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Rollup merge of #99000 - JulianKnodt:allow_resolve_no_substs, r=lcnr

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Move abstract const to middle

Moves AbstractConst (and all associated methods) to rustc middle for use in `rustc_infer`.
This allows for const resolution in infer to use abstract consts to walk consts and check if
they are resolvable.

This attempts to resolve the issue where `Foo<{ concrete const }, generic T>` is incorrectly marked as conflicting, and is independent from the other issue where nested abstract consts must be resolved.

r? `@lcnr`
This commit is contained in:
Dylan DPC 2022-07-14 19:24:04 +05:30 committed by GitHub
commit ecae3d74e2
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GPG Key ID: 4AEE18F83AFDEB23
24 changed files with 800 additions and 751 deletions
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1
Cargo.lock
View File

@ -4514,6 +4514,7 @@ dependencies = [
"rustc_data_structures",
"rustc_errors",
"rustc_hir",
"rustc_index",
"rustc_infer",
"rustc_middle",
"rustc_session",

9
compiler/rustc_infer/src/infer/mod.rs
View File

@ -21,6 +21,7 @@
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;
@ -1651,15 +1652,19 @@ pub fn const_eval_resolve(
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);
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);
let substs_erased = self.tcx.erase_regions(substs);

3
compiler/rustc_metadata/src/rmeta/decoder.rs
View File

@ -21,7 +21,6 @@
use rustc_middle::metadata::ModChild;
use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
use rustc_middle::thir;
use rustc_middle::ty::codec::TyDecoder;
use rustc_middle::ty::fast_reject::SimplifiedType;
use rustc_middle::ty::GeneratorDiagnosticData;
@ -638,7 +637,7 @@ fn decode(decoder: &mut DecodeContext<'a, 'tcx>) -> Span {
}
}
impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for &'tcx [thir::abstract_const::Node<'tcx>] {
impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for &'tcx [ty::abstract_const::Node<'tcx>] {
fn decode(d: &mut DecodeContext<'a, 'tcx>) -> Self {
ty::codec::RefDecodable::decode(d)
}

3
compiler/rustc_metadata/src/rmeta/mod.rs
View File

@ -17,7 +17,6 @@
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
use rustc_middle::mir;
use rustc_middle::thir;
use rustc_middle::ty::fast_reject::SimplifiedType;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, ReprOptions, Ty};
@ -361,7 +360,7 @@ fn encode(&self, buf: &mut MemEncoder) -> LazyTables {
mir_for_ctfe: Table<DefIndex, LazyValue<mir::Body<'static>>>,
promoted_mir: Table<DefIndex, LazyValue<IndexVec<mir::Promoted, mir::Body<'static>>>>,
// FIXME(compiler-errors): Why isn't this a LazyArray?
thir_abstract_const: Table<DefIndex, LazyValue<&'static [thir::abstract_const::Node<'static>]>>,
thir_abstract_const: Table<DefIndex, LazyValue<&'static [ty::abstract_const::Node<'static>]>>,
impl_parent: Table<DefIndex, RawDefId>,
impl_polarity: Table<DefIndex, ty::ImplPolarity>,
constness: Table<DefIndex, hir::Constness>,

4
compiler/rustc_middle/src/query/mod.rs
View File

@ -351,7 +351,7 @@
/// Try to build an abstract representation of the given constant.
query thir_abstract_const(
key: DefId
) -> Result<Option<&'tcx [thir::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
) -> Result<Option<&'tcx [ty::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
desc {
|tcx| "building an abstract representation for {}", tcx.def_path_str(key),
}
@ -360,7 +360,7 @@
/// Try to build an abstract representation of the given constant.
query thir_abstract_const_of_const_arg(
key: (LocalDefId, DefId)
) -> Result<Option<&'tcx [thir::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
) -> Result<Option<&'tcx [ty::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
desc {
|tcx|
"building an abstract representation for the const argument {}",

1
compiler/rustc_middle/src/thir.rs
View File

@ -30,7 +30,6 @@
use std::fmt;
use std::ops::Index;
pub mod abstract_const;
pub mod visit;
newtype_index! {

61
compiler/rustc_middle/src/thir/abstract_const.rs
View File

@ -1,61 +0,0 @@
//! A subset of a mir body used for const evaluatability checking.
use crate::mir;
use crate::ty::{self, Ty, TyCtxt};
use rustc_errors::ErrorGuaranteed;
rustc_index::newtype_index! {
/// An index into an `AbstractConst`.
pub struct NodeId {
derive [HashStable]
DEBUG_FORMAT = "n{}",
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum CastKind {
/// thir::ExprKind::As
As,
/// thir::ExprKind::Use
Use,
}
/// A node of an `AbstractConst`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum Node<'tcx> {
Leaf(ty::Const<'tcx>),
Binop(mir::BinOp, NodeId, NodeId),
UnaryOp(mir::UnOp, NodeId),
FunctionCall(NodeId, &'tcx [NodeId]),
Cast(CastKind, NodeId, Ty<'tcx>),
}
#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum NotConstEvaluatable {
Error(ErrorGuaranteed),
MentionsInfer,
MentionsParam,
}
impl From<ErrorGuaranteed> for NotConstEvaluatable {
fn from(e: ErrorGuaranteed) -> NotConstEvaluatable {
NotConstEvaluatable::Error(e)
}
}
TrivialTypeTraversalAndLiftImpls! {
NotConstEvaluatable,
}
impl<'tcx> TyCtxt<'tcx> {
#[inline]
pub fn thir_abstract_const_opt_const_arg(
self,
def: ty::WithOptConstParam<rustc_hir::def_id::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))
} else {
self.thir_abstract_const(def.did)
}
}
}

2
compiler/rustc_middle/src/traits/mod.rs
View File

@ -10,7 +10,7 @@
pub mod util;
use crate::infer::canonical::Canonical;
use crate::thir::abstract_const::NotConstEvaluatable;
use crate::ty::abstract_const::NotConstEvaluatable;
use crate::ty::subst::SubstsRef;
use crate::ty::{self, AdtKind, Ty, TyCtxt};

