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Auto merge of #24162 - pnkfelix:fsk-detect-duplicate-loop-labels, r=nikomatsakis

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Check for duplicate loop labels in function bodies.

See also: http://internals.rust-lang.org/t/psa-rejecting-duplicate-loop-labels/1833

The change, which we are putting in as future-proofing in preparation for future potential additions to the language (namely labeling arbitrary blocks and using those labels in borrow expressions), means that code like this will start emitting warnings:

```rust
fn main() {
    { 'a: loop { break; } }
    { 'a: loop { break; } }
}
```

To make the above code compile without warnings, write this instead:

```rust
fn main() {
    { 'a: loop { break; } }
    { 'b: loop { break; } }
}
```

Since this change is only introducing a new warnings, this change is non-breaking.

Fix #21633
This commit is contained in:
bors 2015-04-21 21:18:30 +00:00
commit 2baf348253
9 changed files with 489 additions and 15 deletions
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213
src/librustc/middle/resolve_lifetime.rs
View File

@ -24,6 +24,7 @@ use middle::region;
use middle::subst;
use middle::ty;
use std::fmt;
use std::mem::replace;
use syntax::ast;
use syntax::codemap::Span;
use syntax::parse::token::special_idents;
@ -70,6 +71,9 @@ struct LifetimeContext<'a> {
// I'm sorry.
trait_ref_hack: bool,
// List of labels in the function/method currently under analysis.
labels_in_fn: Vec<(ast::Ident, Span)>,
}
enum ScopeChain<'a> {
@ -97,6 +101,7 @@ pub fn krate(sess: &Session, krate: &ast::Crate, def_map: &DefMap) -> NamedRegio
scope: &ROOT_SCOPE,
def_map: def_map,
trait_ref_hack: false,
labels_in_fn: vec![],
}, krate);
sess.abort_if_errors();
named_region_map
@ -104,6 +109,10 @@ pub fn krate(sess: &Session, krate: &ast::Crate, def_map: &DefMap) -> NamedRegio
impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
fn visit_item(&mut self, item: &ast::Item) {
// Items save/restore the set of labels. This way innner items
// can freely reuse names, be they loop labels or lifetimes.
let saved = replace(&mut self.labels_in_fn, vec![]);
// Items always introduce a new root scope
self.with(RootScope, |_, this| {
match item.node {
@ -137,6 +146,9 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
}
}
});
// Done traversing the item; restore saved set of labels.
replace(&mut self.labels_in_fn, saved);
}
fn visit_fn(&mut self, fk: visit::FnKind<'v>, fd: &'v ast::FnDecl,
@ -144,16 +156,16 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
match fk {
visit::FkItemFn(_, generics, _, _, _) => {
self.visit_early_late(subst::FnSpace, generics, |this| {
visit::walk_fn(this, fk, fd, b, s)
this.walk_fn(fk, fd, b, s)
})
}
visit::FkMethod(_, sig, _) => {
self.visit_early_late(subst::FnSpace, &sig.generics, |this| {
visit::walk_fn(this, fk, fd, b, s)
this.walk_fn(fk, fd, b, s)
})
}
visit::FkFnBlock(..) => {
visit::walk_fn(self, fk, fd, b, s)
self.walk_fn(fk, fd, b, s)
}
}
}
@ -190,6 +202,10 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
}
fn visit_trait_item(&mut self, trait_item: &ast::TraitItem) {
// We reset the labels on every trait item, so that different
// methods in an impl can reuse label names.
let saved = replace(&mut self.labels_in_fn, vec![]);
if let ast::MethodTraitItem(ref sig, None) = trait_item.node {
self.visit_early_late(
subst::FnSpace, &sig.generics,
@ -197,6 +213,8 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
} else {
visit::walk_trait_item(self, trait_item);
}
replace(&mut self.labels_in_fn, saved);
}
fn visit_block(&mut self, b: &ast::Block) {
@ -286,7 +304,170 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
}
}
#[derive(Copy, Clone, PartialEq)]
enum ShadowKind { Label, Lifetime }
struct Original { kind: ShadowKind, span: Span }
struct Shadower { kind: ShadowKind, span: Span }
fn original_label(span: Span) -> Original {
Original { kind: ShadowKind::Label, span: span }
}
fn shadower_label(span: Span) -> Shadower {
Shadower { kind: ShadowKind::Label, span: span }
}
fn original_lifetime(l: &ast::Lifetime) -> Original {
Original { kind: ShadowKind::Lifetime, span: l.span }
}
fn shadower_lifetime(l: &ast::Lifetime) -> Shadower {
Shadower { kind: ShadowKind::Lifetime, span: l.span }
}
impl ShadowKind {
fn desc(&self) -> &'static str {
match *self {
ShadowKind::Label => "label",
ShadowKind::Lifetime => "lifetime",
}
}
}
fn signal_shadowing_problem(
sess: &Session, name: ast::Name, orig: Original, shadower: Shadower) {
