Implement textDocument/typeDefinition request

Sources/ClangLanguageService/ClangLanguageService.swift

@@ -490,6 +490,10 @@ extension ClangLanguageService {
     return await workspace.buildServerManager.locationsOrLocationLinksAdjustedForCopiedFiles(result)
   }
 
+  package func typeDefinition(_ req: TypeDefinitionRequest) async throws -> LocationsOrLocationLinksResponse? {
+    return try await forwardRequestToClangd(req)
+  }
+
   package func completion(_ req: CompletionRequest) async throws -> CompletionList {
     return try await forwardRequestToClangd(req)
   }

Sources/SourceKitLSP/CMakeLists.txt

@@ -4,6 +4,7 @@ add_library(SourceKitLSP STATIC
   DocumentManager.swift
   DocumentSnapshot+FromFileContents.swift
   DocumentSnapshot+PositionConversions.swift
+  DefinitionLocations.swift
   GeneratedInterfaceDocumentURLData.swift
   Hooks.swift
   IndexProgressManager.swift

Sources/SourceKitLSP/DefinitionLocations.swift

@@ -0,0 +1,154 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2026 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+package import IndexStoreDB
+@_spi(SourceKitLSP) package import LanguageServerProtocol
+@_spi(SourceKitLSP) import SKLogging
+package import SemanticIndex
+
+/// Converts a location from the symbol index to an LSP location.
+///
+/// - Parameter location: The symbol index location
+/// - Returns: The LSP location
+package func indexToLSPLocation(_ location: SymbolLocation) -> Location? {
+  guard !location.path.isEmpty else { return nil }
+  return Location(
+    uri: location.documentUri,
+    range: Range(
+      Position(
+        // 1-based -> 0-based
+        // Note that we still use max(0, ...) as a fallback if the location is zero.
+        line: max(0, location.line - 1),
+        // Technically we would need to convert the UTF-8 column to a UTF-16 column. This would require reading the
+        // file. In practice they almost always coincide, so we accept the incorrectness here to avoid the file read.
+        utf16index: max(0, location.utf8Column - 1)
+      )
+    )
+  )
+}
+
+/// Return the locations for jump to definition from the given `SymbolDetails`.
+package func definitionLocations(
+  for symbol: SymbolDetails,
+  originatorUri: DocumentURI,
+  index: CheckedIndex?,
+  openGeneratedInterface:
+    @escaping (
+      _ document: DocumentURI,
+      _ moduleName: String,
+      _ groupName: String?,
+      _ symbolUSR: String?
+    ) async throws -> GeneratedInterfaceDetails?
+) async throws -> [Location] {
+  // module symbols generate a textual interface
+  if symbol.kind == .module {
+    let moduleName: String
+    let groupName: String?
+
+    if let systemModule = symbol.systemModule {
+      moduleName = systemModule.moduleName
+      groupName = systemModule.groupName
+    } else if let name = symbol.name {
+      moduleName = name
+      groupName = nil
+    } else {
+      return []
+    }
+
+    let location = try await definitionInInterface(
+      moduleName: moduleName,
+      groupName: groupName,
+      symbolUSR: nil,
+      originatorUri: originatorUri,
+      openGeneratedInterface: openGeneratedInterface
+    )
+    return [location]
+  }
+
+  // system symbols use generated interface
+  if symbol.isSystem ?? false, let systemModule = symbol.systemModule {
+    let location = try await definitionInInterface(
+      moduleName: systemModule.moduleName,
+      groupName: systemModule.groupName,
+      symbolUSR: symbol.usr,
+      originatorUri: originatorUri,
+      openGeneratedInterface: openGeneratedInterface
+    )
+    return [location]
+  }
+
+  // try local declaration first
+  guard let index else {
+    if let bestLocalDeclaration = symbol.bestLocalDeclaration {
+      return [bestLocalDeclaration]
+    }
+    return []
+  }
+
+  guard let usr = symbol.usr else { return [] }
+  logger.info("Performing indexed jump-to-definition with USR \(usr)")
+
+  let occurrences = index.definitionOrDeclarationOccurrences(ofUSR: usr)
+
+  if occurrences.isEmpty {
+    if let bestLocalDeclaration = symbol.bestLocalDeclaration {
+      return [bestLocalDeclaration]
+    }
+    // fallback to generated interface for SDK types without index data
+    if let systemModule = symbol.systemModule {
+      let location = try await definitionInInterface(
+        moduleName: systemModule.moduleName,
+        groupName: systemModule.groupName,
+        symbolUSR: symbol.usr,
+        originatorUri: originatorUri,
+        openGeneratedInterface: openGeneratedInterface
+      )
+      return [location]
+    }
+  }
+
+  return occurrences.compactMap { indexToLSPLocation($0.location) }.sorted()
+}
+
+/// Generate the generated interface for the given module, write it to disk and return the location to which to jump
+/// to get to the definition of `symbolUSR`.
+///
+/// `originatorUri` is the URI of the file from which the definition request is performed. It is used to determine the
+/// compiler arguments to generate the generated interface.
+package func definitionInInterface(
+  moduleName: String,
+  groupName: String?,
+  symbolUSR: String?,
+  originatorUri: DocumentURI,
+  openGeneratedInterface:
+    @escaping (
+      _ document: DocumentURI,
+      _ moduleName: String,
+      _ groupName: String?,
+      _ symbolUSR: String?
+    ) async throws -> GeneratedInterfaceDetails?
+) async throws -> Location {
+  let documentForBuildSettings = originatorUri.buildSettingsFile
+
+  guard
+    let interfaceDetails = try await openGeneratedInterface(
+      documentForBuildSettings,
+      moduleName,
+      groupName,
+      symbolUSR
+    )
+  else {
+    throw ResponseError.unknown("Could not generate Swift Interface for \(moduleName)")
+  }
+  let position = interfaceDetails.position ?? Position(line: 0, utf16index: 0)
+  return Location(uri: interfaceDetails.uri, range: Range(position))
+}

