if we need to read the discriminant.
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needs_to_be_read |= is_multivariant_adt(place.place.ty());
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}
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}
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}
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PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
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// For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
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// against a multivariant enum or struct. In that case, we have to read
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// the discriminant. Otherwise this kind of pattern doesn't actually
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// read anything (we'll get invoked for the `...`, which may indeed
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// perform some reads).
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let place_ty = place.place.ty();
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needs_to_be_read |= is_multivariant_adt(place_ty);
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}
|
||||
PatKind::Lit(_) | PatKind::Range(..) => {
|
||||
// If the PatKind is a Lit or a Range then we want
|
||||
// to borrow discr.
|
||||
needs_to_be_read = true;
|
||||
}
|
||||
PatKind::Or(_)
|
||||
| PatKind::Box(_)
|
||||
| PatKind::Slice(..)
|
||||
| PatKind::Ref(..)
|
||||
| PatKind::Wild => {
|
||||
// If the PatKind is Or, Box, Slice or Ref, the decision is made later
|
||||
// as these patterns contains subpatterns
|
||||
// If the PatKind is Wild, the decision is made based on the other patterns being
|
||||
// examined
|
||||
}
|
||||
}
|
||||
}));
|
||||
}
|
||||
|
||||
if needs_to_be_read {
|
||||
self.borrow_expr(discr, ty::ImmBorrow);
|
||||
} else {
|
||||
let closure_def_id = match discr_place.place.base {
|
||||
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
||||
_ => None,
|
||||
};
|
||||
|
||||
self.delegate.fake_read(
|
||||
&discr_place,
|
||||
FakeReadCause::ForMatchedPlace(closure_def_id),
|
||||
discr_place.hir_id,
|
||||
);
|
||||
|
||||
// We always want to walk the discriminant. We want to make sure, for instance,
|
||||
// that the discriminant has been initialized.
|
||||
self.walk_expr(discr);
|
||||
}
|
||||
}
|
||||
|
||||
fn walk_local<F>(
|
||||
&mut self,
|
||||
expr: &hir::Expr<'_>,
|
||||
pat: &hir::Pat<'_>,
|
||||
els: Option<&hir::Block<'_>>,
|
||||
mut f: F,
|
||||
) where
|
||||
F: FnMut(&mut Self),
|
||||
{
|
||||
self.walk_expr(expr);
|
||||
let expr_place = return_if_err!(self.mc.cat_expr(expr));
|
||||
f(self);
|
||||
if let Some(els) = els {
|
||||
// borrowing because we need to test the discriminant
|
||||
self.maybe_read_scrutinee(expr, expr_place.clone(), from_ref(pat).iter());
|
||||
self.walk_block(els)
|
||||
}
|
||||
self.walk_irrefutable_pat(&expr_place, &pat);
|
||||
}
|
||||
|
||||
/// Indicates that the value of `blk` will be consumed, meaning either copied or moved
|
||||
/// depending on its type.
|
||||
fn walk_block(&mut self, blk: &hir::Block<'_>) {
|
||||
debug!("walk_block(blk.hir_id={})", blk.hir_id);
|
||||
|
||||
for stmt in blk.stmts {
|
||||
self.walk_stmt(stmt);
|
||||
}
|
||||
|
||||
if let Some(ref tail_expr) = blk.expr {
|
||||
self.consume_expr(tail_expr);
|
||||
}
|
||||
}
|
||||
|
||||
fn walk_struct_expr<'hir>(
|
||||
&mut self,
|
||||
fields: &[hir::ExprField<'_>],
|
||||
opt_with: &Option<&'hir hir::Expr<'_>>,
|
||||
) {
|
||||
// Consume the expressions supplying values for each field.
|
||||
for field in fields {
|
||||
self.consume_expr(field.expr);
|
||||
}
|
||||
|
||||
let with_expr = match *opt_with {
|
||||
Some(w) => &*w,
|
||||
None => {
|
||||
return;
|
||||
}
|
||||
};
|
||||
|
||||
let with_place = return_if_err!(self.mc.cat_expr(with_expr));
|
||||
|
||||
// Select just those fields of the `with`
|
||||
// expression that will actually be used
|
||||
match with_place.place.ty().kind() {
|
||||
ty::Adt(adt, substs) if adt.is_struct() => {
|
||||
// Consume those fields of the with expression that are needed.
