bjoernager/rust
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Forbid items with the same name being defined in overlapping inherent

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impl blocks.

For example, the following is now correctly illegal:

```rust
struct Foo;

impl Foo {
    fn id() {}
}

impl Foo {
    fn id() {}
}
```

"Overlapping" here is determined the same way it is for traits (and in
fact shares the same code path): roughly, there must be some way of
substituting any generic types to unify the impls, such that none of the
`where` clauses are provably unsatisfiable under such a unification.

Closes #22889
This commit is contained in:
Aaron Turon 2016-02-26 13:21:44 -08:00
parent 9cc3bfcceb
commit 21df87f515
9 changed files with 113 additions and 45 deletions
Download patch file Download diff file Expand all files Collapse all files

1
src/librustc/dep_graph/mod.rs
View file

@ -58,6 +58,7 @@ pub enum DepNode {
CoherenceCheckImpl(DefId),
CoherenceOverlapCheck(DefId),
CoherenceOverlapCheckSpecial(DefId),
CoherenceOverlapInherentCheck(DefId),
CoherenceOrphanCheck(DefId),
Variance,
WfCheck(DefId),

8
src/librustc/middle/infer/mod.rs
View file

@ -482,14 +482,14 @@ pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
pub fn mk_eq_impl_headers<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
a_is_expected: bool,
origin: TypeOrigin,
a: ty::ImplHeader<'tcx>,
b: ty::ImplHeader<'tcx>)
a: &ty::ImplHeader<'tcx>,
b: &ty::ImplHeader<'tcx>)
-> UnitResult<'tcx>
{
debug!("mk_eq_impl_header({:?} = {:?})", a, b);
match (a.trait_ref, b.trait_ref) {
(Some(a_ref), Some(b_ref)) => mk_eq_trait_refs(cx, a_is_expected, a_ref, b_ref),
(None, None) => mk_eqty(cx, a_is_expected, a.self_ty, b.self_ty),
(Some(a_ref), Some(b_ref)) => mk_eq_trait_refs(cx, a_is_expected, origin, a_ref, b_ref),
(None, None) => mk_eqty(cx, a_is_expected, origin, a.self_ty, b.self_ty),
_ => cx.tcx.sess.bug("mk_eq_impl_headers given mismatched impl kinds"),
}
}

21
src/librustc/middle/traits/coherence.rs
View file

@ -10,18 +10,15 @@
//! See `README.md` for high-level documentation
use super::{Normalized, SelectionContext};
use super::{Obligation, ObligationCause, PredicateObligation};
use super::project;
use super::util;
use super::{SelectionContext};
use super::{Obligation, ObligationCause};
use middle::cstore::LOCAL_CRATE;
use middle::def_id::DefId;
use middle::subst::{Subst, Substs, TypeSpace};
use middle::subst::TypeSpace;
use middle::ty::{self, Ty, TyCtxt};
use middle::ty::error::TypeError;
use middle::infer::{self, InferCtxt, TypeOrigin};
use syntax::codemap::{DUMMY_SP, Span};
use syntax::codemap::DUMMY_SP;
#[derive(Copy, Clone)]
struct InferIsLocal(bool);
@ -31,7 +28,7 @@ struct InferIsLocal(bool);
pub fn overlapping_impls<'cx, 'tcx>(infcx: &InferCtxt<'cx, 'tcx>,
impl1_def_id: DefId,
impl2_def_id: DefId)
-> Option<ImplTy<'tcx>>
-> Option<ty::ImplHeader<'tcx>>
{
debug!("impl_can_satisfy(\
impl1_def_id={:?}, \
@ -48,7 +45,7 @@ pub fn overlapping_impls<'cx, 'tcx>(infcx: &InferCtxt<'cx, 'tcx>,
fn overlap<'cx, 'tcx>(selcx: &mut SelectionContext<'cx, 'tcx>,
a_def_id: DefId,
b_def_id: DefId)
-> Option<ImplHeader<'tcx>>
-> Option<ty::ImplHeader<'tcx>>
{
debug!("overlap(a_def_id={:?}, b_def_id={:?})",
a_def_id,
@ -64,8 +61,8 @@ fn overlap<'cx, 'tcx>(selcx: &mut SelectionContext<'cx, 'tcx>,
if let Err(_) = infer::mk_eq_impl_headers(selcx.infcx(),
true,
TypeOrigin::Misc(DUMMY_SP),
a_impl_header,
b_impl_header) {
&a_impl_header,
&b_impl_header) {
return None;
}
@ -74,7 +71,7 @@ fn overlap<'cx, 'tcx>(selcx: &mut SelectionContext<'cx, 'tcx>,
// Are any of the obligations unsatisfiable? If so, no overlap.
let infcx = selcx.infcx();
let opt_failing_obligation =
a_impl_header.prediates
a_impl_header.predicates
.iter()
.chain(&b_impl_header.predicates)
.map(|p| infcx.resolve_type_vars_if_possible(p))

