Rely on implicit conversion in call sites and initialization.
Removing the explicit conversions is only code simplication.
Moving from `auto x = Y(z)` to `Y x = z;` helps ensure that only
implicit constructors/conversions are happening (whereas the prior
syntax allows explicit conversions) which can help with readability
since implicit conversions are generally "less
complex"/risky/attention-requiring.
The hash table design is heavily based on Abseil's ["Swiss
Tables"][swiss-tables] design. It uses an array of bytes storing
metadata about each entry and an array of entries where each is a pair
of key and value. The metadata byte consists of 7-bits of hash of the
key (distinct from the bits used to index the table), and one bit
indicating the presence of a special entry -- either empty or deleted.
[swiss-tables]: https://abseil.io/about/design/swisstables
There are a large range of optimizations and other nuanced aspects of
this hash table design and implementation, a good point to understand
that context is `raw_hashtable.h` which has an overview of the design
and references to various other files for relevant details.
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Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
David Blaikie
Chandler Carruthandjosh11b