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[SE-0494][StdLib] Add isTriviallyIdentical(to:) Methods to String and Substring #82055

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Merged
lorentey merged 16 commits into from
Dec 11, 2025
Merged

[SE-0494][StdLib] Add isTriviallyIdentical(to:) Methods to String and Substring #82055

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abae2f6
[stdlib] string identical
vanvoorden Oct 16, 2025
794bbb9
[stdlib] Define availability for the 6.4 stdlib and runtime
lorentey Dec 8, 2025
b7e32db
[stdlib] Update availability of isTriviallyIdentical methods
lorentey Dec 8, 2025
a7b152b
[benchmark] Remove new benchmarks
lorentey Dec 8, 2025
3833cbd
[test] Fix ABI expectations
lorentey Dec 8, 2025
c8202c6
Apply suggestions from code review
lorentey Dec 8, 2025
be5ec1a
Add `isTriviallyIdentical` for unicode views
WindowsMEMZ Oct 28, 2025
5b22d2a
Add tests
WindowsMEMZ Oct 28, 2025
14e37a1
Make `isIdentical` opaque for clients
WindowsMEMZ Oct 30, 2025
288a698
Add `isIdentical` to StringGuts and use it for comparation
WindowsMEMZ Oct 30, 2025
8055d91
Update tests for availability checking
WindowsMEMZ Oct 30, 2025
4cde919
[stdlib] Update availability of String view additions
lorentey Dec 8, 2025
e5787c6
[stdlib] String, Substring: Use new _StringGuts helper
lorentey Dec 8, 2025
a3650e7
[test] Update tests, acknowledging new additions
lorentey Dec 8, 2025
8c9f084
substring test nits
vanvoorden Dec 9, 2025
0ab8884
add 6.4 symbols to abi tests
vanvoorden Dec 9, 2025
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4 changes: 2 additions & 2 deletions benchmark/single-source/StringTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ import TestsUtils
@_spi(_Unicode)
import Swift

public var benchmarks: [BenchmarkInfo] {
public let benchmarks: [BenchmarkInfo] = {
var result = [
BenchmarkInfo(
name: "StringEqualPointerComparison",
Expand Down Expand Up @@ -50,7 +50,7 @@ public var benchmarks: [BenchmarkInfo] {
tags: [.validation, .String]))
}
return result
}
}()

// FIXME(string)
public func run_StringHasPrefixAscii(_ n: Int) {
Expand Down
5 changes: 5 additions & 0 deletions include/swift/AST/RuntimeVersions.def
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Expand Up @@ -171,6 +171,11 @@ RUNTIME_VERSION(
FUTURE
)

RUNTIME_VERSION(
(6, 4),
FUTURE
)

END_MAJOR_VERSION(6)

// .......................................................................... //
Expand Down
4 changes: 3 additions & 1 deletion stdlib/public/core/Availability.swift
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Expand Up @@ -258,8 +258,10 @@ extension _SwiftStdlibVersion {
public static var v6_2_0: Self { Self(_value: 0x060200) }
@_alwaysEmitIntoClient
public static var v6_3_0: Self { Self(_value: 0x060300) }
@_alwaysEmitIntoClient
public static var v6_4_0: Self { Self(_value: 0x060400) }
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@vanvoorden vanvoorden Dec 9, 2025

