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Eliminate false-positives in the non-local lint with the type-system

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This commit is contained in:
Urgau 2024-03-14 23:32:15 +01:00
parent 617324095b
commit a1d7bff7ef
3 changed files with 326 additions and 66 deletions
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205
compiler/rustc_lint/src/non_local_def.rs
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@ -1,6 +1,18 @@
use rustc_hir::{def::DefKind, Body, Item, ItemKind, Node, Path, QPath, TyKind};
use rustc_hir::{def::DefKind, Body, Item, ItemKind, Node, TyKind};
use rustc_hir::{Path, QPath};
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::{Obligation, ObligationCause};
use rustc_middle::query::Key;
use rustc_middle::ty::{self, Binder, Ty, TyCtxt, TypeFoldable, TypeFolder};
use rustc_middle::ty::{EarlyBinder, TraitRef, TypeSuperFoldable};
use rustc_span::def_id::{DefId, LOCAL_CRATE};
use rustc_span::Span;
use rustc_span::{sym, symbol::kw, ExpnKind, MacroKind};
use rustc_trait_selection::infer::TyCtxtInferExt;
use rustc_trait_selection::traits::error_reporting::ambiguity::{
compute_applicable_impls_for_diagnostics, CandidateSource,
};
use crate::lints::{NonLocalDefinitionsCargoUpdateNote, NonLocalDefinitionsDiag};
use crate::{LateContext, LateLintPass, LintContext};
@ -66,7 +78,8 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
return;
}
let parent = cx.tcx.parent(item.owner_id.def_id.into());
let def_id = item.owner_id.def_id.into();
let parent = cx.tcx.parent(def_id);
let parent_def_kind = cx.tcx.def_kind(parent);
let parent_opt_item_name = cx.tcx.opt_item_name(parent);
@ -121,6 +134,7 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
None
};
// Part 1: Is the Self type local?
let self_ty_has_local_parent = match impl_.self_ty.kind {
TyKind::Path(QPath::Resolved(_, ty_path)) => {
path_has_local_parent(ty_path, cx, parent, parent_parent)
@ -150,41 +164,70 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
| TyKind::Err(_) => false,
};
if self_ty_has_local_parent {
return;
}
// Part 2: Is the Trait local?
let of_trait_has_local_parent = impl_
.of_trait
.map(|of_trait| path_has_local_parent(of_trait.path, cx, parent, parent_parent))
.unwrap_or(false);
// If none of them have a local parent (LOGICAL NOR) this means that
// this impl definition is a non-local definition and so we lint on it.
if !(self_ty_has_local_parent || of_trait_has_local_parent) {
let const_anon = if self.body_depth == 1
&& parent_def_kind == DefKind::Const
&& parent_opt_item_name != Some(kw::Underscore)
&& let Some(parent) = parent.as_local()
&& let Node::Item(item) = cx.tcx.hir_node_by_def_id(parent)
&& let ItemKind::Const(ty, _, _) = item.kind
&& let TyKind::Tup(&[]) = ty.kind
{
Some(item.ident.span)
} else {
None
};
cx.emit_span_lint(
NON_LOCAL_DEFINITIONS,
item.span,
NonLocalDefinitionsDiag::Impl {
depth: self.body_depth,
body_kind_descr: cx.tcx.def_kind_descr(parent_def_kind, parent),
body_name: parent_opt_item_name
.map(|s| s.to_ident_string())
.unwrap_or_else(|| "<unnameable>".to_string()),
cargo_update: cargo_update(),
const_anon,
},
)
if of_trait_has_local_parent {
return;
}
// Part 3: Is the impl definition leaking outside it's defining scope?
//
// We always consider inherent impls to be leaking.
let impl_has_enough_non_local_candidates = cx
.tcx
.impl_trait_ref(def_id)
.map(|binder| {
impl_trait_ref_has_enough_non_local_candidates(
cx.tcx,
item.span,
def_id,
binder,
|did| did_has_local_parent(did, cx.tcx, parent, parent_parent),
)
})
.unwrap_or(false);
if impl_has_enough_non_local_candidates {
return;
}
// Get the span of the parent const item ident (if it's a not a const anon).
