Combination of ~Copyable + optional chaining + assignment crashes the compiler.
#80261
Labels
assignments
Feature → expressions: assignments
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
compiler
The Swift compiler itself
crash
Bug: A crash, i.e., an abnormal termination of software
expressions
Feature: expressions
noncopyable struct/enum
Feature → declarations: Noncopyable value type declarations
optional chaining
Feature → expressions: optional chaining
Comments
YOCKOW
added
assignments
|
CC: @meg-gupta @eeckstein |
|
This is a problem in the MoveOnlyChecker |
|
I think It may be limited to globals e.g. this doesn't crash: struct S: ~Copyable {
var x: Int
}
func test() {
var s: S? = S(x: 0)
s?.x = 1
}
test() |
Interesting and weird. The compiler still crashes when it's a stored property of a struct NonCopyable: ~Copyable {
var value: Int = 0
}
final class Holder { // The compiler doesn't crash if this is a noncopyable struct.
var nc: NonCopyable? = NonCopyable()
func f() {
nc?.value = 1
}
}Stack dumpSIL verification failed: instruction isn't dominated by its operand: properlyDominates(valueI, I)
Verifying instruction:
%9 = unchecked_take_enum_data_addr %3 : $*Optional<NonCopyable>, #Optional.some!enumelt // users: %8, %12
-> destroy_addr %9 : $*NonCopyable // id: %8
In function:
// Holder.f()
// Isolation: unspecified
sil hidden [ossa] @$s4main6HolderC1fyyF : $@convention(method) (@guaranteed Holder) -> () {
// %0 "self" // users: %2, %1
bb0(%0 : @guaranteed $Holder):
debug_value %0, let, name "self", argno 1 // id: %1
%2 = ref_element_addr %0, #Holder.nc // user: %3
%3 = begin_access [modify] [dynamic] %2 // users: %6, %9, %14, %21
%4 = integer_literal $Builtin.Int1, -1 // user: %6
%5 = integer_literal $Builtin.Int1, 0 // user: %6
%6 = select_enum_addr %3, case #Optional.some!enumelt: %4, default %5 : $Builtin.Int1 // user: %7
cond_br %6, bb1, bb3 // id: %7
bb1: // Preds: bb0
destroy_addr %9 // id: %8
%9 = unchecked_take_enum_data_addr %3, #Optional.some!enumelt // users: %8, %12
%10 = integer_literal $Builtin.Int64, 1 // user: %11
%11 = struct $Int (%10) // user: %13
%12 = struct_element_addr %9, #NonCopyable.value // user: %13
store %11 to [trivial] %12 // id: %13
end_access %3 // id: %14
%15 = tuple () // user: %16
%16 = enum $Optional<()>, #Optional.some!enumelt, %15 // user: %17
br bb2(%16) // id: %17
bb2(%18 : $Optional<()>): // Preds: bb3 bb1
%19 = tuple () // user: %20
return %19 // id: %20
bb3: // Preds: bb0
end_access %3 // id: %21
%22 = enum $Optional<()>, #Optional.none!enumelt // user: %23
br bb2(%22) // id: %23
} // end sil function '$s4main6HolderC1fyyF'
Stack dump:
0. Program arguments: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-03-17-a.xctoolchain/usr/bin/swift-frontend -frontend -interpret GHI-80261_NonCopyable-OptionalChaining-Assignment_StoredProperty.swift -Xllvm -aarch64-use-tbi -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -color-diagnostics -empty-abi-descriptor -resource-dir /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-03-17-a.xctoolchain/usr/lib/swift -no-auto-bridging-header-chaining -module-name main -in-process-plugin-server-path /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-03-17-a.xctoolchain/usr/lib/swift/host/libSwiftInProcPluginServer.dylib -plugin-path /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-03-17-a.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2025-03-17-a.xctoolchain/usr/local/lib/swift/host/plugins -target-sdk-version 15.2 -target-sdk-name macosx15.2 -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server
