Switch StringObject and StringGuts from opaquely storing tagged cocoa
strings into storing small strings. Plumb small string support
throughout the standard library's routines.
Streamline internal String creation. Previously, everything funneled
into a single generic function, however, every single call of the
generic funnel had relevant specific information that could be used
for a more efficient algorithm.
In preparation for efficiently forming small strings, refactor this
logic into a handful of more specialized subroutines to preserve more
specific information from the callers.
Restore (un-revert) sting comparison, with fixes
More exhaustive testing of opaque strings, which consistently reproduces prior sporadic failure. Shims fixups. Some test tweaking.
Include the initial implementation of _StringGuts, a 2-word
replacement for _LegacyStringCore. 64-bit Darwin supported, 32-bit and
Linux support in subsequent commits.
In grand LLVM tradition, the first step to redesigning _StringCore is
to first rename it to _LegacyStringCore. Subsequent commits will
introduce the replacement, and eventually all uses of the old one will
be moved to the new one.
NFC.
* Remove a bunch of Default(Bidirectional|RandomAccess)Indices usage from stdlib and test
* Remove some DefaultRandomAccessIndices and IndexDistance usage from Foundation
* Remove no-longer-used internal type in Existentials.swift
* Get rid of indicesForTraversal
* Eradicate IndexDistance associated type, replacing with Int everywhere
* Consistently use Int for ExistentialCollection’s IndexDistance type.
* Fix test for IndexDistance removal
* Remove a handful of no-longer-needed explicit types
* Add compatibility shims for non-Int index distances
* Test compatibility shim
* Move IndexDistance typealias into the Collection protocol
This necessary for ensuring the property that String doesn't keep
inaccessible memory alive. For example, before this change,
String(s.dropFirst().unicodeScalars)
would compile and produce a String that owned inaccessible memory.
Now it no longer compiles.
String's view's SubSequences are the same as the Substring's
view. E.g. String.UnicodeScalarView.SubSequence is
Substring.UnicodeScalarView.
New compatibility inits added, to work around the fact that many
previously failable initializers are now non-failable.
This is a step along the way toward handling backward-compatiblity of UTF8View
slicing and preventing inadvertent creation of String instances that keep
inaccessible memory alive.
I failed to merge the upstream changes to swift-corelibs-foundation at the same
time as I merged that #9806, and it broke on linux. Going to get it right this
time.
UnsafeBufferPoiunter subscript used in the fast path only checks bounds
in Debug mode, therefore extra checks are needed.
Addresses: <rdar://problem/31992473>
It replaces String initializers taking Character or UnicodeScalar as a repeating value by a more general initializer that takes a String as a repeating value. This is done to avoid the ambiguities in the current String API, which can be only resolved by explicit casting.
String.append(_:UnicodeScalar) APIs is also removed to match these changes.