194
compiler/rustc_middle/src/ty/abstract_const.rs Normal file
View File

@ -0,0 +1,194 @@
//! 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 rustc_hir::def_id::DefId;
use std::cmp;
use std::ops::ControlFlow;
rustc_index::newtype_index! {
/// An index into an `AbstractConst`.
pub struct NodeId {
derive [HashStable]
DEBUG_FORMAT = "n{}",
}
}
/// A tree representing an anonymous constant.
///
/// This is only able to represent a subset of `MIR`,
/// and should not leak any information about desugarings.
#[derive(Debug, Clone, Copy)]
pub struct AbstractConst<'tcx> {
// FIXME: Consider adding something like `IndexSlice`
// and use this here.
inner: &'tcx [Node<'tcx>],
substs: SubstsRef<'tcx>,
}
impl<'tcx> AbstractConst<'tcx> {
pub fn new(
tcx: TyCtxt<'tcx>,
uv: ty::Unevaluated<'tcx, ()>,
) -> Result<Option<AbstractConst<'tcx>>, ErrorGuaranteed> {
let inner = tcx.thir_abstract_const_opt_const_arg(uv.def)?;
debug!("AbstractConst::new({:?}) = {:?}", uv, inner);
Ok(inner.map(|inner| AbstractConst { inner, substs: tcx.erase_regions(uv.substs) }))
}
pub fn from_const(
tcx: TyCtxt<'tcx>,
ct: ty::Const<'tcx>,
) -> Result<Option<AbstractConst<'tcx>>, ErrorGuaranteed> {
match ct.kind() {
ty::ConstKind::Unevaluated(uv) => AbstractConst::new(tcx, uv.shrink()),
ty::ConstKind::Error(DelaySpanBugEmitted { reported, .. }) => Err(reported),
_ => Ok(None),
}
}
#[inline]
pub fn subtree(self, node: NodeId) -> AbstractConst<'tcx> {
AbstractConst { inner: &self.inner[..=node.index()], substs: self.substs }
}
#[inline]
pub fn root(self, tcx: TyCtxt<'tcx>) -> Node<'tcx> {
let node = self.inner.last().copied().unwrap();
match node {
Node::Leaf(leaf) => Node::Leaf(EarlyBinder(leaf).subst(tcx, self.substs)),
Node::Cast(kind, operand, ty) => {
Node::Cast(kind, operand, EarlyBinder(ty).subst(tcx, self.substs))
}
// Don't perform substitution on the following as they can't directly contain generic params
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)]
pub enum CastKind {
/// thir::ExprKind::As
As,
/// thir::ExprKind::Use
Use,
}
/// A node of an `AbstractConst`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum Node<'tcx> {
Leaf(ty::Const<'tcx>),
Binop(mir::BinOp, NodeId, NodeId),
UnaryOp(mir::UnOp, NodeId),
FunctionCall(NodeId, &'tcx [NodeId]),
Cast(CastKind, NodeId, Ty<'tcx>),
}
#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum NotConstEvaluatable {
Error(ErrorGuaranteed),
MentionsInfer,
MentionsParam,
}
impl From<ErrorGuaranteed> for NotConstEvaluatable {
fn from(e: ErrorGuaranteed) -> NotConstEvaluatable {
NotConstEvaluatable::Error(e)
}
}
TrivialTypeTraversalAndLiftImpls! {
NotConstEvaluatable,
}
impl<'tcx> TyCtxt<'tcx> {
#[inline]
pub fn thir_abstract_const_opt_const_arg(
self,
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))
} else {
self.thir_abstract_const(def.did)
}
}
}
#[instrument(skip(tcx, f), level = "debug")]
pub fn walk_abstract_const<'tcx, R, F>(
tcx: TyCtxt<'tcx>,
ct: AbstractConst<'tcx>,
mut f: F,
) -> ControlFlow<R>
where
F: FnMut(AbstractConst<'tcx>) -> ControlFlow<R>,
{
#[instrument(skip(tcx, f), level = "debug")]
fn recurse<'tcx, R>(
tcx: TyCtxt<'tcx>,
ct: AbstractConst<'tcx>,
f: &mut dyn FnMut(AbstractConst<'tcx>) -> ControlFlow<R>,
) -> ControlFlow<R> {
f(ct)?;
let root = ct.root(tcx);
debug!(?root);
match root {
Node::Leaf(_) => ControlFlow::CONTINUE,
Node::Binop(_, l, r) => {
recurse(tcx, ct.subtree(l), f)?;
recurse(tcx, ct.subtree(r), f)
}
Node::UnaryOp(_, v) => recurse(tcx, ct.subtree(v), f),
Node::FunctionCall(func, args) => {
recurse(tcx, ct.subtree(func), f)?;
args.iter().try_for_each(|&arg| recurse(tcx, ct.subtree(arg), f))
}
Node::Cast(_, operand, _) => recurse(tcx, ct.subtree(operand), f),
}
}
recurse(tcx, ct, &mut f)
}
// We were unable to unify the abstract constant with
// a constant found in the caller bounds, there are
// now three possible cases here.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum FailureKind {
/// The abstract const still references an inference
/// variable, in this case we return `TooGeneric`.
MentionsInfer,
/// The abstract const references a generic parameter,
/// this means that we emit an error here.
MentionsParam,
/// The substs are concrete enough that we can simply
/// try and evaluate the given constant.
Concrete,
}

5
compiler/rustc_middle/src/ty/codec.rs
View File

@ -12,7 +12,6 @@
self,
interpret::{AllocId, ConstAllocation},
};
use crate::thir;
use crate::traits;
use crate::ty::subst::SubstsRef;
use crate::ty::{self, AdtDef, Ty};
@ -346,7 +345,7 @@ fn decode(decoder: &mut D) -> &'tcx Self {
}
impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
for [thir::abstract_const::Node<'tcx>]
for [ty::abstract_const::Node<'tcx>]
{
fn decode(decoder: &mut D) -> &'tcx Self {
decoder.interner().arena.alloc_from_iter(
@ -356,7 +355,7 @@ fn decode(decoder: &mut D) -> &'tcx Self {
}
impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
for [thir::abstract_const::NodeId]
for [ty::abstract_const::NodeId]
{
fn decode(decoder: &mut D) -> &'tcx Self {
decoder.interner().arena.alloc_from_iter(

