diff --git a/Sources/LanguageServerProtocol/ClientCapabilities.swift b/Sources/LanguageServerProtocol/ClientCapabilities.swift
index 5ad462d3c..07b663514 100644
--- a/Sources/LanguageServerProtocol/ClientCapabilities.swift
+++ b/Sources/LanguageServerProtocol/ClientCapabilities.swift
@@ -225,11 +225,23 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
 
     /// Capabilities specific to `SignatureInformation`.
     public struct SignatureInformation: Hashable, Codable {
+      public struct ParameterInformation: Hashable, Codable {
+        /// The client supports processing label offsets instead of a simple label string.
+        var labelOffsetSupport: Bool? = nil
+
+        public init(labelOffsetSupport: Bool? = nil) {
+          self.labelOffsetSupport = labelOffsetSupport
+        }
+      }
+
       /// Documentation formats supported by the client from most to least preferred.
-      public var signatureInformation: [MarkupKind]? = nil
+      public var documentationFormat: [MarkupKind]? = nil
+
+      public var parameterInformation: ParameterInformation? = nil
 
-      public init(signatureInformation: [MarkupKind]? = nil) {
-        self.signatureInformation = signatureInformation
+      public init(signatureInformation: [MarkupKind]? = nil, parameterInformation: ParameterInformation? = nil) {
+        self.documentationFormat = signatureInformation
+        self.parameterInformation = parameterInformation
       }
     }
 
@@ -276,6 +288,19 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
     }
   }
 
+  public struct DynamicRegistrationLinkSupportCapability: Hashable, Codable {
+    /// Whether the client supports dynamic registaration of this request.
+    public var dynamicRegistration: Bool? = nil
+
+    /// The client supports additional metadata in the form of declaration links.
+    public var linkSupport: Bool? = nil
+
+    public init(dynamicRegistration: Bool? = nil, linkSupport: Bool?) {
+      self.dynamicRegistration = dynamicRegistration
+      self.linkSupport = linkSupport
+    }
+  }
+
   /// Capabilities specific to the `textDocument/codeAction` request.
   public struct CodeAction: Hashable, Codable {
 
@@ -294,24 +319,38 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
         }
       }
 
-      /// Whether the client supports dynamic registaration of this request.
-      public var dynamicRegistration: Bool? = nil
-
       public var codeActionKind: CodeActionKind
 
-      public init(dynamicRegistration: Bool? = nil, codeActionKind: CodeActionKind) {
-        self.dynamicRegistration = dynamicRegistration
+      public init(codeActionKind: CodeActionKind) {
         self.codeActionKind = codeActionKind
       }
     }
 
+    /// Whether the client supports dynamic registaration of this request.
+    public var dynamicRegistration: Bool?
+
     public var codeActionLiteralSupport: CodeActionLiteralSupport? = nil
 
-    public init(codeActionLiteralSupport: CodeActionLiteralSupport? = nil) {
+    public init(dynamicRegistration: Bool? = nil, codeActionLiteralSupport: CodeActionLiteralSupport? = nil) {
       self.codeActionLiteralSupport = codeActionLiteralSupport
     }
   }
 
+  /// Capabilities specific to `textDocument/rename`.
+  public struct Rename: Hashable, Codable {
+
+    /// Whether the client supports dynamic registaration of this request.
+    public var dynamicRegistration: Bool?
+
+    /// The client supports testing for validity of rename operations before execution.
+    public var prepareSupport: Bool?
+
+    public init(dynamicRegistration: Bool? = nil, prepareSupport: Bool? = nil) {
+      self.dynamicRegistration = dynamicRegistration
+      self.prepareSupport = prepareSupport
+    }
+  }
+
   /// Capabilities specific to `textDocument/publishDiagnostics`.
   public struct PublishDiagnostics: Hashable, Codable {
     /// Whether the client accepts diagnostics with related information.
@@ -364,11 +403,13 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
 
   public var onTypeFormatting: DynamicRegistrationCapability? = nil
 
-  public var definition: DynamicRegistrationCapability? = nil
+  public var declaration: DynamicRegistrationLinkSupportCapability? = nil
+
+  public var definition: DynamicRegistrationLinkSupportCapability? = nil
 
-  public var typeDefinition: DynamicRegistrationCapability? = nil
+  public var typeDefinition: DynamicRegistrationLinkSupportCapability? = nil
 
