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No tracing of nop traceable fields (#29926)
* Add `no_trace` option to JSTraceable derive * NoTrace wrapper * Port some types to no_trace schematics * Fixing my unsafe mistakes (not tracing traceables) * Add docs & safety guards for no_trace Safety guards (trait shenanigans) guarantees safety usage of `no_trace` * Port canvas_traits to no_trace * Port servo_media to no_trace * Port net_traits to no_trace * Port style to no_trace * Port webgpu to no_trace * Port script_traits to no_trace * Port canvas_traits, devtools_traits, embedder_traits, profile_traits to no_trace * unrooted_must_root lint in seperate file * Add trace_in_no_trace_lint as script_plugin * Composable types in must_not_have_traceable * Introduced HashMapTracedValues wrapper * `HashMap<NoTrace<K>,V>`->`HashMapTracedValues<K,V>` * Port rest of servo's types to no_trace * Port html5ever, euclid, mime and http to no_trace * Port remaining externals to no_trace * Port webxr and Arc<Mutex<_>> * Fix spelling in notrace doc
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167 changed files with 1903 additions and 1020 deletions
204
components/script_plugins/trace_in_no_trace.rs
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204
components/script_plugins/trace_in_no_trace.rs
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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use crate::{get_trait_def_id, implements_trait, symbols};
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use rustc_ast::ast::{AttrKind, Attribute};
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use rustc_ast::token::TokenKind;
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use rustc_ast::tokenstream::TokenTree;
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use rustc_ast::AttrArgs;
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use rustc_driver::plugin::Registry;
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use rustc_error_messages::MultiSpan;
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use rustc_hir::{self as hir};
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use rustc_lint::{LateContext, LateLintPass, LintContext, LintPass};
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use rustc_middle::ty;
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use rustc_session::declare_lint;
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use rustc_span::symbol::Symbol;
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declare_lint!(
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TRACE_IN_NO_TRACE,
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Deny,
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"Warn and report incorrect usage of Traceable (jsmanaged) objects in must_not_have_traceable marked wrappers"
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);
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declare_lint!(
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EMPTY_TRACE_IN_NO_TRACE,
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Warn,
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"Warn about usage of empty Traceable objects in must_not_have_traceable marked wrappers"
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);
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const EMPTY_TRACE_IN_NO_TRACE_MSG: &str =
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"must_not_have_traceable marked wrapper is not needed for types that implements \
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empty Traceable (like primitive types). Consider removing the wrapper.";
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pub fn register(reg: &mut Registry) {
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let symbols = Symbols::new();
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reg.lint_store
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.register_lints(&[&TRACE_IN_NO_TRACE, &EMPTY_TRACE_IN_NO_TRACE]);
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reg.lint_store
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.register_late_pass(move |_| Box::new(NotracePass::new(symbols.clone())));
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}
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/// Lint for ensuring safe usage of NoTrace wrappers
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///
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/// This lint (disable with `-A trace-in-no-trace`/`#[allow(trace_in_no_trace)]`) ensures that
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/// wrappers marked with must_not_have_traceable(i: usize) only stores
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/// non-jsmanaged (DOES NOT implement JSTraceble) type in i-th generic
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///
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/// For example usage look at the tests
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pub(crate) struct NotracePass {
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symbols: Symbols,
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}
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impl NotracePass {
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pub(crate) fn new(symbols: Symbols) -> Self {
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Self { symbols }
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}
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}
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impl LintPass for NotracePass {
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fn name(&self) -> &'static str {
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"ServoNotracePass"
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}
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}
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fn get_must_not_have_traceable(sym: &Symbols, attrs: &[Attribute]) -> Option<usize> {
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attrs
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.iter()
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.find(|attr| {
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matches!(
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&attr.kind,
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AttrKind::Normal(normal)
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if normal.item.path.segments.len() == 2 &&
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normal.item.path.segments[0].ident.name == sym.trace_in_no_trace_lint &&
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normal.item.path.segments[1].ident.name == sym.must_not_have_traceable
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)
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})
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.map(|x| match &x.get_normal_item().args {
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AttrArgs::Empty => 0,
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AttrArgs::Delimited(a) => match a
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.tokens
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.trees()
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.next()
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.expect("Arguments not found for must_not_have_traceable")
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{
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TokenTree::Token(tok, _) => match tok.kind {
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TokenKind::Literal(lit) => lit.symbol.as_str().parse().unwrap(),
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_ => panic!("must_not_have_traceable expected integer literal here"),
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},
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TokenTree::Delimited(_, _, _) => {
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todo!("must_not_have_traceable does not support multiple notraceable positions")
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},
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},
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_ => {
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panic!("must_not_have_traceable does not support key-value arguments")
