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Add ConstArgKind::Path and make ConstArg its own HIR node

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This is a very large commit since a lot needs to be changed in order to
make the tests pass. The salient changes are:

- `ConstArgKind` gets a new `Path` variant, and all const params are now
  represented using it. Non-param paths still use `ConstArgKind::Anon`
  to prevent this change from getting too large, but they will soon use
  the `Path` variant too.

- `ConstArg` gets a distinct `hir_id` field and its own variant in
  `hir::Node`. This affected many parts of the compiler that expected
  the parent of an `AnonConst` to be the containing context (e.g., an
  array repeat expression). They have been changed to check the
  "grandparent" where necessary.

- Some `ast::AnonConst`s now have their `DefId`s created in
  rustc_ast_lowering rather than `DefCollector`. This is because in some
  cases they will end up becoming a `ConstArgKind::Path` instead, which
  has no `DefId`. We have to solve this in a hacky way where we guess
  whether the `AnonConst` could end up as a path const since we can't
  know for sure until after name resolution (`N` could refer to a free
  const or a nullary struct). If it has no chance as being a const
  param, then we create a `DefId` in `DefCollector` -- otherwise we
  decide during ast_lowering. This will have to be updated once all path
  consts use `ConstArgKind::Path`.

- We explicitly use `ConstArgHasType` for array lengths, rather than
  implicitly relying on anon const type feeding -- this is due to the
  addition of `ConstArgKind::Path`.

- Some tests have their outputs changed, but the changes are for the
  most part minor (including removing duplicate or almost-duplicate
  errors). One test now ICEs, but it is for an incomplete, unstable
  feature and is now tracked at #127009.
This commit is contained in:
Noah Lev
2024-07-16 19:07:36 -07:00
parent 1c49d406b6
commit 37ed7a4438
61 changed files with 542 additions and 415 deletions
Download Patch File Download Diff File Expand all files Collapse all files