-  public var implementation: DynamicRegistrationCapability? = nil
+  public var implementation: DynamicRegistrationLinkSupportCapability? = nil
 
   public var codeAction: CodeAction? = nil
 
@@ -384,13 +425,27 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
 
   public var foldingRange: FoldingRange? = nil
 
-  public init(synchronization: Synchronization? = nil, completion: Completion? = nil, hover: Hover? = nil,
-              signatureHelp: SignatureHelp? = nil, references: DynamicRegistrationCapability? = nil, documentHighlight: DynamicRegistrationCapability? = nil,
-              documentSymbol: DocumentSymbol? = nil, formatting: DynamicRegistrationCapability? = nil, rangeFormatting: DynamicRegistrationCapability? = nil,
-              onTypeFormatting: DynamicRegistrationCapability? = nil, definition: DynamicRegistrationCapability? = nil, typeDefinition: DynamicRegistrationCapability? = nil,
-              implementation: DynamicRegistrationCapability? = nil, codeAction: CodeAction? = nil, codeLens: DynamicRegistrationCapability? = nil,
-              documentLink: DynamicRegistrationCapability? = nil, colorProvider: DynamicRegistrationCapability? = nil, rename: DynamicRegistrationCapability? = nil,
-              publishDiagnostics: PublishDiagnostics? = nil, foldingRange: FoldingRange? = nil) {
+  public init(synchronization: Synchronization? = nil,
+              completion: Completion? = nil,
+              hover: Hover? = nil,
+              signatureHelp: SignatureHelp? = nil,
+              references: DynamicRegistrationCapability? = nil,
+              documentHighlight: DynamicRegistrationCapability? = nil,
+              documentSymbol: DocumentSymbol? = nil,
+              formatting: DynamicRegistrationCapability? = nil,
+              rangeFormatting: DynamicRegistrationCapability? = nil,
+              onTypeFormatting: DynamicRegistrationCapability? = nil,
+              declaration: DynamicRegistrationLinkSupportCapability? = nil,
+              definition: DynamicRegistrationLinkSupportCapability? = nil,
+              typeDefinition: DynamicRegistrationLinkSupportCapability? = nil,
+              implementation: DynamicRegistrationLinkSupportCapability? = nil,
+              codeAction: CodeAction? = nil,
+              codeLens: DynamicRegistrationCapability? = nil,
+              documentLink: DynamicRegistrationCapability? = nil,
+              colorProvider: DynamicRegistrationCapability? = nil,
+              rename: DynamicRegistrationCapability? = nil,
+              publishDiagnostics: PublishDiagnostics? = nil,
+              foldingRange: FoldingRange? = nil) {
     self.synchronization = synchronization
     self.completion = completion
     self.hover = hover
@@ -401,6 +456,7 @@ public struct TextDocumentClientCapabilities: Hashable, Codable {
     self.formatting = formatting
     self.rangeFormatting = rangeFormatting
     self.onTypeFormatting = onTypeFormatting
+    self.declaration = declaration
     self.definition = definition
     self.typeDefinition = typeDefinition
     self.implementation = implementation
diff --git a/Sources/LanguageServerProtocol/Completion.swift b/Sources/LanguageServerProtocol/Completion.swift
index d7e72d0dd..f74c8e9ec 100644
--- a/Sources/LanguageServerProtocol/Completion.swift
+++ b/Sources/LanguageServerProtocol/Completion.swift
@@ -32,7 +32,7 @@ public struct CompletionRequest: TextDocumentRequest, Hashable {
 
   public var position: Position
 
-  // public var context: CompletionContext?
+  public var context: CompletionContext?
 
   public init(textDocument: TextDocumentIdentifier, position: Position) {
     self.textDocument = textDocument
@@ -40,6 +40,37 @@ public struct CompletionRequest: TextDocumentRequest, Hashable {
   }
 }
 
