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elijah-semyonov opened this issue Apr 9, 2025 · 1 comment · May be fixed by #80913
Open

Crash when using Self in KeyPath expression #80669

elijah-semyonov opened this issue Apr 9, 2025 · 1 comment · May be fixed by #80913
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. crash Bug: A crash, i.e., an abnormal termination of software triage needed This issue needs more specific labels

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@elijah-semyonov
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Description

The program crashes with Fatal error: could not demangle keypath type from '��.

Reproduction

public func type<Root, Value>(at keyPath: KeyPath<Root, Value>) -> Value.Type {
    return Value.self
}

extension Int {
    static func bar() {
        print("Hello")
    }
}

class Foo {
    var int = 10
    
    static func staticFunc() {
        type(at: \Self.int).bar()
    }
}

Foo.staticFunc() // crashes
public func type<Root, Value>(at keyPath: KeyPath<Root, Value>) -> Value.Type {
    return Value.self
}

extension Int {
    static func bar() {
        print("Hello")
    }
}

class Foo {
    var int = 10
    
    static func staticFunc() {
        type(at: \Foo.int).bar()
    }
}

Foo.staticFunc() // Prints `Hello` correctly

Stack dump

#0	0x00000001adb1c95c in _swift_runtime_on_report ()
#1	0x00000001adbf49c8 in _swift_stdlib_reportFatalErrorInFile ()
#2	0x00000001ad7bc080 in closure #1 (Swift.UnsafeBufferPointer<Swift.UInt8>) -> () in Swift._assertionFailure(_: Swift.StaticString, _: Swift.String, file: Swift.StaticString, line: Swift.UInt, flags: Swift.UInt32) -> Swift.Never ()
#3	0x00000001ad7bb1f8 in Swift._assertionFailure(_: Swift.StaticString, _: Swift.String, file: Swift.StaticString, line: Swift.UInt, flags: Swift.UInt32) -> Swift.Never ()
#4	0x00000001ad8ed61c in Swift._resolveKeyPathGenericArgReference(_: Swift.UnsafeRawPointer, genericEnvironment: Swift.Optional<Swift.UnsafeRawPointer>, arguments: Swift.Optional<Swift.UnsafeRawPointer>) -> Swift.UnsafeRawPointer ()
#5	0x00000001ad8ed9cc in generic specialization <Swift.GetKeyPathClassAndInstanceSizeFromPattern> of Swift._walkKeyPathPattern<τ_0_0 where τ_0_0: Swift.KeyPathPatternVisitor>(_: Swift.UnsafeRawPointer, walker: inout τ_0_0) -> () ()
#6	0x00000001ad8ece30 in Swift._getKeyPathClassAndInstanceSizeFromPattern(Swift.UnsafeRawPointer, Swift.UnsafeRawPointer) -> (keyPathClass: Swift.AnyKeyPath.Type, rootType: Any.Type, size: Swift.Int, alignmentMask: Swift.Int) ()
#7	0x00000001ad8ecc04 in Swift._swift_getKeyPath(pattern: Swift.UnsafeMutableRawPointer, arguments: Swift.UnsafeRawPointer) -> Swift.UnsafeRawPointer ()

Expected behavior

No crash should happen

Environment

Swift compiler in toolchain shipped with Xcode 16.3 (16E140)

Additional information

No response
@elijah-semyonov elijah-semyonov added bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. crash Bug: A crash, i.e., an abnormal termination of software triage needed This issue needs more specific labels labels Apr 9, 2025
@stzn
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stzn commented Apr 13, 2025

While debugging the compiler, I encountered the following crash with the same code:

SIL verification failed: can't upcast to same type: UI->getType() != UI->getOperand()->getType()
Verifying instruction:
     %4 = load [take] %2 : $*Foo                  // user: %5
->   %5 = upcast %4 : $Foo to $Foo                // users: %11, %6
     %6 = begin_borrow %5 : $Foo                  // users: %9, %8, %7
     destroy_value %5 : $Foo                      // id: %11
In function:
// key path getter for Foo.other : Self
sil shared [thunk] [ossa] @$s4main3FooC5otherACvpACXDTK : $@convention(keypath_accessor_getter) (@in_guaranteed Foo) -> @out Foo {
// %0                                             // user: %10
// %1                                             // user: %3
bb0(%0 : $*Foo, %1 : $*Foo):
  %2 = alloc_stack $Foo                           // users: %12, %4, %3
  copy_addr %1 to [init] %2                       // id: %3
  %4 = load [take] %2                             // user: %5
  %5 = upcast %4 to $Foo                          // users: %11, %6
  %6 = begin_borrow %5                            // users: %9, %8, %7
  %7 = class_method %6, #Foo.other!getter : (Foo) -> () -> Foo, $@convention(method) (@guaranteed Foo) -> @owned Foo // user: %8
  %8 = apply %7(%6) : $@convention(method) (@guaranteed Foo) -> @owned Foo // user: %10
  end_borrow %6                                   // id: %9
  store %8 to [init] %0                           // id: %10
  destroy_value %5                                // id: %11
  dealloc_stack %2                                // id: %12
  %13 = tuple ()                                  // user: %14
  return %13                                      // id: %14
} // end sil function '$s4main3FooC5otherACvpACXDTK'
Stack dump:
0.      Program arguments: /usr/bin/swift-frontend -frontend -interpret - -disable-objc-interop -color-diagnostics -enable-bare-slash-regex -empty-abi-descriptor -resource-dir /usr/lib/swift -no-auto-bridging-header-chaining -module-name main -in-process-plugin-server-path /usr/lib/swift/host/libSwiftInProcPluginServer.so -plugin-path /usr/lib/swift/host/plugins -plugin-path /usr/local/lib/swift/host/plugins
1.      Swift version 6.2-dev (LLVM a3e32cdaae72f3d, Swift fa8609703528715)
2.      Compiling with effective version 5.10
3.      While evaluating request ASTLoweringRequest(Lowering AST to SIL for module main)
4.      While verifying SIL function "@$s4main3FooC5otherACvpACXDTK".
 for <<debugloc at "<compiler-generated>":0:0>>
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 0x00006316761cd618
1  swift-frontend 0x00006316761cb13e
2  swift-frontend 0x00006316761cdcb1
3  libc.so.6      0x00007db1ff5ca520
4  libc.so.6      0x00007db1ff61e9fc pthread_kill + 300
5  libc.so.6      0x00007db1ff5ca476 raise + 22
6  libc.so.6      0x00007db1ff5b07f3 abort + 211
7  swift-frontend 0x000063166f9fab99
8  swift-frontend 0x000063166fa17837
9  swift-frontend 0x000063166fa0478f
10 swift-frontend 0x000063166fa02b9b
11 swift-frontend 0x000063166f9fad9b
12 swift-frontend 0x000063166f9fe6a8
13 swift-frontend 0x000063166f9fe55f
14 swift-frontend 0x000063166ee157a0
15 swift-frontend 0x000063166ee20b6d
16 swift-frontend 0x000063166ef2d026
17 swift-frontend 0x000063166ee258e3
18 swift-frontend 0x000063166ee20d33
19 swift-frontend 0x000063166e615240
20 swift-frontend 0x000063166e6264ea
21 swift-frontend 0x000063166e617f5e
22 swift-frontend 0x000063166e617054
23 swift-frontend 0x000063166e3b45ab
24 libc.so.6      0x00007db1ff5b1d90
25 libc.so.6      0x00007db1ff5b1e40 __libc_start_main + 128
26 swift-frontend 0x000063166e3b35a5

Environment: Swift version 6.2-dev (LLVM a3e32cdaae72f3d, Swift fa86097)

It seems that in the case of \Self, the baseType is DynamicSelfType, which prevents retrieving the baseClass using getClassOrBoundGenericClass.
https://github.com/swiftlang/swift/blob/main/lib/SILGen/SILGenExpr.cpp#L3402

If this is the cause, is it okay for me to deal with this issue?

@stzn stzn linked a pull request Apr 18, 2025 that will close this issue
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. crash Bug: A crash, i.e., an abnormal termination of software triage needed This issue needs more specific labels
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[SILGen]Check if baseType is DynamicSelfType stzn/swift
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@elijah-semyonov @stzn