`use` declarations will be reformatted in #125443. Very rarely, there is
a desire to force a group of `use` declarations together in a way that
auto-formatting will break up. E.g. when you want a single comment to
apply to a group. #126776 dealt with all of these in the codebase,
ensuring that no comments intended for multiple `use` declarations would
end up in the wrong place. But some people were unhappy with it.
This commit uses `#[rustfmt::skip]` to create these custom `use` groups
in an idiomatic way for a few of the cases changed in #126776. This
works because rustfmt treats any `use` item annotated with
`#[rustfmt::skip]` as a barrier and won't reorder other `use` items
around it.
There are some comments describing multiple subsequent `use` items. When
the big `use` reformatting happens some of these `use` items will be
reordered, possibly moving them away from the comment. With this
additional level of formatting it's not really feasible to have comments
of this type. This commit removes them in various ways:
- merging separate `use` items when appropriate;
- inserting blank lines between the comment and the first `use` item;
- outright deletion (for comments that are relatively low-value);
- adding a separate "top-level" comment.
We also entirely skip formatting for four library files that contain
nothing but `pub use` re-exports, where reordering would be painful.
This adds a dedicated check for the lower bound
(if it is outside of ASCII range) to the output of the `unicode-table-generator` tool.
This generalized the ASCII-only fast-path, but only for the `Grapheme_Extend` property for now,
as that is the only one with a lower bound outside of ASCII.
The indices are encoded as `u32`s in the range of invalid `char`s, so
that we know that if any mapping fails to parse as a `char` we should
use the value for lookup in the multi-table.
This avoids the second binary search in cases where a multi-`char`
mapping is needed.
Idea from @nikic
The majority of char case replacements are single char replacements,
so storing them as [char; 3] wastes a lot of space.
This commit splits the replacement tables for both `to_lower` and
`to_upper` into two separate tables, one with single-character mappings
and one with multi-character mappings.
This reduces the binary size for programs using all of these tables
with roughly 24K bytes.
Since ascii chars are already handled by a special case in the
`to_lower` and `to_upper` functions, there's no need to waste space on
them in the LUTs.
Before, it would enter the full expensive check even for normal ascii
characters. Now, it skips the check for the ascii characters in
`32..127`. This range was checked manually from the current behavior.