if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
// lifetime/lifetime shadowing is an error
sess.span_err(shadower.span,
&format!("{} name `{}` shadows a \
{} name that is already in scope",
shadower.kind.desc(), name, orig.kind.desc()));
} else {
// shadowing involving a label is only a warning, due to issues with
// labels and lifetimes not being macro-hygienic.
sess.span_warn(shadower.span,
&format!("{} name `{}` shadows a \
{} name that is already in scope",
shadower.kind.desc(), name, orig.kind.desc()));
}
sess.span_note(orig.span,
&format!("shadowed {} `{}` declared here",
orig.kind.desc(), name));
}
// Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
// if one of the label shadows a lifetime or another label.
fn extract_labels<'v, 'a>(ctxt: &mut LifetimeContext<'a>, b: &'v ast::Block) {
struct GatherLabels<'a> {
sess: &'a Session,
scope: Scope<'a>,
labels_in_fn: &'a mut Vec<(ast::Ident, Span)>,
}
let mut gather = GatherLabels {
sess: ctxt.sess,
scope: ctxt.scope,
labels_in_fn: &mut ctxt.labels_in_fn,
};
gather.visit_block(b);
return;
impl<'v, 'a> Visitor<'v> for GatherLabels<'a> {
fn visit_expr(&mut self, ex: &'v ast::Expr) {
if let Some(label) = expression_label(ex) {
for &(prior, prior_span) in &self.labels_in_fn[..] {
// FIXME (#24278): non-hygienic comparision
if label.name == prior.name {
signal_shadowing_problem(self.sess,
label.name,
original_label(prior_span),
shadower_label(ex.span));
}
}
check_if_label_shadows_lifetime(self.sess,
self.scope,
label,
ex.span);
self.labels_in_fn.push((label, ex.span));
}
visit::walk_expr(self, ex)
}
fn visit_item(&mut self, _: &ast::Item) {
// do not recurse into items defined in the block
}
}
fn expression_label(ex: &ast::Expr) -> Option<ast::Ident> {
match ex.node {
ast::ExprWhile(_, _, Some(label)) |
ast::ExprWhileLet(_, _, _, Some(label)) |
ast::ExprForLoop(_, _, _, Some(label)) |
ast::ExprLoop(_, Some(label)) => Some(label),
_ => None,
}
}
fn check_if_label_shadows_lifetime<'a>(sess: &'a Session,
mut scope: Scope<'a>,
label: ast::Ident,
label_span: Span) {
loop {
match *scope {
BlockScope(_, s) => { scope = s; }
RootScope => { return; }
EarlyScope(_, lifetimes, s) |
LateScope(lifetimes, s) => {
for lifetime_def in lifetimes {
// FIXME (#24278): non-hygienic comparision
if label.name == lifetime_def.lifetime.name {
signal_shadowing_problem(
sess,
label.name,
original_lifetime(&lifetime_def.lifetime),
shadower_label(label_span));
return;
}
}
scope = s;
}
}
}
}
}
impl<'a> LifetimeContext<'a> {
// This is just like visit::walk_fn, except that it extracts the
// labels of the function body and swaps them in before visiting
// the function body itself.
fn walk_fn<'b>(&mut self,
fk: visit::FnKind,
fd: &ast::FnDecl,
fb: &'b ast::Block,
_span: Span) {
match fk {
visit::FkItemFn(_, generics, _, _, _) => {
visit::walk_fn_decl(self, fd);
self.visit_generics(generics);
}
visit::FkMethod(_, sig, _) => {
visit::walk_fn_decl(self, fd);
self.visit_generics(&sig.generics);
self.visit_explicit_self(&sig.explicit_self);
}
visit::FkFnBlock(..) => {
visit::walk_fn_decl(self, fd);
}
}
// After inpsecting the decl, add all labels from the body to
// `self.labels_in_fn`.
extract_labels(self, fb);
self.visit_block(fb);
}
fn with<F>(&mut self, wrap_scope: ScopeChain, f: F) where
F: FnOnce(Scope, &mut LifetimeContext),
{
@ -297,6 +478,7 @@ impl<'a> LifetimeContext<'a> {
scope: &wrap_scope,
def_map: self.def_map,
trait_ref_hack: self.trait_ref_hack,
labels_in_fn: self.labels_in_fn.clone(),
};
debug!("entering scope {:?}", this.scope);
f(self.scope, &mut this);
@ -494,6 +676,17 @@ impl<'a> LifetimeContext<'a> {
mut old_scope: Scope,
lifetime: &ast::Lifetime)
{
for &(label, label_span) in &self.labels_in_fn {
// FIXME (#24278): non-hygienic comparision
if lifetime.name == label.name {
signal_shadowing_problem(self.sess,
lifetime.name,
original_label(label_span),
shadower_lifetime(&lifetime));
return;
}
}
loop {
match *old_scope {
BlockScope(_, s) => {
@ -507,15 +700,11 @@ impl<'a> LifetimeContext<'a> {
EarlyScope(_, lifetimes, s) |
LateScope(lifetimes, s) => {
if let Some((_, lifetime_def)) = search_lifetimes(lifetimes, lifetime) {
self.sess.span_err(
lifetime.span,
&format!("lifetime name `{}` shadows another \
lifetime name that is already in scope",
token::get_name(lifetime.name)));
self.sess.span_note(
lifetime_def.span,
&format!("shadowed lifetime `{}` declared here",
token::get_name(lifetime.name)));
signal_shadowing_problem(
self.sess,
lifetime.name,
original_lifetime(&lifetime_def),
shadower_lifetime(&lifetime));
return;
}

