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Auto merge of #129137 - camelid:lazy-def-macro-const, r=BoxyUwU

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Fix anon const def-creation when macros are involved

Fixes #128016.

Ever since #125915, some `ast::AnonConst`s turn into `hir::ConstArgKind::Path`s,
which don't have associated `DefId`s. To deal with the fact that we don't have
resolution information in `DefCollector`, we decided to implement a process
where if the anon const *appeared* to be trivial (i.e., `N` or `{ N }`), we
would avoid creating a def for it in `DefCollector`. If later, in AST lowering,
we realized it turned out to be a unit struct literal, or we were lowering it
to something that didn't use `hir::ConstArg`, we'd create its def there.

However, let's say we have a macro `m!()` that expands to a reference to a free
constant `FOO`. If we use `m!()` in the body of an anon const (e.g., `Foo<{ m!() }>`),
then in def collection, it appears to be a nontrivial anon const and we create
a def. But the macro expands to something that looks like a trivial const arg,
but is not, so in AST lowering we "fix" the mistake we assumed def collection
made and create a def for it. This causes a duplicate definition ICE.

The long-term fix for this is to delay the creation of defs for all expression-like
nodes until AST lowering (see #128844 for an incomplete attempt at this). This
would avoid issues like this one that are caused by hacky workarounds. However,
doing this uncovers a pre-existing bug with opaque types that is quite involved
to fix (see #129023).

In the meantime, this PR fixes the bug by delaying def creation for anon consts
whose bodies are macro invocations until after we expand the macro and know
what is inside it. This is accomplished by adding information to create the
anon const's def to the data in `Resolver.invocation_parents`.

r? `@BoxyUwU`
This commit is contained in:
bors 2024-09-13 01:10:51 +00:00
commit d3a8524e80
37 changed files with 182 additions and 246 deletions
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20
compiler/rustc_ast/src/ast.rs
View file

@ -1188,14 +1188,7 @@ impl Expr {
///
/// Does not ensure that the path resolves to a const param, the caller should check this.
pub fn is_potential_trivial_const_arg(&self) -> bool {
let this = if let ExprKind::Block(block, None) = &self.kind
&& let [stmt] = block.stmts.as_slice()
&& let StmtKind::Expr(expr) = &stmt.kind
{
expr
} else {
self
};
let this = self.maybe_unwrap_block();
if let ExprKind::Path(None, path) = &this.kind
&& path.is_potential_trivial_const_arg()
@ -1206,6 +1199,17 @@ impl Expr {
}
}
pub fn maybe_unwrap_block(&self) -> &Expr {
if let ExprKind::Block(block, None) = &self.kind
&& let [stmt] = block.stmts.as_slice()
&& let StmtKind::Expr(expr) = &stmt.kind
{
expr
} else {
self
}
}
pub fn to_bound(&self) -> Option<GenericBound> {
match &self.kind {
ExprKind::Path(None, path) => Some(GenericBound::Trait(

4
compiler/rustc_ast_lowering/src/asm.rs
View file

@ -220,9 +220,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let parent_def_id = self.current_def_id_parent;
let node_id = self.next_node_id();
// HACK(min_generic_const_args): see lower_anon_const
if !self.tcx.features().const_arg_path
|| !expr.is_potential_trivial_const_arg()
{
if !expr.is_potential_trivial_const_arg() {
self.create_def(
parent_def_id,
node_id,

2
compiler/rustc_ast_lowering/src/expr.rs
View file

@ -387,7 +387,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let node_id = self.next_node_id();
// HACK(min_generic_const_args): see lower_anon_const
if !self.tcx.features().const_arg_path || !arg.is_potential_trivial_const_arg() {
if !arg.is_potential_trivial_const_arg() {
// Add a definition for the in-band const def.
self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, f.span);
}