1
compiler/rustc_middle/src/ty/mod.rs
View File

@ -92,6 +92,7 @@
pub use self::trait_def::TraitDef;
pub mod _match;
pub mod abstract_const;
pub mod adjustment;
pub mod binding;
pub mod cast;

2
compiler/rustc_middle/src/ty/parameterized.rs
View File

@ -3,7 +3,7 @@
use crate::middle::exported_symbols::ExportedSymbol;
use crate::mir::Body;
use crate::thir::abstract_const::Node;
use crate::ty::abstract_const::Node;
use crate::ty::{
self, Const, FnSig, GeneratorDiagnosticData, GenericPredicates, Predicate, TraitRef, Ty,
};

5
compiler/rustc_privacy/src/lib.rs
View File

@ -23,7 +23,7 @@
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::privacy::{AccessLevel, AccessLevels};
use rustc_middle::span_bug;
use rustc_middle::thir::abstract_const::Node as ACNode;
use rustc_middle::ty::abstract_const::{walk_abstract_const, AbstractConst, Node as ACNode};
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::subst::InternalSubsts;
use rustc_middle::ty::{self, Const, DefIdTree, GenericParamDefKind};
@ -32,7 +32,6 @@
use rustc_span::hygiene::Transparency;
use rustc_span::symbol::{kw, Ident};
use rustc_span::Span;
use rustc_trait_selection::traits::const_evaluatable::{self, AbstractConst};
use std::marker::PhantomData;
use std::ops::ControlFlow;
@ -164,7 +163,7 @@ fn visit_abstract_const_expr(
tcx: TyCtxt<'tcx>,
ct: AbstractConst<'tcx>,
) -> ControlFlow<V::BreakTy> {
const_evaluatable::walk_abstract_const(tcx, ct, |node| match node.root(tcx) {
walk_abstract_const(tcx, ct, |node| match node.root(tcx) {
ACNode::Leaf(leaf) => self.visit_const(leaf),
ACNode::Cast(_, _, ty) => self.visit_ty(ty),
ACNode::Binop(..) | ACNode::UnaryOp(..) | ACNode::FunctionCall(_, _) => {

3
compiler/rustc_query_impl/src/on_disk_cache.rs
View File

@ -9,7 +9,6 @@
use rustc_middle::dep_graph::{DepNodeIndex, SerializedDepNodeIndex};
use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
use rustc_middle::mir::{self, interpret};
use rustc_middle::thir;
use rustc_middle::ty::codec::{RefDecodable, TyDecoder, TyEncoder};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_query_system::dep_graph::DepContext;
@ -766,7 +765,7 @@ fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
}
}
impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [thir::abstract_const::Node<'tcx>] {
impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [ty::abstract_const::Node<'tcx>] {
fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
RefDecodable::decode(d)
}