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[2025-12-09T04:52:54.512Z] FAIL: Swift(macosx-x86_64) :: abi/macOS/x86_64/stdlib-asserts.swift (10622 of 20420, 6 of 6 attempts)
[2025-12-09T04:52:54.512Z] ******************** TEST 'Swift(macosx-x86_64) :: abi/macOS/x86_64/stdlib-asserts.swift' FAILED ********************
[2025-12-09T04:52:54.512Z] Exit Code: 1
[2025-12-09T04:52:54.512Z] 
[2025-12-09T04:52:54.512Z] Command Output (stdout):
[2025-12-09T04:52:54.512Z] --
[2025-12-09T04:52:54.512Z] --- /Users/ec2-user/jenkins/workspace/swift-PR-macos/branch-main/swift/test/abi/macOS/x86_64/../../Inputs/macOS/x86_64/stdlib/baseline-asserts	2025-12-09 02:24:28
[2025-12-09T04:52:54.512Z] +++ /Users/ec2-user/jenkins/workspace/swift-PR-macos/branch-main/build/buildbot_incremental/swift-macosx-x86_64/test-macosx-x86_64/abi/macOS/x86_64/Output/stdlib-asserts.swift.tmp/symbols	2025-12-09 04:52:54
[2025-12-09T04:52:54.512Z] @@ -3385,6 +3385,7 @@
[2025-12-09T04:52:54.512Z]  _$sSo19_SwiftStdlibVersionas23CustomStringConvertiblesWP
[2025-12-09T04:52:54.512Z]  _$sSo19_SwiftStdlibVersionasE11descriptionSSvg
[2025-12-09T04:52:54.512Z]  _$sSo19_SwiftStdlibVersionasE11descriptionSSvpMV
[2025-12-09T04:52:54.512Z] +_$sSo19_SwiftStdlibVersionasE6v6_4_0ABvpZMV
[2025-12-09T04:52:54.512Z]  _$sSo19_SwiftStdlibVersionasE7currentABvgZ
[2025-12-09T04:52:54.512Z]  _$sSp10deallocate8capacityySi_tF
[2025-12-09T04:52:54.512Z]  _$sSp10deallocateyyF

@lorentey I think this one led to a failure from the stdlib-asserts.swift… but I thought aeic did not trigger the ABI tests?

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@vanvoorden vanvoorden Dec 9, 2025

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I found 58dec75 and 1434440. So I think we also need to add the 6.4 here?

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@lorentey lorentey Dec 9, 2025

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@lorentey I think this one led to a failure from the stdlib-asserts.swift… but I thought aeic did not trigger the ABI tests?

This is a property descriptor to support reflection; its export is somewhat questionable, but it's expected! It should be added to the expectation files (for both arm64 and Intel), just like the others.

The property itself is backdeployable; do not add an availability declaration to it.


private static var _current: Self { .v6_3_0 }
private static var _current: Self { .v6_4_0 }

#if hasFeature(Macros)
@available(SwiftStdlib 5.7, *)
Expand Down
39 changes: 38 additions & 1 deletion stdlib/public/core/String.swift
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Expand Up @@ -1112,4 +1112,41 @@ extension String {
}
}


extension String {
/// Returns a boolean value indicating whether this string is identical to
/// `other`.
///
/// Two string values are identical if there is no way to distinguish between
/// them.
///
/// For any values `a`, `b`, and `c`:
///
/// - `a.isTriviallyIdentical(to: a)` is always `true`. (Reflexivity)
/// - `a.isTriviallyIdentical(to: b)` implies `b.isTriviallyIdentical(to: a)`.
/// (Symmetry)
/// - If `a.isTriviallyIdentical(to: b)` and `b.isTriviallyIdentical(to: c)`
/// are both `true`, then `a.isTriviallyIdentical(to: c)` is also `true`.
/// (Transitivity)
/// - `a.isTriviallyIdentical(b)` implies `a == b`. `a == b` does not imply `a.isTriviallyIdentical(b)`
///
/// Values produced by copying the same value, with no intervening mutations,
/// will compare identical:
///
/// ```swift
/// let d = c
/// print(c.isTriviallyIdentical(to: d))
/// // Prints true
/// ```
///
/// Comparing strings this way includes comparing (normally) hidden
/// implementation details such as the memory location of any underlying
/// string storage object. Therefore, identical strings are guaranteed to
/// compare equal with `==`, but not all equal strings are considered
/// identical.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._guts.isTriviallyIdentical(to: other._guts)
}
}
7 changes: 7 additions & 0 deletions stdlib/public/core/StringGuts.swift
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Expand Up @@ -418,6 +418,13 @@ extension _StringGuts {
}
}

extension _StringGuts {
@inline(__always) // Performance
internal func isTriviallyIdentical(to other: Self) -> Bool {
self.rawBits == other.rawBits
}
}