16
src/librustc/middle/ty/mod.rs
View file

@ -164,9 +164,9 @@ pub struct ImplHeader<'tcx> {
}
impl<'tcx> ImplHeader<'tcx> {
pub fn with_fresh_ty_vars<'a,'tcx>(selcx: &mut traits::SelectionContext<'a,'tcx>,
impl_def_id: DefId)
-> ImplHeader<'tcx>
pub fn with_fresh_ty_vars<'a>(selcx: &mut traits::SelectionContext<'a, 'tcx>,
impl_def_id: DefId)
-> ImplHeader<'tcx>
{
let tcx = selcx.tcx();
let impl_generics = tcx.lookup_item_type(impl_def_id).generics;
@ -174,13 +174,13 @@ impl<'tcx> ImplHeader<'tcx> {
let header = ImplHeader {
impl_def_id: impl_def_id,
self_ty: tcx.lookup_item_type(impl_def_id),
self_ty: tcx.lookup_item_type(impl_def_id).ty,
trait_ref: tcx.impl_trait_ref(impl_def_id),
predicates: tcx.lookup_predicates(impl_def_id),
}.subst(tcx, impl_substs);
predicates: tcx.lookup_predicates(impl_def_id).predicates.into_vec(),
}.subst(tcx, &impl_substs);
let Normalized { value: mut header, obligations: obligations } =
proect::normalize(selcx, ObligationCause::dummy(), &header);
let traits::Normalized { value: mut header, obligations } =
traits::normalize(selcx, traits::ObligationCause::dummy(), &header);
header.predicates.extend(obligations.into_iter().map(|o| o.predicate));
header

3
src/librustc/middle/ty/structural_impls.rs
View file

@ -452,8 +452,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ImplHeader<'tcx> {
impl_def_id: self.impl_def_id,
self_ty: self.self_ty.fold_with(folder),
trait_ref: self.trait_ref.map(|t| t.fold_with(folder)),
predicates: self.predicates.into_iter().map(|p| p.fold_with(folder)).collect(),
polarity: self.polarity,
predicates: self.predicates.iter().map(|p| p.fold_with(folder)).collect(),
}
}

9
src/librustc_typeck/coherence/mod.rs
View file

@ -35,7 +35,9 @@ use CrateCtxt;
use middle::infer::{self, InferCtxt, TypeOrigin, new_infer_ctxt};
use std::cell::RefCell;
use std::rc::Rc;
use syntax::ast;
use syntax::codemap::Span;
use syntax::errors::DiagnosticBuilder;
use util::nodemap::{DefIdMap, FnvHashMap};
use rustc::dep_graph::DepNode;
use rustc::front::map as hir_map;
@ -519,6 +521,13 @@ fn enforce_trait_manually_implementable(tcx: &TyCtxt, sp: Span, trait_def_id: De
err.emit();
}
// Factored out into helper because the error cannot be defined in multiple locations.
pub fn report_duplicate_item<'tcx>(tcx: &TyCtxt<'tcx>, sp: Span, name: ast::Name)
-> DiagnosticBuilder<'tcx>
{
struct_span_err!(tcx.sess, sp, E0201, "duplicate definitions with name `{}`:", name)
}
pub fn check_coherence(crate_context: &CrateCtxt) {
let _task = crate_context.tcx.dep_graph.in_task(DepNode::Coherence);
let infcx = new_infer_ctxt(crate_context.tcx, &crate_context.tcx.tables, None);

