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use std::assert_matches::assert_matches;
use std::ops::ControlFlow;
use hir::intravisit::{self, Visitor};
use hir::{GenericParamKind, HirId, Node};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::LocalDefId;
use rustc_middle::ty::{self, TyCtxt};
use rustc_session::lint;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::Span;
use tracing::{debug, instrument};
use crate::delegation::inherit_generics_for_delegation_item;
use crate::middle::resolve_bound_vars as rbv;
#[instrument(level = "debug", skip(tcx), ret)]
pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
use rustc_hir::*;
// For an RPITIT, synthesize generics which are equal to the opaque's generics
// and parent fn's generics compressed into one list.
if let Some(ty::ImplTraitInTraitData::Trait { fn_def_id, opaque_def_id }) =
tcx.opt_rpitit_info(def_id.to_def_id())
{
let trait_def_id = tcx.parent(fn_def_id);
let opaque_ty_generics = tcx.generics_of(opaque_def_id);
let opaque_ty_parent_count = opaque_ty_generics.parent_count;
let mut own_params = opaque_ty_generics.own_params.clone();
let parent_generics = tcx.generics_of(trait_def_id);
let parent_count = parent_generics.parent_count + parent_generics.own_params.len();
let mut trait_fn_params = tcx.generics_of(fn_def_id).own_params.clone();
for param in &mut own_params {
param.index = param.index + parent_count as u32 + trait_fn_params.len() as u32
- opaque_ty_parent_count as u32;
}
trait_fn_params.extend(own_params);
own_params = trait_fn_params;
let param_def_id_to_index =
own_params.iter().map(|param| (param.def_id, param.index)).collect();
return ty::Generics {
parent: Some(trait_def_id),
parent_count,
own_params,
param_def_id_to_index,
has_self: opaque_ty_generics.has_self,
has_late_bound_regions: opaque_ty_generics.has_late_bound_regions,
host_effect_index: parent_generics.host_effect_index,
};
}
let hir_id = tcx.local_def_id_to_hir_id(def_id);
let node = tcx.hir_node(hir_id);
let parent_def_id = match node {
Node::ImplItem(_)
| Node::TraitItem(_)
| Node::Variant(_)
| Node::Ctor(..)
| Node::Field(_) => {
let parent_id = tcx.hir().get_parent_item(hir_id);
Some(parent_id.to_def_id())
}
// FIXME(#43408) always enable this once `lazy_normalization` is
// stable enough and does not need a feature gate anymore.
Node::AnonConst(_) => {
let parent_did = tcx.parent(def_id.to_def_id());
// We don't do this unconditionally because the `DefId` parent of an anon const
// might be an implicitly created closure during `async fn` desugaring. This would
// have the wrong generics.
//
// i.e. `async fn foo<'a>() { let a = [(); { 1 + 2 }]; bar().await() }`
// would implicitly have a closure in its body that would be the parent of
// the `{ 1 + 2 }` anon const. This closure's generics is simply a witness
// instead of `['a]`.
let parent_did = if let DefKind::AnonConst = tcx.def_kind(parent_did) {
parent_did
} else {
tcx.hir().get_parent_item(hir_id).to_def_id()
};
debug!(?parent_did);
let mut in_param_ty = false;
for (_parent, node) in tcx.hir().parent_iter(hir_id) {
if let Some(generics) = node.generics() {
let mut visitor = AnonConstInParamTyDetector { in_param_ty: false, ct: hir_id };
in_param_ty = visitor.visit_generics(generics).is_break();
break;
}
}
if in_param_ty {
// We do not allow generic parameters in anon consts if we are inside
// of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
None
} else if tcx.features().generic_const_exprs {
let parent_node = tcx.parent_hir_node(hir_id);
debug!(?parent_node);
if let Node::Variant(Variant { disr_expr: Some(constant), .. }) = parent_node
&& constant.hir_id == hir_id
{
// enum variant discriminants are not allowed to use any kind of generics
None
} else if let Some(param_id) =
tcx.hir().opt_const_param_default_param_def_id(hir_id)
{
// If the def_id we are calling generics_of on is an anon ct default i.e:
//
// struct Foo<const N: usize = { .. }>;
// ^^^ ^ ^^^^^^ def id of this anon const
// ^ ^ param_id
// ^ parent_def_id
//
// then we only want to return generics for params to the left of `N`. If we don't do that we
// end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, args: [N#0])`.
