bjoernager/rust
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Fix overlapping impls

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This commit is contained in:
kadmin 2022-07-12 07:11:05 +00:00
parent e612e2603c
commit 20fb8aba8f
6 changed files with 215 additions and 172 deletions
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11
compiler/rustc_infer/src/infer/mod.rs
View file

@ -21,6 +21,7 @@ use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
use rustc_middle::traits::select;
use rustc_middle::ty::abstract_const::AbstractConst;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::relate::RelateResult;
@ -1651,14 +1652,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
unevaluated: ty::Unevaluated<'tcx>,
span: Option<Span>,
) -> EvalToValTreeResult<'tcx> {
let substs = self.resolve_vars_if_possible(unevaluated.substs);
let mut substs = self.resolve_vars_if_possible(unevaluated.substs);
debug!(?substs);
// Postpone the evaluation of constants whose substs depend on inference
// variables
if substs.has_infer_types_or_consts() {
debug!("substs have infer types or consts: {:?}", substs);
return Err(ErrorHandled::TooGeneric);
let ac = AbstractConst::new(self.tcx, unevaluated.shrink());
if let Ok(None) = ac {
substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
} else {
return Err(ErrorHandled::TooGeneric);
}
}
let param_env_erased = self.tcx.erase_regions(param_env);

