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```
bitflags::bitflags! {
/// Flags that we track on types. These flags are propagated upwards
/// through the type during type construction, so that we can quickly check
/// whether the type has various kinds of types in it without recursing
/// over the type itself.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct TypeFlags: u32 {
// Does this have parameters? Used to determine whether instantiation is
// required.
/// Does this have `Param`?
const HAS_TY_PARAM = 1 << 0;
/// Does this have `ReEarlyParam`?
const HAS_RE_PARAM = 1 << 1;
/// Does this have `ConstKind::Param`?
const HAS_CT_PARAM = 1 << 2;
const HAS_PARAM = TypeFlags::HAS_TY_PARAM.bits()
| TypeFlags::HAS_RE_PARAM.bits()
| TypeFlags::HAS_CT_PARAM.bits();
/// Does this have `Infer`?
const HAS_TY_INFER = 1 << 3;
/// Does this have `ReVar`?
const HAS_RE_INFER = 1 << 4;
/// Does this have `ConstKind::Infer`?
const HAS_CT_INFER = 1 << 5;
/// Does this have inference variables? Used to determine whether
/// inference is required.
const HAS_INFER = TypeFlags::HAS_TY_INFER.bits()
| TypeFlags::HAS_RE_INFER.bits()
| TypeFlags::HAS_CT_INFER.bits();
/// Does this have `Placeholder`?
const HAS_TY_PLACEHOLDER = 1 << 6;
/// Does this have `RePlaceholder`?
const HAS_RE_PLACEHOLDER = 1 << 7;
/// Does this have `ConstKind::Placeholder`?
const HAS_CT_PLACEHOLDER = 1 << 8;
/// Does this have placeholders?
const HAS_PLACEHOLDER = TypeFlags::HAS_TY_PLACEHOLDER.bits()
| TypeFlags::HAS_RE_PLACEHOLDER.bits()
| TypeFlags::HAS_CT_PLACEHOLDER.bits();
/// `true` if there are "names" of regions and so forth
/// that are local to a particular fn/inferctxt
const HAS_FREE_LOCAL_REGIONS = 1 << 9;
/// `true` if there are "names" of types and regions and so forth
/// that are local to a particular fn
const HAS_FREE_LOCAL_NAMES = TypeFlags::HAS_TY_PARAM.bits()
| TypeFlags::HAS_CT_PARAM.bits()
| TypeFlags::HAS_TY_INFER.bits()
| TypeFlags::HAS_CT_INFER.bits()
| TypeFlags::HAS_TY_PLACEHOLDER.bits()
| TypeFlags::HAS_CT_PLACEHOLDER.bits()
// We consider 'freshened' types and constants
// to depend on a particular fn.
// The freshening process throws away information,
// which can make things unsuitable for use in a global
// cache. Note that there is no 'fresh lifetime' flag -
// freshening replaces all lifetimes with `ReErased`,
// which is different from how types/const are freshened.
| TypeFlags::HAS_TY_FRESH.bits()
| TypeFlags::HAS_CT_FRESH.bits()
| TypeFlags::HAS_FREE_LOCAL_REGIONS.bits()
| TypeFlags::HAS_RE_ERASED.bits();
/// Does this have `Projection`?
const HAS_TY_PROJECTION = 1 << 10;
/// Does this have `Weak`?
const HAS_TY_WEAK = 1 << 11;
/// Does this have `Opaque`?
const HAS_TY_OPAQUE = 1 << 12;
/// Does this have `Inherent`?
const HAS_TY_INHERENT = 1 << 13;
/// Does this have `ConstKind::Unevaluated`?
const HAS_CT_PROJECTION = 1 << 14;
/// Does this have `Alias` or `ConstKind::Unevaluated`?
///
/// Rephrased, could this term be normalized further?
const HAS_ALIASES = TypeFlags::HAS_TY_PROJECTION.bits()
| TypeFlags::HAS_TY_WEAK.bits()
| TypeFlags::HAS_TY_OPAQUE.bits()
| TypeFlags::HAS_TY_INHERENT.bits()
| TypeFlags::HAS_CT_PROJECTION.bits();
/// Is an error type/lifetime/const reachable?
const HAS_ERROR = 1 << 15;
/// Does this have any region that "appears free" in the type?
/// Basically anything but `ReBound` and `ReErased`.
const HAS_FREE_REGIONS = 1 << 16;
/// Does this have any `ReBound` regions?
const HAS_RE_BOUND = 1 << 17;
/// Does this have any `Bound` types?
const HAS_TY_BOUND = 1 << 18;
/// Does this have any `ConstKind::Bound` consts?
const HAS_CT_BOUND = 1 << 19;
/// Does this have any bound variables?
/// Used to check if a global bound is safe to evaluate.
const HAS_BOUND_VARS = TypeFlags::HAS_RE_BOUND.bits()
| TypeFlags::HAS_TY_BOUND.bits()
| TypeFlags::HAS_CT_BOUND.bits();
/// Does this have any `ReErased` regions?
const HAS_RE_ERASED = 1 << 20;
/// Does this value have parameters/placeholders/inference variables which could be
/// replaced later, in a way that would change the results of `impl` specialization?
const STILL_FURTHER_SPECIALIZABLE = 1 << 21;
/// Does this value have `InferTy::FreshTy/FreshIntTy/FreshFloatTy`?
const HAS_TY_FRESH = 1 << 22;
/// Does this value have `InferConst::Fresh`?
const HAS_CT_FRESH = 1 << 23;
/// Does this have `Coroutine` or `CoroutineWitness`?
const HAS_TY_COROUTINE = 1 << 24;
/// Does this have any binders with bound vars (e.g. that need to be anonymized)?
const HAS_BINDER_VARS = 1 << 25;
}
}
```