Fix boxed_local suggestion

Don't warn about an argument that is moved into a closure.

ExprUseVisitor doesn't walk into nested bodies so use a new
visitor that collects the variables that are moved into closures.

Fixes #3739
This commit is contained in:
Michael Wright 2019-02-21 06:59:10 +02:00
parent 027dde92e2
commit 9d6ecc7485
3 changed files with 66 additions and 4 deletions

View file

@ -1,11 +1,12 @@
use crate::utils::span_lint;
use rustc::hir::intravisit as visit;
use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::middle::expr_use_visitor::*;
use rustc::middle::mem_categorization::{cmt_, Categorization};
use rustc::ty::layout::LayoutOf;
use rustc::ty::{self, Ty};
use rustc::ty::{self, Ty, UpvarCapture};
use rustc::util::nodemap::NodeSet;
use rustc::{declare_tool_lint, lint_array};
use syntax::ast::NodeId;
@ -88,11 +89,17 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
let region_scope_tree = &cx.tcx.region_scope_tree(fn_def_id);
ExprUseVisitor::new(&mut v, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None).consume_body(body);
for node in v.set {
let mut capture_visitor = CaptureVisitor {
cx,
moved: NodeSet::default(),
};
capture_visitor.visit_body(body);
for node in v.set.difference(&capture_visitor.moved) {
span_lint(
cx,
BOXED_LOCAL,
cx.tcx.hir().span(node),
cx.tcx.hir().span(*node),
"local variable doesn't need to be boxed here",
);
}
@ -192,3 +199,32 @@ impl<'a, 'tcx> EscapeDelegate<'a, 'tcx> {
}
}
}
struct CaptureVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
moved: NodeSet,
}
impl<'a, 'tcx> Visitor<'tcx> for CaptureVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if let ExprKind::Closure(..) = expr.node {
if let ty::Closure(def_id, _) = &self.cx.tables.expr_ty(expr).sty {
if let Some(upvar_list) = &self.cx.tables.upvar_list.get(&def_id) {
for upvar_id in upvar_list.iter() {
if let UpvarCapture::ByValue = self.cx.tables.upvar_capture(*upvar_id) {
let hir_id = upvar_id.var_path.hir_id;
let id = &self.cx.tcx.hir().hir_to_node_id(hir_id);
self.moved.insert(*id);
}
}
}
}
} else {
walk_expr(self, expr);
}
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}

View file

@ -148,3 +148,23 @@ trait MyTrait {
impl<T> MyTrait for Box<T> {
fn do_sth(self) {}
}
// Issue #3739 - capture in closures
mod issue_3739 {
use super::A;
fn consume<T>(_: T) {}
fn borrow<T>(_: &T) {}
fn closure_consume(x: Box<A>) {
let _ = move || {
consume(x);
};
}
fn closure_borrow(x: Box<A>) {
let _ = || {
borrow(&x);
};
}
}

View file

@ -12,5 +12,11 @@ error: local variable doesn't need to be boxed here
LL | pub fn new(_needs_name: Box<PeekableSeekable<&()>>) -> () {}
| ^^^^^^^^^^^
error: aborting due to 2 previous errors
error: local variable doesn't need to be boxed here
--> $DIR/escape_analysis.rs:165:23
|
LL | fn closure_borrow(x: Box<A>) {
| ^
error: aborting due to 3 previous errors