DocC crashes when blockquote contains quote character and trailing colon

[coenttb]

Description

DocC crashes (exit code 133) when processing documentation that contains a blockquote with both a quote character and a trailing colon.

Reproduction

Minimal example that crashes:

/// Title
///
/// > "Term" means a definition that:
public struct Test {}

Steps to reproduce:

mkdir -p /tmp/docc-bug-test/Sources/TestModule/TestModule.docc

cat > /tmp/docc-bug-test/Package.swift << 'PKGEOF'
// swift-tools-version: 5.9
import PackageDescription
let package = Package(
    name: "TestModule",
    products: [.library(name: "TestModule", targets: ["TestModule"])],
    targets: [.target(name: "TestModule")]
)
PKGEOF

cat > /tmp/docc-bug-test/Sources/TestModule/Test.swift << 'SRCEOF'
/// Title
///
/// > "Term" means a definition that:
public struct Test {}
SRCEOF

cat > /tmp/docc-bug-test/Sources/TestModule/TestModule.docc/TestModule.md << 'DOCEOF'
# ``TestModule``
Test module.
DOCEOF

cd /tmp/docc-bug-test
swift build --target TestModule -Xswiftc -emit-symbol-graph -Xswiftc -emit-symbol-graph-dir -Xswiftc .build/symbol-graph

docc convert \
  --fallback-display-name "TestModule" \
  --fallback-bundle-identifier "TestModule" \
  --output-dir /tmp/docc-output \
  --additional-symbol-graph-dir .build/symbol-graph \
  Sources/TestModule/TestModule.docc
# Exit code: 133

Variations tested

Pattern	Result
/// > "Term" means:	❌ CRASHES
/// > 'Term' means:	❌ CRASHES
/// > "Term" means: (curly quotes)	❌ CRASHES
/// > Term means: (no quotes)	✅ Works
/// > \"Term\" means: (escaped)	✅ Works
/// > \Term` means:` (backticks)	✅ Works
/// > "Term" means (no colon)	✅ Works

The crash occurs when ANY quote character (", ', ", ") is combined with a trailing colon (:) in a blockquote.

Environment

• docc from Xcode 26.0 beta (16A5171c) toolchain
• Also reproduces with Xcode's Build Documentation
• Swift 6.2
• macOS 26.0 (Tahoe)

Expected behavior

DocC should process the documentation without crashing, rendering the blockquote with the quote characters and colon as written.

Actual behavior

DocC crashes with exit code 133. No diagnostic messages are produced.

Workaround

Escape the quote characters with backslashes: /// > \"Term\" means:

[heckj]

I ran this off the latest main branch from the toolchain, and got a backtrace with the development build from there (so also, a verification that this breaks on main):

Swift/arm64e-apple-macos.swiftinterface:19659: Fatal error: Range requires lowerBound <= upperBound

💣 Program crashed: System trap at 0x00000001aa9cdd20

Platform: arm64 macOS 26.2 (25C56)

Thread 1 crashed:

  0 0x00000001aa9cdd20 _assertionFailure(_:_:file:line:flags:) + 364 in libswiftCore.dylib
  1 closure swiftlang/swift-docc#3 in BlockQuote.parseAsideTag(tagRequirement:) + 512 in docc at /Users/joeheck/src/swift-project/swift-markdown/Sources/Markdown/Interpretive Nodes/Aside.swift:234:28

   232│             var newStart = originalRange.lowerBound
   233│             newStart.column += shiftCount
   234│             return newStart..<originalRange.upperBound
      │                            ▲
   235│         })
   236│

  2 BlockQuote.parseAsideTag(tagRequirement:) + 2892 in docc at /Users/joeheck/src/swift-project/swift-markdown/Sources/Markdown/Interpretive Nodes/Aside.swift:231:57

   229│             $0 == " " || $0 == "\t"
   230│         }).count
   231│         let textRange: SourceRange? = initialText.range.map({ originalRange in
      │                                                         ▲
   232│             var newStart = originalRange.lowerBound
   233│             newStart.column += shiftCount

  3 RenderContentCompiler.visitBlockQuote(_:) + 92 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderContentCompiler.swift:36:21