1. Apple Swift version 6.2-dev (LLVM 21406e90d7382d7, Swift 90340a069a706c3)
2. Compiling with effective version 5.10
3. While verifying SIL function "@$s4main6HolderC1fyyF".
for 'f()' (at GHI-80261_NonCopyable-OptionalChaining-Assignment_StoredProperty.swift:8:3)
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0 swift-frontend 0x0000000105bc0184 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1 swift-frontend 0x0000000105bbe8b0 llvm::sys::RunSignalHandlers() + 112
2 swift-frontend 0x0000000105bc07cc SignalHandler(int, __siginfo*, void*) + 296
3 libsystem_platform.dylib 0x000000018f996de4 _sigtramp + 56
4 libsystem_pthread.dylib 0x000000018f95ff70 pthread_kill + 288
5 libsystem_c.dylib 0x000000018f86c908 abort + 128
6 swift-frontend 0x000000010136f828 swift::SILModule::print(llvm::raw_ostream&, swift::ModuleDecl*, swift::SILOptions const&, bool) const + 0
7 swift-frontend 0x000000010139187c (anonymous namespace)::SILVerifier::visitSILInstruction(swift::SILInstruction*) + 1584
8 swift-frontend 0x000000010137c568 swift::SILVisitorBase<(anonymous namespace)::SILVerifier, void>::visitSILBasicBlock(swift::SILBasicBlock*) + 22648
9 swift-frontend 0x0000000101376c30 (anonymous namespace)::SILVerifier::visitSILBasicBlock(swift::SILBasicBlock*) + 24
10 swift-frontend 0x0000000101375590 (anonymous namespace)::SILVerifier::visitSILFunction(swift::SILFunction*) + 10464
11 swift-frontend 0x000000010136f9e0 swift::SILFunction::verify(swift::CalleeCache*, bool, bool, bool) const + 224
12 swift-frontend 0x00000001013726f4 swift::SILModule::verify(swift::CalleeCache*, bool, bool) const + 192
13 swift-frontend 0x00000001013725cc swift::SILModule::verify(bool, bool) const + 140
14 swift-frontend 0x0000000100723228 swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 148
15 swift-frontend 0x00000001004ea340 performCompileStepsPostSILGen(swift::CompilerInstance&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 820
16 swift-frontend 0x00000001004e9cf8 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1320
17 swift-frontend 0x00000001004f5f48 withSemanticAnalysis(swift::CompilerInstance&, swift::FrontendObserver*, llvm::function_ref<bool (swift::CompilerInstance&)>, bool) + 164
18 swift-frontend 0x00000001004eb6f4 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 716
19 swift-frontend 0x00000001004eaf10 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2244
20 swift-frontend 0x00000001002a2c8c swift::mainEntry(int, char const**) + 3060
21 dyld 0x000000018f5e0274 start + 2840 |
|
@YOCKOW From my understanding it looks the nc?.value = 1Similar error happens when doing: var nc1: NonCopyable? = NonCopyable()
nc1?.value = 1
func f(nc1: consuming NonCopyable?) {
var nc2: NonCopyable? = nc1
}Or even: var nc1: NonCopyable? = NonCopyable()
nc1?.value = 1
func f(nc1: consuming NonCopyable?) {
var nc2: NonCopyable? = NonCopyable(value: nc1!.value)
}Same issue happens with Specifically in these passes is where the dominator tree seems broken: Pass 72: *** SIL function after #72, stage Mandatory Diagnostic Passes + Enabling Optimization Passes, pass 18: LowerTupleAddrConstructor (lower-tuple-addr-constructor)
// main
// Isolation: unspecified
sil [ossa] @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
alloc_global @$s4main2ncAA11NonCopyableVSgvp // id: %2
%3 = global_addr @$s4main2ncAA11NonCopyableVSgvp : $*Optional<NonCopyable> // users: %9, %8
%4 = metatype $@thin NonCopyable.Type // user: %6
// function_ref NonCopyable.init()
%5 = function_ref @$s4main11NonCopyableVACycfC : $@convention(method) (@thin NonCopyable.Type) -> @owned NonCopyable // user: %6
%6 = apply %5(%4) : $@convention(method) (@thin NonCopyable.Type) -> @owned NonCopyable // user: %7
%7 = enum $Optional<NonCopyable>, #Optional.some!enumelt, %6 // user: %8
store %7 to [init] %3 // id: %8
%9 = begin_access [modify] [dynamic] %3 // users: %24, %15, %10
%10 = mark_unresolved_non_copyable_value [assignable_but_not_consumable] %9 // users: %17, %13
%11 = integer_literal $Builtin.Int1, -1 // user: %13
%12 = integer_literal $Builtin.Int1, 0 // user: %13