|
||||
for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
|
||||
let is_mentioned = fields.iter().any(|f| {
|
||||
self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
|
||||
});
|
||||
if !is_mentioned {
|
||||
let field_place = self.mc.cat_projection(
|
||||
&*with_expr,
|
||||
with_place.clone(),
|
||||
with_field.ty(self.tcx(), substs),
|
||||
ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
|
||||
);
|
||||
self.delegate_consume(&field_place, field_place.hir_id);
|
||||
}
|
||||
}
|
||||
}
|
||||
_ => {
|
||||
// the base expression should always evaluate to a
|
||||
// struct; however, when EUV is run during typeck, it
|
||||
// may not. This will generate an error earlier in typeck,
|
||||
// so we can just ignore it.
|
||||
if !self.tcx().sess.has_errors().is_some() {
|
||||
span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// walk the with expression so that complex expressions
|
||||
// are properly handled.
|
||||
self.walk_expr(with_expr);
|
||||
}
|
||||
|
||||
/// Invoke the appropriate delegate calls for anything that gets
|
||||
/// consumed or borrowed as part of the automatic adjustment
|
||||
/// process.
|
||||
fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
|
||||
let adjustments = self.mc.typeck_results.expr_adjustments(expr);
|
||||
let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
|
||||
for adjustment in adjustments {
|
||||
debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
|
||||
match adjustment.kind {
|
||||
adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
|
||||
// Creating a closure/fn-pointer or unsizing consumes
|
||||
// the input and stores it into the resulting rvalue.
|
||||
self.delegate_consume(&place_with_id, place_with_id.hir_id);
|
||||
}
|
||||
|
||||
adjustment::Adjust::Deref(None) => {}
|
||||
|
||||
// Autoderefs for overloaded Deref calls in fact reference
|
||||
// their receiver. That is, if we have `(*x)` where `x`
|
||||
// is of type `Rc<T>`, then this in fact is equivalent to
|
||||
// `x.deref()`. Since `deref()` is declared with `&self`,
|
||||
// this is an autoref of `x`.
|
||||
adjustment::Adjust::Deref(Some(ref deref)) => {
|
||||
let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
|
||||
self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
|
||||
}
|
||||
|
||||
adjustment::Adjust::Borrow(ref autoref) => {
|
||||
self.walk_autoref(expr, &place_with_id, autoref);
|
||||
}
|
||||
}
|
||||
place_with_id =
|
||||
return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
|
||||
}
|
||||
}
|
||||
|
||||
/// Walks the autoref `autoref` applied to the autoderef'd
|
||||
/// `expr`. `base_place` is the mem-categorized form of `expr`
|
||||
/// after all relevant autoderefs have occurred.
|
||||
fn walk_autoref(
|
||||
&mut self,
|
||||
expr: &hir::Expr<'_>,
|
||||
base_place: &PlaceWithHirId<'tcx>,
|
||||
autoref: &adjustment::AutoBorrow<'tcx>,
|
||||
) {
|
||||
debug!(
|
||||
"walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
|
||||
expr.hir_id, base_place, autoref
|
||||
);
|
||||
|
||||
match *autoref {
|
||||
adjustment::AutoBorrow::Ref(_, m) => {
|
||||
self.delegate.borrow(
|
||||
base_place,
|
||||
base_place.hir_id,
|
||||
ty::BorrowKind::from_mutbl(m.into()),
|
||||
);
|
||||
}
|
||||
|
||||
adjustment::AutoBorrow::RawPtr(m) => {
|
||||
debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
|
||||
|
||||
self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
|
||||
let closure_def_id = match discr_place.place.base {
|
||||
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
||||
_ => None,
|
||||
};
|
||||
|
||||
self.delegate.fake_read(
|
||||
discr_place,
|
||||
FakeReadCause::ForMatchedPlace(closure_def_id),
|
||||
discr_place.hir_id,
|
||||
);
|
||||
self.walk_pat(discr_place, arm.pat, arm.guard.is_some());
|
||||
|
||||
if let Some(hir::Guard::If(e)) = arm.guard {
|
||||
self.consume_expr(e)
|
||||
} else if let Some(hir::Guard::IfLet(ref l)) = arm.guard {
|
||||
self.consume_expr(l.init)
|
||||
}
|
||||
|
||||
self.consume_expr(arm.body);
|
||||
}
|
||||
|
||||
/// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
|
||||
/// let binding, and *not* a match arm or nested pat.)