    34│
    35│     mutating func visitBlockQuote(_ blockQuote: BlockQuote) -> [any RenderContent] {
    36│         let aside = Aside(blockQuote)
      │                     ▲
    37│
    38│         let newAside = RenderBlockContent.Aside(

  4 BlockQuote.accept<A>(_:) + 68 in docc at /Users/joeheck/src/swift-project/swift-markdown/Sources/Markdown/Block Nodes/Block Container Blocks/BlockQuote.swift:45:24

    43│
    44│     func accept<V: MarkupVisitor>(_ visitor: inout V) -> V.Result {
    45│         return visitor.visitBlockQuote(self)
      │                        ▲
    46│     }
    47│ }

  5 MarkupVisitor.visit(_:) + 112 in docc at /Users/joeheck/src/swift-project/swift-markdown/Sources/Markdown/Visitor/MarkupVisitor.swift:324:23

   322│     // dispatches to the correct visit___ method.
   323│     public mutating func visit(_ markup: Markup) -> Result {
   324│         return markup.accept(&self)
      │                       ▲
   325│     }
   326│     public mutating func visitBlockQuote(_ blockQuote: BlockQuote) -> Result {

  6 closure swiftlang/swift-docc#1 in RenderNodeTranslator.visitMarkupContainer(_:) + 92 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift:320:125

   318│     public mutating func visitMarkupContainer(_ markupContainer: MarkupContainer) -> (any RenderTree)? {
   319│         var contentCompiler = RenderContentCompiler(context: context, identifier: identifier)
   320│         let content = markupContainer.elements.reduce(into: [], { result, item in result.append(contentsOf: contentCompiler.visit(item))}) as! [RenderBlockContent]
      │                                                                                                                             ▲
   321│         collectedTopicReferences.append(contentsOf: contentCompiler.collectedTopicReferences)
   322│         // Copy all the image references found in the markup container.

  7 0x00000001aaa40e90 Sequence.reduce<A>(into:_:) + 764 in libswiftCore.dylib
  8 RenderNodeTranslator.visitMarkupContainer(_:) + 360 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift:320:48

   318│     public mutating func visitMarkupContainer(_ markupContainer: MarkupContainer) -> (any RenderTree)? {
   319│         var contentCompiler = RenderContentCompiler(context: context, identifier: identifier)
   320│         let content = markupContainer.elements.reduce(into: [], { result, item in result.append(contentsOf: contentCompiler.visit(item))}) as! [RenderBlockContent]
      │                                                ▲
   321│         collectedTopicReferences.append(contentsOf: contentCompiler.collectedTopicReferences)
   322│         // Copy all the image references found in the markup container.

  9 closure swiftlang/swift-docc#1 in DiscussionSectionTranslator.translateSection(for:renderNode:renderNodeTranslator:) + 216 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderSectionTranslator/DiscussionSectionTranslator.swift:24:64

    22│             documentationDataVariants: symbol.discussionVariants
    23│         ) { _, discussion in
    24│             guard let discussionContent = renderNodeTranslator.visitMarkupContainer(MarkupContainer(discussion.content)) as? [RenderBlockContent],
      │                                                                ▲
    25│                   !discussionContent.isEmpty
    26│             else {

 10 closure swiftlang/swift-docc#1 in RenderSectionTranslator.translateSectionToVariantCollection<A>(documentationDataVariants:transform:) + 144 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderSectionTranslator/RenderSectionTranslator.swift:32:17

    30│             from: documentationDataVariants,
    31│             transform: { trait, value in
    32│                 transform(trait, value).map(CodableContentSection.init)
      │                 ▲
    33│             }
    34│         )

 11 closure swiftlang/swift-docc#1 in VariantCollection.init<A>(from:transform:) + 292 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/Variants/VariantCollection+Symbol.swift:27:84

    25│         transform: (DocumentationDataVariantsTrait, SymbolValue) -> Value
    26│     ) {
    27│         self.init(from: documentationDataVariants, anyTransform: { trait, value in transform(trait, value as! SymbolValue) })
      │                                                                                    ▲
    28│     }
    29│

