[SR-9043] Missing checks of inout/mutating captures

[swift-ci]

Previous ID	SR-9043
Radar	rdar://problem/45511834
Original Reporter	koher (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

Xcode Version 10.0 (10A255)

Additional Detail from JIRA

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

md5: 23f0e6aa3983c486dcd3930dc0b1232d

relates to:

• SR-8546 Enforce @escaping for for all but the most trivial uses of captured variables.

Issue Description:

The following code causes a compile-time error correctly.

func run(_ body: @escaping () -> Void) { body() }


struct S {
    var a: Int = 3
    
    mutating func foo() {
        func _foo() {
            if a == 0 { return }
            a -= 1
            print(a)
            run(_foo)
        }
        _foo()
    }
}


var s = S()
s.foo()

error: nested function with an implicitly captured inout parameter can only be used as a non-escaping argument
             run(_foo)
             ^

However, when `run(_foo)` is changed to `run { _foo() }`, it can be compiled. I guess the compiler lacks some checks.

[rintaro]

Crash in master:

$ cat test.swift
func run(_ body: @escaping () -> Void) { }

struct S {
    var a: Int
    mutating func foo() {
        func _foo() {
            _ = a
            run { _foo() }
        }
    }
}
$ ../build/Ninja-ReleaseAssert/swift-macosx-x86_64/bin/swift test.swift
Applied argument must be @noescape function type:   %11 = partial_apply [callee_guaranteed] %10(%0) : $@convention(thin) (@inout_aliasable S) -> () // users: %14, %13
A partial_apply with @inout_aliasable may only be used as a @noescape function type argument.
UNREACHABLE executed at /Users/rintaro/Repositories/swift-oss/swift/lib/SILOptimizer/Mandatory/DiagnoseStaticExclusivity.cpp:1078!
Stack dump:
0.  Program arguments: /Users/rintaro/Repositories/swift-oss/build/Ninja-ReleaseAssert/swift-macosx-x86_64/bin/swift -frontend -interpret test.swift -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -color-diagnostics -module-name test 
1.  While running pass #​7 SILFunctionTransform "DiagnoseStaticExclusivity" on SILFunction "@$s4test1SV3fooyyF01_B0L_yyF".
 for '_foo()' at test.swift:6:9
0  swift                    0x000000010a44e2b8 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x000000010a44d288 llvm::sys::RunSignalHandlers() + 248
2  swift                    0x000000010a44e8d2 SignalHandler(int) + 258
3  libsystem_platform.dylib 0x00007fff6e3ceb3d _sigtramp + 29
4  swift                    0x000000010b717678 llvm::dbgs()::thestrm + 16
5  libsystem_c.dylib        0x00007fff6e28d1c9 abort + 127
6  swift                    0x000000010a3e14ee llvm::llvm_unreachable_internal(char const*, char const*, unsigned int) + 542
7  swift                    0x0000000107141d12 checkStaticExclusivity(swift::SILFunction&, swift::PostOrderFunctionInfo*, swift::AccessSummaryAnalysis*) + 13298
8  swift                    0x000000010715e905 swift::SILPassManager::runPassOnFunction(unsigned int, swift::SILFunction*) + 1925
9  swift                    0x000000010715fab3 swift::SILPassManager::runFunctionPasses(unsigned int, unsigned int) + 1299
10 swift                    0x0000000107160bdf swift::SILPassManager::execute() + 607
11 swift                    0x000000010673336b swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 187
12 swift                    0x00000001071695b4 swift::runSILDiagnosticPasses(swift::SILModule&) + 132
13 swift                    0x00000001065c01db performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 10923
14 swift                    0x00000001065bc69d swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3021
15 swift                    0x000000010656ea8e main + 686
16 libdyld.dylib            0x00007fff6e1e50a5 start + 1
Abort trap: 6

[belkadan]

@swift-ci create

[atrick]

Note that the closure

{ _foo }

captures inout self, then is passed as an @escaping closure. This clearly violates the type system but the type checker can't catch it. Asserting in a diagnostic pass is better than nothing, until the type checker is fixed. We can't easily convert the assert into a diagnostic (even if we wanted to), because the code doing the verification is only run in the asserts compiler.

Hopefully, the fix for SR-8546 will cover this.

SR-8546: Enforce @escaping for nested functions named inside conditional expressions.

But the test case is sufficiently different that it should probably be two bugs.

[slavapestov]

#23923