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},
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})
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}
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fn is_jstraceable<'tcx>(cx: &LateContext<'tcx>, ty: ty::Ty<'tcx>) -> bool {
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// TODO(sagudev): get_trait_def_id is expensive, use lazy and cache it for whole pass
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if let Some(trait_id) =
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get_trait_def_id(cx, &["script", "dom", "bindings", "trace", "JSTraceable"])
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{
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return implements_trait(cx, ty, trait_id, &[]);
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}
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// when running tests
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if let Some(trait_id) = get_trait_def_id(
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cx,
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&[
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"script_plugins_tests",
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"trace_in_no_trace_lint",
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"JSTraceable",
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],
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) {
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return implements_trait(cx, ty, trait_id, &[]);
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}
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panic!("JSTraceable not found");
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}
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/// Gives warrning or errors for incorect usage of NoTrace like `NoTrace<impl Traceable>`.
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fn incorrect_no_trace<'tcx, I: Into<MultiSpan> + Copy>(
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sym: &'_ Symbols,
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cx: &LateContext<'tcx>,
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ty: ty::Ty<'tcx>,
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span: I,
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) {
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let mut walker = ty.walk();
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while let Some(generic_arg) = walker.next() {
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let t = match generic_arg.unpack() {
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rustc_middle::ty::subst::GenericArgKind::Type(t) => t,
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_ => {
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walker.skip_current_subtree();
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continue;
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},
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};
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let recur_into_subtree = match t.kind() {
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ty::Adt(did, substs) => {
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if let Some(pos) =
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get_must_not_have_traceable(sym, &cx.tcx.get_attrs_unchecked(did.did()))
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{
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let inner = substs.type_at(pos);
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if inner.is_primitive_ty() {
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cx.lint(
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EMPTY_TRACE_IN_NO_TRACE,
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EMPTY_TRACE_IN_NO_TRACE_MSG,
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|lint| lint.set_span(span),
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)
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} else if is_jstraceable(cx, inner) {
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cx.lint(
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TRACE_IN_NO_TRACE,
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format!(
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"must_not_have_traceable marked wrapper must not have \
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jsmanaged inside on {pos}-th position. Consider removing the wrapper."
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),
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|lint| lint.set_span(span),
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)
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}
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false
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} else {
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true
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}
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},
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_ => !t.is_primitive_ty(),
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};
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if !recur_into_subtree {
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walker.skip_current_subtree();
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}
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}
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}
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// NoTrace correct usage of NoTrace must only be checked on Struct (item) and Enums (variants)
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// as these are the only ones that are actually traced
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impl<'tcx> LateLintPass<'tcx> for NotracePass {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item) {
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// TODO: better performance if we limit with lint attr???
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/*let attrs = cx.tcx.hir().attrs(item.hir_id());
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if has_lint_attr(&self.symbols, &attrs, self.symbols.must_root) {
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return;
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}*/
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if let hir::ItemKind::Struct(def, ..) = &item.kind {
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for ref field in def.fields() {
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let field_type = cx.tcx.type_of(field.def_id);
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incorrect_no_trace(&self.symbols, cx, field_type, field.span);
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}
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}
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}
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fn check_variant(&mut self, cx: &LateContext, var: &hir::Variant) {
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match var.data {
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hir::VariantData::Tuple(fields, ..) => {
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for field in fields {
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let field_type = cx.tcx.type_of(field.def_id);
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incorrect_no_trace(&self.symbols, cx, field_type, field.ty.span);
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}
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},
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_ => (), // Struct variants already caught by check_struct_def
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}
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}
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}
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symbols! {
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trace_in_no_trace_lint
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must_not_have_traceable
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}
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