 12 RenderSectionTranslator.translateSectionToVariantCollection<A>(documentationDataVariants:transform:) + 336 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderSectionTranslator/RenderSectionTranslator.swift:29:49

    27│         transform: (DocumentationDataVariantsTrait, SymbolValue) -> (any RenderSection)?
    28│     ) -> VariantCollection<CodableContentSection?>? {
    29│         VariantCollection<CodableContentSection?>(
      │                                                 ▲
    30│             from: documentationDataVariants,
    31│             transform: { trait, value in

 13 DiscussionSectionTranslator.translateSection(for:renderNode:renderNodeTranslator:) + 236 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderSectionTranslator/DiscussionSectionTranslator.swift:21:9

    19│         renderNodeTranslator: inout RenderNodeTranslator
    20│     ) -> VariantCollection<CodableContentSection?>? {
    21│         translateSectionToVariantCollection(
      │         ▲
    22│             documentationDataVariants: symbol.discussionVariants
    23│         ) { _, discussion in

 14 closure swiftlang/swift-docc#1 in RenderNodeTranslator.createRenderSections(for:renderNode:translators:) + 128 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift:1847:24

  1845│     ) -> [VariantCollection<CodableContentSection?>] {
  1846│         translators.compactMap { translator in
  1847│             translator.translateSection(for: symbol, renderNode: &renderNode, renderNodeTranslator: &self)
      │                        ▲
  1848│         }
  1849│     }

 15 0x00000001aab66a54 Sequence._compactMap<A>(_:) + 1328 in libswiftCore.dylib
 16 0x00000001aab6651c Sequence.compactMap<A>(_:) + 16 in libswiftCore.dylib
 17 RenderNodeTranslator.createRenderSections(for:renderNode:translators:) + 200 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift:1846:21

  1844│         translators: [any RenderSectionTranslator]
  1845│     ) -> [VariantCollection<CodableContentSection?>] {
  1846│         translators.compactMap { translator in
      │                     ▲
  1847│             translator.translateSection(for: symbol, renderNode: &renderNode, renderNodeTranslator: &self)
  1848│         }

 18 RenderNodeTranslator.visitSymbol(_:) + 11492 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift:1365:25

  1363│
  1364│         node.primaryContentSectionsVariants.append(
  1365│             contentsOf: createRenderSections(
      │                         ▲
  1366│                 for: symbol,
  1367│                 renderNode: &node,

 19 Symbol.accept<A>(_:) + 68 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Semantics/Symbol/Symbol.swift:395:24

   393│
   394│     public override func accept<V: SemanticVisitor>(_ visitor: inout V) -> V.Result {
   395│         return visitor.visitSymbol(self)
      │                        ▲
   396│     }
   397│

 20 SemanticVisitor.visit(_:) + 72 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Semantics/Visitor/SemanticVisitor.swift:148:25

   146│ extension SemanticVisitor {
   147│     public mutating func visit(_ semantic: Semantic) -> Result {
   148│         return semantic.accept(&self)
      │                         ▲
   149│     }
   150│ }

 21 DocumentationContextConverter.renderNode(for:) + 644 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Converter/DocumentationContextConverter.swift:114:27

   112│             symbolIdentifiersWithExpandedDocumentation: symbolIdentifiersWithExpandedDocumentation
   113│         )
   114│         return translator.visit(node.semantic) as? RenderNode
      │                           ▲
   115│     }
   116│ }

 22 closure swiftlang/swift-docc#1 in closure swiftlang/swift-docc#2 in static ConvertActionConverter.convert<A>(context:outputConsumer:sourceRepository:emitDigest:documentationCoverageOptions:) + 852 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Infrastructure/ConvertActionConverter.swift:115:54

   113│                     let entity = try context.entity(with: identifier)
   114│
   115│                     guard let renderNode = converter.renderNode(for: entity) else {
      │                                                      ▲
   116│                         // No render node was produced for this entity, so just skip it.
   117│                         return

 23 closure swiftlang/swift-docc#2 in static ConvertActionConverter.convert<A>(context:outputConsumer:sourceRepository:emitDigest:documentationCoverageOptions:) + 804 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Infrastructure/ConvertActionConverter.swift:111:13

