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[SR-10987] Compiler crashes on invalid reference to 'subscript' member #53377

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hamishknight opened this issue Jun 20, 2019 · 4 comments
Closed

[SR-10987] Compiler crashes on invalid reference to 'subscript' member #53377

hamishknight opened this issue Jun 20, 2019 · 4 comments
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@gregomni
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software type checker Area → compiler: Semantic analysis

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@hamishknight
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Previous ID SR-10987
Radar None
Original Reporter @hamishknight
Type Bug
Status Closed
Resolution Done
Environment

Swift version 5.1-dev (LLVM af1f73e9e9, Swift 93d98f8eec)
Target: x86_64-apple-darwin18.5.0

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, CompilerCrash, TypeChecker
Assignee @gregomni
Priority Medium

md5: c5c3521c3d8d6e3c1a30d4d8f6d85919

Issue Description:

The following trips an assertion on diagnosis:

struct S {
  subscript(_ x: Int) -> String { "" }
}

let s = S()
s.subscript
Assertion failed: (parentExpr && "Couldn't find a parent expression for a member call?!"), function diagnoseAsError, file /Users/hamishknight/Desktop/swift-dev/swift/lib/Sema/CSDiagnostics.cpp, line 1916.
Stack dump:
0.  Program arguments: ./swift -frontend -typecheck /Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
1.  Swift version 5.1-dev (LLVM af1f73e9e9, Swift 93d98f8eec)
2.  While type-checking statement at [/Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:225:1 - line:225:3] RangeText="s."
3.  While type-checking expression at [/Users/hamishknight/Desktop/Stochastic Projects/newnew/newnew/main.swift:225:1 - line:225:3] RangeText="s."
0  swift                    0x0000000108bbe215 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift                    0x0000000108bbd218 llvm::sys::RunSignalHandlers() + 248
2  swift                    0x0000000108bbe818 SignalHandler(int) + 264
3  libsystem_platform.dylib 0x00007fff649e3b5d _sigtramp + 29
4  swift                    0x000000010a22ebf0 cmark_strbuf__initbuf + 131435
5  libsystem_c.dylib        0x00007fff648a36a6 abort + 127
6  libsystem_c.dylib        0x00007fff6486c20d basename_r + 0
7  swift                    0x0000000108ec7e43 swift::constraints::SubscriptMisuseFailure::diagnoseAsError() (.cold.2) + 35
8  swift                    0x00000001057b34fa swift::constraints::SubscriptMisuseFailure::diagnoseAsError() + 730
9  swift                    0x00000001057a85e8 swift::constraints::UseSubscriptOperator::diagnose(swift::Expr*, bool) const + 104
10 swift                    0x000000010571385b swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&)::$_12::operator()(swift::Expr*) const + 203
11 swift                    0x00000001057136d0 swift::constraints::ConstraintSystem::applySolutionFixes(swift::Expr*, swift::constraints::Solution const&) + 544
12 swift                    0x000000010571398d swift::constraints::ConstraintSystem::applySolution(swift::constraints::Solution&, swift::Expr*, swift::Type, bool, bool) + 141
13 swift                    0x000000010584f333 swift::TypeChecker::typeCheckExpressionImpl(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener&, swift::constraints::ConstraintSystem*) + 1107
14 swift                    0x000000010584eecf swift::TypeChecker::typeCheckExpression(swift::Expr*&, swift::DeclContext*, swift::TypeLoc, swift::ContextualTypePurpose, swift::OptionSet<swift::TypeCheckExprFlags, unsigned int>, swift::ExprTypeCheckListener*, swift::constraints::ConstraintSystem*) + 63
15 swift                    0x00000001058e81d6 swift::ASTVisitor<(anonymous namespace)::StmtChecker, void, swift::Stmt*, void, void, void, void>::visit(swift::Stmt*) + 614
16 swift                    0x00000001058e72f8 bool (anonymous namespace)::StmtChecker::typeCheckStmt<swift::BraceStmt>(swift::BraceStmt*&) + 136
17 swift                    0x00000001058e73ee swift::TypeChecker::typeCheckTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 174
18 swift                    0x0000000105907862 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int, unsigned int, unsigned int, unsigned int) + 914
19 swift                    0x00000001050bd266 swift::CompilerInstance::parseAndTypeCheckMainFileUpTo(swift::SourceFile::ASTStage_t, swift::PersistentParserState&, swift::DelayedParsingCallbacks*, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>) + 502
20 swift                    0x00000001050bc076 swift::CompilerInstance::parseAndCheckTypesUpTo(swift::CompilerInstance::ImplicitImports const&, swift::SourceFile::ASTStage_t) + 342
21 swift                    0x00000001050bba1a swift::CompilerInstance::performSemaUpTo(swift::SourceFile::ASTStage_t) + 618
22 swift                    0x0000000104eab912 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 1730
23 swift                    0x0000000104eaa271 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3025
24 swift                    0x0000000104e537c9 main + 729
25 libdyld.dylib            0x00007fff647fe3d5 start + 1
fish: './swift -frontend -typecheck /U…' terminated by signal SIGABRT (Abort)
@belkadan
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cc @xedin

@theblixguy
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Hmm the problem is that its expecting a CallExpr (so `s.subscript(0)`) but in this case, we just have:

unresolved_dot_expr type='<null>' field 'subscript' function_ref=single
    (declref_expr type='<null>' decl=test.(file).s@/Users/suyashsrijan/Desktop/test.swift:5:5 function_ref=unapplied))

so it crashes when trying to find the parent expression. Maybe we should take into consideration that there might not be a parent here and just use the `unresolved_dot_expr` to emit the diagnostic. We'll also have to tweak the fix-it locs otherwise it will replace the entire `s.subscript` with [], where as we just want to append it.

There's another case where if we do `s.subscript = 10` then it causes the same crash, so in this case the fix-it would then have to remove the `=` and add the [], so the code ends up being `s.subscript[10]`. Not sure if its worth covering all these edge cases with special fix-its.

@gregomni
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Done in #25892

@hamishknight
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Thanks Greg!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 2022
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@gregomni gregomni

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software type checker Area → compiler: Semantic analysis
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@belkadan @theblixguy @hamishknight @gregomni @AnthonyLatsis