Sources/SourceKitLSP/LanguageService.swift

@@ -242,6 +242,7 @@ package protocol LanguageService: AnyObject, Sendable {
   func definition(_ request: DefinitionRequest) async throws -> LocationsOrLocationLinksResponse?
 
   func declaration(_ request: DeclarationRequest) async throws -> LocationsOrLocationLinksResponse?
+  func typeDefinition(_ request: TypeDefinitionRequest) async throws -> LocationsOrLocationLinksResponse?
   func documentSymbolHighlight(_ req: DocumentHighlightRequest) async throws -> [DocumentHighlight]?
   func foldingRange(_ req: FoldingRangeRequest) async throws -> [FoldingRange]?
   func documentSymbol(_ req: DocumentSymbolRequest) async throws -> DocumentSymbolResponse?
@@ -438,6 +439,10 @@ package extension LanguageService {
     throw ResponseError.requestNotImplemented(DeclarationRequest.self)
   }
 
+  func typeDefinition(_ request: TypeDefinitionRequest) async throws -> LocationsOrLocationLinksResponse? {
+    throw ResponseError.requestNotImplemented(TypeDefinitionRequest.self)
+  }
+
   func documentSymbolHighlight(_ req: DocumentHighlightRequest) async throws -> [DocumentHighlight]? {
     throw ResponseError.requestNotImplemented(DocumentHighlightRequest.self)
   }

Sources/SourceKitLSP/SourceKitLSPServer.swift

@@ -790,6 +790,8 @@ extension SourceKitLSPServer: QueueBasedMessageHandler {
       await self.handleRequest(for: request, requestHandler: self.declaration)
     case let request as RequestAndReply<DefinitionRequest>:
       await self.handleRequest(for: request, requestHandler: self.definition)
+    case let request as RequestAndReply<TypeDefinitionRequest>:
+      await self.handleRequest(for: request, requestHandler: self.typeDefinition)
     case let request as RequestAndReply<DoccDocumentationRequest>:
       await self.handleRequest(for: request, requestHandler: self.doccDocumentation)
     case let request as RequestAndReply<DocumentColorRequest>:
@@ -1146,6 +1148,7 @@ extension SourceKitLSPServer {
       completionProvider: completionOptions,
       signatureHelpProvider: signatureHelpOptions,
       definitionProvider: .bool(true),
+      typeDefinitionProvider: .bool(true),
       implementationProvider: .bool(true),
       referencesProvider: .bool(true),
       documentHighlightProvider: .bool(true),
@@ -1974,27 +1977,6 @@ extension SourceKitLSPServer {
     return try await languageService.documentDiagnostic(req)
   }
 
-  /// Converts a location from the symbol index to an LSP location.
-  ///
-  /// - Parameter location: The symbol index location
-  /// - Returns: The LSP location
-  private nonisolated func indexToLSPLocation(_ location: SymbolLocation) -> Location? {
-    guard !location.path.isEmpty else { return nil }
-    return Location(
-      uri: location.documentUri,
-      range: Range(
-        Position(
-          // 1-based -> 0-based
-          // Note that we still use max(0, ...) as a fallback if the location is zero.
-          line: max(0, location.line - 1),
-          // Technically we would need to convert the UTF-8 column to a UTF-16 column. This would require reading the
-          // file. In practice they almost always coincide, so we accept the incorrectness here to avoid the file read.
-          utf16index: max(0, location.utf8Column - 1)
-        )
-      )
-    )
-  }
-
   func declaration(
     _ req: DeclarationRequest,
     workspace: Workspace,
@@ -2003,6 +1985,14 @@ extension SourceKitLSPServer {
     return try await languageService.declaration(req)
   }
 
