[SR-14893] Assertion failed: (underlyingType) in ConstraintSystem::buildDisjunctionForOptionalVsUnderlying

[ahoppen]

Previous ID	SR-14893
Radar	rdar://80271666
Original Reporter	@ahoppen
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash
Assignee	None
Priority	Medium

md5: 1e001e8e2a637dc8d1d9773ff1d28e77

Issue Description:

Typechecking the following code hits an assertion in the type checker.

enum Category {
    case first
}

protocol View2 {}

extension View2 {
    func sag(_ tag: Category) -> some View2 {
        fatalError()
    }
}

@resultBuilder public struct ViewBuilder2 {
  static func buildBlock<Content>(_ content: Content) -> Content where Content : View2 { fatalError() }
}

@frozen public struct Fmage : View2 {
}

struct UserListFormView {
    @ViewBuilder2 var body: some View2 {
        let icon: Category! = Category.first
        Fmage(icon).sag()
    }
}

Stack trace:

Stack dump:
0.  Program arguments: ./swift-frontend -typecheck /Users/alex/swift-src/swift/test/SourceKit/test.swift
1.  Swift version 5.5-dev (LLVM 3c96a2f1c42ab1c, Swift c3e9676cb1aac5d)
2.  
3.  While evaluating request TypeCheckSourceFileRequest(source_file "/Users/alex/swift-src/swift/test/SourceKit/test.swift")
4.  While evaluating request TypeCheckFunctionBodyRequest(test.(file).UserListFormView._@/Users/alex/swift-src/swift/test/SourceKit/test.swift:21:40)
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x000000010f5dc267 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 39
1  swift-frontend           0x000000010f5db148 llvm::sys::RunSignalHandlers() + 248
2  swift-frontend           0x000000010f5dc896 SignalHandler(int) + 262
3  libsystem_platform.dylib 0x00007fff20552d7d _sigtramp + 29
4  libsystem_platform.dylib 000000000000000000 _sigtramp + 18446603339973710496
5  libsystem_c.dylib        0x00007fff20462411 abort + 120
6  libsystem_c.dylib        0x00007fff204617e8 err + 0
7  swift-frontend           0x000000010fa3e763 swift::constraints::ConstraintSystem::buildDisjunctionForOptionalVsUnderlying(swift::Type, swift::Type, swift::constraints::ConstraintLocator*) (.cold.7) + 35
8  swift-frontend           0x000000010b7a9784 swift::constraints::ConstraintSystem::buildDisjunctionForOptionalVsUnderlying(swift::Type, swift::Type, swift::constraints::ConstraintLocator*) + 804
9  swift-frontend           0x000000010b79b331 swift::constraints::ConstraintSystem::bindOverloadType(swift::constraints::SelectedOverload const&, swift::Type, swift::constraints::ConstraintLocator*, swift::DeclContext*, llvm::function_ref<void (unsigned int, swift::Type, swift::constraints::ConstraintLocator*)>) + 2977
10 swift-frontend           0x000000010b79cde5 swift::constraints::ConstraintSystem::resolveOverload(swift::constraints::ConstraintLocator*, swift::Type, swift::constraints::OverloadChoice, swift::DeclContext*) + 5269
11 swift-frontend           0x000000010b6caa29 swift::ASTVisitor<(anonymous namespace)::ConstraintGenerator, swift::Type, void, void, void, void, void>::visit(swift::Expr*) + 11449
12 swift-frontend           0x000000010b6c5e1b (anonymous namespace)::ConstraintWalker::walkToExprPost(swift::Expr*) + 171
13 swift-frontend           0x000000010bafec0b swift::ASTVisitor<(anonymous namespace)::Traversal, swift::Expr*, swift::Stmt*, bool, swift::Pattern*, bool, void>::visit(swift::Expr*) + 315
14 swift-frontend           0x000000010bb00ee2 (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 210
15 swift-frontend           0x000000010bafebdf swift::ASTVisitor<(anonymous namespace)::Traversal, swift::Expr*, swift::Stmt*, bool, swift::Pattern*, bool, void>::visit(swift::Expr*) + 271
