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Remove the coherence impls pass that was specialized to builtin bounds,

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since there are separate checks that apply to Copy (and Send uses the
generic defaulted trait rules). Also prohibit `Sized` from being
manually implemented for now.
This commit is contained in:
Niko Matsakis 2015-03-06 15:55:30 -05:00
parent 2e216896e4
commit 4e789e03be
11 changed files with 184 additions and 90 deletions
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47
src/librustc_typeck/coherence/impls.rs
View File

@ -1,47 +0,0 @@
// 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.
//! Implementations checker: builtin traits and default impls are allowed just
//! for structs and enums.
use middle::ty;
use syntax::ast::{Item, ItemImpl};
use syntax::ast;
use syntax::visit;
pub fn check(tcx: &ty::ctxt) {
let mut impls = ImplsChecker { tcx: tcx };
visit::walk_crate(&mut impls, tcx.map.krate());
}
struct ImplsChecker<'cx, 'tcx:'cx> {
tcx: &'cx ty::ctxt<'tcx>
}
impl<'cx, 'tcx,'v> visit::Visitor<'v> for ImplsChecker<'cx, 'tcx> {
fn visit_item(&mut self, item: &'v ast::Item) {
match item.node {
ast::ItemImpl(_, _, _, Some(_), _, _) => {
let trait_ref = ty::impl_id_to_trait_ref(self.tcx, item.id);
if let Some(_) = self.tcx.lang_items.to_builtin_kind(trait_ref.def_id) {
match trait_ref.self_ty().sty {
ty::ty_struct(..) | ty::ty_enum(..) => {}
_ => {
span_err!(self.tcx.sess, item.span, E0209,
"builtin traits can only be \
implemented on structs or enums");
}
}
}
}
_ => {}
}
}
}

2
src/librustc_typeck/coherence/mod.rs
View File

@ -49,7 +49,6 @@ use syntax::visit;
use util::nodemap::{DefIdMap, FnvHashMap};
use util::ppaux::Repr;
mod impls;
mod orphan;
mod overlap;
mod unsafety;
@ -583,7 +582,6 @@ pub fn check_coherence(crate_context: &CrateCtxt) {
inference_context: new_infer_ctxt(crate_context.tcx),
inherent_impls: RefCell::new(FnvHashMap()),
}.check(crate_context.tcx.map.krate());
impls::check(crate_context.tcx);
unsafety::check(crate_context.tcx);
orphan::check(crate_context.tcx);
overlap::check(crate_context.tcx);