|
||||
fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
|
||||
let closure_def_id = match discr_place.place.base {
|
||||
PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
|
||||
_ => None,
|
||||
};
|
||||
|
||||
self.delegate.fake_read(
|
||||
discr_place,
|
||||
FakeReadCause::ForLet(closure_def_id),
|
||||
discr_place.hir_id,
|
||||
);
|
||||
self.walk_pat(discr_place, pat, false);
|
||||
}
|
||||
|
||||
/// The core driver for walking a pattern
|
||||
fn walk_pat(
|
||||
&mut self,
|
||||
discr_place: &PlaceWithHirId<'tcx>,
|
||||
pat: &hir::Pat<'_>,
|
||||
has_guard: bool,
|
||||
) {
|
||||
debug!("walk_pat(discr_place={:?}, pat={:?}, has_guard={:?})", discr_place, pat, has_guard);
|
||||
|
||||
let tcx = self.tcx();
|
||||
let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
|
||||
return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
|
||||
if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
|
||||
debug!("walk_pat: binding place={:?} pat={:?}", place, pat);
|
||||
if let Some(bm) =
|
||||
mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
|
||||
{
|
||||
debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
|
||||
|
||||
// pat_ty: the type of the binding being produced.
|
||||
let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
|
||||
debug!("walk_pat: pat_ty={:?}", pat_ty);
|
||||
|
||||
let def = Res::Local(canonical_id);
|
||||
if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
|
||||
delegate.bind(binding_place, binding_place.hir_id);
|
||||
}
|
||||
|
||||
// Subtle: MIR desugaring introduces immutable borrows for each pattern
|
||||
// binding when lowering pattern guards to ensure that the guard does not
|
||||
// modify the scrutinee.
|
||||
if has_guard {
|
||||
delegate.borrow(place, discr_place.hir_id, ImmBorrow);
|
||||
}
|
||||
|
||||
// It is also a borrow or copy/move of the value being matched.
|
||||
// In a cases of pattern like `let pat = upvar`, don't use the span
|
||||
// of the pattern, as this just looks confusing, instead use the span
|
||||
// of the discriminant.
|
||||
match bm {
|
||||
ty::BindByReference(m) => {
|
||||
let bk = ty::BorrowKind::from_mutbl(m);
|
||||
delegate.borrow(place, discr_place.hir_id, bk);
|
||||
}
|
||||
ty::BindByValue(..) => {
|
||||
debug!("walk_pat binding consuming pat");
|
||||
delegate_consume(mc, *delegate, place, discr_place.hir_id);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}));
|
||||
}
|
||||
|
||||
/// Handle the case where the current body contains a closure.
|
||||
///
|
||||
/// When the current body being handled is a closure, then we must make sure that
|
||||
/// - The parent closure only captures Places from the nested closure that are not local to it.
|
||||
///
|
||||
/// In the following example the closures `c` only captures `p.x` even though `incr`
|
||||
/// is a capture of the nested closure
|
||||
///
|
||||
/// ```
|
||||
/// struct P { x: i32 }
|
||||
/// let mut p = P { x: 4 };
|
||||
/// let c = || {
|
||||
/// let incr = 10;
|
||||
/// let nested = || p.x += incr;
|
||||
/// };
|
||||
/// ```
|
||||
///
|
||||
/// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
|
||||
/// closure as the DefId.
|
||||
fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
|
||||
fn upvar_is_local_variable<'tcx>(
|
||||
upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
|
||||
upvar_id: hir::HirId,
|
||||
body_owner_is_closure: bool,
|
||||
) -> bool {
|
||||
upvars.map(|upvars| !upvars.contains_key(&upvar_id)).unwrap_or(body_owner_is_closure)
|
||||
}
|
||||
|
||||
debug!("walk_captures({:?})", closure_expr);
|
||||
|
||||
let tcx = self.tcx();
|
||||
let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id);
|
||||
let upvars = tcx.upvars_mentioned(self.body_owner);
|
||||
|
||||
// For purposes of this function, generator and closures are equivalent.
|
||||
let body_owner_is_closure =
|
||||
matches!(tcx.hir().body_owner_kind(self.body_owner), hir::BodyOwnerKind::Closure,);
|
||||
|
||||
// If we have a nested closure, we want to include the fake reads present in the nested closure.
|
||||
if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
|
||||
for (fake_read, cause, hir_id) in fake_reads.iter() {
|
||||
match fake_read.base {
|
||||
PlaceBase::Upvar(upvar_id) => {
|
||||
if upvar_is_local_variable(
|
||||
upvars,
|
||||
upvar_id.var_path.hir_id,
|
||||
body_owner_is_closure,
|
||||
) {
|
||||
// The nested closure might be fake reading the current (enclosing) closure's local variables.
|
||||
// The only places we want to fake read before creating the parent closure are the ones that
|
||||
// are not local to it/ defined by it.
|
||||
//
|
||||
// ```rust,ignore(cannot-test-this-because-pseudo-code)
|
||||
// let v1 = (0, 1);
|
||||
// let c = || { // fake reads: v1
|
||||
// let v2 = (0, 1);
|
||||
// let e = || { // fake reads: v1, v2
|
||||
// let (_, t1) = v1;
|
||||
// let (_, t2) = v2;
|
||||
// }
|
||||
// }
|
||||
// ```
|
||||
// This check is performed when visiting the body of the outermost closure (`c`) and ensures
|
||||
// that we don't add a fake read of v2 in c.