//
// This causes ICEs (#86580) when building the args for Foo in `fn foo() -> Foo { .. }` as
// we instantiate the defaults with the partially built args when we build the args. Instantiating
// the `N#0` on the unevaluated const indexes into the empty args we're in the process of building.
//
// We fix this by having this function return the parent's generics ourselves and truncating the
// generics to only include non-forward declared params (with the exception of the `Self` ty)
//
// For the above code example that means we want `args: []`
// For the following struct def we want `args: [N#0]` when generics_of is called on
// the def id of the `{ N + 1 }` anon const
// struct Foo<const N: usize, const M: usize = { N + 1 }>;
//
// This has some implications for how we get the predicates available to the anon const
// see `explicit_predicates_of` for more information on this
let generics = tcx.generics_of(parent_did);
let param_def_idx = generics.param_def_id_to_index[¶m_id.to_def_id()];
// In the above example this would be .params[..N#0]
let own_params = generics.params_to(param_def_idx as usize, tcx).to_owned();
let param_def_id_to_index =
own_params.iter().map(|param| (param.def_id, param.index)).collect();
return ty::Generics {
// we set the parent of these generics to be our parent's parent so that we
// dont end up with args: [N, M, N] for the const default on a struct like this:
// struct Foo<const N: usize, const M: usize = { ... }>;
parent: generics.parent,
parent_count: generics.parent_count,
own_params,
param_def_id_to_index,
has_self: generics.has_self,
has_late_bound_regions: generics.has_late_bound_regions,
host_effect_index: None,
};
} else {
// HACK(eddyb) this provides the correct generics when
// `feature(generic_const_expressions)` is enabled, so that const expressions
// used with const generics, e.g. `Foo<{N+1}>`, can work at all.
//
// Note that we do not supply the parent generics when using
// `min_const_generics`.
Some(parent_did)
}
} else {
let parent_node = tcx.parent_hir_node(hir_id);
let parent_node = match parent_node {
Node::ConstArg(ca) => tcx.parent_hir_node(ca.hir_id),
_ => parent_node,
};
match parent_node {
// HACK(eddyb) this provides the correct generics for repeat
// expressions' count (i.e. `N` in `[x; N]`), and explicit
// `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
// as they shouldn't be able to cause query cycle errors.
Node::Expr(Expr { kind: ExprKind::Repeat(_, ArrayLen::Body(ct)), .. })
if ct.anon_const_hir_id() == Some(hir_id) =>
{
Some(parent_did)
}
// Exclude `GlobalAsm` here which cannot have generics.
Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
if asm.operands.iter().any(|(op, _op_sp)| match op {
hir::InlineAsmOperand::Const { anon_const }
| hir::InlineAsmOperand::SymFn { anon_const } => {
anon_const.hir_id == hir_id
}
_ => false,
}) =>
{
Some(parent_did)
}
_ => None,
}
}
}
Node::ConstBlock(_)
| Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
Some(tcx.typeck_root_def_id(def_id.to_def_id()))
}
Node::Item(item) => match item.kind {
ItemKind::OpaqueTy(&hir::OpaqueTy {
origin:
hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
in_trait,
..
}) => {
if in_trait {
assert_matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn);
} else {
assert_matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn | DefKind::Fn);
}
Some(fn_def_id.to_def_id())
}
ItemKind::OpaqueTy(&hir::OpaqueTy {
origin: hir::OpaqueTyOrigin::TyAlias { parent, in_assoc_ty },
..
}) => {
if in_assoc_ty {
assert_matches!(tcx.def_kind(parent), DefKind::AssocTy);
} else {
assert_matches!(tcx.def_kind(parent), DefKind::TyAlias);
}
debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent);
// Opaque types are always nested within another item, and
// inherit the generics of the item.
Some(parent.to_def_id())
}
ItemKind::Fn(sig, _, _) => {
// For a delegation item inherit generics from callee.
if let Some(sig_id) = sig.decl.opt_delegation_sig_id()
&& let Some(generics) =
inherit_generics_for_delegation_item(tcx, def_id, sig_id)
{
return generics;
}
None
}
_ => None,
},
_ => None,
};
enum Defaults {
Allowed,
// See #36887
FutureCompatDisallowed,
Deny,
}
let hir_generics = node.generics().unwrap_or(hir::Generics::empty());
let (opt_self, allow_defaults) = match node {
Node::Item(item) => {
match item.kind {
ItemKind::Trait(..) | ItemKind::TraitAlias(..) => {
// Add in the self type parameter.
//
// Something of a hack: use the node id for the trait, also as
// the node id for the Self type parameter.
let opt_self = Some(ty::GenericParamDef {
index: 0,
name: kw::SelfUpper,
def_id: def_id.to_def_id(),
pure_wrt_drop: false,
kind: ty::GenericParamDefKind::Type {
has_default: false,
synthetic: false,
},
});
(opt_self, Defaults::Allowed)
}
ItemKind::TyAlias(..)
| ItemKind::Enum(..)
| ItemKind::Struct(..)
| ItemKind::OpaqueTy(..)
| ItemKind::Union(..) => (None, Defaults::Allowed),
ItemKind::Const(..) => (None, Defaults::Deny),
_ => (None, Defaults::FutureCompatDisallowed),
}
}
// GATs
Node::TraitItem(item) if matches!(item.kind, TraitItemKind::Type(..)) => {
(None, Defaults::Deny)
}
Node::ImplItem(item) if matches!(item.kind, ImplItemKind::Type(..)) => {
(None, Defaults::Deny)
}
_ => (None, Defaults::FutureCompatDisallowed),
};
let has_self = opt_self.is_some();
let mut parent_has_self = false;
let mut own_start = has_self as u32;
let mut host_effect_index = None;
let parent_count = parent_def_id.map_or(0, |def_id| {
let generics = tcx.generics_of(def_id);
assert!(!has_self);
parent_has_self = generics.has_self;
host_effect_index = generics.host_effect_index;
own_start = generics.count() as u32;
generics.parent_count + generics.own_params.len()
});
let mut own_params: Vec<_> = Vec::with_capacity(hir_generics.params.len() + has_self as usize);
if let Some(opt_self) = opt_self {
own_params.push(opt_self);
}
let early_lifetimes = super::early_bound_lifetimes_from_generics(tcx, hir_generics);
own_params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
name: param.name.ident().name,
index: own_start + i as u32,
def_id: param.def_id.to_def_id(),
pure_wrt_drop: param.pure_wrt_drop,
kind: ty::GenericParamDefKind::Lifetime,
}));
// Now create the real type and const parameters.
let type_start = own_start - has_self as u32 + own_params.len() as u32;
let mut i: u32 = 0;
let mut next_index = || {
let prev = i;
i += 1;
prev + type_start
};
const TYPE_DEFAULT_NOT_ALLOWED: &'static str = "defaults for type parameters are only allowed in \
`struct`, `enum`, `type`, or `trait` definitions";
own_params.extend(hir_generics.params.iter().filter_map(|param| match param.kind {
GenericParamKind::Lifetime { .. } => None,
GenericParamKind::Type { default, synthetic, .. } => {
if default.is_some() {
match allow_defaults {
Defaults::Allowed => {}
Defaults::FutureCompatDisallowed => {
tcx.node_span_lint(
lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
param.hir_id,
param.span,
|lint| {
lint.primary_message(TYPE_DEFAULT_NOT_ALLOWED);
},
);
}
Defaults::Deny => {
tcx.dcx().span_err(param.span, TYPE_DEFAULT_NOT_ALLOWED);
}
}
}
let kind = ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic };
Some(ty::GenericParamDef {
index: next_index(),
name: param.name.ident().name,
def_id: param.def_id.to_def_id(),
pure_wrt_drop: param.pure_wrt_drop,
kind,
})
}
GenericParamKind::Const { ty: _, default, is_host_effect, synthetic } => {
if !matches!(allow_defaults, Defaults::Allowed)
&& default.is_some()
// `host` effect params are allowed to have defaults.
&& !is_host_effect
{
tcx.dcx().span_err(
param.span,
"defaults for const parameters are only allowed in \
`struct`, `enum`, `type`, or `trait` definitions",
);
}
let index = next_index();
if is_host_effect {
if let Some(idx) = host_effect_index {
tcx.dcx().span_delayed_bug(
param.span,
format!("parent also has host effect param? index: {idx}, def: {def_id:?}"),
);
}
host_effect_index = Some(index as usize);
}
Some(ty::GenericParamDef {
index,
name: param.name.ident().name,
def_id: param.def_id.to_def_id(),
pure_wrt_drop: param.pure_wrt_drop,
kind: ty::GenericParamDefKind::Const {
has_default: default.is_some(),
is_host_effect,
synthetic,
},
})
}
}));
// provide junk type parameter defs - the only place that
// cares about anything but the length is instantiation,
// and we don't do that for closures.
if let Node::Expr(&hir::Expr {
kind: hir::ExprKind::Closure(hir::Closure { kind, .. }), ..
