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Spruce up the docs of several queries related to the type/trait system and const eval

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León Orell Valerian Liehr 2024-12-26 14:09:27 +01:00
parent f3343420c8
commit 454c09e355
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3 changed files with 224 additions and 107 deletions
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14
compiler/rustc_const_eval/src/const_eval/fn_queries.rs
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@ -15,20 +15,14 @@ fn parent_impl_constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness
}
}
/// Checks whether an item is considered to be `const`. If it is a constructor, it is const.
/// If it is an assoc method or function,
/// return if it has a `const` modifier. If it is an intrinsic, report whether said intrinsic
/// has a `rustc_const_{un,}stable` attribute. Otherwise, panic.
/// Checks whether a function-like definition is considered to be `const`.
fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
let node = tcx.hir_node_by_def_id(def_id);
match node {
hir::Node::Ctor(hir::VariantData::Tuple(..))
| hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. }) => {
hir::Constness::Const
}
hir::Node::ForeignItem(_) => {
// Foreign items cannot be evaluated at compile-time.
hir::Node::Ctor(hir::VariantData::Tuple(..)) => hir::Constness::Const,
hir::Node::ForeignItem(item) if let hir::ForeignItemKind::Fn(..) = item.kind => {
// Foreign functions cannot be evaluated at compile-time.
hir::Constness::NotConst
}
hir::Node::Expr(e) if let hir::ExprKind::Closure(c) = e.kind => c.constness,