|
||||
continue;
|
||||
}
|
||||
}
|
||||
_ => {
|
||||
bug!(
|
||||
"Do not know how to get HirId out of Rvalue and StaticItem {:?}",
|
||||
fake_read.base
|
||||
);
|
||||
}
|
||||
};
|
||||
self.delegate.fake_read(
|
||||
&PlaceWithHirId { place: fake_read.clone(), hir_id: *hir_id },
|
||||
*cause,
|
||||
*hir_id,
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
|
||||
{
|
||||
for (var_hir_id, min_list) in min_captures.iter() {
|
||||
if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
|
||||
// The nested closure might be capturing the current (enclosing) closure's local variables.
|
||||
// We check if the root variable is ever mentioned within the enclosing closure, if not
|
||||
// then for the current body (if it's a closure) these aren't captures, we will ignore them.
|
||||
continue;
|
||||
}
|
||||
for captured_place in min_list {
|
||||
let place = &captured_place.place;
|
||||
let capture_info = captured_place.info;
|
||||
|
||||
let place_base = if body_owner_is_closure {
|
||||
// Mark the place to be captured by the enclosing closure
|
||||
PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
|
||||
} else {
|
||||
// If the body owner isn't a closure then the variable must
|
||||
// be a local variable
|
||||
PlaceBase::Local(*var_hir_id)
|
||||
};
|
||||
let place_with_id = PlaceWithHirId::new(
|
||||
capture_info.path_expr_id.unwrap_or(
|
||||
capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
|
||||
),
|
||||
place.base_ty,
|
||||
place_base,
|
||||
place.projections.clone(),
|
||||
);
|
||||
|
||||
match capture_info.capture_kind {
|
||||
ty::UpvarCapture::ByValue => {
|
||||
self.delegate_consume(&place_with_id, place_with_id.hir_id);
|
||||
}
|
||||
ty::UpvarCapture::ByRef(upvar_borrow) => {
|
||||
self.delegate.borrow(
|
||||
&place_with_id,
|
||||
place_with_id.hir_id,
|
||||
upvar_borrow,
|
||||
);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn copy_or_move<'a, 'tcx>(
|
||||
mc: &mc::MemCategorizationContext<'a, 'tcx>,
|
||||
place_with_id: &PlaceWithHirId<'tcx>,
|
||||
) -> ConsumeMode {
|
||||
if !mc.type_is_copy_modulo_regions(
|
||||
place_with_id.place.ty(),
|
||||
mc.tcx().hir().span(place_with_id.hir_id),
|
||||
) {
|
||||
ConsumeMode::Move
|
||||
} else {
|
||||
ConsumeMode::Copy
|
||||
}
|
||||
}
|
||||
|
||||
// - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
|
||||
// - If the place that is a `Copy` type consider it an `ImmBorrow`.
|
||||
fn delegate_consume<'a, 'tcx>(
|
||||
mc: &mc::MemCategorizationContext<'a, 'tcx>,
|
||||
delegate: &mut (dyn Delegate<'tcx> + 'a),
|
||||
place_with_id: &PlaceWithHirId<'tcx>,
|
||||
diag_expr_id: hir::HirId,
|
||||
) {
|
||||
debug!("delegate_consume(place_with_id={:?})", place_with_id);
|
||||
|
||||
let mode = copy_or_move(mc, place_with_id);
|
||||
|
||||
match mode {
|
||||
ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
|
||||
ConsumeMode::Copy => delegate.copy(place_with_id, diag_expr_id),
|
||||
}
|
||||
}
|
||||
|
||||
fn is_multivariant_adt(ty: Ty<'_>) -> bool {
|
||||
if let ty::Adt(def, _) = ty.kind() {
|
||||
// Note that if a non-exhaustive SingleVariant is defined in another crate, we need
|
||||
// to assume that more cases will be added to the variant in the future. This mean
|
||||
// that we should handle non-exhaustive SingleVariant the same way we would handle
|
||||
// a MultiVariant.
|
||||
// If the variant is not local it must be defined in another crate.
|
||||
let is_non_exhaustive = match def.adt_kind() {
|
||||
AdtKind::Struct | AdtKind::Union => {
|
||||
def.non_enum_variant().is_field_list_non_exhaustive()
|
||||
}
|
||||
AdtKind::Enum => def.is_variant_list_non_exhaustive(),
|
||||
};
|
||||
def.variants().len() > 1 || (!def.did().is_local() && is_non_exhaustive)
|
||||
} else {
|
||||
false
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue