Previously a `Symbol` was stored there, but this ended up causing hash
collisions in situations that otherwise shouldn't have a hash collision. Only
the symbol's string value was hashed, but it was possible for distinct symbols
to have the same string value, fooling various calcuations into thinking that
these paths *didn't* need disambiguating data when in fact they did!
By storing `InternedString` instead we're hopefully triggering all the exising
logic to disambiguate paths with same-name `Symbol` but actually distinct
locations.
Unfortunately, the NodeId->HirId array is not sorted. Since this search is only
done right before calling bug!(), let's not waste time allocating a faster lookup.
Instead of finding the next free disambiguator by incrementing it until
you find a place, store the next available disambiguator in an hash-map.
This avoids O(n^2) performance when lots of items have the same
un-disambiguated `DefPathData` - e.g. all `use` items have
`DefPathData::Misc`.
HirId has a more stable representation than NodeId, meaning that
modifications to one item don't influence (part of) the IDs within
other items. The other part is a DefIndex for which there already
is a way of stable hashing and persistence.
This commit introduces the HirId type and generates a HirId for
every NodeId during HIR lowering, but the resulting values are
not yet used anywhere, except in consistency checks.
The standard implementations of Hasher have architecture-dependent
results when hashing integers. This causes problems when the hashes are
stored within metadata - metadata written by one host architecture can't
be read by another.
To fix that, implement an architecture-independent StableHasher and use
it in all places an architecture-independent hasher is needed.
Fixes#38177.
This commit is intended to be backported to the 1.13 branch, and works with the
following APIs:
Stabilized
* `i32::checked_abs`
* `i32::wrapping_abs`
* `i32::overflowing_abs`
* `RefCell::try_borrow`
* `RefCell::try_borrow_mut`
* `DefaultHasher`
* `DefaultHasher::new`
* `DefaultHasher::default`
Deprecated
* `BinaryHeap::push_pop`
* `BinaryHeap::replace`
* `SipHash13`
* `SipHash24`
* `SipHasher` - use `DefaultHasher` instead in the `std::collections::hash_map`
module
Closes#28147Closes#34767Closes#35057Closes#35070