2
src/test/compile-fail/loop-labeled-break-value.rs
View File

@ -16,6 +16,6 @@ fn main() {
let _: i32 = 'inner: loop { break 'inner }; //~ ERROR mismatched types
}
loop {
let _: i32 = 'inner: loop { loop { break 'inner } }; //~ ERROR mismatched types
let _: i32 = 'inner2: loop { loop { break 'inner2 } }; //~ ERROR mismatched types
}
}

51
src/test/compile-fail/loops-reject-duplicate-labels-2.rs Normal file
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@ -0,0 +1,51 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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.
#![feature(rustc_attrs)]
// ignore-tidy-linelength
// Issue #21633: reject duplicate loop labels in function bodies.
//
// This is testing the generalization (to the whole function body)
// discussed here:
// http://internals.rust-lang.org/t/psa-rejecting-duplicate-loop-labels/1833
pub fn foo() {
{ 'fl: for _ in 0..10 { break; } } //~ NOTE shadowed label `'fl` declared here
{ 'fl: loop { break; } } //~ WARN label name `'fl` shadows a label name that is already in scope
{ 'lf: loop { break; } } //~ NOTE shadowed label `'lf` declared here
{ 'lf: for _ in 0..10 { break; } } //~ WARN label name `'lf` shadows a label name that is already in scope
{ 'wl: while 2 > 1 { break; } } //~ NOTE shadowed label `'wl` declared here
{ 'wl: loop { break; } } //~ WARN label name `'wl` shadows a label name that is already in scope
{ 'lw: loop { break; } } //~ NOTE shadowed label `'lw` declared here
{ 'lw: while 2 > 1 { break; } } //~ WARN label name `'lw` shadows a label name that is already in scope
{ 'fw: for _ in 0..10 { break; } } //~ NOTE shadowed label `'fw` declared here
{ 'fw: while 2 > 1 { break; } } //~ WARN label name `'fw` shadows a label name that is already in scope
{ 'wf: while 2 > 1 { break; } } //~ NOTE shadowed label `'wf` declared here
{ 'wf: for _ in 0..10 { break; } } //~ WARN label name `'wf` shadows a label name that is already in scope
{ 'tl: while let Some(_) = None::<i32> { break; } } //~ NOTE shadowed label `'tl` declared here
{ 'tl: loop { break; } } //~ WARN label name `'tl` shadows a label name that is already in scope
{ 'lt: loop { break; } } //~ NOTE shadowed label `'lt` declared here
{ 'lt: while let Some(_) = None::<i32> { break; } }
//~^ WARN label name `'lt` shadows a label name that is already in scope
}
#[rustc_error]
pub fn main() { //~ ERROR compilation successful
foo();
}