16 swift-frontend           0x000000010bb00e66 (anonymous namespace)::Traversal::visitApplyExpr(swift::ApplyExpr*) + 86
17 swift-frontend           0x000000010bafeb5d swift::ASTVisitor<(anonymous namespace)::Traversal, swift::Expr*, swift::Stmt*, bool, swift::Pattern*, bool, void>::visit(swift::Expr*) + 141
18 swift-frontend           0x000000010bafe371 swift::Expr::walk(swift::ASTWalker&) + 81
19 swift-frontend           0x000000010b6c135d swift::constraints::ConstraintSystem::generateConstraints(swift::Expr*, swift::DeclContext*, bool) + 237
20 swift-frontend           0x000000010b674458 (anonymous namespace)::BuilderClosureVisitor::captureExpr(swift::Expr*, bool, llvm::PointerUnion<swift::Stmt*, swift::Expr*>) + 104
21 swift-frontend           0x000000010b673496 (anonymous namespace)::BuilderClosureVisitor::visitBraceStmt(swift::BraceStmt*) + 1158
22 swift-frontend           0x000000010b66c24e swift::constraints::ConstraintSystem::matchResultBuilder(swift::AnyFunctionRef, swift::Type, swift::Type, swift::constraints::ConstraintKind, swift::constraints::ConstraintLocatorBuilder) + 1470
23 swift-frontend           0x000000010b66b310 swift::TypeChecker::applyResultBuilderBodyTransform(swift::FuncDecl*, swift::Type) + 784
24 swift-frontend           0x000000010b91eb49 swift::TypeCheckFunctionBodyRequest::evaluate(swift::Evaluator&, swift::AbstractFunctionDecl*) const + 281
25 swift-frontend           0x000000010bbf752c llvm::Expected<swift::TypeCheckFunctionBodyRequest::OutputType> swift::Evaluator::getResultUncached<swift::TypeCheckFunctionBodyRequest>(swift::TypeCheckFunctionBodyRequest const&) + 428
26 swift-frontend           0x000000010bbf72a7 llvm::Expected<swift::TypeCheckFunctionBodyRequest::OutputType> swift::Evaluator::getResultCached<swift::TypeCheckFunctionBodyRequest, (void*)0>(swift::TypeCheckFunctionBodyRequest const&) + 119
27 swift-frontend           0x000000010bb5b1d3 swift::TypeCheckFunctionBodyRequest::OutputType swift::evaluateOrDefault<swift::TypeCheckFunctionBodyRequest>(swift::Evaluator&, swift::TypeCheckFunctionBodyRequest, swift::TypeCheckFunctionBodyRequest::OutputType) + 51
28 swift-frontend           0x000000010b955fed swift::TypeCheckSourceFileRequest::evaluate(swift::Evaluator&, swift::SourceFile*) const + 333
29 swift-frontend           0x000000010b956f2d llvm::Expected<swift::TypeCheckSourceFileRequest::OutputType> swift::Evaluator::getResultUncached<swift::TypeCheckSourceFileRequest>(swift::TypeCheckSourceFileRequest const&) + 429
30 swift-frontend           0x000000010b956cb2 llvm::Expected<swift::TypeCheckSourceFileRequest::OutputType> swift::Evaluator::getResultCached<swift::TypeCheckSourceFileRequest, (void*)0>(swift::TypeCheckSourceFileRequest const&) + 114
31 swift-frontend           0x000000010b955d9e swift::TypeCheckSourceFileRequest::OutputType swift::evaluateOrDefault<swift::TypeCheckSourceFileRequest>(swift::Evaluator&, swift::TypeCheckSourceFileRequest, swift::TypeCheckSourceFileRequest::OutputType) + 46
32 swift-frontend           0x000000010ab7b9ce swift::CompilerInstance::forEachFileToTypeCheck(llvm::function_ref<void (swift::SourceFile&)>) + 158
33 swift-frontend           0x000000010ab7b87a swift::CompilerInstance::performSema() + 74
34 swift-frontend           0x000000010aa3aa9f swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 6367
35 swift-frontend           0x000000010a98bc66 main + 566
36 libdyld.dylib            0x00007fff20528f5d start + 1
37 libdyld.dylib            0x0000000000000003 start + 18446603339973882023
fish: Job 1, './swift-frontend -typecheck /Us…' terminated by signal SIGABRT (Abort)

[LucianoPAlmeida]

Fixed by @xedin in #39096 and [#39142| #39142]