7
compiler/rustc_ast_lowering/src/lib.rs
View file

@ -2335,7 +2335,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
span: Span,
) -> &'hir hir::ConstArg<'hir> {
let ct_kind = match res {
Res::Def(DefKind::ConstParam, _) if self.tcx.features().const_arg_path => {
Res::Def(DefKind::ConstParam, _) => {
let qpath = self.lower_qpath(
ty_id,
&None,
@ -2410,8 +2410,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.resolver.get_partial_res(expr.id).and_then(|partial_res| partial_res.full_res());
debug!("res={:?}", maybe_res);
// FIXME(min_generic_const_args): for now we only lower params to ConstArgKind::Path
if self.tcx.features().const_arg_path
&& let Some(res) = maybe_res
if let Some(res) = maybe_res
&& let Res::Def(DefKind::ConstParam, _) = res
&& let ExprKind::Path(qself, path) = &expr.kind
{
@ -2442,7 +2441,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
/// See [`hir::ConstArg`] for when to use this function vs
/// [`Self::lower_anon_const_to_const_arg`].
fn lower_anon_const_to_anon_const(&mut self, c: &AnonConst) -> &'hir hir::AnonConst {
if self.tcx.features().const_arg_path && c.value.is_potential_trivial_const_arg() {
if c.value.is_potential_trivial_const_arg() {
// HACK(min_generic_const_args): see DefCollector::visit_anon_const
// Over there, we guess if this is a bare param and only create a def if
// we think it's not. However we may can guess wrong (see there for example)

2
compiler/rustc_feature/src/unstable.rs
View file

@ -193,8 +193,6 @@ declare_features! (
(unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
/// Allows identifying the `compiler_builtins` crate.
(internal, compiler_builtins, "1.13.0", None),
/// Gating for a new desugaring of const arguments of usages of const parameters
(internal, const_arg_path, "1.81.0", None),
/// Allows writing custom MIR
(internal, custom_mir, "1.65.0", None),
/// Outputs useful `assert!` messages

18
compiler/rustc_middle/src/ty/consts.rs
View file

@ -295,20 +295,12 @@ impl<'tcx> Const<'tcx> {
_ => expr,
};
if let hir::ExprKind::Path(
qpath @ hir::QPath::Resolved(
_,
&hir::Path { res: Res::Def(DefKind::ConstParam, _), .. },
),
) = expr.kind
if let hir::ExprKind::Path(hir::QPath::Resolved(
_,
&hir::Path { res: Res::Def(DefKind::ConstParam, _), .. },
)) = expr.kind
{
if tcx.features().const_arg_path {
span_bug!(
expr.span,
"try_from_lit: received const param which shouldn't be possible"
);
}
return Some(Const::from_param(tcx, qpath, expr.hir_id));
span_bug!(expr.span, "try_from_lit: received const param which shouldn't be possible");
};
let lit_input = match expr.kind {