110
src/librustc_typeck/coherence/orphan.rs
View File

@ -37,10 +37,13 @@ impl<'cx, 'tcx> OrphanChecker<'cx, 'tcx> {
a trait or new type instead");
}
}
}
impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
fn visit_item(&mut self, item: &ast::Item) {
/// Checks exactly one impl for orphan rules and other such
/// restrictions. In this fn, it can happen that multiple errors
/// apply to a specific impl, so just return after reporting one
/// to prevent inundating the user with a bunch of similar error
/// reports.
fn check_item(&self, item: &ast::Item) {
let def_id = ast_util::local_def(item.id);
match item.node {
ast::ItemImpl(_, _, _, None, _, _) => {
@ -63,6 +66,7 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
span_err!(self.tcx.sess, item.span, E0118,
"no base type found for inherent implementation; \
implement a trait or new type instead");
return;
}
}
}
@ -81,6 +85,7 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
types defined in this crate; \
only traits defined in the current crate can be \
implemented for arbitrary types");
return;
}
}
Err(traits::OrphanCheckErr::UncoveredTy(param_ty)) => {
@ -90,11 +95,44 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
some local type (e.g. `MyStruct<T>`); only traits defined in \
the current crate can be implemented for a type parameter",
param_ty.user_string(self.tcx));
return;
}
}
}
// Impls of a defaulted trait face additional rules.
// In addition to the above rules, we restrict impls of defaulted traits
// so that they can only be implemented on structs/enums. To see why this
// restriction exists, consider the following example (#22978). Imagine
// that crate A defines a defaulted trait `Foo` and a fn that operates
// on pairs of types:
//
// ```
// // Crate A
// trait Foo { }
// impl Foo for .. { }
// fn two_foos<A:Foo,B:Foo>(..) {
// one_foo::<(A,B)>(..)
// }
// fn one_foo<T:Foo>(..) { .. }
// ```
//
// This type-checks fine; in particular the fn
// `two_foos` is able to conclude that `(A,B):Foo`
// because `A:Foo` and `B:Foo`.
//
// Now imagine that crate B comes along and does the following:
//
// ```
// struct A { }
// struct B { }
// impl Foo for A { }
// impl Foo for B { }
// impl !Send for (A, B) { }
// ```
//
// This final impl is legal according to the orpan
// rules, but it invalidates the reasoning from
// `two_foos` above.
debug!("trait_ref={} trait_def_id={} trait_has_default_impl={}",
trait_ref.repr(self.tcx),
trait_def_id.repr(self.tcx),
@ -104,28 +142,52 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
trait_def_id.krate != ast::LOCAL_CRATE
{
let self_ty = trait_ref.self_ty();
match self_ty.sty {
ty::ty_struct(self_def_id, _) | ty::ty_enum(self_def_id, _) => {
// The orphan check often rules this out,
// but not always. For example, the orphan
// check would accept `impl Send for
// Box<SomethingLocal>`, but we want to
// forbid that.
if self_def_id.krate != ast::LOCAL_CRATE {
self.tcx.sess.span_err(
item.span,
"cross-crate traits with a default impl \
let opt_self_def_id = match self_ty.sty {
ty::ty_struct(self_def_id, _) | ty::ty_enum(self_def_id, _) =>
Some(self_def_id),
ty::ty_uniq(..) =>
self.tcx.lang_items.owned_box(),
_ =>
None
};
let msg = match opt_self_def_id {
// We only want to permit structs/enums, but not *all* structs/enums.
// They must be local to the current crate, so that people
// can't do `unsafe impl Send for Rc<SomethingLocal>` or
// `unsafe impl !Send for Box<SomethingLocalAndSend>`.
Some(self_def_id) => {
if self_def_id.krate == ast::LOCAL_CRATE {
None
} else {
Some(format!(
"cross-crate traits with a default impl, like `{}`, \
can only be implemented for a struct/enum type \
defined in the current crate");
defined in the current crate",
ty::item_path_str(self.tcx, trait_def_id)))
}
}
_ => {
self.tcx.sess.span_err(
item.span,
"cross-crate traits with a default impl \
can only be implemented for a struct or enum type");
Some(format!(
"cross-crate traits with a default impl, like `{}`, \
can only be implemented for a struct/enum type, \
not `{}`",
ty::item_path_str(self.tcx, trait_def_id),
self_ty.user_string(self.tcx)))
}
};
if let Some(msg) = msg {
span_err!(self.tcx.sess, item.span, E0321, "{}", msg);
return;
}
}
// Disallow *all* explicit impls of `Sized` for now.
if Some(trait_def_id) == self.tcx.lang_items.sized_trait() {
span_err!(self.tcx.sess, item.span, E0322,
"explicit impls for the `Sized` trait are not permitted");
return;
}
}
ast::ItemDefaultImpl(..) => {
@ -135,14 +197,20 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
if trait_ref.def_id.krate != ast::LOCAL_CRATE {
span_err!(self.tcx.sess, item.span, E0318,
"cannot create default implementations for traits outside the \
crate they're defined in; define a new trait instead.");
crate they're defined in; define a new trait instead");
return;
}
}
_ => {
// Not an impl
}
}
}
}
impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
fn visit_item(&mut self, item: &ast::Item) {
self.check_item(item);
visit::walk_item(self, item);
}
}

4
src/librustc_typeck/diagnostics.rs
View File

@ -175,7 +175,9 @@ register_diagnostics! {
E0250, // expected constant expr for array length
E0318, // can't create default impls for traits outside their crates
E0319, // trait impls for defaulted traits allowed just for structs/enums
E0320 // recursive overflow during dropck
E0320, // recursive overflow during dropck
E0321, // extended coherence rules for defaulted traits violated
E0322 // cannot implement Sized explicitly
}
__build_diagnostic_array! { DIAGNOSTICS }

2
src/test/auxiliary/typeck-default-trait-impl-cross-crate-coherence-lib.rs
View File

@ -15,3 +15,5 @@ use std::marker::MarkerTrait;
pub trait DefaultedTrait : MarkerTrait { }
impl DefaultedTrait for .. { }
pub struct Something<T> { t: T }