60
src/test/compile-fail/loops-reject-duplicate-labels.rs Normal file
View File

@ -0,0 +1,60 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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.
#![feature(rustc_attrs)]
// ignore-tidy-linelength
// Issue #21633: reject duplicate loop labels in function bodies.
// This is testing the exact cases that are in the issue description.
fn foo() {
'fl: for _ in 0..10 { break; } //~ NOTE shadowed label `'fl` declared here
'fl: loop { break; } //~ WARN label name `'fl` shadows a label name that is already in scope
'lf: loop { break; } //~ NOTE shadowed label `'lf` declared here
'lf: for _ in 0..10 { break; } //~ WARN label name `'lf` shadows a label name that is already in scope
'wl: while 2 > 1 { break; } //~ NOTE shadowed label `'wl` declared here
'wl: loop { break; } //~ WARN label name `'wl` shadows a label name that is already in scope
'lw: loop { break; } //~ NOTE shadowed label `'lw` declared here
'lw: while 2 > 1 { break; } //~ WARN label name `'lw` shadows a label name that is already in scope
'fw: for _ in 0..10 { break; } //~ NOTE shadowed label `'fw` declared here
'fw: while 2 > 1 { break; } //~ WARN label name `'fw` shadows a label name that is already in scope
'wf: while 2 > 1 { break; } //~ NOTE shadowed label `'wf` declared here
'wf: for _ in 0..10 { break; } //~ WARN label name `'wf` shadows a label name that is already in scope
'tl: while let Some(_) = None::<i32> { break; } //~ NOTE shadowed label `'tl` declared here
'tl: loop { break; } //~ WARN label name `'tl` shadows a label name that is already in scope
'lt: loop { break; } //~ NOTE shadowed label `'lt` declared here
'lt: while let Some(_) = None::<i32> { break; }
//~^ WARN label name `'lt` shadows a label name that is already in scope
}
// Note however that it is okay for the same label to be reused in
// different methods of one impl, as illustrated here.
struct S;
impl S {
fn m1(&self) { 'okay: loop { break 'okay; } }
fn m2(&self) { 'okay: loop { break 'okay; } }
}
#[rustc_error]
pub fn main() { //~ ERROR compilation successful
let s = S;
s.m1();
s.m2();
foo();
}

120
src/test/compile-fail/loops-reject-labels-shadowing-lifetimes.rs Normal file
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@ -0,0 +1,120 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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.
// Issue #21633: reject duplicate loop labels in function bodies.
// This is testing interaction between lifetime-params and labels.
#![feature(rustc_attrs)]
#![allow(dead_code, unused_variables)]
fn foo() {
fn foo<'a>() { //~ NOTE shadowed lifetime `'a` declared here
'a: loop { break 'a; }
//~^ WARN label name `'a` shadows a lifetime name that is already in scope
}
struct Struct<'b, 'c> { _f: &'b i8, _g: &'c i8 }
enum Enum<'d, 'e> { A(&'d i8), B(&'e i8) }
impl<'d, 'e> Struct<'d, 'e> {
fn meth_okay() {
'a: loop { break 'a; }
'b: loop { break 'b; }
'c: loop { break 'c; }
}
}
impl <'d, 'e> Enum<'d, 'e> {
fn meth_okay() {
'a: loop { break 'a; }
'b: loop { break 'b; }
'c: loop { break 'c; }
}
}
impl<'bad, 'c> Struct<'bad, 'c> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_bad(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
impl<'b, 'bad> Struct<'b, 'bad> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_bad2(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
impl<'b, 'c> Struct<'b, 'c> {
fn meth_bad3<'bad>(x: &'bad i8) { //~ NOTE shadowed lifetime `'bad` declared here
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
fn meth_bad4<'a,'bad>(x: &'a i8, y: &'bad i8) {
//~^ NOTE shadowed lifetime `'bad` declared here
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
impl <'bad, 'e> Enum<'bad, 'e> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_bad(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
impl <'d, 'bad> Enum<'d, 'bad> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_bad2(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
impl <'d, 'e> Enum<'d, 'e> {
fn meth_bad3<'bad>(x: &'bad i8) { //~ NOTE shadowed lifetime `'bad` declared here
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
fn meth_bad4<'a,'bad>(x: &'bad i8) { //~ NOTE shadowed lifetime `'bad` declared here
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
trait HasDefaultMethod1<'bad> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_okay() {
'c: loop { break 'c; }
}
fn meth_bad(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
trait HasDefaultMethod2<'a,'bad> { //~ NOTE shadowed lifetime `'bad` declared here
fn meth_bad(&self) {
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
trait HasDefaultMethod3<'a,'b> {
fn meth_bad<'bad>(&self) { //~ NOTE shadowed lifetime `'bad` declared here
'bad: loop { break 'bad; }
//~^ WARN label name `'bad` shadows a lifetime name that is already in scope
}
}
}
#[rustc_error]
pub fn main() { //~ ERROR compilation successful
foo();
}