146
compiler/rustc_ast_lowering/src/lib.rs
View File

@@ -54,7 +54,9 @@ use rustc_errors::{DiagArgFromDisplay, DiagCtxtHandle, StashKey};
use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
use rustc_hir::def_id::{LocalDefId, LocalDefIdMap, CRATE_DEF_ID, LOCAL_CRATE};
use rustc_hir::{self as hir};
use rustc_hir::{GenericArg, HirId, ItemLocalMap, MissingLifetimeKind, ParamName, TraitCandidate};
use rustc_hir::{
ConstArg, GenericArg, HirId, ItemLocalMap, MissingLifetimeKind, ParamName, TraitCandidate,
};
use rustc_index::{Idx, IndexSlice, IndexVec};
use rustc_macros::extension;
use rustc_middle::span_bug;
@@ -124,7 +126,7 @@ struct LoweringContext<'a, 'hir> {
/// they do get their own DefIds. Some of these DefIds have to be created during
/// AST lowering, rather than def collection, because we can't tell until after
/// name resolution whether an anonymous constant will end up instead being a
/// [`rustc_hir::ConstArgKind::Path`]. However, to compute which generics are
/// [`hir::ConstArgKind::Path`]. However, to compute which generics are
/// available to an anonymous constant nested inside another, we need to make
/// sure that the parent is recorded as the parent anon const, not the enclosing
/// item. So we need to track parent defs differently from HIR owners, since they
@@ -2349,64 +2351,146 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
}
#[instrument(level = "debug", skip(self))]
fn lower_const_path_to_const_arg(
&mut self,
path: &Path,
_res: Res<NodeId>,
res: Res<NodeId>,
ty_id: NodeId,
span: Span,
) -> &'hir hir::ConstArg<'hir> {
// Construct an AnonConst where the expr is the "ty"'s path.
let ct_kind = match res {
Res::Def(DefKind::ConstParam, _) => {
let qpath = self.lower_qpath(
ty_id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
hir::ConstArgKind::Path(qpath)
}
_ => {
// Construct an AnonConst where the expr is the "ty"'s path.
let parent_def_id = self.current_def_id_parent;
let node_id = self.next_node_id();
let span = self.lower_span(span);
let parent_def_id = self.current_def_id_parent;
let node_id = self.next_node_id();
let span = self.lower_span(span);
// Add a definition for the in-band const def.
let def_id = self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, span);
// Add a definition for the in-band const def.
let def_id =
self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, span);
let hir_id = self.lower_node_id(node_id);
let path_expr = Expr {
id: ty_id,
kind: ExprKind::Path(None, path.clone()),
span,
attrs: AttrVec::new(),
tokens: None,
let path_expr = Expr {
id: ty_id,
kind: ExprKind::Path(None, path.clone()),
span,
attrs: AttrVec::new(),
tokens: None,
};
let ct = self.with_new_scopes(span, |this| {
self.arena.alloc(hir::AnonConst {
def_id,
hir_id,
body: this.with_def_id_parent(def_id, |this| {
this.lower_const_body(path_expr.span, Some(&path_expr))
}),
span,
})
});
hir::ConstArgKind::Anon(ct)
}
};
let ct = self.with_new_scopes(span, |this| {
self.arena.alloc(hir::AnonConst {
def_id,
hir_id: this.lower_node_id(node_id),
body: this.lower_const_body(path_expr.span, Some(&path_expr)),
span,
})
});
self.arena.alloc(hir::ConstArg {
kind: hir::ConstArgKind::Anon(ct),
hir_id: self.next_id(),
kind: ct_kind,
is_desugared_from_effects: false,
})
}
/// See [`hir::ConstArg`] for when to use this function vs
/// [`Self::lower_anon_const_to_anon_const`].
fn lower_anon_const_to_const_arg(&mut self, anon: &AnonConst) -> &'hir hir::ConstArg<'hir> {
self.arena.alloc(self.lower_anon_const_to_const_arg_direct(anon))
}
#[instrument(level = "debug", skip(self))]
fn lower_anon_const_to_const_arg_direct(&mut self, anon: &AnonConst) -> hir::ConstArg<'hir> {
// Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
// currently have to be wrapped in curly brackets, so it's necessary to special-case.
let expr = if let ExprKind::Block(block, _) = &anon.value.kind
&& let [stmt] = block.stmts.as_slice()
&& let StmtKind::Expr(expr) = &stmt.kind
&& let ExprKind::Path(..) = &expr.kind
{
expr
} else {
&anon.value
};
let maybe_res =
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 let Some(res) = maybe_res
&& let Res::Def(DefKind::ConstParam, _) = res
&& let ExprKind::Path(qself, path) = &expr.kind
{
let qpath = self.lower_qpath(
expr.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
return ConstArg {
hir_id: self.next_id(),
kind: hir::ConstArgKind::Path(qpath),
is_desugared_from_effects: false,
};
}
let lowered_anon = self.lower_anon_const_to_anon_const(anon);
hir::ConstArg {
ConstArg {
hir_id: self.next_id(),
kind: hir::ConstArgKind::Anon(lowered_anon),
is_desugared_from_effects: false,
}
}
/// 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 {
self.arena.alloc(self.with_new_scopes(c.value.span, |this| hir::AnonConst {
def_id: this.local_def_id(c.id),
hir_id: this.lower_node_id(c.id),
body: this.lower_const_body(c.value.span, Some(&c.value)),
span: this.lower_span(c.value.span),
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)
// in which case we have to create the def here.
self.create_def(
self.current_def_id_parent,
c.id,
kw::Empty,
DefKind::AnonConst,
c.value.span,
);
}
self.arena.alloc(self.with_new_scopes(c.value.span, |this| {
let def_id = this.local_def_id(c.id);
let hir_id = this.lower_node_id(c.id);
hir::AnonConst {
def_id,
hir_id,
body: this.with_def_id_parent(def_id, |this| {
this.lower_const_body(c.value.span, Some(&c.value))
}),
span: this.lower_span(c.value.span),
}
}))
}