782
compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
View File

@ -10,22 +10,153 @@
//! generic constants mentioned in the `caller_bounds` of the current environment.
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_index::vec::IndexVec;
use rustc_infer::infer::InferCtxt;
use rustc_middle::mir;
use rustc_middle::mir::interpret::{ErrorHandled, LitToConstError, LitToConstInput};
use rustc_middle::thir;
use rustc_middle::thir::abstract_const::{self, Node, NodeId, NotConstEvaluatable};
use rustc_middle::ty::subst::{Subst, SubstsRef};
use rustc_middle::ty::{self, DelaySpanBugEmitted, EarlyBinder, TyCtxt, TypeVisitable};
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::abstract_const::{
walk_abstract_const, AbstractConst, FailureKind, Node, NotConstEvaluatable,
};
use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
use rustc_session::lint;
use rustc_span::def_id::LocalDefId;
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>(
@ -41,48 +172,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
if satisfied_from_param_env(tcx, ct, param_env)? {
return Ok(());
}
// We were unable to unify the abstract constant with
// a constant found in the caller bounds, there are
// now three possible cases here.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
enum FailureKind {
/// The abstract const still references an inference
/// variable, in this case we return `TooGeneric`.
MentionsInfer,
/// The abstract const references a generic parameter,
/// this means that we emit an error here.
MentionsParam,
/// The substs are concrete enough that we can simply
/// try and evaluate the given constant.
Concrete,
}
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);
}
@ -216,593 +306,3 @@ fn satisfied_from_param_env<'tcx>(
Ok(false)
}
/// A tree representing an anonymous constant.
///
/// This is only able to represent a subset of `MIR`,
/// and should not leak any information about desugarings.
#[derive(Debug, Clone, Copy)]
pub struct AbstractConst<'tcx> {
// FIXME: Consider adding something like `IndexSlice`
// and use this here.
inner: &'tcx [Node<'tcx>],
substs: SubstsRef<'tcx>,
}
impl<'tcx> AbstractConst<'tcx> {
pub fn new(
tcx: TyCtxt<'tcx>,
uv: ty::Unevaluated<'tcx, ()>,
) -> Result<Option<AbstractConst<'tcx>>, ErrorGuaranteed> {
let inner = tcx.thir_abstract_const_opt_const_arg(uv.def)?;
debug!("AbstractConst::new({:?}) = {:?}", uv, inner);
Ok(inner.map(|inner| AbstractConst { inner, substs: tcx.erase_regions(uv.substs) }))
}
pub fn from_const(
tcx: TyCtxt<'tcx>,
ct: ty::Const<'tcx>,
) -> Result<Option<AbstractConst<'tcx>>, ErrorGuaranteed> {
match ct.kind() {
ty::ConstKind::Unevaluated(uv) => AbstractConst::new(tcx, uv.shrink()),
ty::ConstKind::Error(DelaySpanBugEmitted { reported, .. }) => Err(reported),
_ => Ok(None),
}
}
#[inline]
pub fn subtree(self, node: NodeId) -> AbstractConst<'tcx> {
AbstractConst { inner: &self.inner[..=node.index()], substs: self.substs }
}
#[inline]
pub fn root(self, tcx: TyCtxt<'tcx>) -> Node<'tcx> {
let node = self.inner.last().copied().unwrap();
match node {
Node::Leaf(leaf) => Node::Leaf(EarlyBinder(leaf).subst(tcx, self.substs)),
Node::Cast(kind, operand, ty) => {
Node::Cast(kind, operand, EarlyBinder(ty).subst(tcx, self.substs))
}
// Don't perform substitution on the following as they can't directly contain generic params
Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => node,
}
}
}
struct AbstractConstBuilder<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
body_id: thir::ExprId,
body: &'a thir::Thir<'tcx>,
/// The current WIP node tree.
nodes: IndexVec<NodeId, Node<'tcx>>,
}
impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
fn root_span(&self) -> Span {
self.body.exprs[self.body_id].span
}
fn error(&mut self, span: Span, msg: &str) -> Result<!, ErrorGuaranteed> {
let reported = self
.tcx
.sess
.struct_span_err(self.root_span(), "overly complex generic constant")
.span_label(span, msg)
.help("consider moving this anonymous constant into a `const` function")
.emit();
Err(reported)
}
fn maybe_supported_error(&mut self, span: Span, msg: &str) -> Result<!, ErrorGuaranteed> {
let reported = self
.tcx
.sess
.struct_span_err(self.root_span(), "overly complex generic constant")
.span_label(span, msg)
.help("consider moving this anonymous constant into a `const` function")
.note("this operation may be supported in the future")
.emit();
Err(reported)
}
#[instrument(skip(tcx, body, body_id), level = "debug")]
fn new(
tcx: TyCtxt<'tcx>,
(body, body_id): (&'a thir::Thir<'tcx>, thir::ExprId),
) -> Result<Option<AbstractConstBuilder<'a, 'tcx>>, ErrorGuaranteed> {
let builder = AbstractConstBuilder { tcx, body_id, body, nodes: IndexVec::new() };
struct IsThirPolymorphic<'a, 'tcx> {
is_poly: bool,
thir: &'a thir::Thir<'tcx>,
}
use crate::rustc_middle::thir::visit::Visitor;
use thir::visit;
impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
fn expr_is_poly(&mut self, expr: &thir::Expr<'tcx>) -> bool {
if expr.ty.has_param_types_or_consts() {
return true;
}
match expr.kind {
thir::ExprKind::NamedConst { substs, .. } => substs.has_param_types_or_consts(),
thir::ExprKind::ConstParam { .. } => true,
thir::ExprKind::Repeat { value, count } => {
self.visit_expr(&self.thir()[value]);
count.has_param_types_or_consts()
}
_ => false,
}
}
fn pat_is_poly(&mut self, pat: &thir::Pat<'tcx>) -> bool {
if pat.ty.has_param_types_or_consts() {
return true;
}
match pat.kind.as_ref() {
thir::PatKind::Constant { value } => value.has_param_types_or_consts(),
thir::PatKind::Range(thir::PatRange { lo, hi, .. }) => {
lo.has_param_types_or_consts() || hi.has_param_types_or_consts()
}
_ => false,
}
}
}
impl<'a, 'tcx> visit::Visitor<'a, 'tcx> for IsThirPolymorphic<'a, 'tcx> {
fn thir(&self) -> &'a thir::Thir<'tcx> {
&self.thir
}
#[instrument(skip(self), level = "debug")]
fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) {
self.is_poly |= self.expr_is_poly(expr);
if !self.is_poly {
visit::walk_expr(self, expr)
}
}
#[instrument(skip(self), level = "debug")]
fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) {
self.is_poly |= self.pat_is_poly(pat);
if !self.is_poly {
visit::walk_pat(self, pat);
}
}
}
let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body };
visit::walk_expr(&mut is_poly_vis, &body[body_id]);
debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly);
if !is_poly_vis.is_poly {
return Ok(None);
}
Ok(Some(builder))
}
/// We do not allow all binary operations in abstract consts, so filter disallowed ones.
fn check_binop(op: mir::BinOp) -> bool {
use mir::BinOp::*;
match op {
Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Shl | Shr | Eq | Lt | Le
| Ne | Ge | Gt => true,
Offset => false,
}
}
/// While we currently allow all unary operations, we still want to explicitly guard against
/// future changes here.
fn check_unop(op: mir::UnOp) -> bool {
use mir::UnOp::*;
match op {
Not | Neg => true,
}
}
/// Builds the abstract const by walking the thir and bailing out when
/// encountering an unsupported operation.
fn build(mut self) -> Result<&'tcx [Node<'tcx>], ErrorGuaranteed> {
debug!("Abstractconstbuilder::build: body={:?}", &*self.body);
self.recurse_build(self.body_id)?;
for n in self.nodes.iter() {
if let Node::Leaf(ct) = n {
if let ty::ConstKind::Unevaluated(ct) = ct.kind() {
// `AbstractConst`s should not contain any promoteds as they require references which
// are not allowed.
assert_eq!(ct.promoted, None);
assert_eq!(ct, self.tcx.erase_regions(ct));
}
}
}
Ok(self.tcx.arena.alloc_from_iter(self.nodes.into_iter()))
}
fn recurse_build(&mut self, node: thir::ExprId) -> Result<NodeId, ErrorGuaranteed> {
use thir::ExprKind;
let node = &self.body.exprs[node];
Ok(match &node.kind {
// I dont know if handling of these 3 is correct
&ExprKind::Scope { value, .. } => self.recurse_build(value)?,
