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use rustc::lint::*;
use rustc_front::hir::*;
use rustc_front::intravisit as visit;
use rustc::front::map::Node;
use rustc::middle::ty;
use rustc::middle::ty::adjustment::AutoAdjustment;
use rustc::middle::expr_use_visitor::*;
use rustc::middle::infer;
use rustc::middle::mem_categorization::{cmt, Categorization};
use rustc::util::nodemap::NodeSet;
use syntax::ast::NodeId;
use syntax::codemap::Span;
use utils::span_lint;
pub struct EscapePass;
declare_lint!(pub BOXED_LOCAL, Warn, "using Box<T> where unnecessary");
struct EscapeDelegate<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
set: NodeSet,
}
impl LintPass for EscapePass {
fn get_lints(&self) -> LintArray {
lint_array!(BOXED_LOCAL)
}
}
impl LateLintPass for EscapePass {
fn check_fn(&mut self,
cx: &LateContext,
_: visit::FnKind,
decl: &FnDecl,
body: &Block,
_: Span,
id: NodeId) {
let param_env = ty::ParameterEnvironment::for_item(cx.tcx, id);
let infcx = infer::new_infer_ctxt(cx.tcx, &cx.tcx.tables, Some(param_env), false);
let mut v = EscapeDelegate {
cx: cx,
set: NodeSet(),
};
{
let mut vis = ExprUseVisitor::new(&mut v, &infcx);
vis.walk_fn(decl, body);
}
for node in v.set {
span_lint(cx,
BOXED_LOCAL,
cx.tcx.map.span(node),
"local variable doesn't need to be boxed here");
}
}
}
impl<'a, 'tcx: 'a> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
fn consume(&mut self,
_: NodeId,
_: Span,
cmt: cmt<'tcx>,
mode: ConsumeMode) {
if let Categorization::Local(lid) = cmt.cat {
if self.set.contains(&lid) {
if let Move(DirectRefMove) = mode {
// moved out or in. clearly can't be localized
self.set.remove(&lid);
}
}
}
}
fn matched_pat(&mut self, _: &Pat, _: cmt<'tcx>, _: MatchMode) {}
fn consume_pat(&mut self, consume_pat: &Pat, cmt: cmt<'tcx>, _: ConsumeMode) {
if let Categorization::Rvalue(..) = cmt.cat {
if let Some(Node::NodeStmt(st)) = self.cx
.tcx
.map
.find(self.cx.tcx.map.get_parent_node(cmt.id)) {
if let StmtDecl(ref decl, _) = st.node {
if let DeclLocal(ref loc) = decl.node {
if let Some(ref ex) = loc.init {
if let ExprBox(..) = ex.node {
if let ty::TyBox(..) = cmt.ty.sty {
// let x = box (...)
self.set.insert(consume_pat.id);
}
// TODO Box::new
// TODO vec![]
// TODO "foo".to_owned() and friends
}
}
}
}
}
}
if let Categorization::Local(lid) = cmt.cat {
if self.set.contains(&lid) {
// let y = x where x is known
// remove x, insert y
self.set.insert(consume_pat.id);
self.set.remove(&lid);
}
}
}
fn borrow(&mut self,
borrow_id: NodeId,
_: Span,
cmt: cmt<'tcx>,
_: ty::Region,
_: ty::BorrowKind,
loan_cause: LoanCause) {
if let Categorization::Local(lid) = cmt.cat {
if self.set.contains(&lid) {
if let Some(&AutoAdjustment::AdjustDerefRef(adj)) = self.cx
.tcx
.tables
.borrow()
.adjustments
.get(&borrow_id) {
if LoanCause::AutoRef == loan_cause {
// x.foo()
if adj.autoderefs <= 0 {
self.set.remove(&lid); // Used without autodereffing (i.e. x.clone())
}
} else {
self.cx.sess().span_bug(cmt.span, "Unknown adjusted AutoRef");
}
} else if LoanCause::AddrOf == loan_cause {
// &x
if let Some(&AutoAdjustment::AdjustDerefRef(adj)) =
self.cx.tcx.tables.borrow().adjustments
.get(&self.cx.tcx.map.get_parent_node(borrow_id)) {
if adj.autoderefs <= 1 {
// foo(&x) where no extra autoreffing is happening
self.set.remove(&lid);
}
}
} else if LoanCause::MatchDiscriminant == loan_cause {
self.set.remove(&lid); // `match x` can move
}
// do nothing for matches, etc. These can't escape
}
}
}
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
fn mutate(&mut self,
_: NodeId,
_: Span,
_: cmt<'tcx>,
_: MutateMode) {
}
}