//
// Used to suggest changing the const item to a const anon.
let span_for_const_anon_suggestion = if self.body_depth == 1
&& parent_def_kind == DefKind::Const
&& parent_opt_item_name != Some(kw::Underscore)
&& let Some(parent) = parent.as_local()
&& let Node::Item(item) = cx.tcx.hir_node_by_def_id(parent)
&& let ItemKind::Const(ty, _, _) = item.kind
&& let TyKind::Tup(&[]) = ty.kind
{
Some(item.ident.span)
} else {
None
};
cx.emit_span_lint(
NON_LOCAL_DEFINITIONS,
item.span,
NonLocalDefinitionsDiag::Impl {
depth: self.body_depth,
body_kind_descr: cx.tcx.def_kind_descr(parent_def_kind, parent),
body_name: parent_opt_item_name
.map(|s| s.to_ident_string())
.unwrap_or_else(|| "<unnameable>".to_string()),
cargo_update: cargo_update(),
const_anon: span_for_const_anon_suggestion,
},
)
}
ItemKind::Macro(_macro, MacroKind::Bang)
if cx.tcx.has_attr(item.owner_id.def_id, sym::macro_export) =>
@ -207,6 +250,81 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
}
}
// Detecting if the impl definition is leaking outside of it's defining scope.
//
// Rule: for each impl, instantiate all local types with inference vars and
// then assemble candidates for that goal, if there are more than 1 (non-private
// impls), it does not leak.
//
// https://github.com/rust-lang/rust/issues/121621#issuecomment-1976826895
fn impl_trait_ref_has_enough_non_local_candidates<'tcx>(
tcx: TyCtxt<'tcx>,
infer_span: Span,
trait_def_id: DefId,
binder: EarlyBinder<TraitRef<'tcx>>,
mut did_has_local_parent: impl FnMut(DefId) -> bool,
) -> bool {
let infcx = tcx.infer_ctxt().build();
let trait_ref = binder.instantiate(tcx, infcx.fresh_args_for_item(infer_span, trait_def_id));
let trait_ref = trait_ref.fold_with(&mut ReplaceLocalTypesWithInfer {
infcx: &infcx,
infer_span,
did_has_local_parent: &mut did_has_local_parent,
});
let poly_trait_obligation = Obligation::new(
tcx,
ObligationCause::dummy(),
ty::ParamEnv::empty(),
Binder::dummy(trait_ref),
);
let ambiguities = compute_applicable_impls_for_diagnostics(&infcx, &poly_trait_obligation);
let mut it = ambiguities.iter().filter(|ambi| match ambi {
CandidateSource::DefId(did) => !did_has_local_parent(*did),
CandidateSource::ParamEnv(_) => unreachable!(),
});
let _ = it.next();
it.next().is_some()
}
/// Replace every local type by inference variable.
///
/// ```text
/// <Global<Local> as std::cmp::PartialEq<Global<Local>>>
/// to
/// <Global<_> as std::cmp::PartialEq<Global<_>>>
/// ```
struct ReplaceLocalTypesWithInfer<'a, 'tcx, F: FnMut(DefId) -> bool> {
infcx: &'a InferCtxt<'tcx>,
did_has_local_parent: F,
infer_span: Span,
}
impl<'a, 'tcx, F: FnMut(DefId) -> bool> TypeFolder<TyCtxt<'tcx>>
for ReplaceLocalTypesWithInfer<'a, 'tcx, F>
{
fn interner(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if let Some(ty_did) = t.ty_def_id()
&& (self.did_has_local_parent)(ty_did)
{
self.infcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span: self.infer_span,
})
} else {
t.super_fold_with(self)
}
}
}
/// Given a path and a parent impl def id, this checks if the if parent resolution
/// def id correspond to the def id of the parent impl definition.
///
@ -216,16 +334,29 @@ impl<'tcx> LateLintPass<'tcx> for NonLocalDefinitions {
/// std::convert::PartialEq<Foo<Bar>>
/// ^^^^^^^^^^^^^^^^^^^^^^^
/// ```
#[inline]
fn path_has_local_parent(
path: &Path<'_>,
cx: &LateContext<'_>,
impl_parent: DefId,
impl_parent_parent: Option<DefId>,
) -> bool {
path.res.opt_def_id().is_some_and(|did| {
did.is_local() && {
let res_parent = cx.tcx.parent(did);
res_parent == impl_parent || Some(res_parent) == impl_parent_parent
}
})
path.res
.opt_def_id()
.is_some_and(|did| did_has_local_parent(did, cx.tcx, impl_parent, impl_parent_parent))
}
/// Given a def id and a parent impl def id, this checks if the parent
/// def id correspond to the def id of the parent impl definition.
#[inline]
fn did_has_local_parent(
did: DefId,
tcx: TyCtxt<'_>,
impl_parent: DefId,
impl_parent_parent: Option<DefId>,
) -> bool {
did.is_local() && {
let res_parent = tcx.parent(did);
res_parent == impl_parent || Some(res_parent) == impl_parent_parent
}
}