#if _runtime(_ObjC)
extension _StringGuts {

Expand Down
11 changes: 11 additions & 0 deletions stdlib/public/core/StringUTF16View.swift
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Expand Up @@ -1056,3 +1056,14 @@ extension String.UTF16View {
}
}
}

extension String.UTF16View {
/// Returns a boolean value indicating whether this UTF16 view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._guts.isTriviallyIdentical(to: other._guts)
}
}
11 changes: 11 additions & 0 deletions stdlib/public/core/StringUTF8View.swift
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Expand Up @@ -684,3 +684,14 @@ extension String.UTF8View {
return unsafe try _guts.withFastUTF8(body)
}
}

extension String.UTF8View {
/// Returns a boolean value indicating whether this UTF8 view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._guts.isTriviallyIdentical(to: other._guts)
}
}
11 changes: 11 additions & 0 deletions stdlib/public/core/StringUnicodeScalarView.swift
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Expand Up @@ -527,3 +527,14 @@ extension String.UnicodeScalarView {
return r._knownUTF16
}
}

extension String.UnicodeScalarView {
/// Returns a boolean value indicating whether this unicode scalar view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._guts.isTriviallyIdentical(to: other._guts)
}
}
76 changes: 76 additions & 0 deletions stdlib/public/core/Substring.swift
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Expand Up @@ -882,6 +882,18 @@ extension Substring.UTF8View {
#endif // !(os(watchOS) && _pointerBitWidth(_32))
}

extension Substring.UTF8View {
/// Returns a boolean value indicating whether this UTF8 view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._base.isTriviallyIdentical(to: other._base)
&& self._bounds == other._bounds
}
}

extension Substring {
@inlinable
public var utf8: UTF8View {
Expand Down Expand Up @@ -1037,6 +1049,18 @@ extension Substring.UTF16View: BidirectionalCollection {
}
}

extension Substring.UTF16View {
/// Returns a boolean value indicating whether this UTF16 view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._base.isTriviallyIdentical(to: other._base)
&& self._bounds == other._bounds
}
}

extension Substring {
@inlinable
public var utf16: UTF16View {
Expand Down Expand Up @@ -1281,6 +1305,18 @@ extension Substring.UnicodeScalarView: RangeReplaceableCollection {
}
}

extension Substring.UnicodeScalarView {
/// Returns a boolean value indicating whether this unicode scalar view
/// is trivially identical to `other`.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._slice._base.isTriviallyIdentical(to: other._slice._base)
&& self._bounds == other._bounds
}
}

extension Substring: RangeReplaceableCollection {
@_specialize(where S == String)
@_specialize(where S == Substring)
Expand Down Expand Up @@ -1385,3 +1421,43 @@ extension Substring {
return Substring(_unchecked: Slice(base: base, bounds: r))
}
}

extension Substring {
/// Returns a boolean value indicating whether this substring is identical to
/// `other`.
///
/// Two substring values are identical if there is no way to distinguish
/// between them.
///
/// For any values `a`, `b`, and `c`:
///
/// - `a.isTriviallyIdentical(to: a)` is always `true`. (Reflexivity)
/// - `a.isTriviallyIdentical(to: b)` implies `b.isTriviallyIdentical(to: a)`.
/// (Symmetry)
/// - If `a.isTriviallyIdentical(to: b)` and `b.isTriviallyIdentical(to: c)`
/// are both `true`, then `a.isTriviallyIdentical(to: c)` is also `true`.
/// (Transitivity)
/// - `a.isTriviallyIdentical(b)` implies `a == b`. `a == b` does not imply `a.isTriviallyIdentical(b)`
///
/// Values produced by copying the same value, with no intervening mutations,
/// will compare identical:
///
/// ```swift
/// let d = c
/// print(c.isTriviallyIdentical(to: d))
/// // Prints true
/// ```
///
/// Comparing substrings this way includes comparing (normally) hidden
/// implementation details such as the memory location of any underlying
/// substring storage object. Therefore, identical substrings are guaranteed
/// to compare equal with `==`, but not all equal substrings are considered
/// identical.
///
/// - Complexity: O(1)
@available(StdlibDeploymentTarget 6.4, *)
public func isTriviallyIdentical(to other: Self) -> Bool {
self._wholeGuts.isTriviallyIdentical(to: other._wholeGuts) &&
self._offsetRange == other._offsetRange
}
}
1 change: 1 addition & 0 deletions test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift
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Expand Up @@ -124,6 +124,7 @@
// CHECK: SWIFT_INLINE_THUNK uint8_t operator [](const __StringNested::Index& i) const SWIFT_SYMBOL({{.*}});
// CHECK: SWIFT_INLINE_THUNK String getDescription() const SWIFT_SYMBOL({{.*}});
// CHECK: SWIFT_INLINE_THUNK swift::Int getCount() const SWIFT_SYMBOL({{.*}});
// CHECK: SWIFT_INLINE_THUNK bool isTriviallyIdenticalTo(const __StringNested::UTF8View& other) const SWIFT_SYMBOL({{.*}}) {{.*}};
// CHECK-NEXT: private:

// CHECK: class AnyKeyPath { } SWIFT_UNAVAILABLE_MSG("class 'AnyKeyPath' is not yet exposed to C++");
Expand Down
11 changes: 11 additions & 0 deletions test/abi/macOS/arm64/stdlib.swift
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Expand Up @@ -771,6 +771,7 @@ Added: _$ss7UnicodeO5UTF32O27encodedReplacementCharacters15CollectionOfOneVys6UI
Added: _$sSo19_SwiftStdlibVersionasE6v6_1_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_2_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_3_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_4_0ABvpZMV
Added: _$sSBsE5radixSivpZMV
Added: _$sSFsE8ulpOfOnexvpZMV
Added: _$sSUsE8isSignedSbvpZMV
Expand Down Expand Up @@ -1161,3 +1162,13 @@ Added: _$ss13EncodingErrorO16debugDescriptionSSvg
Added: _$ss13EncodingErrorO16debugDescriptionSSvpMV
Added: _$ss13EncodingErrorOs28CustomDebugStringConvertiblesMc
Added: _$ss13EncodingErrorOs28CustomDebugStringConvertiblesWP

// SE-0494 Add isTriviallyIdentical(to:) Methods to String and Substring
Added: _$sSS20isTriviallyIdentical2toSbSS_tF
Added: _$sSs20isTriviallyIdentical2toSbSs_tF
Added: _$sSS17UnicodeScalarViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSS8UTF8ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSS9UTF16ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs17UnicodeScalarViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs8UTF8ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs9UTF16ViewV20isTriviallyIdentical2toSbAB_tF
11 changes: 11 additions & 0 deletions test/abi/macOS/x86_64/stdlib.swift
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Expand Up @@ -752,6 +752,7 @@ Added: _$ss8SIMDMaskVss6SIMD64Vys5Int64VGRszrlE7allTrueAByAGGvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_1_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_2_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_3_0ABvpZMV
Added: _$sSo19_SwiftStdlibVersionasE6v6_4_0ABvpZMV
Added: _$ss7Float80V12signalingNaNABvpZMV
Added: _$ss7Float80V13_exponentBiasSuvpZMV
Added: _$ss7Float80V13_quietNaNMasks6UInt64VvpZMV
Expand Down Expand Up @@ -1156,3 +1157,13 @@ Added: _$ss13EncodingErrorO16debugDescriptionSSvg
Added: _$ss13EncodingErrorO16debugDescriptionSSvpMV
Added: _$ss13EncodingErrorOs28CustomDebugStringConvertiblesMc
Added: _$ss13EncodingErrorOs28CustomDebugStringConvertiblesWP

// SE-0494 Add isTriviallyIdentical(to:) Methods to String and Substring
Added: _$sSS20isTriviallyIdentical2toSbSS_tF
Added: _$sSs20isTriviallyIdentical2toSbSs_tF
Added: _$sSS17UnicodeScalarViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSS8UTF8ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSS9UTF16ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs17UnicodeScalarViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs8UTF8ViewV20isTriviallyIdentical2toSbAB_tF
Added: _$sSs9UTF16ViewV20isTriviallyIdentical2toSbAB_tF
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