120
compiler/rustc_resolve/src/def_collector.rs
View file

@ -12,15 +12,23 @@ use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;
use tracing::debug;
use crate::{ImplTraitContext, Resolver};
use crate::{ImplTraitContext, InvocationParent, PendingAnonConstInfo, Resolver};
pub(crate) fn collect_definitions(
resolver: &mut Resolver<'_, '_>,
fragment: &AstFragment,
expansion: LocalExpnId,
) {
let (parent_def, impl_trait_context, in_attr) = resolver.invocation_parents[&expansion];
let mut visitor = DefCollector { resolver, parent_def, expansion, impl_trait_context, in_attr };
let InvocationParent { parent_def, pending_anon_const_info, impl_trait_context, in_attr } =
resolver.invocation_parents[&expansion];
let mut visitor = DefCollector {
resolver,
parent_def,
pending_anon_const_info,
expansion,
impl_trait_context,
in_attr,
};
fragment.visit_with(&mut visitor);
}
@ -28,6 +36,13 @@ pub(crate) fn collect_definitions(
struct DefCollector<'a, 'ra, 'tcx> {
resolver: &'a mut Resolver<'ra, 'tcx>,
parent_def: LocalDefId,
/// If we have an anon const that consists of a macro invocation, e.g. `Foo<{ m!() }>`,
/// we need to wait until we know what the macro expands to before we create the def for
/// the anon const. That's because we lower some anon consts into `hir::ConstArgKind::Path`,
/// which don't have defs.
///
/// See `Self::visit_anon_const()`.
pending_anon_const_info: Option<PendingAnonConstInfo>,
impl_trait_context: ImplTraitContext,
in_attr: bool,
expansion: LocalExpnId,
@ -111,10 +126,16 @@ impl<'a, 'ra, 'tcx> DefCollector<'a, 'ra, 'tcx> {
fn visit_macro_invoc(&mut self, id: NodeId) {
let id = id.placeholder_to_expn_id();
let old_parent = self
.resolver
.invocation_parents
.insert(id, (self.parent_def, self.impl_trait_context, self.in_attr));
let pending_anon_const_info = self.pending_anon_const_info.take();
let old_parent = self.resolver.invocation_parents.insert(
id,
InvocationParent {
parent_def: self.parent_def,
pending_anon_const_info,
impl_trait_context: self.impl_trait_context,
in_attr: self.in_attr,
},
);
assert!(old_parent.is_none(), "parent `LocalDefId` is reset for an invocation");
}
}
@ -326,46 +347,65 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
}
fn visit_anon_const(&mut self, constant: &'a AnonConst) {
if self.resolver.tcx.features().const_arg_path
&& constant.value.is_potential_trivial_const_arg()
{
// HACK(min_generic_const_args): don't create defs for anon consts if we think they will
// later be turned into ConstArgKind::Path's. because this is before resolve is done, we
// may accidentally identify a construction of a unit struct as a param and not create a
// def. we'll then create a def later in ast lowering in this case. the parent of nested
// items will be messed up, but that's ok because there can't be any if we're just looking
// for bare idents.
visit::walk_anon_const(self, constant)
} else {
let def =
self.create_def(constant.id, kw::Empty, DefKind::AnonConst, constant.value.span);
self.with_parent(def, |this| visit::walk_anon_const(this, constant));
// HACK(min_generic_const_args): don't create defs for anon consts if we think they will
// later be turned into ConstArgKind::Path's. because this is before resolve is done, we
// may accidentally identify a construction of a unit struct as a param and not create a
// def. we'll then create a def later in ast lowering in this case. the parent of nested
// items will be messed up, but that's ok because there can't be any if we're just looking
// for bare idents.
if matches!(constant.value.maybe_unwrap_block().kind, ExprKind::MacCall(..)) {
// See self.pending_anon_const_info for explanation
self.pending_anon_const_info =
Some(PendingAnonConstInfo { id: constant.id, span: constant.value.span });
return visit::walk_anon_const(self, constant);
} else if constant.value.is_potential_trivial_const_arg() {
return visit::walk_anon_const(self, constant);
}
let def = self.create_def(constant.id, kw::Empty, DefKind::AnonConst, constant.value.span);
self.with_parent(def, |this| visit::walk_anon_const(this, constant));
}
fn visit_expr(&mut self, expr: &'a Expr) {
let parent_def = match expr.kind {
ExprKind::MacCall(..) => return self.visit_macro_invoc(expr.id),
ExprKind::Closure(..) | ExprKind::Gen(..) => {
self.create_def(expr.id, kw::Empty, DefKind::Closure, expr.span)
if matches!(expr.kind, ExprKind::MacCall(..)) {
return self.visit_macro_invoc(expr.id);
}
let grandparent_def = if let Some(pending_anon) = self.pending_anon_const_info.take() {
// See self.pending_anon_const_info for explanation
if !expr.is_potential_trivial_const_arg() {
self.create_def(pending_anon.id, kw::Empty, DefKind::AnonConst, pending_anon.span)
} else {
self.parent_def
}
ExprKind::ConstBlock(ref constant) => {
for attr in &expr.attrs {
visit::walk_attribute(self, attr);
}
let def = self.create_def(
constant.id,
kw::Empty,
DefKind::InlineConst,
constant.value.span,
);
self.with_parent(def, |this| visit::walk_anon_const(this, constant));
return;
}
_ => self.parent_def,
} else {
self.parent_def
};
self.with_parent(parent_def, |this| visit::walk_expr(this, expr));
self.with_parent(grandparent_def, |this| {
let parent_def = match expr.kind {
ExprKind::Closure(..) | ExprKind::Gen(..) => {
this.create_def(expr.id, kw::Empty, DefKind::Closure, expr.span)
}
ExprKind::ConstBlock(ref constant) => {
for attr in &expr.attrs {
visit::walk_attribute(this, attr);
}
let def = this.create_def(
constant.id,
kw::Empty,
DefKind::InlineConst,
constant.value.span,
);
this.with_parent(def, |this| visit::walk_anon_const(this, constant));
return;
}
_ => this.parent_def,
};
this.with_parent(parent_def, |this| visit::walk_expr(this, expr))
})
}
fn visit_ty(&mut self, ty: &'a Ty) {