%13 = select_enum_addr %10, case #Optional.some!enumelt: %11, default %12 : $Builtin.Int1 // user: %14
cond_br %13, bb2, bb1 // id: %14
bb1: // Preds: bb0
end_access %9 // id: %15
br bb4 // id: %16
bb2: // Preds: bb0
%17 = unchecked_take_enum_data_addr %10, #Optional.some!enumelt // user: %22
%18 = integer_literal $Builtin.IntLiteral, 1 // user: %21
%19 = metatype $@thin Int.Type // user: %21
// function_ref Int.init(_builtinIntegerLiteral:)
%20 = function_ref @$sSi22_builtinIntegerLiteralSiBI_tcfC : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int // user: %21
%21 = apply %20(%18, %19) : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int // user: %23
%22 = struct_element_addr %17, #NonCopyable.value // user: %23
store %21 to [trivial] %22 // id: %23
end_access %9 // id: %24
%25 = tuple () // user: %26
%26 = enum $Optional<()>, #Optional.some!enumelt, %25 // user: %27
br bb3(%26) // id: %27
bb3(%28 : $Optional<()>): // Preds: bb4 bb2
%29 = integer_literal $Builtin.Int32, 0 // user: %30
%30 = struct $Int32 (%29) // user: %31
return %30 // id: %31
bb4: // Preds: bb1
%32 = enum $Optional<()>, #Optional.none!enumelt // user: %33
br bb3(%32) // id: %33
} // end sil function 'main'And then we destroy Pass 89: *** SIL function after #89, stage Mandatory Diagnostic Passes + Enabling Optimization Passes, pass 21: MoveOnlyChecker (sil-move-only-checker)
// main
// Isolation: unspecified
sil [ossa] @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
alloc_global @$s4main3nc1AA11NonCopyableVSgvp // id: %2
%3 = global_addr @$s4main3nc1AA11NonCopyableVSgvp : $*Optional<NonCopyable> // users: %9, %8
%4 = metatype $@thin NonCopyable.Type // user: %6
// function_ref NonCopyable.init()
%5 = function_ref @$s4main11NonCopyableVACycfC : $@convention(method) (@thin NonCopyable.Type) -> @owned NonCopyable // user: %6
%6 = apply %5(%4) : $@convention(method) (@thin NonCopyable.Type) -> @owned NonCopyable // user: %7
%7 = enum $Optional<NonCopyable>, #Optional.some!enumelt, %6 // user: %8
store %7 to [init] %3 // id: %8
%9 = begin_access [modify] [dynamic] %3 // users: %12, %17, %24, %14
%10 = integer_literal $Builtin.Int1, -1 // user: %12
%11 = integer_literal $Builtin.Int1, 0 // user: %12
%12 = select_enum_addr %9, case #Optional.some!enumelt: %10, default %11 : $Builtin.Int1 // user: %13
cond_br %12, bb2, bb1 // id: %13
bb1: // Preds: bb0
end_access %9 // id: %14
br bb4 // id: %15
bb2: // Preds: bb0
destroy_addr %17 // id: %16
%17 = unchecked_take_enum_data_addr %9, #Optional.some!enumelt // users: %16, %22
%18 = integer_literal $Builtin.IntLiteral, 1 // user: %21
%19 = metatype $@thin Int.Type // user: %21
// function_ref Int.init(_builtinIntegerLiteral:)
%20 = function_ref @$sSi22_builtinIntegerLiteralSiBI_tcfC : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int // user: %21
%21 = apply %20(%18, %19) : $@convention(method) (Builtin.IntLiteral, @thin Int.Type) -> Int // user: %23
%22 = struct_element_addr %17, #NonCopyable.value // user: %23
store %21 to [trivial] %22 // id: %23
end_access %9 // id: %24
%25 = tuple () // user: %26
%26 = enum $Optional<()>, #Optional.some!enumelt, %25 // user: %27
br bb3(%26) // id: %27
bb3(%28 : $Optional<()>): // Preds: bb4 bb2
%29 = integer_literal $Builtin.Int32, 0 // user: %30
%30 = struct $Int32 (%29) // user: %31
return %30 // id: %31
bb4: // Preds: bb1
%32 = enum $Optional<()>, #Optional.none!enumelt // user: %33
br bb3(%32) // id: %33
} // end sil function 'main'It would be great if you provide right pointers to it in the codebase which handle this to at least give it a try. |
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Description
The compiler crashes when you try to assign a value to a property of optional-chained non-copyable type.
Reproduction
Stack dump
Expected behavior
The compiler doesn't crash.
Environment
Additional information
This may be related to #75999, but this issue occurs even if you use
!instead of?.(Related post: https://forums.swift.org/t/how-can-i-borrow-with-conditional-binding/78759/11)
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