166
compiler/rustc_middle/src/ty/abstract_const.rs
View file

@ -1,8 +1,10 @@
//! A subset of a mir body used for const evaluatability checking.
use crate::mir;
use crate::ty::visit::TypeVisitable;
use crate::ty::{self, subst::Subst, DelaySpanBugEmitted, EarlyBinder, SubstsRef, Ty, TyCtxt};
use rustc_errors::ErrorGuaranteed;
use std::iter;
use rustc_hir::def_id::DefId;
use std::cmp;
use std::ops::ControlFlow;
rustc_index::newtype_index! {
@ -63,6 +65,31 @@ impl<'tcx> AbstractConst<'tcx> {
Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => node,
}
}
pub fn unify_failure_kind(self, tcx: TyCtxt<'tcx>) -> FailureKind {
let mut failure_kind = FailureKind::Concrete;
walk_abstract_const::<!, _>(tcx, self, |node| {
match node.root(tcx) {
Node::Leaf(leaf) => {
if leaf.has_infer_types_or_consts() {
failure_kind = FailureKind::MentionsInfer;
} else if leaf.has_param_types_or_consts() {
failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
}
}
Node::Cast(_, _, ty) => {
if ty.has_infer_types_or_consts() {
failure_kind = FailureKind::MentionsInfer;
} else if ty.has_param_types_or_consts() {
failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
}
}
Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => {}
}
ControlFlow::CONTINUE
});
failure_kind
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
@ -104,7 +131,7 @@ impl<'tcx> TyCtxt<'tcx> {
#[inline]
pub fn thir_abstract_const_opt_const_arg(
self,
def: ty::WithOptConstParam<rustc_hir::def_id::DefId>,
def: ty::WithOptConstParam<DefId>,
) -> Result<Option<&'tcx [Node<'tcx>]>, ErrorGuaranteed> {
if let Some((did, param_did)) = def.as_const_arg() {
self.thir_abstract_const_of_const_arg((did, param_did))
@ -114,28 +141,6 @@ impl<'tcx> TyCtxt<'tcx> {
}
}
#[instrument(skip(tcx), level = "debug")]
pub fn try_unify_abstract_consts<'tcx>(
tcx: TyCtxt<'tcx>,
(a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>),
param_env: ty::ParamEnv<'tcx>,
) -> bool {
(|| {
if let Some(a) = AbstractConst::new(tcx, a)? {
if let Some(b) = AbstractConst::new(tcx, b)? {
let const_unify_ctxt = ConstUnifyCtxt { tcx, param_env };
return Ok(const_unify_ctxt.try_unify(a, b));
}
}
Ok(false)
})()
.unwrap_or_else(|_: ErrorGuaranteed| true)
// FIXME(generic_const_exprs): We should instead have this
// method return the resulting `ty::Const` and return `ConstKind::Error`
// on `ErrorGuaranteed`.
}
#[instrument(skip(tcx, f), level = "debug")]
pub fn walk_abstract_const<'tcx, R, F>(
tcx: TyCtxt<'tcx>,
@ -172,119 +177,6 @@ where
recurse(tcx, ct, &mut f)
}
pub struct ConstUnifyCtxt<'tcx> {
pub tcx: TyCtxt<'tcx>,
pub param_env: ty::ParamEnv<'tcx>,
}
impl<'tcx> ConstUnifyCtxt<'tcx> {
// Substitutes generics repeatedly to allow AbstractConsts to unify where a
// ConstKind::Unevaluated could be turned into an AbstractConst that would unify e.g.
// Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
#[inline]
#[instrument(skip(self), level = "debug")]
fn try_replace_substs_in_root(
&self,
mut abstr_const: AbstractConst<'tcx>,
) -> Option<AbstractConst<'tcx>> {
while let Node::Leaf(ct) = abstr_const.root(self.tcx) {
match AbstractConst::from_const(self.tcx, ct) {
Ok(Some(act)) => abstr_const = act,
Ok(None) => break,
Err(_) => return None,
}
}
Some(abstr_const)
}
/// Tries to unify two abstract constants using structural equality.
#[instrument(skip(self), level = "debug")]
pub fn try_unify(&self, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool {
let a = if let Some(a) = self.try_replace_substs_in_root(a) {
a
} else {
return true;
};
let b = if let Some(b) = self.try_replace_substs_in_root(b) {
b
} else {
return true;
};
let a_root = a.root(self.tcx);
let b_root = b.root(self.tcx);
debug!(?a_root, ?b_root);
match (a_root, b_root) {
(Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
let a_ct = a_ct.eval(self.tcx, self.param_env);
debug!("a_ct evaluated: {:?}", a_ct);
let b_ct = b_ct.eval(self.tcx, self.param_env);
debug!("b_ct evaluated: {:?}", b_ct);
if a_ct.ty() != b_ct.ty() {
return false;
}
match (a_ct.kind(), b_ct.kind()) {
// We can just unify errors with everything to reduce the amount of
// emitted errors here.
(ty::ConstKind::Error(_), _) | (_, ty::ConstKind::Error(_)) => true,
(ty::ConstKind::Param(a_param), ty::ConstKind::Param(b_param)) => {
a_param == b_param
}
(ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val,
// If we have `fn a<const N: usize>() -> [u8; N + 1]` and `fn b<const M: usize>() -> [u8; 1 + M]`
// we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This
// means that we only allow inference variables if they are equal.
(ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val,
// We expand generic anonymous constants at the start of this function, so this
// branch should only be taking when dealing with associated constants, at
// which point directly comparing them seems like the desired behavior.
//
// FIXME(generic_const_exprs): This isn't actually the case.
// We also take this branch for concrete anonymous constants and
// expand generic anonymous constants with concrete substs.
(ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => {
a_uv == b_uv
}
// FIXME(generic_const_exprs): We may want to either actually try
// to evaluate `a_ct` and `b_ct` if they are are fully concrete or something like
// this, for now we just return false here.
_ => false,
}
}
(Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => {
self.try_unify(a.subtree(al), b.subtree(bl))
&& self.try_unify(a.subtree(ar), b.subtree(br))
}
(Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => {
self.try_unify(a.subtree(av), b.subtree(bv))
}
(Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args))
if a_args.len() == b_args.len() =>
{
self.try_unify(a.subtree(a_f), b.subtree(b_f))
&& iter::zip(a_args, b_args)
.all(|(&an, &bn)| self.try_unify(a.subtree(an), b.subtree(bn)))
}
(Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty))
if (a_ty == b_ty) && (a_kind == b_kind) =>
{
self.try_unify(a.subtree(a_operand), b.subtree(b_operand))
}
// use this over `_ => false` to make adding variants to `Node` less error prone
(Node::Cast(..), _)
| (Node::FunctionCall(..), _)
| (Node::UnaryOp(..), _)
| (Node::Binop(..), _)
| (Node::Leaf(..), _) => false,
}
}
}
// We were unable to unify the abstract constant with
// a constant found in the caller bounds, there are
// now three possible cases here.

