rust-clippy/clippy_lints/src/escape.rs

202 lines
6.4 KiB
Rust
Raw Normal View History

2018-10-06 16:18:06 +00:00
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
2018-05-30 08:15:50 +00:00
use crate::utils::span_lint;
use rustc::hir::intravisit as visit;
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::util::nodemap::NodeSet;
use rustc::{declare_tool_lint, lint_array};
use syntax::ast::NodeId;
use syntax::source_map::Span;
2015-12-04 10:12:53 +00:00
2016-07-10 13:23:50 +00:00
pub struct Pass {
pub too_large_for_stack: u64,
}
2015-12-04 10:12:53 +00:00
/// **What it does:** Checks for usage of `Box<T>` where an unboxed `T` would
/// work fine.
2015-12-13 03:38:58 +00:00
///
/// **Why is this bad?** This is an unnecessary allocation, and bad for
/// performance. It is only necessary to allocate if you wish to move the box
/// into something.
2015-12-13 03:38:58 +00:00
///
/// **Known problems:** None.
2015-12-13 03:38:58 +00:00
///
/// **Example:**
/// ```rust
/// fn main() {
/// let x = Box::new(1);
/// foo(*x);
/// println!("{}", *x);
/// }
2015-12-14 20:17:11 +00:00
/// ```
2018-03-28 13:24:26 +00:00
declare_clippy_lint! {
pub BOXED_LOCAL,
2018-03-28 13:24:26 +00:00
perf,
"using `Box<T>` where unnecessary"
}
2015-12-04 10:12:53 +00:00
2018-07-23 11:01:12 +00:00
fn is_non_trait_box(ty: Ty<'_>) -> bool {
2017-02-03 10:52:13 +00:00
ty.is_box() && !ty.boxed_ty().is_trait()
2015-12-28 14:12:57 +00:00
}
struct EscapeDelegate<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
2015-12-04 10:12:53 +00:00
set: NodeSet,
2016-07-10 13:23:50 +00:00
too_large_for_stack: u64,
2015-12-04 10:12:53 +00:00
}
2016-06-10 14:17:20 +00:00
impl LintPass for Pass {
2015-12-04 10:12:53 +00:00
fn get_lints(&self) -> LintArray {
lint_array!(BOXED_LOCAL)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_fn(
&mut self,
cx: &LateContext<'a, 'tcx>,
_: visit::FnKind<'tcx>,
_: &'tcx FnDecl,
body: &'tcx Body,
_: Span,
2017-08-09 07:30:56 +00:00
node_id: NodeId,
) {
// If the method is an impl for a trait, don't warn
let parent_id = cx.tcx.hir().get_parent(node_id);
let parent_node = cx.tcx.hir().find(parent_id);
if let Some(Node::Item(item)) = parent_node {
if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
return;
}
}
2015-12-04 10:12:53 +00:00
let mut v = EscapeDelegate {
cx,
set: NodeSet::default(),
2016-07-10 13:23:50 +00:00
too_large_for_stack: self.too_large_for_stack,
2015-12-04 10:12:53 +00:00
};
let fn_def_id = cx.tcx.hir().local_def_id(node_id);
2017-09-04 14:10:36 +00:00
let region_scope_tree = &cx.tcx.region_scope_tree(fn_def_id);
2017-10-19 16:27:58 +00:00
ExprUseVisitor::new(&mut v, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None).consume_body(body);
2015-12-04 10:12:53 +00:00
for node in v.set {
2017-08-09 07:30:56 +00:00
span_lint(
cx,
BOXED_LOCAL,
cx.tcx.hir().span(node),
2017-08-09 07:30:56 +00:00
"local variable doesn't need to be boxed here",
);