&ExprKind::PlaceTypeAscription { source, .. }
| &ExprKind::ValueTypeAscription { source, .. } => self.recurse_build(source)?,
&ExprKind::Literal { lit, neg} => {
let sp = node.span;
let constant =
match self.tcx.at(sp).lit_to_const(LitToConstInput { lit: &lit.node, ty: node.ty, neg }) {
Ok(c) => c,
Err(LitToConstError::Reported) => {
self.tcx.const_error(node.ty)
}
Err(LitToConstError::TypeError) => {
bug!("encountered type error in lit_to_const")
}
};
self.nodes.push(Node::Leaf(constant))
}
&ExprKind::NonHirLiteral { lit , user_ty: _} => {
let val = ty::ValTree::from_scalar_int(lit);
self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty)))
}
&ExprKind::ZstLiteral { user_ty: _ } => {
let val = ty::ValTree::zst();
self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty)))
}
&ExprKind::NamedConst { def_id, substs, user_ty: _ } => {
let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs);
let constant = self.tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Unevaluated(uneval),
ty: node.ty,
});
self.nodes.push(Node::Leaf(constant))
}
ExprKind::ConstParam {param, ..} => {
let const_param = self.tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Param(*param),
ty: node.ty,
});
self.nodes.push(Node::Leaf(const_param))
}
ExprKind::Call { fun, args, .. } => {
let fun = self.recurse_build(*fun)?;
let mut new_args = Vec::<NodeId>::with_capacity(args.len());
for &id in args.iter() {
new_args.push(self.recurse_build(id)?);
}
let new_args = self.tcx.arena.alloc_slice(&new_args);
self.nodes.push(Node::FunctionCall(fun, new_args))
}
&ExprKind::Binary { op, lhs, rhs } if Self::check_binop(op) => {
let lhs = self.recurse_build(lhs)?;
let rhs = self.recurse_build(rhs)?;
self.nodes.push(Node::Binop(op, lhs, rhs))
}
&ExprKind::Unary { op, arg } if Self::check_unop(op) => {
let arg = self.recurse_build(arg)?;
self.nodes.push(Node::UnaryOp(op, arg))
}
// This is necessary so that the following compiles:
//
// ```
// fn foo<const N: usize>(a: [(); N + 1]) {
// bar::<{ N + 1 }>();
// }
// ```
ExprKind::Block { body: thir::Block { stmts: box [], expr: Some(e), .. } } => {
self.recurse_build(*e)?
}
// `ExprKind::Use` happens when a `hir::ExprKind::Cast` is a
// "coercion cast" i.e. using a coercion or is a no-op.
// This is important so that `N as usize as usize` doesnt unify with `N as usize`. (untested)
&ExprKind::Use { source } => {
let arg = self.recurse_build(source)?;
self.nodes.push(Node::Cast(abstract_const::CastKind::Use, arg, node.ty))
}
&ExprKind::Cast { source } => {
let arg = self.recurse_build(source)?;
self.nodes.push(Node::Cast(abstract_const::CastKind::As, arg, node.ty))
}
ExprKind::Borrow{ arg, ..} => {
let arg_node = &self.body.exprs[*arg];
// 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 {
self.recurse_build(arg)?
} else {
self.maybe_supported_error(
node.span,
"borrowing is not supported in generic constants",
)?
}
}
// FIXME(generic_const_exprs): We may want to support these.
ExprKind::AddressOf { .. } | ExprKind::Deref {..}=> self.maybe_supported_error(
node.span,
"dereferencing or taking the address is not supported in generic constants",
)?,
ExprKind::Repeat { .. } | ExprKind::Array { .. } => self.maybe_supported_error(
node.span,
"array construction is not supported in generic constants",
)?,
ExprKind::Block { .. } => self.maybe_supported_error(
node.span,
"blocks are not supported in generic constant",
)?,
ExprKind::NeverToAny { .. } => self.maybe_supported_error(
node.span,
"converting nevers to any is not supported in generic constant",
)?,
ExprKind::Tuple { .. } => self.maybe_supported_error(
node.span,
"tuple construction is not supported in generic constants",
)?,
ExprKind::Index { .. } => self.maybe_supported_error(
node.span,
"indexing is not supported in generic constant",
)?,
ExprKind::Field { .. } => self.maybe_supported_error(
node.span,
"field access is not supported in generic constant",
)?,
ExprKind::ConstBlock { .. } => self.maybe_supported_error(
node.span,
"const blocks are not supported in generic constant",
)?,
ExprKind::Adt(_) => self.maybe_supported_error(
node.span,
"struct/enum construction is not supported in generic constants",
)?,
// dont know if this is correct
ExprKind::Pointer { .. } =>
self.error(node.span, "pointer casts are not allowed in generic constants")?,
ExprKind::Yield { .. } =>
self.error(node.span, "generator control flow is not allowed in generic constants")?,
ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Loop { .. } => self
.error(
node.span,
"loops and loop control flow are not supported in generic constants",
)?,
ExprKind::Box { .. } =>
self.error(node.span, "allocations are not allowed in generic constants")?,
ExprKind::Unary { .. } => unreachable!(),
// we handle valid unary/binary ops above
ExprKind::Binary { .. } =>
self.error(node.span, "unsupported binary operation in generic constants")?,
ExprKind::LogicalOp { .. } =>
self.error(node.span, "unsupported operation in generic constants, short-circuiting operations would imply control flow")?,
ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => {
self.error(node.span, "assignment is not supported in generic constants")?
}
ExprKind::Closure { .. } | ExprKind::Return { .. } => self.error(
node.span,
"closures and function keywords are not supported in generic constants",
)?,
// let expressions imply control flow
ExprKind::Match { .. } | ExprKind::If { .. } | ExprKind::Let { .. } =>
self.error(node.span, "control flow is not supported in generic constants")?,
ExprKind::InlineAsm { .. } => {
self.error(node.span, "assembly is not supported in generic constants")?
}
// we dont permit let stmts so `VarRef` and `UpvarRef` cant happen
ExprKind::VarRef { .. }
| ExprKind::UpvarRef { .. }
| ExprKind::StaticRef { .. }
| ExprKind::ThreadLocalRef(_) => {
self.error(node.span, "unsupported operation in generic constant")?
}
})
}
}
/// Builds an abstract const, do not use this directly, but use `AbstractConst::new` instead.
pub(super) fn thir_abstract_const<'tcx>(
tcx: TyCtxt<'tcx>,
def: ty::WithOptConstParam<LocalDefId>,
) -> Result<Option<&'tcx [thir::abstract_const::Node<'tcx>]>, ErrorGuaranteed> {
if tcx.features().generic_const_exprs {
match tcx.def_kind(def.did) {
// FIXME(generic_const_exprs): We currently only do this for anonymous constants,
// meaning that we do not look into associated constants. I(@lcnr) am not yet sure whether
// we want to look into them or treat them as opaque projections.
//
// Right now we do neither of that and simply always fail to unify them.
DefKind::AnonConst | DefKind::InlineConst => (),
_ => return Ok(None),
}
let body = tcx.thir_body(def)?;
AbstractConstBuilder::new(tcx, (&*body.0.borrow(), body.1))?
.map(AbstractConstBuilder::build)
.transpose()
} else {
Ok(None)
}
}
#[instrument(skip(tcx), level = "debug")]
pub(super) 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>,
ct: AbstractConst<'tcx>,
mut f: F,
) -> ControlFlow<R>
where
F: FnMut(AbstractConst<'tcx>) -> ControlFlow<R>,
{
#[instrument(skip(tcx, f), level = "debug")]
fn recurse<'tcx, R>(
tcx: TyCtxt<'tcx>,
ct: AbstractConst<'tcx>,
f: &mut dyn FnMut(AbstractConst<'tcx>) -> ControlFlow<R>,
) -> ControlFlow<R> {
f(ct)?;
let root = ct.root(tcx);
debug!(?root);
match root {
Node::Leaf(_) => ControlFlow::CONTINUE,
Node::Binop(_, l, r) => {
recurse(tcx, ct.subtree(l), f)?;
recurse(tcx, ct.subtree(r), f)
}
Node::UnaryOp(_, v) => recurse(tcx, ct.subtree(v), f),
Node::FunctionCall(func, args) => {
recurse(tcx, ct.subtree(func), f)?;
args.iter().try_for_each(|&arg| recurse(tcx, ct.subtree(arg), f))
}
Node::Cast(_, operand, _) => recurse(tcx, ct.subtree(operand), f),
}
}
recurse(tcx, ct, &mut f)
}
struct ConstUnifyCtxt<'tcx> {
tcx: TyCtxt<'tcx>,
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")]
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,
}
}
}