168
compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
View file

@ -8,19 +8,155 @@
//! In this case we try to build an abstract representation of this constant using
//! `thir_abstract_const` which can then be checked for structural equality with other
//! generic constants mentioned in the `caller_bounds` of the current environment.
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_infer::infer::InferCtxt;
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::abstract_const::{
walk_abstract_const, AbstractConst, ConstUnifyCtxt, FailureKind, Node, NotConstEvaluatable,
walk_abstract_const, AbstractConst, FailureKind, Node, NotConstEvaluatable,
};
use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
use rustc_session::lint;
use rustc_span::Span;
use std::cmp;
use std::iter;
use std::ops::ControlFlow;
pub struct ConstUnifyCtxt<'tcx> {
pub tcx: TyCtxt<'tcx>,
pub param_env: ty::ParamEnv<'tcx>,
}
impl<'tcx> ConstUnifyCtxt<'tcx> {
// Substitutes generics repeatedly to allow AbstractConsts to unify where a
// ConstKind::Unevaluated could be turned into an AbstractConst that would unify e.g.
// Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
#[inline]
#[instrument(skip(self), level = "debug")]
fn try_replace_substs_in_root(
&self,
mut abstr_const: AbstractConst<'tcx>,
) -> Option<AbstractConst<'tcx>> {
while let Node::Leaf(ct) = abstr_const.root(self.tcx) {
match AbstractConst::from_const(self.tcx, ct) {
Ok(Some(act)) => abstr_const = act,
Ok(None) => break,
Err(_) => return None,
}
}
Some(abstr_const)
}
/// Tries to unify two abstract constants using structural equality.
#[instrument(skip(self), level = "debug")]
pub fn try_unify(&self, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool {
let a = if let Some(a) = self.try_replace_substs_in_root(a) {
a
} else {
return true;
};
let b = if let Some(b) = self.try_replace_substs_in_root(b) {
b
} else {
return true;
};
let a_root = a.root(self.tcx);
let b_root = b.root(self.tcx);
debug!(?a_root, ?b_root);
match (a_root, b_root) {
(Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
let a_ct = a_ct.eval(self.tcx, self.param_env);
debug!("a_ct evaluated: {:?}", a_ct);
let b_ct = b_ct.eval(self.tcx, self.param_env);
debug!("b_ct evaluated: {:?}", b_ct);
if a_ct.ty() != b_ct.ty() {
return false;
}
match (a_ct.kind(), b_ct.kind()) {
// We can just unify errors with everything to reduce the amount of
// emitted errors here.
(ty::ConstKind::Error(_), _) | (_, ty::ConstKind::Error(_)) => true,
(ty::ConstKind::Param(a_param), ty::ConstKind::Param(b_param)) => {
a_param == b_param
}
(ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val,
// If we have `fn a<const N: usize>() -> [u8; N + 1]` and `fn b<const M: usize>() -> [u8; 1 + M]`
// we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This
// means that we only allow inference variables if they are equal.
(ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val,
// We expand generic anonymous constants at the start of this function, so this
// branch should only be taking when dealing with associated constants, at
// which point directly comparing them seems like the desired behavior.
//
// FIXME(generic_const_exprs): This isn't actually the case.
// We also take this branch for concrete anonymous constants and
// expand generic anonymous constants with concrete substs.
(ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => {
a_uv == b_uv
}
// FIXME(generic_const_exprs): We may want to either actually try
// to evaluate `a_ct` and `b_ct` if they are are fully concrete or something like
// this, for now we just return false here.
_ => false,
}
}
(Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => {
self.try_unify(a.subtree(al), b.subtree(bl))
&& self.try_unify(a.subtree(ar), b.subtree(br))
}
(Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => {
self.try_unify(a.subtree(av), b.subtree(bv))
}
(Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args))
if a_args.len() == b_args.len() =>
{
self.try_unify(a.subtree(a_f), b.subtree(b_f))
&& iter::zip(a_args, b_args)
.all(|(&an, &bn)| self.try_unify(a.subtree(an), b.subtree(bn)))
}
(Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty))
if (a_ty == b_ty) && (a_kind == b_kind) =>
{
self.try_unify(a.subtree(a_operand), b.subtree(b_operand))
}
// use this over `_ => false` to make adding variants to `Node` less error prone
(Node::Cast(..), _)
| (Node::FunctionCall(..), _)
| (Node::UnaryOp(..), _)
| (Node::Binop(..), _)
| (Node::Leaf(..), _) => false,
}
}
}
#[instrument(skip(tcx), level = "debug")]
pub fn try_unify_abstract_consts<'tcx>(
tcx: TyCtxt<'tcx>,
(a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>),
param_env: ty::ParamEnv<'tcx>,
) -> bool {
(|| {
if let Some(a) = AbstractConst::new(tcx, a)? {
if let Some(b) = AbstractConst::new(tcx, b)? {
let const_unify_ctxt = ConstUnifyCtxt { tcx, param_env };
return Ok(const_unify_ctxt.try_unify(a, b));
}
}
Ok(false)
})()
.unwrap_or_else(|_: ErrorGuaranteed| true)
// FIXME(generic_const_exprs): We should instead have this
// method return the resulting `ty::Const` and return `ConstKind::Error`
// on `ErrorGuaranteed`.
}
/// Check if a given constant can be evaluated.
#[instrument(skip(infcx), level = "debug")]
pub fn is_const_evaluatable<'cx, 'tcx>(
@ -36,33 +172,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
if satisfied_from_param_env(tcx, ct, param_env)? {
return Ok(());
}
let mut failure_kind = FailureKind::Concrete;
walk_abstract_const::<!, _>(tcx, ct, |node| match node.root(tcx) {
Node::Leaf(leaf) => {
if leaf.has_infer_types_or_consts() {
failure_kind = FailureKind::MentionsInfer;
} else if leaf.has_param_types_or_consts() {
failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
}
ControlFlow::CONTINUE
}
Node::Cast(_, _, ty) => {
if ty.has_infer_types_or_consts() {
failure_kind = FailureKind::MentionsInfer;
} else if ty.has_param_types_or_consts() {
failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
}
ControlFlow::CONTINUE
}
Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => {
ControlFlow::CONTINUE
}
});
match failure_kind {
match ct.unify_failure_kind(tcx) {
FailureKind::MentionsInfer => {
return Err(NotConstEvaluatable::MentionsInfer);
}