41
src/test/compile-fail/loops-reject-lifetime-shadowing-label.rs Normal file
View File

@ -0,0 +1,41 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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.
#![feature(rustc_attrs)]
#![allow(dead_code, unused_variables)]
// Issue #21633: reject duplicate loop labels in function bodies.
//
// Test rejection of lifetimes in *expressions* that shadow loop labels.
fn foo() {
// Reusing lifetime `'a` in function item is okay.
fn foo<'a>(x: &'a i8) -> i8 { *x }
// So is reusing `'a` in struct item
struct S1<'a> { x: &'a i8 } impl<'a> S1<'a> { fn m(&self) {} }
// and a method item
struct S2; impl S2 { fn m<'a>(&self) {} }
let z = 3_i8;
'a: loop { //~ NOTE shadowed label `'a` declared here
let b = Box::new(|x: &i8| *x) as Box<for <'a> Fn(&'a i8) -> i8>;
//~^ WARN lifetime name `'a` shadows a label name that is already in scope
assert_eq!((*b)(&z), z);
break 'a;
}
}
#[rustc_error]
pub fn main() { //~ ERROR compilation successful
foo();
}

4
src/test/compile-fail/shadowed-lifetime.rs
View File

@ -15,14 +15,14 @@ struct Foo<'a>(&'a isize);
impl<'a> Foo<'a> {
//~^ NOTE shadowed lifetime `'a` declared here
fn shadow_in_method<'a>(&'a self) -> &'a isize {
//~^ ERROR lifetime name `'a` shadows another lifetime name that is already in scope
//~^ ERROR lifetime name `'a` shadows a lifetime name that is already in scope
self.0
}
fn shadow_in_type<'b>(&'b self) -> &'b isize {
//~^ NOTE shadowed lifetime `'b` declared here
let x: for<'b> fn(&'b isize) = panic!();
//~^ ERROR lifetime name `'b` shadows another lifetime name that is already in scope
//~^ ERROR lifetime name `'b` shadows a lifetime name that is already in scope
self.0
}

8
src/test/run-pass/hygienic-labels-in-let.rs
View File

@ -10,6 +10,14 @@
// ignore-pretty: pprust doesn't print hygiene output
// Test that labels injected by macros do not break hygiene. This
// checks cases where the macros invocations are under the rhs of a
// let statement.
// Issue #24278: The label/lifetime shadowing checker from #24162
// conservatively ignores hygiene, and thus issues warnings that are
// both true- and false-positives for this test.
macro_rules! loop_x {
($e: expr) => {
// $e shouldn't be able to interact with this 'x

5
src/test/run-pass/hygienic-labels.rs
View File

@ -8,6 +8,11 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Test that labels injected by macros do not break hygiene.
// Issue #24278: The label/lifetime shadowing checker from #24162
// conservatively ignores hygiene, and thus issues warnings that are
// both true- and false-positives for this test.
macro_rules! loop_x {
($e: expr) => {