   109│
   110│             // Wrap JSON encoding in an autorelease pool to avoid retaining the autoreleased ObjC objects returned by `JSONSerialization`
   111│             autoreleasepool {
      │             ▲
   112│                 do {
   113│                     let entity = try context.entity(with: identifier)

 24 closure swiftlang/swift-docc#2 in Collection<>.concurrentPerform<A>(batches:block:) + 1348 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocC/Utility/Collection+ConcurrentPerform.swift:137:17

   135│             // Run serially `block` over the elements
   136│             for offset in startOffset ..< startOffset + batchCount {
   137│                 block(self[offset], &batchResults)
      │                 ▲
   138│             }
   139│

 25 0x000000019745eaec _dispatch_client_callout2 + 16 in libdispatch.dylib
 26 0x00000001974597f8 _dispatch_apply_invoke3 + 336 in libdispatch.dylib
...
 38 ConvertAction._perform(logHandle:temporaryFolder:) + 4876 in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocCUtilities/Action/Actions/Convert/ConvertAction.swift:319:49

   317│         let conversionProblems: [Problem]
   318│         do {
   319│             conversionProblems = try signposter.withIntervalSignpost("Process") {
      │                                                 ▲
   320│                 try ConvertActionConverter.convert(
   321│                     context: context,

 39 ConvertAction.perform(logHandle:) in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocCUtilities/Action/Actions/Convert/ConvertAction.swift:202

   200│         let temporaryFolder = try createTempFolder(with: htmlTemplateDirectory)
   201│         do {
   202│             let result = try await _perform(logHandle: &logHandle, temporaryFolder: temporaryFolder)
      │             ▲
   203│             diagnosticEngine.flush()
   204│             try? fileManager.removeItem(at: temporaryFolder)

 40 ConvertAction.perform(logHandle:) in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocCUtilities/Action/Actions/Convert/ConvertAction.swift:195

   193│     /// saves the results in the given output alongside the template files.
   194│     public func perform(logHandle: inout LogHandle) async throws -> ActionResult {
   195│         try await perform(logHandle: &logHandle).0
      │         ▲
   196│     }
   197│

 41 AsyncAction.performAndHandleResult(logHandle:) in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocCUtilities/ArgumentParsing/ActionExtensions/Action+performAndHandleResult.swift:23

    21│         var logHandle = logHandle
    22│         // Perform the Action and collect the result
    23│         let result = try await perform(logHandle: &logHandle)
      │         ▲
    24│
    25│         // Throw if any errors were encountered. Errors will have already been

 42 Docc.Convert.run() in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/SwiftDocCUtilities/ArgumentParsing/Subcommands/Convert.swift:700

   698│         public func run() async throws {
   699│             let convertAction = try ConvertAction(fromConvertCommand: self)
   700│             try await convertAction.performAndHandleResult()
      │             ▲
   701│         }
   702│

 43 static AsyncParsableCommand.main(_:) in docc at /Users/joeheck/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsable Types/AsyncParsableCommand.swift:41

    39│       var command = try parseAsRoot(arguments)
    40│       if var asyncCommand = command as? AsyncParsableCommand {
    41│         try await asyncCommand.run()
      │         ▲
    42│       } else {
    43│         try command.run()

 44 static AsyncParsableCommand.main() in docc at /Users/joeheck/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsable Types/AsyncParsableCommand.swift:61

    59│   /// if necessary.
    60│   public static func main() async {
    61│     await self.main(nil)
      │     ▲
    62│   }
    63│ }

 45 closure swiftlang/swift-docc#1 in  in docc at /Users/joeheck/src/swift-project/swift-docc/Sources/docc/main.swift:15

    13│
    14│ await Task {
    15│     await Docc.main()
      │     ▲
    16│ }.value
    17│ #else

...

Backtrace took 3.37s

[1]    2364 trace trap  /Users/joeheck/src/swift-project/swift-docc/.build/debug/docc convert

[d-ronnqvist]

That crash is happening inside Swift-Markdown