2
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View File

@ -24,8 +24,8 @@
use rustc_hir::Node;
use rustc_infer::infer::error_reporting::same_type_modulo_infer;
use rustc_infer::traits::{AmbiguousSelection, TraitEngine};
use rustc_middle::thir::abstract_const::NotConstEvaluatable;
use rustc_middle::traits::select::OverflowError;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::error::ExpectedFound;
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::{

2
compiler/rustc_trait_selection/src/traits/fulfill.rs
View File

@ -6,7 +6,7 @@
use rustc_infer::traits::ProjectionCacheKey;
use rustc_infer::traits::{SelectionError, TraitEngine, TraitEngineExt as _, TraitObligation};
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::thir::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::ToPredicate;

14
compiler/rustc_trait_selection/src/traits/mod.rs
View File

@ -845,20 +845,6 @@ pub fn provide(providers: &mut ty::query::Providers) {
vtable_entries,
vtable_trait_upcasting_coercion_new_vptr_slot,
subst_and_check_impossible_predicates,
thir_abstract_const: |tcx, def_id| {
let def_id = def_id.expect_local();
if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
tcx.thir_abstract_const_of_const_arg(def)
} else {
const_evaluatable::thir_abstract_const(tcx, ty::WithOptConstParam::unknown(def_id))
}
},
thir_abstract_const_of_const_arg: |tcx, (did, param_did)| {
const_evaluatable::thir_abstract_const(
tcx,
ty::WithOptConstParam { did, const_param_did: Some(param_did) },
)
},
try_unify_abstract_consts: |tcx, param_env_and| {
let (param_env, (a, b)) = param_env_and.into_parts();
const_evaluatable::try_unify_abstract_consts(tcx, (a, b), param_env)

8
compiler/rustc_trait_selection/src/traits/object_safety.rs
View File

@ -11,12 +11,12 @@
use super::elaborate_predicates;
use crate::infer::TyCtxtInferExt;
use crate::traits::const_evaluatable::{self, AbstractConst};
use crate::traits::query::evaluate_obligation::InferCtxtExt;
use crate::traits::{self, Obligation, ObligationCause};
use rustc_errors::{FatalError, MultiSpan};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_middle::ty::abstract_const::{walk_abstract_const, AbstractConst};
use rustc_middle::ty::subst::{GenericArg, InternalSubsts, Subst};
use rustc_middle::ty::{
self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
@ -841,16 +841,14 @@ fn visit_unevaluated(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::
//
// This shouldn't really matter though as we can't really use any
// constants which are not considered const evaluatable.
use rustc_middle::thir::abstract_const::Node;
use rustc_middle::ty::abstract_const::Node;
if let Ok(Some(ct)) = AbstractConst::new(self.tcx, uv.shrink()) {
const_evaluatable::walk_abstract_const(self.tcx, ct, |node| {
match node.root(self.tcx) {
walk_abstract_const(self.tcx, ct, |node| match node.root(self.tcx) {
Node::Leaf(leaf) => self.visit_const(leaf),
Node::Cast(_, _, ty) => self.visit_ty(ty),
Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => {
ControlFlow::CONTINUE
}
}
})
} else {
ControlFlow::CONTINUE

2
compiler/rustc_trait_selection/src/traits/select/mod.rs
View File

@ -32,7 +32,7 @@
use rustc_infer::infer::LateBoundRegionConversionTime;
use rustc_middle::dep_graph::{DepKind, DepNodeIndex};
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::thir::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::print::with_no_trimmed_paths;

1
compiler/rustc_ty_utils/Cargo.toml
View File

@ -15,3 +15,4 @@ rustc_session = { path = "../rustc_session" }
rustc_target = { path = "../rustc_target" }
rustc_trait_selection = { path = "../rustc_trait_selection" }
rustc_type_ir = { path = "../rustc_type_ir" }
rustc_index = { path = "../rustc_index" }