}) = node
{
// See `ClosureArgsParts`, `CoroutineArgsParts`, and `CoroutineClosureArgsParts`
// for info on the usage of each of these fields.
let dummy_args = match kind {
ClosureKind::Closure => &["<closure_kind>", "<closure_signature>", "<upvars>"][..],
ClosureKind::Coroutine(_) => &[
"<coroutine_kind>",
"<resume_ty>",
"<yield_ty>",
"<return_ty>",
"<witness>",
"<upvars>",
][..],
ClosureKind::CoroutineClosure(_) => &[
"<closure_kind>",
"<closure_signature_parts>",
"<upvars>",
"<bound_captures_by_ref>",
"<witness>",
][..],
};
own_params.extend(dummy_args.iter().map(|&arg| ty::GenericParamDef {
index: next_index(),
name: Symbol::intern(arg),
def_id: def_id.to_def_id(),
pure_wrt_drop: false,
kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
}));
}
// provide junk type parameter defs for const blocks.
if let Node::ConstBlock(_) = node {
own_params.push(ty::GenericParamDef {
index: next_index(),
name: Symbol::intern("<const_ty>"),
def_id: def_id.to_def_id(),
pure_wrt_drop: false,
kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
});
}
let param_def_id_to_index =
own_params.iter().map(|param| (param.def_id, param.index)).collect();
ty::Generics {
parent: parent_def_id,
parent_count,
own_params,
param_def_id_to_index,
has_self: has_self || parent_has_self,
has_late_bound_regions: has_late_bound_regions(tcx, node),
host_effect_index,
}
}
fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
struct LateBoundRegionsDetector<'tcx> {
tcx: TyCtxt<'tcx>,
outer_index: ty::DebruijnIndex,
}
impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
type Result = ControlFlow<Span>;
fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) -> ControlFlow<Span> {
match ty.kind {
hir::TyKind::BareFn(..) => {
self.outer_index.shift_in(1);
let res = intravisit::walk_ty(self, ty);
self.outer_index.shift_out(1);
res
}
_ => intravisit::walk_ty(self, ty),
}
}
fn visit_poly_trait_ref(&mut self, tr: &'tcx hir::PolyTraitRef<'tcx>) -> ControlFlow<Span> {
self.outer_index.shift_in(1);
let res = intravisit::walk_poly_trait_ref(self, tr);
self.outer_index.shift_out(1);
res
}
fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) -> ControlFlow<Span> {
match self.tcx.named_bound_var(lt.hir_id) {
Some(rbv::ResolvedArg::StaticLifetime | rbv::ResolvedArg::EarlyBound(..)) => {
ControlFlow::Continue(())
}
Some(rbv::ResolvedArg::LateBound(debruijn, _, _))
if debruijn < self.outer_index =>
{
ControlFlow::Continue(())
}
Some(
rbv::ResolvedArg::LateBound(..)
| rbv::ResolvedArg::Free(..)
| rbv::ResolvedArg::Error(_),
)
| None => ControlFlow::Break(lt.ident.span),
}
}
}
fn has_late_bound_regions<'tcx>(
tcx: TyCtxt<'tcx>,
generics: &'tcx hir::Generics<'tcx>,
decl: &'tcx hir::FnDecl<'tcx>,
) -> Option<Span> {
let mut visitor = LateBoundRegionsDetector { tcx, outer_index: ty::INNERMOST };
for param in generics.params {
if let GenericParamKind::Lifetime { .. } = param.kind {
if tcx.is_late_bound(param.hir_id) {
return Some(param.span);
}
}
}
visitor.visit_fn_decl(decl).break_value()
}
let decl = node.fn_decl()?;
let generics = node.generics()?;
has_late_bound_regions(tcx, generics, decl)
}
struct AnonConstInParamTyDetector {
in_param_ty: bool,
ct: HirId,
}
impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
type Result = ControlFlow<()>;
fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) -> Self::Result {
if let GenericParamKind::Const { ty, default: _, is_host_effect: _, synthetic: _ } = p.kind
{
let prev = self.in_param_ty;
self.in_param_ty = true;
let res = self.visit_ty(ty);
self.in_param_ty = prev;
res
} else {
ControlFlow::Continue(())
}
}
fn visit_anon_const(&mut self, c: &'v hir::AnonConst) -> Self::Result {
if self.in_param_ty && self.ct == c.hir_id {
return ControlFlow::Break(());
}
intravisit::walk_anon_const(self, c)
}
}