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Migrations first pass

This commit is contained in:
Aman Arora 2020-12-15 03:38:15 -05:00
parent d3e85014a7
commit cc5e6db5f2
2 changed files with 134 additions and 4 deletions

View file

@ -30,6 +30,7 @@
//! then mean that all later passes would have to check for these figments
//! and report an error, and it just seems like more mess in the end.)
use super::writeback::Resolver;
use super::FnCtxt;
use crate::expr_use_visitor as euv;
@ -40,7 +41,9 @@ use rustc_hir::def_id::LocalDefId;
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_infer::infer::UpvarRegion;
use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, ProjectionKind};
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeckResults, UpvarSubsts};
use rustc_session::lint;
use rustc_span::sym;
use rustc_span::{MultiSpan, Span, Symbol};
@ -97,7 +100,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
&self,
closure_hir_id: hir::HirId,
span: Span,
body: &hir::Body<'_>,
body: &'tcx hir::Body<'tcx>,
capture_clause: hir::CaptureBy,
) {
debug!("analyze_closure(id={:?}, body.id={:?})", closure_hir_id, body.id());
@ -157,6 +160,38 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
self.compute_min_captures(closure_def_id, delegate.capture_information);
let closure_hir_id = self.tcx.hir().local_def_id_to_hir_id(local_def_id);
if should_do_migration_analysis(self.tcx, closure_hir_id) {
let need_migrations = self.compute_2229_migrations_first_pass(
closure_def_id,
span,
capture_clause,
body,
self.typeck_results.borrow().closure_min_captures.get(&closure_def_id),
);
if !need_migrations.is_empty() {
let need_migrations_hir_id =
need_migrations.iter().map(|m| m.0).collect::<Vec<_>>();
let migrations_text =
migration_suggestion_for_2229(self.tcx, &need_migrations_hir_id);
self.tcx.struct_span_lint_hir(
lint::builtin::DISJOINT_CAPTURE_DROP_REORDER,
closure_hir_id,
span,
|lint| {
let mut diagnostics_builder = lint.build(
"drop order affected for closure because of `capture_disjoint_fields`",
);
diagnostics_builder.note(&migrations_text);
diagnostics_builder.emit();
},
);
}
}
// We now fake capture information for all variables that are mentioned within the closure
// We do this after handling migrations so that min_captures computes before
if !self.tcx.features().capture_disjoint_fields {
@ -520,6 +555,86 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
typeck_results.closure_min_captures.insert(closure_def_id, root_var_min_capture_list);
}
/// Figures out the list of root variables (and their types) that aren't completely
/// captured by the closure when `capture_disjoint_fields` is enabled and drop order of
/// some path starting at that root variable **might** be affected.
///
/// The output list would include a root variable if:
/// - It would have been moved into the closure when `capture_disjoint_fields` wasn't
/// enabled, **and**
/// - It wasn't completely captured by the closure, **and**
/// - The type of the root variable needs Drop.
fn compute_2229_migrations_first_pass(
&self,
closure_def_id: DefId,
closure_span: Span,
closure_clause: hir::CaptureBy,
body: &'tcx hir::Body<'tcx>,
min_captures: Option<&ty::RootVariableMinCaptureList<'tcx>>,
) -> Vec<(hir::HirId, Ty<'tcx>)> {
fn resolve_ty<T: TypeFoldable<'tcx>>(
fcx: &FnCtxt<'_, 'tcx>,
span: Span,
body: &'tcx hir::Body<'tcx>,
ty: T,
) -> T {
let mut resolver = Resolver::new(fcx, &span, body);
ty.fold_with(&mut resolver)
}
let upvars = if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {
upvars
} else {
return vec![];
};
let mut need_migrations = Vec::new();
for (&var_hir_id, _) in upvars.iter() {
let ty = resolve_ty(self, closure_span, body, self.node_ty(var_hir_id));
if !ty.needs_drop(self.tcx, self.tcx.param_env(closure_def_id.expect_local())) {
continue;
}
let root_var_min_capture_list = if let Some(root_var_min_capture_list) =
min_captures.and_then(|m| m.get(&var_hir_id))
{
root_var_min_capture_list
} else {
// The upvar is mentioned within the closure but no path starting from it is
// used.
match closure_clause {
// Only migrate if closure is a move closure
hir::CaptureBy::Value => need_migrations.push((var_hir_id, ty)),
hir::CaptureBy::Ref => {}
}
continue;
};
let is_moved = root_var_min_capture_list
.iter()
.find(|capture| matches!(capture.info.capture_kind, ty::UpvarCapture::ByValue(_)))
.is_some();
// 1. If we capture more than one path starting at the root variabe then the root variable
// isn't being captured in its entirety
// 2. If we only capture one path starting at the root variable, it's still possible
// that it isn't the root variable completely.
if is_moved
&& ((root_var_min_capture_list.len() > 1)
|| (root_var_min_capture_list[0].place.projections.len() > 0))
{
need_migrations.push((var_hir_id, ty));
}
}
need_migrations
}
fn init_capture_kind(
&self,
capture_clause: hir::CaptureBy,
@ -1136,6 +1251,21 @@ fn var_name(tcx: TyCtxt<'_>, var_hir_id: hir::HirId) -> Symbol {
tcx.hir().name(var_hir_id)
}
fn should_do_migration_analysis(tcx: TyCtxt<'_>, closure_id: hir::HirId) -> bool {
let (level, _) =
tcx.lint_level_at_node(lint::builtin::DISJOINT_CAPTURE_DROP_REORDER, closure_id);
!matches!(level, lint::Level::Allow)
}
fn migration_suggestion_for_2229(tcx: TyCtxt<'_>, need_migrations: &Vec<hir::HirId>) -> String {
let need_migrations_strings =
need_migrations.iter().map(|v| format!("{}", var_name(tcx, *v))).collect::<Vec<_>>();
let migrations_list_concat = need_migrations_strings.join(", ");
format!("let ({}) = ({});", migrations_list_concat, migrations_list_concat)
}
/// Helper function to determine if we need to escalate CaptureKind from
/// CaptureInfo A to B and returns the escalated CaptureInfo.
/// (Note: CaptureInfo contains CaptureKind and an expression that led to capture it in that way)

View file

@ -650,7 +650,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
}
}
trait Locatable {
crate trait Locatable {
fn to_span(&self, tcx: TyCtxt<'_>) -> Span;
}
@ -668,7 +668,7 @@ impl Locatable for hir::HirId {
/// The Resolver. This is the type folding engine that detects
/// unresolved types and so forth.
struct Resolver<'cx, 'tcx> {
crate struct Resolver<'cx, 'tcx> {
tcx: TyCtxt<'tcx>,
infcx: &'cx InferCtxt<'cx, 'tcx>,
span: &'cx dyn Locatable,
@ -679,7 +679,7 @@ struct Resolver<'cx, 'tcx> {
}
impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
fn new(
crate fn new(
fcx: &'cx FnCtxt<'cx, 'tcx>,
span: &'cx dyn Locatable,
body: &'tcx hir::Body<'tcx>,