[SR-598] String initialized with [Any] causes runtime crash

[jepers]

Previous ID	SR-598
Radar	None
Original Reporter	@jepers
Type	Bug
Status	Closed
Resolution	Cannot Reproduce

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, TypeChecker
Assignee	@jepers
Priority	Medium

md5: 28a457a2eebf994c177f8f5e2ca4a7d3

Issue Description:

I have only tested this in swift-2.2-SNAPSHOT-2016-01-06-a-osx.pkg
(So maybe it's fixed in current master)

This program (cmd line prj, no imports) compiles fine but the resulting binary crashes at runtime:

let a: [Any] = [] // (Could as well be eg [1, "two"])
let s = String(a) // <-- Runtime crash here.
print(s)

Jumping to definition on the init of String.init(a) takes me here:

    /// Create an instance containing `characters`.
    public init<S : SequenceType where S.Generator.Element == Character>(_ characters: S)

which seems a bit strange (since the elements of a are not Characters).

[jepers]

cc @atrick (according to https://twitter.com/jckarter/status/690567279428313088 )

[atrick]

I verified the crash on master.
This is crash is in String.init(Character)

• frame #0: 0x000000010008fed5 libswiftCore.dylib`Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.UInt) -> () + 389 at /s/s/swift/stdlib/public/core/AssertCommon.swift:180
  frame Redundant Load Elimination Patches #1: 0x00000001001e622d libswiftCore.dylib`Swift._HeapBuffer._nativeObject.getter : Builtin.NativeObject + 221 at /s/s/swift/stdlib/public/core/HeapBuffer.swift:204
  frame Remove unnecessary unsafeUnwrap calls. #2: 0x00000001001e6129 libswiftCore.dylib`Swift._HeapBuffer._address.getter : Swift.UnsafeMutablePointer<Swift.Int8> + 25 at /s/s/swift/stdlib/public/core/HeapBuffer.swift:96
  frame Initial implementation of a @_cdecl attribute to export top-level functions to C #3: 0x00000001000d2920 libswiftCore.dylib`Swift._HeapBuffer.baseAddress.getter : Swift.UnsafeMutablePointer<B> + 64 at /s/s/swift/stdlib/public/core/HeapBuffer.swift:106
  frame install Foundation via the ninja script and add the test phase for Foundation #4: 0x000000010009e502 libswiftCore.dylib`Swift._StringBuffer.start.getter : Swift.UnsafeMutablePointer<Swift.RawByte> + 66 at /s/s/swift/stdlib/public/core/StringBuffer.swift:133
  frame Only run bindings-build-record on OS X due to test flakiness on Liunx… #5: 0x00000001000a7f79 libswiftCore.dylib`Swift._StringCore.init (Swift._StringBuffer) -> Swift._StringCore + 41 at /s/s/swift/stdlib/public/core/StringCore.swift:167
  frame Debug Info: Don't reset the debug scope after leaving the outermost s… #6: 0x00000001000a65ef libswiftCore.dylib`Swift.String.init (Swift.Character) -> Swift.String + 719 at /s/s/swift/stdlib/public/core/Character.swift:288
  frame Fix a bug in SILValue's hoistAddressProjections #7: 0x00000001002ca23c libswiftCore.dylib`Swift.String.CharacterView.append (Swift.Character) -> () + 284 at /s/s/swift/stdlib/public/core/StringCharacterView.swift:303
  frame Simplify configure pass for Foundation to use a defined variable for XCTest's build directory #8: 0x00000001002cb6cc libswiftCore.dylib`Swift.String.CharacterView.appendContentsOf <A where A: Swift.SequenceType, A.Generator.Element == Swift.Character> (A) -> () + 460 at /s/s/swift/stdlib/public/core/StringCharacterView.swift:314
  frame update related projects list to include Foundation and XCTest #9: 0x00000001002cb7c6 libswiftCore.dylib`Swift.String.CharacterView.init <A where A: Swift.SequenceType, A.Generator.Element == Swift.Character> (A) -> Swift.String.CharacterView + 166 at /s/s/swift/stdlib/public/core/StringCharacterView.swift:324
  frame Remove the FunctionEnumeration data structure from CalleeAnalysis #10: 0x00000001002d35dc libswiftCore.dylib`Swift.String.init <A where A: Swift.SequenceType, A.Generator.Element == Swift.Character> (A) -> Swift.String + 140 at /s/s/swift/stdlib/public/core/String.swift:605

As Jens pointed out, it's strange that we dispatch to String.init where Element == Character. At any rate, that attempts to initialize a String from a character with nil storage:

(Character) $R2 = {
_representation = Large {
Large = {
_storage = nil
}
}
}

I'm not sure why the code invokes the wrong String.init. It occurs at -Onone, with a debug stdlib and doesn't look like a runtime problem.

[jepers]

Possibly related to https://bugs.swift.org/browse/SR-550

[jepers]

Seems to have been fixed. Could not reproduce in dev snapshot 2016-08-04.