398
compiler/rustc_ty_utils/src/consts.rs
View File

@ -1,4 +1,12 @@
use rustc_middle::ty::{self, TyCtxt};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::LocalDefId;
use rustc_index::vec::IndexVec;
use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
use rustc_middle::ty::abstract_const::{CastKind, Node, NodeId};
use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
use rustc_middle::{mir, thir};
use rustc_span::Span;
use rustc_target::abi::VariantIdx;
use std::iter;
@ -72,6 +80,390 @@ pub(crate) fn destructure_const<'tcx>(
ty::DestructuredConst { variant, fields }
}
pub fn provide(providers: &mut ty::query::Providers) {
*providers = ty::query::Providers { destructure_const, ..*providers };
pub struct AbstractConstBuilder<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
body_id: thir::ExprId,
body: &'a thir::Thir<'tcx>,
/// The current WIP node tree.
nodes: IndexVec<NodeId, Node<'tcx>>,
}
impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
fn root_span(&self) -> Span {
self.body.exprs[self.body_id].span
}
fn error(&mut self, span: Span, msg: &str) -> Result<!, ErrorGuaranteed> {
let reported = self
.tcx
.sess
.struct_span_err(self.root_span(), "overly complex generic constant")
.span_label(span, msg)
.help("consider moving this anonymous constant into a `const` function")
.emit();
Err(reported)
}
fn maybe_supported_error(&mut self, span: Span, msg: &str) -> Result<!, ErrorGuaranteed> {
let reported = self
.tcx
.sess
.struct_span_err(self.root_span(), "overly complex generic constant")
.span_label(span, msg)
.help("consider moving this anonymous constant into a `const` function")
.note("this operation may be supported in the future")
.emit();
Err(reported)
}
#[instrument(skip(tcx, body, body_id), level = "debug")]
pub fn new(
tcx: TyCtxt<'tcx>,
(body, body_id): (&'a thir::Thir<'tcx>, thir::ExprId),
) -> Result<Option<AbstractConstBuilder<'a, 'tcx>>, ErrorGuaranteed> {
let builder = AbstractConstBuilder { tcx, body_id, body, nodes: IndexVec::new() };
struct IsThirPolymorphic<'a, 'tcx> {
is_poly: bool,
thir: &'a thir::Thir<'tcx>,
}
use crate::rustc_middle::thir::visit::Visitor;
use thir::visit;
impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
fn expr_is_poly(&mut self, expr: &thir::Expr<'tcx>) -> bool {
if expr.ty.has_param_types_or_consts() {
return true;
}
match expr.kind {
thir::ExprKind::NamedConst { substs, .. } => substs.has_param_types_or_consts(),
thir::ExprKind::ConstParam { .. } => true,
thir::ExprKind::Repeat { value, count } => {
self.visit_expr(&self.thir()[value]);
count.has_param_types_or_consts()
}
_ => false,
}
}
fn pat_is_poly(&mut self, pat: &thir::Pat<'tcx>) -> bool {
if pat.ty.has_param_types_or_consts() {
return true;
}
match pat.kind.as_ref() {
thir::PatKind::Constant { value } => value.has_param_types_or_consts(),
thir::PatKind::Range(thir::PatRange { lo, hi, .. }) => {
lo.has_param_types_or_consts() || hi.has_param_types_or_consts()
}
_ => false,
}
}
}
impl<'a, 'tcx> visit::Visitor<'a, 'tcx> for IsThirPolymorphic<'a, 'tcx> {
fn thir(&self) -> &'a thir::Thir<'tcx> {
&self.thir
}
#[instrument(skip(self), level = "debug")]
fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) {
self.is_poly |= self.expr_is_poly(expr);
if !self.is_poly {
visit::walk_expr(self, expr)
}
}
#[instrument(skip(self), level = "debug")]
fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) {
self.is_poly |= self.pat_is_poly(pat);
if !self.is_poly {
visit::walk_pat(self, pat);
}
}
}
let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body };
visit::walk_expr(&mut is_poly_vis, &body[body_id]);
debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly);
if !is_poly_vis.is_poly {
return Ok(None);
}
Ok(Some(builder))
}
/// We do not allow all binary operations in abstract consts, so filter disallowed ones.
fn check_binop(op: mir::BinOp) -> bool {
use mir::BinOp::*;
match op {
Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Shl | Shr | Eq | Lt | Le
| Ne | Ge | Gt => true,
Offset => false,
}
}
/// While we currently allow all unary operations, we still want to explicitly guard against
/// future changes here.
fn check_unop(op: mir::UnOp) -> bool {
use mir::UnOp::*;
match op {
Not | Neg => true,
}
}
/// 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);
self.recurse_build(self.body_id)?;
for n in self.nodes.iter() {
if let Node::Leaf(ct) = n {
if let ty::ConstKind::Unevaluated(ct) = ct.kind() {
// `AbstractConst`s should not contain any promoteds as they require references which
// are not allowed.
assert_eq!(ct.promoted, None);
assert_eq!(ct, self.tcx.erase_regions(ct));
}
}
}
Ok(self.tcx.arena.alloc_from_iter(self.nodes.into_iter()))
}
fn recurse_build(&mut self, node: thir::ExprId) -> Result<NodeId, ErrorGuaranteed> {
use thir::ExprKind;
let node = &self.body.exprs[node];
Ok(match &node.kind {
// I dont know if handling of these 3 is correct
&ExprKind::Scope { value, .. } => self.recurse_build(value)?,
&ExprKind::PlaceTypeAscription { source, .. }
| &ExprKind::ValueTypeAscription { source, .. } => self.recurse_build(source)?,
&ExprKind::Literal { lit, neg} => {
let sp = node.span;
let constant =
match self.tcx.at(sp).lit_to_const(LitToConstInput { lit: &lit.node, ty: node.ty, neg }) {
Ok(c) => c,
Err(LitToConstError::Reported) => {
self.tcx.const_error(node.ty)
}
Err(LitToConstError::TypeError) => {
bug!("encountered type error in lit_to_const")
}
};
self.nodes.push(Node::Leaf(constant))
}
&ExprKind::NonHirLiteral { lit , user_ty: _} => {
let val = ty::ValTree::from_scalar_int(lit);
self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty)))
}
&ExprKind::ZstLiteral { user_ty: _ } => {
let val = ty::ValTree::zst();
self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty)))
}
&ExprKind::NamedConst { def_id, substs, user_ty: _ } => {
let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs);
let constant = self.tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Unevaluated(uneval),
ty: node.ty,
});
self.nodes.push(Node::Leaf(constant))
}
ExprKind::ConstParam {param, ..} => {
let const_param = self.tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Param(*param),
ty: node.ty,
});
self.nodes.push(Node::Leaf(const_param))
}
ExprKind::Call { fun, args, .. } => {