28
compiler/rustc_resolve/src/lib.rs
View file

@ -171,6 +171,29 @@ impl<'ra> ParentScope<'ra> {
}
}
#[derive(Copy, Debug, Clone)]
struct InvocationParent {
parent_def: LocalDefId,
pending_anon_const_info: Option<PendingAnonConstInfo>,
impl_trait_context: ImplTraitContext,
in_attr: bool,
}
impl InvocationParent {
const ROOT: Self = Self {
parent_def: CRATE_DEF_ID,
pending_anon_const_info: None,
impl_trait_context: ImplTraitContext::Existential,
in_attr: false,
};
}
#[derive(Copy, Debug, Clone)]
struct PendingAnonConstInfo {
id: NodeId,
span: Span,
}
#[derive(Copy, Debug, Clone)]
enum ImplTraitContext {
Existential,
@ -1144,7 +1167,7 @@ pub struct Resolver<'ra, 'tcx> {
/// When collecting definitions from an AST fragment produced by a macro invocation `ExpnId`
/// we know what parent node that fragment should be attached to thanks to this table,
/// and how the `impl Trait` fragments were introduced.
invocation_parents: FxHashMap<LocalExpnId, (LocalDefId, ImplTraitContext, bool /*in_attr*/)>,
invocation_parents: FxHashMap<LocalExpnId, InvocationParent>,
/// Some way to know that we are in a *trait* impl in `visit_assoc_item`.
/// FIXME: Replace with a more general AST map (together with some other fields).
@ -1382,8 +1405,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
node_id_to_def_id.insert(CRATE_NODE_ID, crate_feed);
let mut invocation_parents = FxHashMap::default();
invocation_parents
.insert(LocalExpnId::ROOT, (CRATE_DEF_ID, ImplTraitContext::Existential, false));
invocation_parents.insert(LocalExpnId::ROOT, InvocationParent::ROOT);
let mut extern_prelude: FxHashMap<Ident, ExternPreludeEntry<'_>> = tcx
.sess

16
compiler/rustc_resolve/src/macros.rs
View file

@ -42,9 +42,9 @@ use crate::errors::{
use crate::imports::Import;
use crate::Namespace::*;
use crate::{
BindingKey, BuiltinMacroState, DeriveData, Determinacy, Finalize, MacroData, ModuleKind,
ModuleOrUniformRoot, NameBinding, NameBindingKind, ParentScope, PathResult, ResolutionError,
Resolver, ScopeSet, Segment, ToNameBinding, Used,
BindingKey, BuiltinMacroState, DeriveData, Determinacy, Finalize, InvocationParent, MacroData,
ModuleKind, ModuleOrUniformRoot, NameBinding, NameBindingKind, ParentScope, PathResult,
ResolutionError, Resolver, ScopeSet, Segment, ToNameBinding, Used,
};
type Res = def::Res<NodeId>;
@ -183,7 +183,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
}
fn invocation_parent(&self, id: LocalExpnId) -> LocalDefId {
self.invocation_parents[&id].0
self.invocation_parents[&id].parent_def
}
fn resolve_dollar_crates(&mut self) {
@ -303,12 +303,12 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
.invocation_parents
.get(&invoc_id)
.or_else(|| self.invocation_parents.get(&eager_expansion_root))
.filter(|&&(mod_def_id, _, in_attr)| {
.filter(|&&InvocationParent { parent_def: mod_def_id, in_attr, .. }| {
in_attr
&& invoc.fragment_kind == AstFragmentKind::Expr
&& self.tcx.def_kind(mod_def_id) == DefKind::Mod
})
.map(|&(mod_def_id, ..)| mod_def_id);
.map(|&InvocationParent { parent_def: mod_def_id, .. }| mod_def_id);
let (ext, res) = self.smart_resolve_macro_path(
path,
kind,
@ -951,7 +951,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
let node_id = self
.invocation_parents
.get(&parent_scope.expansion)
.map_or(ast::CRATE_NODE_ID, |id| self.def_id_to_node_id[id.0]);
.map_or(ast::CRATE_NODE_ID, |parent| {
self.def_id_to_node_id[parent.parent_def]
});
self.lint_buffer.buffer_lint(
LEGACY_DERIVE_HELPERS,
node_id,

1
compiler/rustc_span/src/symbol.rs
View file

@ -599,7 +599,6 @@ symbols! {
conservative_impl_trait,
console,
const_allocate,
const_arg_path,
const_async_blocks,
const_closures,
const_compare_raw_pointers,