bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Only borrow place for matching under specific conditions

Browse source
This commit is contained in:
Roxane 2021-02-23 23:39:33 -05:00
parent 685a4c6b6b
commit 74fc64303f
11 changed files with 193 additions and 49 deletions
Download patch file Download diff file Expand all files Collapse all files

38
compiler/rustc_typeck/src/expr_use_visitor.rs
View file

@ -8,10 +8,10 @@ pub use self::ConsumeMode::*;
pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def::Res;
use rustc_hir::def_id::LocalDefId;
use rustc_hir::PatKind;
use rustc_hir::QPath;
//use rustc_hir::QPath;
use rustc_index::vec::Idx;
use rustc_infer::infer::InferCtxt;
use rustc_middle::hir::place::ProjectionKind;
@ -54,7 +54,6 @@ pub trait Delegate<'tcx> {
// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
// [FIXME] RFC2229 This should also affect clippy ref: https://github.com/sexxi-goose/rust/pull/27
fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause);
}
@ -235,24 +234,30 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
hir::ExprKind::Match(ref discr, arms, _) => {
let discr_place = return_if_err!(self.mc.cat_expr(&discr));
// Matching should not always be considered a use of the place, hence
// discr does not necessarily need to be borrowed.
// We only want to borrow discr if the pattern contain something other
// than wildcards
// than wildcards.
let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
let mut needs_to_be_read = false;
for arm in arms.iter() {
return_if_err!(mc.cat_pattern(discr_place.clone(), &arm.pat, |_place, pat| {
if let PatKind::Binding(_, _, _, opt_sub_pat) = pat.kind {
if let None = opt_sub_pat {
needs_to_be_read = true;
}
} else if let PatKind::TupleStruct(qpath, _, _) = &pat.kind {
// If a TupleStruct has a Some PathSegment, we should read the discr_place
// regardless if it contains a Wild pattern later
if let QPath::Resolved(_, path) = qpath {
if let Res::Def(DefKind::Ctor(_, _), _) = path.res {
match &pat.kind {
PatKind::Binding(_, _, _, opt_sub_pat) => {
// If the opt_sub_pat is None, than the binding does not count as
// a wildcard for the purpose of borrowing discr
if let None = opt_sub_pat {
needs_to_be_read = true;
}
}
PatKind::TupleStruct(_, _, _)
| PatKind::Struct(_, _, _)
| PatKind::Lit(_) => {
// If the PatKind is a TupleStruct, Struct, or Lit then we want
// to borrow discr
needs_to_be_read = true;
}
_ => {}
}
}));
}
@ -629,6 +634,8 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
/// - 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<'_>) {
debug!("walk_captures({:?})", closure_expr);
let closure_def_id = self.tcx().hir().local_def_id(closure_expr.hir_id).to_def_id();
let upvars = self.tcx().upvars_mentioned(self.body_owner);
@ -645,10 +652,9 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
if upvars.map_or(body_owner_is_closure, |upvars| {
!upvars.contains_key(&upvar_id.var_path.hir_id)
}) {
// [FIXME] RFC2229 Update this comment
// The nested closure might be capturing the current (enclosing) closure's local variables.
// The nested closure might be fake reading 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.
// then for the current body (if it's a closure) these do not require fake_read, we will ignore them.
continue;
}
}