2
compiler/rustc_trait_selection/src/traits/mod.rs
View file

@ -847,7 +847,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
subst_and_check_impossible_predicates,
try_unify_abstract_consts: |tcx, param_env_and| {
let (param_env, (a, b)) = param_env_and.into_parts();
rustc_middle::ty::abstract_const::try_unify_abstract_consts(tcx, (a, b), param_env)
const_evaluatable::try_unify_abstract_consts(tcx, (a, b), param_env)
},
..*providers
};

4
compiler/rustc_ty_utils/src/consts.rs
View file

@ -218,7 +218,7 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
/// Builds the abstract const by walking the thir and bailing out when
/// encountering an unsupported operation.
pub fn build(mut self) -> Result<&'tcx [Node<'tcx>], ErrorGuaranteed> {
debug!("Abstractconstbuilder::build: body={:?}", &*self.body);
debug!("AbstractConstBuilder::build: body={:?}", &*self.body);
self.recurse_build(self.body_id)?;
for n in self.nodes.iter() {
@ -331,7 +331,7 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
// Skip reborrows for now until we allow Deref/Borrow/AddressOf
// expressions.
// FIXME(generic_const_exprs): Verify/explain why this is sound
if let ExprKind::Deref {arg} = arg_node.kind {
if let ExprKind::Deref { arg } = arg_node.kind {
self.recurse_build(arg)?
} else {
self.maybe_supported_error(

36
src/test/ui/const-generics/overlapping_impls.rs Normal file
View file

@ -0,0 +1,36 @@
// check-pass
#![allow(incomplete_features)]
#![feature(adt_const_params)]
#![feature(generic_const_exprs)]
use std::marker::PhantomData;
struct Foo<const I: i32, const J: i32> {}
const ONE: i32 = 1;
const TWO: i32 = 2;
impl<const I: i32> Foo<I, ONE> {
pub fn foo() {}
}
impl<const I: i32> Foo<I, TWO> {
pub fn foo() {}
}
pub struct Foo2<const P: Protocol, T> {
_marker: PhantomData<T>,
}
#[derive(PartialEq, Eq)]
pub enum Protocol {
Variant1,
Variant2,
}
pub trait Bar {}
impl<T> Bar for Foo2<{ Protocol::Variant1 }, T> {}
impl<T> Bar for Foo2<{ Protocol::Variant2 }, T> {}
fn main() {}