39
src/test/compile-fail/coherence-impls-copy.rs Normal file
View File

@ -0,0 +1,39 @@
// 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(optin_builtin_traits)]
use std::marker::Copy;
enum TestE {
A
}
struct MyType;
struct NotSync;
impl !Sync for NotSync {}
impl Copy for TestE {}
impl Copy for MyType {}
impl Copy for (MyType, MyType) {}
//~^ ERROR E0206
impl Copy for &'static NotSync {}
//~^ ERROR E0206
impl Copy for [MyType] {}
//~^ ERROR E0206
impl Copy for &'static [NotSync] {}
//~^ ERROR E0206
fn main() {
}

15
src/test/compile-fail/coherence-impls-builtin.rs → src/test/compile-fail/coherence-impls-send.rs
View File

@ -10,7 +10,7 @@
#![feature(optin_builtin_traits)]
use std::marker::Send;
use std::marker::Copy;
enum TestE {
A
@ -24,20 +24,17 @@ impl !Sync for NotSync {}
unsafe impl Send for TestE {}
unsafe impl Send for MyType {}
unsafe impl Send for (MyType, MyType) {}
//~^ ERROR builtin traits can only be implemented on structs or enums
//~^ ERROR E0321
unsafe impl Send for &'static NotSync {}
//~^ ERROR builtin traits can only be implemented on structs or enums
//~^ ERROR E0321
unsafe impl Send for [MyType] {}
//~^ ERROR builtin traits can only be implemented on structs or enums
//~^ ERROR E0321
unsafe impl Send for &'static [NotSync] {}
//~^ ERROR builtin traits can only be implemented on structs or enums
//~^^ ERROR conflicting implementations for trait `core::marker::Send`
fn is_send<T: Send>() {}
//~^ ERROR E0321
//~| ERROR conflicting implementations
fn main() {
is_send::<(MyType, TestE)>();
}

33
src/test/compile-fail/coherence-impls-sized.rs Normal file
View File

@ -0,0 +1,33 @@
// 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(optin_builtin_traits)]
use std::marker::Copy;
enum TestE {
A
}
struct MyType;
struct NotSync;
impl !Sync for NotSync {}
impl Sized for TestE {} //~ ERROR E0322
impl Sized for MyType {} //~ ERROR E0322
impl Sized for (MyType, MyType) {} //~ ERROR E0322
impl Sized for &'static NotSync {} //~ ERROR E0322
impl Sized for [MyType] {} //~ ERROR E0322
//~^ ERROR E0277
impl Sized for &'static [NotSync] {} //~ ERROR E0322
fn main() {
}

8
src/test/compile-fail/coherence-orphan.rs
View File

@ -19,13 +19,15 @@ use lib::TheTrait;
struct TheType;
impl TheTrait<usize> for isize { } //~ ERROR E0117
impl TheTrait<usize> for isize { }
//~^ ERROR E0117
impl TheTrait<TheType> for isize { }
impl TheTrait<isize> for TheType { }
impl !Send for Vec<isize> { } //~ ERROR E0117
//~^ ERROR conflicting
impl !Send for Vec<isize> { }
//~^ ERROR E0117
//~| ERROR E0119
fn main() { }

12
src/test/compile-fail/typeck-default-trait-impl-cross-crate-coherence.rs
View File

@ -20,15 +20,15 @@ extern crate "typeck-default-trait-impl-cross-crate-coherence-lib" as lib;
use lib::DefaultedTrait;
struct A;
impl DefaultedTrait for (A,) { }
//~^ ERROR can only be implemented for a struct or enum type
impl DefaultedTrait for (A,) { } //~ ERROR E0321
struct B;
impl !DefaultedTrait for (B,) { }
//~^ ERROR can only be implemented for a struct or enum type
impl !DefaultedTrait for (B,) { } //~ ERROR E0321
struct C;
impl DefaultedTrait for Box<C> { }
//~^ ERROR can only be implemented for a struct or enum type
struct D<T>(T);
impl DefaultedTrait for Box<C> { } //~ ERROR E0321
impl DefaultedTrait for lib::Something<C> { } //~ ERROR E0321
impl DefaultedTrait for D<C> { } // OK
fn main() { }

2
src/test/compile-fail/typeck-default-trait-impl-outside-crate.rs
View File

@ -13,6 +13,6 @@
#![feature(optin_builtin_traits)]
impl Copy for .. {}
//~^ ERROR cannot create default implementations for traits outside the crate they're defined in; define a new trait instead.
//~^ ERROR E0318
fn main() {}