72
src/librustc_typeck/coherence/overlap.rs
View file

@ -9,7 +9,8 @@
// except according to those terms.
//! Overlap: No two impls for the same trait are implemented for the
//! same type.
//! same type. Likewise, no two inherent impls for a given type
//! constructor provide a method with the same name.
use middle::cstore::{CrateStore, LOCAL_CRATE};
use middle::def_id::DefId;
@ -115,7 +116,6 @@ impl<'cx, 'tcx> OverlapChecker<'cx, 'tcx> {
}
}
fn check_if_impls_overlap(&self,
impl1_def_id: DefId,
impl2_def_id: DefId)
@ -128,8 +128,8 @@ impl<'cx, 'tcx> OverlapChecker<'cx, 'tcx> {
impl2_def_id);
let infcx = infer::new_infer_ctxt(self.tcx, &self.tcx.tables, None);
if let Some(trait_ref) = traits::overlapping_impls(&infcx, impl1_def_id, impl2_def_id) {
self.report_overlap_error(impl1_def_id, impl2_def_id, trait_ref);
if let Some(header) = traits::overlapping_impls(&infcx, impl1_def_id, impl2_def_id) {
self.report_overlap_error(impl1_def_id, impl2_def_id, header.trait_ref.unwrap());
}
}
}
@ -150,13 +150,13 @@ impl<'cx, 'tcx> OverlapChecker<'cx, 'tcx> {
}).unwrap_or(String::new())
};
let mut err = struct_span_err!(self.tcx.sess, self.span_of_impl(impl1), E0119,
let mut err = struct_span_err!(self.tcx.sess, self.span_of_def_id(impl1), E0119,
"conflicting implementations of trait `{}`{}:",
trait_ref,
self_type);
if impl2.is_local() {
span_note!(&mut err, self.span_of_impl(impl2),
span_note!(&mut err, self.span_of_def_id(impl2),
"conflicting implementation is here:");
} else {
let cname = self.tcx.sess.cstore.crate_name(impl2.krate);
@ -165,10 +165,61 @@ impl<'cx, 'tcx> OverlapChecker<'cx, 'tcx> {
err.emit();
}
fn span_of_impl(&self, impl_did: DefId) -> Span {
let node_id = self.tcx.map.as_local_node_id(impl_did).unwrap();
fn span_of_def_id(&self, did: DefId) -> Span {
let node_id = self.tcx.map.as_local_node_id(did).unwrap();
self.tcx.map.span(node_id)
}
fn check_for_common_items_in_impls(&self, impl1: DefId, impl2: DefId) {
#[derive(Copy, Clone, PartialEq)]
enum Namespace { Type, Value }
fn name_and_namespace(tcx: &TyCtxt, item: &ty::ImplOrTraitItemId)
-> (ast::Name, Namespace)
{
let name = tcx.impl_or_trait_item(item.def_id()).name();
(name, match *item {
ty::TypeTraitItemId(..) => Namespace::Type,
ty::ConstTraitItemId(..) => Namespace::Value,
ty::MethodTraitItemId(..) => Namespace::Value,
})
}
let impl_items = self.tcx.impl_items.borrow();
for item1 in &impl_items[&impl1] {
let (name, namespace) = name_and_namespace(&self.tcx, item1);
for item2 in &impl_items[&impl2] {
if (name, namespace) == name_and_namespace(&self.tcx, item2) {
let mut err = super::report_duplicate_item(
&self.tcx, self.span_of_def_id(item1.def_id()), name);
span_note!(&mut err, self.span_of_def_id(item2.def_id()),
"conflicting definition is here:");
err.emit();
}
}
}
}
fn check_for_overlapping_inherent_impls(&self, ty_def_id: DefId) {
let _task = self.tcx.dep_graph.in_task(DepNode::CoherenceOverlapInherentCheck(ty_def_id));
let inherent_impls = self.tcx.inherent_impls.borrow();
let impls = match inherent_impls.get(&ty_def_id) {
Some(impls) => impls,
None => return
};
for (i, &impl1_def_id) in impls.iter().enumerate() {
for &impl2_def_id in &impls[(i+1)..] {
let infcx = infer::new_infer_ctxt(self.tcx, &self.tcx.tables, None);
if traits::overlapping_impls(&infcx, impl1_def_id, impl2_def_id).is_some() {
self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id)
}
}
}
}
}
@ -180,6 +231,11 @@ impl<'cx, 'tcx,'v> intravisit::Visitor<'v> for OverlapChecker<'cx, 'tcx> {
self.check_for_overlapping_impls_of_trait(trait_def_id);
}
hir::ItemEnum(..) | hir::ItemStruct(..) => {
let type_def_id = self.tcx.map.local_def_id(item.id);
self.check_for_overlapping_inherent_impls(type_def_id);
}
hir::ItemDefaultImpl(..) => {
// look for another default impl; note that due to the
// general orphan/coherence rules, it must always be

13
src/librustc_typeck/collect.rs
View file

@ -63,6 +63,7 @@ use lint;
use middle::def::Def;
use middle::def_id::DefId;
use constrained_type_params as ctp;
use coherence;
use middle::lang_items::SizedTraitLangItem;
use middle::resolve_lifetime;
use middle::const_eval::{self, ConstVal};
@ -750,17 +751,7 @@ fn convert_item(ccx: &CrateCtxt, it: &hir::Item) {
_ => &mut seen_value_items,
};
if !seen_items.insert(impl_item.name) {
let desc = match impl_item.node {
hir::ImplItemKind::Const(_, _) => "associated constant",
hir::ImplItemKind::Type(_) => "associated type",
hir::ImplItemKind::Method(ref sig, _) =>
match sig.explicit_self.node {
hir::SelfStatic => "associated function",
_ => "method",
},
};
span_err!(tcx.sess, impl_item.span, E0201, "duplicate {}", desc);
coherence::report_duplicate_item(tcx, impl_item.span, impl_item.name).emit();
}
if let hir::ImplItemKind::Const(ref ty, _) = impl_item.node {

15
src/librustc_typeck/diagnostics.rs
View file

@ -2285,6 +2285,21 @@ impl Baz for Foo {
type Quux = u32;
}
```
Note, however, that items with the same name are allowed for inherent `impl`
blocks that don't overlap:
```
struct Foo<T>(T);
impl Foo<u8> {
fn bar(&self) -> bool { self.0 > 5 }
}
impl Foo<bool> {
fn bar(&self) -> bool { self.0 }
}
```
"##,
E0202: r##"