[SR-4888] Crash: Tuple KeyPaths

[stephencelis]

Previous ID	SR-4888
Radar	rdar://problem/34186458
Original Reporter	@stephencelis
Type	Bug
Status	Reopened
Resolution

Environment

Swift Development Snapshot 2017-05-12 (a)
Xcode 8.3.2
macOS 10.12.5 Beta (16F71b)

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, CompilerCrash
Assignee	@jckarter
Priority	Medium

md5: e43e68b9511248f280cf77762db2a6d0

Issue Description:

Right now, tuple KeyPaths crash the compiler.

Assertion failed: (isDecl() && "Not a declaration"), function getDecl, file /Users/buildnode/jenkins/workspace/oss-swift-package-osx/swift/lib/Sema/OverloadChoice.h, line 251.
0  swift                    0x000000010efc8b18 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x000000010efc7ae6 llvm::sys::RunSignalHandlers() + 86
2  swift                    0x000000010efc90d9 SignalHandler(int) + 361
3  libsystem_platform.dylib 0x00007fffb72cbb3a _sigtramp + 26
4  libsystem_platform.dylib 0x00007fff53e6fbb8 _sigtramp + 2629451928
5  libsystem_c.dylib        0x00007fffb7150420 abort + 129
6  libsystem_c.dylib        0x00007fffb7117893 basename_r + 0
7  swift                    0x000000010cba0f20 swift::constraints::ConstraintSystem::simplifyKeyPathConstraint(swift::Type, swift::Type, swift::Type, swift::OptionSet<swift::constraints::ConstraintSystem::TypeMatchFlags, unsigned int>, swift::constraints::ConstraintLocatorBuilder) + 2064

Basic case:

struct User {
  let names: (first: String, last: String)

  func test() {
    _ = \User.names.0
    _ = \User.names.first
  }
}

Ideally the KeyPath works in a read-only fashion! Less ideally we get a compiler error.

[jckarter]

@swift-ci create

[jckarter]

PR for master: #9618
and 4.0: #9620

[jckarter]

Merged. Support for tuple elements will have to wait for another time, but the compiler shouldn't crash anymore. Thanks!

[ffried]

I'm seeing this again in the current Xcode 9 beta 6.

The only difference is that I'm using a typealias.

struct Container {
typealias Element = (name: String, count: Int)

let elem: Element? = (name: "test", count: 2)
}

let keyPath: KeyPath<Container, String> = \Container.elem?.0
let keyPath: KeyPath<Container, String> = \Container.elem?.name

When compiling, Swift fails with a Segfault 11:

0  swift                    0x000000011133942a PrintStackTraceSignalHandler(void*) + 42
1  swift                    0x0000000111338866 SignalHandler(int) + 662
2  libsystem_platform.dylib 0x00007fff983c6b3a _sigtramp + 26
3  swift                    0x000000010ef16164 swift::Type::transformRec(llvm::function_ref<llvm::Optional<swift::Type> (swift::TypeBase*)>) const + 148
4  swift                    0x000000010ec34869 (anonymous namespace)::ExprWalker::walkToExprPost(swift::Expr*) + 25
5  swift                    0x000000010ed50f44 swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 1540
6  swift                    0x000000010ec5d52b (anonymous namespace)::FailureDiagnosis::typeCheckChildIndependently(swift::Expr*, swift::Type, swift::ContextualTypePurpose, swift::OptionSet<TCCFlags, unsigned int>, swift::ExprTypeCheckListener*, bool) + 1963
7  swift                    0x000000010ec56076 (anonymous namespace)::FailureDiagnosis::diagnoseContextualConversionError(swift::Expr*, swift::Type) + 86
8  swift                    0x000000010ec4da05 swift::constraints::ConstraintSystem::diagnoseFailureForExpr(swift::Expr*) + 101
9  swift                    0x000000010ec837f7 swift::constraints::ConstraintSystem::salvage(llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::Expr*) + 6199
10 swift                    0x000000010ed507a1 swift::TypeChecker::solveForExpression(swift::Expr*&, swift::DeclContext*, swift::Type, swift::FreeTypeVariableBinding, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem&, llvm::SmallVectorImpl<swift::constraints::Solution>&, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>) + 8353
11 swift                    0x000000010ed50c1d swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 733
12 swift                    0x000000010ed53e1e swift::TypeChecker::typeCheckBinding(swift::Pattern*&, swift::Expr*&, swift::DeclContext*, bool) + 366
13 swift                    0x000000010ed543dc swift::TypeChecker::typeCheckPatternBinding(swift::PatternBindingDecl*, unsigned int, bool) + 188
14 swift                    0x000000010ed671d5 (anonymous namespace)::DeclChecker::visit(swift::Decl*) + 1349
15 swift                    0x000000010edd64ad swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 13805
16 swift                    0x000000010edd8fdc swift::TypeChecker::typeCheckTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 220
17 swift                    0x000000010edf56a5 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int) + 1861
18 swift                    0x000000010e926144 swift::CompilerInstance::performSema() + 4628
19 swift                    0x000000010dcaaa62 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1378
20 swift                    0x000000010dca8c94 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7716
21 swift                    0x000000010dc5dbb8 main + 12248
22 libdyld.dylib            0x00007fff981b7235 start + 1
23 libdyld.dylib            0x000000000000000a start + 1743031766
Stack dump:
0.  Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -interpret s4_keypath_tuple.swift -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -color-diagnostics -module-name s4_keypath_tuple 
1.  While type-checking declaration 0x7ff386859398 at s4_keypath_tuple.swift:7:1
2.  While type-checking expression at [s4_keypath_tuple.swift:7:43 - line:7:60] RangeText="\Container.elem?.0"
3.  While type-checking expression at [s4_keypath_tuple.swift:7:43 - line:7:60] RangeText="\Container.elem?.0"

$ swift --version
Apple Swift version 4.0 (swiftlang-900.0.63.10 clang-900.0.36)
Target: x86_64-apple-macosx10.9

[jckarter]

@swift-ci create

[xAlien95]

Both the code snippets of @stephencelis and @ffried do not crash the compiler using Swift version 5.3 (swiftlang-1200.0.22.4 clang-1200.0.25.1).

A quick note on @ffried's example:

let keyPath: KeyPath<Container, String> = \Container.elem?.0
let keyPath: KeyPath<Container, String> = \Container.elem?.name

In order to return String, you need to force unwrap the elem key:

let keyPath: KeyPath<Container, String> = \Container.elem!.0
let keyPath: KeyPath<Container, String> = \Container.elem!.name

[ffried]

@xAlien95 Thanks. Yea, the KeyPath Value should be String? in my example of course. Or force-unwrapping them - true.

[typesanitizer]

Should this be marked as resolved/closed now?

[stephencelis]

Fixed.