2015-12-04 10:12:53 +00:00
}
}
}
impl<'a, 'tcx> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
fn consume(&mut self, _: NodeId, _: Span, cmt: &cmt_<'tcx>, mode: ConsumeMode) {
2015-12-04 10:12:53 +00:00
if let Categorization::Local(lid) = cmt.cat {
2017-06-04 21:28:01 +00:00
if let Move(DirectRefMove) = mode {
// moved out or in. clearly can't be localized
self.set.remove(&lid);
2015-12-04 10:12:53 +00:00
}
}
}
fn matched_pat(&mut self, _: &Pat, _: &cmt_<'tcx>, _: MatchMode) {}
fn consume_pat(&mut self, consume_pat: &Pat, cmt: &cmt_<'tcx>, _: ConsumeMode) {
let map = &self.cx.tcx.hir();
if map.is_argument(consume_pat.id) {
// Skip closure arguments
2018-08-28 11:13:42 +00:00
if let Some(Node::Expr(..)) = map.find(map.get_parent_node(consume_pat.id)) {
return;
}
2016-07-10 13:23:50 +00:00
if is_non_trait_box(cmt.ty) && !self.is_large_box(cmt.ty) {
2015-12-28 14:12:57 +00:00
self.set.insert(consume_pat.id);
}
return;
}
2015-12-04 10:12:53 +00:00
if let Categorization::Rvalue(..) = cmt.cat {
2018-07-03 08:52:59 +00:00
let id = map.hir_to_node_id(cmt.hir_id);
2018-08-28 11:13:42 +00:00
if let Some(Node::Stmt(st)) = map.find(map.get_parent_node(id)) {
2018-07-12 08:53:53 +00:00
if let StmtKind::Decl(ref decl, _) = st.node {
2018-07-16 13:07:39 +00:00
if let DeclKind::Local(ref loc) = decl.node {
2015-12-04 10:12:53 +00:00
if let Some(ref ex) = loc.init {
2018-07-12 07:30:57 +00:00
if let ExprKind::Box(..) = ex.node {
2016-07-10 13:23:50 +00:00
if is_non_trait_box(cmt.ty) && !self.is_large_box(cmt.ty) {
2015-12-04 10:12:53 +00:00
// 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);
}
}
}
2018-11-27 20:14:15 +00:00
fn borrow(
&mut self,
_: NodeId,
_: Span,
cmt: &cmt_<'tcx>,
_: ty::Region<'_>,
_: ty::BorrowKind,
loan_cause: LoanCause,
) {
2015-12-04 10:12:53 +00:00
if let Categorization::Local(lid) = cmt.cat {
2017-06-04 21:28:01 +00:00
match loan_cause {
// x.foo()
// Used without autodereffing (i.e. x.clone())
LoanCause::AutoRef |
2015-12-04 10:12:53 +00:00
2017-06-04 21:28:01 +00:00
// &x
// foo(&x) where no extra autoreffing is happening
LoanCause::AddrOf |
// `match x` can move
LoanCause::MatchDiscriminant => {
self.set.remove(&lid);
2015-12-04 10:12:53 +00:00
}
2017-06-04 21:28:01 +00:00
2015-12-04 10:12:53 +00:00
// do nothing for matches, etc. These can't escape
2017-06-04 21:28:01 +00:00
_ => {}
2015-12-04 10:12:53 +00:00
}
}
}
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
fn mutate(&mut self, _: NodeId, _: Span, _: &cmt_<'tcx>, _: MutateMode) {}
2015-12-04 10:12:53 +00:00
}
2016-07-10 13:23:50 +00:00
impl<'a, 'tcx> EscapeDelegate<'a, 'tcx> {
fn is_large_box(&self, ty: Ty<'tcx>) -> bool {
2016-07-10 13:23:50 +00:00
// Large types need to be boxed to avoid stack
// overflows.
2017-02-03 10:52:13 +00:00
if ty.is_box() {
self.cx.layout_of(ty.boxed_ty()).ok().map_or(0, |l| l.size.bytes()) > self.too_large_for_stack
} else {
false
2016-07-10 13:23:50 +00:00
}
}
}