let fun = self.recurse_build(*fun)?;
let mut new_args = Vec::<NodeId>::with_capacity(args.len());
for &id in args.iter() {
new_args.push(self.recurse_build(id)?);
}
let new_args = self.tcx.arena.alloc_slice(&new_args);
self.nodes.push(Node::FunctionCall(fun, new_args))
}
&ExprKind::Binary { op, lhs, rhs } if Self::check_binop(op) => {
let lhs = self.recurse_build(lhs)?;
let rhs = self.recurse_build(rhs)?;
self.nodes.push(Node::Binop(op, lhs, rhs))
}
&ExprKind::Unary { op, arg } if Self::check_unop(op) => {
let arg = self.recurse_build(arg)?;
self.nodes.push(Node::UnaryOp(op, arg))
}
// This is necessary so that the following compiles:
//
// ```
// fn foo<const N: usize>(a: [(); N + 1]) {
// bar::<{ N + 1 }>();
// }
// ```
ExprKind::Block { body: thir::Block { stmts: box [], expr: Some(e), .. } } => {
self.recurse_build(*e)?
}
// `ExprKind::Use` happens when a `hir::ExprKind::Cast` is a
// "coercion cast" i.e. using a coercion or is a no-op.
// This is important so that `N as usize as usize` doesnt unify with `N as usize`. (untested)
&ExprKind::Use { source } => {
let arg = self.recurse_build(source)?;
self.nodes.push(Node::Cast(CastKind::Use, arg, node.ty))
}
&ExprKind::Cast { source } => {
let arg = self.recurse_build(source)?;
self.nodes.push(Node::Cast(CastKind::As, arg, node.ty))
}
ExprKind::Borrow{ arg, ..} => {
let arg_node = &self.body.exprs[*arg];
// 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 {
self.recurse_build(arg)?
} else {
self.maybe_supported_error(
node.span,
"borrowing is not supported in generic constants",
)?
}
}
// FIXME(generic_const_exprs): We may want to support these.
ExprKind::AddressOf { .. } | ExprKind::Deref {..}=> self.maybe_supported_error(
node.span,
"dereferencing or taking the address is not supported in generic constants",
)?,
ExprKind::Repeat { .. } | ExprKind::Array { .. } => self.maybe_supported_error(
node.span,
"array construction is not supported in generic constants",
)?,
ExprKind::Block { .. } => self.maybe_supported_error(
node.span,
"blocks are not supported in generic constant",
)?,
ExprKind::NeverToAny { .. } => self.maybe_supported_error(
node.span,
"converting nevers to any is not supported in generic constant",
)?,
ExprKind::Tuple { .. } => self.maybe_supported_error(
node.span,
"tuple construction is not supported in generic constants",
)?,
ExprKind::Index { .. } => self.maybe_supported_error(
node.span,
"indexing is not supported in generic constant",
)?,
ExprKind::Field { .. } => self.maybe_supported_error(
node.span,
"field access is not supported in generic constant",
)?,
ExprKind::ConstBlock { .. } => self.maybe_supported_error(
node.span,
"const blocks are not supported in generic constant",
)?,
ExprKind::Adt(_) => self.maybe_supported_error(
node.span,
"struct/enum construction is not supported in generic constants",
)?,
// dont know if this is correct
ExprKind::Pointer { .. } =>
self.error(node.span, "pointer casts are not allowed in generic constants")?,
ExprKind::Yield { .. } =>
self.error(node.span, "generator control flow is not allowed in generic constants")?,
ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Loop { .. } => self
.error(
node.span,
"loops and loop control flow are not supported in generic constants",
)?,
ExprKind::Box { .. } =>
self.error(node.span, "allocations are not allowed in generic constants")?,
ExprKind::Unary { .. } => unreachable!(),
// we handle valid unary/binary ops above
ExprKind::Binary { .. } =>
self.error(node.span, "unsupported binary operation in generic constants")?,
ExprKind::LogicalOp { .. } =>
self.error(node.span, "unsupported operation in generic constants, short-circuiting operations would imply control flow")?,
ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => {
self.error(node.span, "assignment is not supported in generic constants")?
}
ExprKind::Closure { .. } | ExprKind::Return { .. } => self.error(
node.span,
"closures and function keywords are not supported in generic constants",
)?,
// let expressions imply control flow
ExprKind::Match { .. } | ExprKind::If { .. } | ExprKind::Let { .. } =>
self.error(node.span, "control flow is not supported in generic constants")?,
ExprKind::InlineAsm { .. } => {
self.error(node.span, "assembly is not supported in generic constants")?
}
// we dont permit let stmts so `VarRef` and `UpvarRef` cant happen
ExprKind::VarRef { .. }
| ExprKind::UpvarRef { .. }
| ExprKind::StaticRef { .. }
| ExprKind::ThreadLocalRef(_) => {
self.error(node.span, "unsupported operation in generic constant")?
}
})
}
}
/// Builds an abstract const, do not use this directly, but use `AbstractConst::new` instead.
pub fn thir_abstract_const<'tcx>(
tcx: TyCtxt<'tcx>,
def: ty::WithOptConstParam<LocalDefId>,
) -> Result<Option<&'tcx [Node<'tcx>]>, ErrorGuaranteed> {
if tcx.features().generic_const_exprs {
match tcx.def_kind(def.did) {
// FIXME(generic_const_exprs): We currently only do this for anonymous constants,
// meaning that we do not look into associated constants. I(@lcnr) am not yet sure whether
// we want to look into them or treat them as opaque projections.
//
// Right now we do neither of that and simply always fail to unify them.
DefKind::AnonConst | DefKind::InlineConst => (),
_ => return Ok(None),
}
let body = tcx.thir_body(def)?;
AbstractConstBuilder::new(tcx, (&*body.0.borrow(), body.1))?
.map(AbstractConstBuilder::build)
.transpose()
} else {
Ok(None)
}
}
pub fn provide(providers: &mut ty::query::Providers) {
*providers = ty::query::Providers {
destructure_const,
thir_abstract_const: |tcx, def_id| {
let def_id = def_id.expect_local();
if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
tcx.thir_abstract_const_of_const_arg(def)
} else {
thir_abstract_const(tcx, ty::WithOptConstParam::unknown(def_id))
}
},
thir_abstract_const_of_const_arg: |tcx, (did, param_did)| {
thir_abstract_const(
tcx,
ty::WithOptConstParam { did, const_param_did: Some(param_did) },
)
},
..*providers
};
}

2
compiler/rustc_ty_utils/src/lib.rs
View File

@ -7,6 +7,8 @@
#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
#![feature(control_flow_enum)]
#![feature(let_else)]
#![feature(never_type)]
#![feature(box_patterns)]
#![recursion_limit = "256"]
#[macro_use]

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() {}