[SR-10305] Type Checker SegFault

[swift-ci]

Previous ID	SR-10305
Radar	rdar://problem/49609518
Original Reporter	calebkleveter (JIRA User)
Type	Bug
Status	Closed
Resolution	Done

Environment

Apple Swift version 5.0 (swiftlang-1001.0.69.5 clang-1001.0.46.3)
Target: x86_64-apple-darwin18.5.0

Additional Detail from JIRA

Votes	2
Component/s	Compiler
Labels	Bug, 5.0Regression, CompilerCrash, TypeChecker
Assignee	calebkleveter (JIRA)
Priority	Medium

md5: e4a5f8345ebf8ab1fdd4181d3edcf4df

is duplicated by:

• SR-10493 compiler crasher on [Substring].map(Int.init)
• SR-10561 Compiler crash Type Checker
• SR-10784 Compiler crash: Segmentation fault

Issue Description:

The Swift 5 type checker is crashing with a segfault when I try to convert an optional Substring to an Int:

public struct Version {
    public init?(_ string: String) {
        let components: [Substring] = string.split(separator: ".")
        guard let major: Int = components.first.flatMap(Int.init) else { return nil }
    }
}

The program compiles if I map over the Substring array and convert them so Strings.

Here is the gist with the compiler output: https://gist.github.com/calebkleveter/e6a7f3943b50e022ecd2beefbed44a6e

The crash occurs in both Xcode and the Terminal.

[theblixguy]

This doesn't crash on 5.1 (near master), but it does crash for me on 5.0 (Xcode 10.2).

[weissi]

4.2

$ jw-swift-4.2 swiftc /tmp/test.swift
/tmp/test.swift:4:49: error: 'flatMap' produces 'U?', not the expected contextual result type 'Int?'
        guard let major: Int = components.first.flatMap(Int.init) else { return nil }
                                                ^

5.0:

$ jw-swift-5.0 swiftc /tmp/test.swift
Assertion failed: (AffectedDecl), function RequirementFailure, file /Users/buildnode/jenkins/workspace/oss-swift-5.0-package-osx/swift/lib/Sema/CSDiagnostics.h, line 172.
Stack dump:
0.  Program arguments: /Library/Developer/Toolchains/swift-5.0-RELEASE.xctoolchain/usr/bin/swift -frontend -c -primary-file /tmp/test.swift -target x86_64-apple-darwin18.5.0 -enable-objc-interop -sdk /Volumes/Xcode11A301_m19A426z_i17A446z_t17J441z_w17R445z_b17P421z_32bitSupport_FastSim_Boost_37GB/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -color-diagnostics -module-name test -o /var/folders/lj/qfjqv9_x6b972r7l6f49lvmh0000gn/T/test-556ccb.o 
1.  While type-checking 'init(_:)' (at /tmp/test.swift:2:12)
2.  While type-checking statement at [/tmp/test.swift:2:36 - line:5:5] RangeText="{
        let components: [Substring] = string.split(separator: ".")
        guard let major: Int = components.first.flatMap(Int.init) else { return nil }
    "
3.  While type-checking statement at [/tmp/test.swift:4:9 - line:4:85] RangeText="guard let major: Int = components.first.flatMap(Int.init) else { return nil "
4.  While type-checking expression at [/tmp/test.swift:4:32 - line:4:65] RangeText="components.first.flatMap(Int.init"
0  swift                    0x0000000107876245 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift                    0x00000001078754e5 llvm::sys::RunSignalHandlers() + 85
2  swift                    0x0000000107876832 SignalHandler(int) + 258
3  libsystem_platform.dylib 0x00007fff65365b5d _sigtramp + 29
4  swift                    0x0000000108b8c9a1 cmark_strbuf__initbuf + 131204
5  libsystem_c.dylib        0x00007fff652256a6 abort + 127
6  libsystem_c.dylib        0x00007fff651ee20d basename_r + 0
7  swift                    0x0000000104bce7da swift::constraints::RequirementFailure::RequirementFailure(swift::constraints::ConstraintSystem&, swift::Expr*, swift::RequirementKind, swift::constraints::ConstraintLocator*) + 330
8  swift                    0x0000000104bcdae7 swift::constraints::MissingConformance::diagnose(swift::Expr*, bool) const + 55
9  swift                    0x0000000104b52a14 swift::Expr* llvm::function_ref<swift::Expr* (swift::Expr*)>::callback_fn<swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&)::$_11>(long, swift::Expr*) + 244
10 swift                    0x0000000104fd7cae swift::Expr::forEachChildExpr(llvm::function_ref<swift::Expr* (swift::Expr*)>)::ChildWalker::walkToExprPre(swift::Expr*) + 14
11 swift                    0x0000000104f6e199 swift::ASTVisitor<(anonymous namespace)::Traversal, swift::Expr*, swift::Stmt*, bool, swift::Pattern*, bool, void>::visit(swift::Expr*) + 201
12 swift                    0x0000000104f70b4f (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 207
13 swift                    0x0000000104f6da84 swift::Expr::walk(swift::ASTWalker&) + 84
14 swift                    0x0000000104fca303 swift::Expr::forEachChildExpr(llvm::function_ref<swift::Expr* (swift::Expr*)>) + 51
15 swift                    0x0000000104b32478 swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&) + 536
16 swift                    0x0000000104b326bb swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool) + 59
17 swift                    0x0000000104c65b47 swift::TypeChecker::typeCheckExpressionImpl(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener&, swift::constraints::ConstraintSystem*) + 1159
18 swift                    0x0000000104c6719d swift::TypeChecker::typeCheckBinding(swift::Pattern*&, swift::Expr*&, swift::DeclContext*, bool) + 397
19 swift                    0x0000000104c678e5 swift::TypeChecker::typeCheckStmtCondition(llvm::MutableArrayRef<swift::StmtConditionElement>&, swift::DeclContext*, swift::Diag<>) + 357
20 swift                    0x0000000104cfc23b swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 2363
21 swift                    0x0000000104cfe518 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::Stmt>(swift::Stmt*&) + 136
22 swift                    0x0000000104cfba08 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 264
23 swift                    0x0000000104cfad18 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::BraceStmt>(swift::BraceStmt*&) + 136
24 swift                    0x0000000104cf9cae swift::TypeChecker::typeCheckConstructorBodyUntil(swift::ConstructorDecl*, swift::SourceLoc) + 718
25 swift                    0x0000000104cfa3df swift::TypeChecker::typeCheckAbstractFunctionBody(swift::AbstractFunctionDecl*) + 271
26 swift                    0x0000000104d1b6a2 typeCheckFunctionsAndExternalDecls(swift::SourceFile&, swift::TypeChecker&) + 290
27 swift                    0x0000000104d1c449 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 1065
28 swift                    0x00000001044d7ce6 swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 502
29 swift                    0x00000001044d6663 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 435
30 swift                    0x00000001044d5d17 swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 615
31 swift                    0x0000000103cb6188 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1192
32 swift                    0x0000000103cb4c78 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3016
33 swift                    0x0000000103c66d52 main + 690
34 libdyld.dylib            0x00007fff651803d5 start + 1
35 libdyld.dylib            0x000000000000000f start + 2598894651
<unknown>:0: error: unable to execute command: Abort trap: 6
<unknown>:0: error: compile command failed due to signal 6 (use -v to see invocation)

[theblixguy]

5.1

error: initializer 'init(exactly:)' requires that 'Substring' conform to 'BinaryInteger'
        guard let major: Int = components.first.flatMap(Int.init) else { return nil }
                                                            ^
Swift.SignedInteger:3:23: note: where 'T' = 'Substring'
    @inlinable public init?<T>(exactly source: T) where T : BinaryInteger
                      ^

[belkadan]

I don't think Int has an initializer from Substring (or StringProtocol), but it shouldn't crash. Thanks, Caleb.

[swift-ci]

Comment by Caleb Kleveter (JIRA)

Alright, that's what I suspected.

[xedin]

This should be addressed by one of my PRs in 5.1/master and produces diagnostic @theblixguy mentioned. Unfortunately the change didn't make it in time for 5.0 release...

Please verify using the latest 5.1/master snapshot.

[AnnaZaks]

calebkleveter (JIRA User), Could you verify if the problem is fixed and if so move the JIRA to "Closed"?

Thanks!
Anna

[swift-ci]

Comment by Caleb Kleveter (JIRA)

Yep! I get the expected compiler error now.