+  func typeDefinition(
+    _ req: TypeDefinitionRequest,
+    workspace: Workspace,
+    languageService: any LanguageService
+  ) async throws -> LocationsOrLocationLinksResponse? {
+    return try await languageService.typeDefinition(req)
+  }
+
   /// Return the locations for jump to definition from the given `SymbolDetails`.
   private func definitionLocations(
     for symbol: SymbolDetails,
@@ -2025,23 +2015,37 @@ extension SourceKitLSPServer {
         return []
       }
 
-      let interfaceLocation = try await self.definitionInInterface(
+      let interfaceLocation = try await definitionInInterface(
         moduleName: moduleName,
         groupName: groupName,
         symbolUSR: nil,
         originatorUri: uri,
-        languageService: languageService
+        openGeneratedInterface: { document, moduleName, groupName, symbolUSR in
+          try await languageService.openGeneratedInterface(
+            document: document,
+            moduleName: moduleName,
+            groupName: groupName,
+            symbolUSR: symbolUSR
+          )
+        }
       )
       return [interfaceLocation]
     }
 
     if symbol.isSystem ?? false, let systemModule = symbol.systemModule {
-      let location = try await self.definitionInInterface(
+      let location = try await definitionInInterface(
         moduleName: systemModule.moduleName,
         groupName: systemModule.groupName,
         symbolUSR: symbol.usr,
         originatorUri: uri,
-        languageService: languageService
+        openGeneratedInterface: { document, moduleName, groupName, symbolUSR in
+          try await languageService.openGeneratedInterface(
+            document: document,
+            moduleName: moduleName,
+            groupName: groupName,
+            symbolUSR: symbolUSR
+          )
+        }
       )
       return [location]
     }
@@ -2095,12 +2099,19 @@ extension SourceKitLSPServer {
       // third-party binary frameworks or libraries where indexing data is missing.
       // If module info is available, fallback to generating the textual interface.
       if let systemModule = symbol.systemModule {
-        let location = try await self.definitionInInterface(
+        let location = try await definitionInInterface(
           moduleName: systemModule.moduleName,
           groupName: systemModule.groupName,
           symbolUSR: symbol.usr,
           originatorUri: uri,
-          languageService: languageService
+          openGeneratedInterface: { document, moduleName, groupName, symbolUSR in
+            try await languageService.openGeneratedInterface(
+              document: document,
+              moduleName: moduleName,
+              groupName: groupName,
+              symbolUSR: symbolUSR
+            )
+          }
         )
         return [location]
       }
@@ -2230,36 +2241,6 @@ extension SourceKitLSPServer {
     return .locations(remappedLocations)
   }
 
-  /// Generate the generated interface for the given module, write it to disk and return the location to which to jump
-  /// to get to the definition of `symbolUSR`.
-  ///
-  /// `originatorUri` is the URI of the file from which the definition request is performed. It is used to determine the
-  /// compiler arguments to generate the generated interface.
-  func definitionInInterface(
-    moduleName: String,
-    groupName: String?,
-    symbolUSR: String?,
-    originatorUri: DocumentURI,
-    languageService: any LanguageService
-  ) async throws -> Location {
-    // Let openGeneratedInterface handle all the logic, including checking if we're already in the right interface
-    let documentForBuildSettings = originatorUri.buildSettingsFile
-
-    guard
-      let interfaceDetails = try await languageService.openGeneratedInterface(
-        document: documentForBuildSettings,
-        moduleName: moduleName,
-        groupName: groupName,
-        symbolUSR: symbolUSR
-      )
-    else {
-      throw ResponseError.unknown("Could not generate Swift Interface for \(moduleName)")
-    }
-    let position = interfaceDetails.position ?? Position(line: 0, utf16index: 0)
-    let loc = Location(uri: interfaceDetails.uri, range: Range(position))
-    return loc
-  }
-
   func implementation(
     _ req: ImplementationRequest,
     workspace: Workspace,
@@ -2434,7 +2415,7 @@ extension SourceKitLSPServer {
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed
     func indexToLSPLocation2(_ location: SymbolLocation) -> Location? {
-      return self.indexToLSPLocation(location)
+      return indexToLSPLocation(location)
     }
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed
@@ -2478,7 +2459,7 @@ extension SourceKitLSPServer {
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed
     func indexToLSPLocation2(_ location: SymbolLocation) -> Location? {
-      return self.indexToLSPLocation(location)
+      return indexToLSPLocation(location)
     }
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed
@@ -2600,7 +2581,7 @@ extension SourceKitLSPServer {
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed
     func indexToLSPLocation2(_ location: SymbolLocation) -> Location? {
-      return self.indexToLSPLocation(location)
+      return indexToLSPLocation(location)
     }
 
     // TODO: Remove this workaround once https://github.com/swiftlang/swift/issues/75600 is fixed