+/// How a completion was triggered
+public struct CompletionTriggerKind: RawRepresentable, Codable, Hashable {
+  /// Completion was triggered by typing an identifier (24x7 code complete), manual invocation (e.g Ctrl+Space) or via API.
+  public static let invoked = CompletionTriggerKind(rawValue: 1)
+
+  /// Completion was triggered by a trigger character specified by the `triggerCharacters` properties of the `CompletionRegistrationOptions`.
+  public static let triggerCharacter = CompletionTriggerKind(rawValue: 2)
+
+  /// Completion was re-triggered as the current completion list is incomplete.
+  public static let triggerFromIncompleteCompletions = CompletionTriggerKind(rawValue: 3)
+
+  public let rawValue: Int
+  public init(rawValue: Int) {
+    self.rawValue = rawValue
+  }
+}
+
+/// Contains additional information about the context in which a completion request is triggered.
+public struct CompletionContext: Codable, Hashable {
+  /// How the completion was triggered.
+  public var triggerKind: CompletionTriggerKind
+
+  /// The trigger character (a single character) that has trigger code complete. Is undefined if `triggerKind !== CompletionTriggerKind.TriggerCharacter`
+  public var triggerCharacter: String?
+
+  public init(triggerKind: CompletionTriggerKind, triggerCharacter: String? = nil) {
+    self.triggerKind = triggerKind
+    self.triggerCharacter = triggerCharacter
+  }
+}
+
 /// List of completion items. If this list has been filtered already, the `isIncomplete` flag
 /// indicates that the client should re-query code-completions if the filter text changes.
 public struct CompletionList: ResponseType, Hashable {
@@ -56,4 +87,24 @@ public struct CompletionList: ResponseType, Hashable {
     self.isIncomplete = isIncomplete
     self.items = items
   }
+
+  public init(from decoder: Decoder) throws {
+    // Try decoding as CompletionList
+    do {
+      let container = try decoder.container(keyedBy: CodingKeys.self)
+      self.isIncomplete = try container.decode(Bool.self, forKey: .isIncomplete)
+      self.items = try container.decode([CompletionItem].self, forKey: .items)
+      return
+    } catch {}
+
+    // Try decoding as [CompletionItem]
+    do {
+      self.items = try [CompletionItem](from: decoder)
+      self.isIncomplete = false
+      return
+    } catch {}
+
+    let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected CompletionList or [CompletionItem]")
+    throw DecodingError.dataCorrupted(context)
+  }
 }
diff --git a/Sources/LanguageServerProtocol/CompletionItem.swift b/Sources/LanguageServerProtocol/CompletionItem.swift
index 02c587aaf..62914948c 100644
--- a/Sources/LanguageServerProtocol/CompletionItem.swift
+++ b/Sources/LanguageServerProtocol/CompletionItem.swift
@@ -16,9 +16,15 @@ public struct CompletionItem: Codable, Hashable {
   /// The display name of the completion.
   public var label: String
 
+  /// The kind of completion item - e.g. method, property.
+  public var kind: CompletionItemKind
+
   /// An extended human-readable name (longer than `label`, but simpler than `documentation`).
   public var detail: String?
 
+  /// A human-readable string that represents a doc-comment.
+  public var documentation: CompletionItemDocumentation?
+
   /// The name to use for sorting the result. If `nil`, use `label.
   public var sortText: String?
 
@@ -40,23 +46,19 @@ public struct CompletionItem: Codable, Hashable {
   /// The format of the `textEdit.nextText` or `insertText` value.
   public var insertTextFormat: InsertTextFormat?
 
-  /// The kind of completion item - e.g. method, property.
-  public var kind: CompletionItemKind
-
   /// Whether the completion is for a deprecated symbol.
   public var deprecated: Bool?
 
-  // TODO: remaining members
-
   public init(
     label: String,
+    kind: CompletionItemKind,
     detail: String? = nil,
+    documentation: CompletionItemDocumentation? = nil,
     sortText: String? = nil,
     filterText: String? = nil,
     textEdit: TextEdit? = nil,
     insertText: String? = nil,
     insertTextFormat: InsertTextFormat? = nil,
-    kind: CompletionItemKind,
     deprecated: Bool? = nil)
   {
     self.label = label
@@ -80,3 +82,30 @@ public enum InsertTextFormat: Int, Codable, Hashable {
   /// The text to insert is a "snippet", which may contain placeholders.
   case snippet = 2
 }
+
+public enum CompletionItemDocumentation: Hashable {
+  case string(String)
+  case markupContent(MarkupContent)
+}
+
+extension CompletionItemDocumentation: Codable {
+  public init(from decoder: Decoder) throws {
+    if let string = try? String(from: decoder) {
+      self = .string(string)
+    } else if let markupContent = try? MarkupContent(from: decoder) {
+      self = .markupContent(markupContent)
+    } else {
+      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected String or MarkupContent")
+      throw DecodingError.dataCorrupted(context)
+    }
+  }
+
+  public func encode(to encoder: Encoder) throws {
+    switch self {
+    case .string(let string):
+      try string.encode(to: encoder)
+    case .markupContent(let markupContent):
+      try markupContent.encode(to: encoder)
+    }
+  }
+}
diff --git a/Sources/LanguageServerProtocol/DefinitionRequest.swift b/Sources/LanguageServerProtocol/DefinitionRequest.swift
index f0e652ccd..0b7520a73 100644
--- a/Sources/LanguageServerProtocol/DefinitionRequest.swift
+++ b/Sources/LanguageServerProtocol/DefinitionRequest.swift
@@ -24,7 +24,7 @@
 /// - Returns: The location of the definition(s).
 public struct DefinitionRequest: TextDocumentRequest, Hashable {
   public static let method: String = "textDocument/definition"
-  public typealias Response = [Location]
+  public typealias Response = LocationsOrLocationLinksResponse?
 
   /// The document in which to lookup the symbol location.
   public var textDocument: TextDocumentIdentifier
diff --git a/Sources/LanguageServerProtocol/DocumentSymbol.swift b/Sources/LanguageServerProtocol/DocumentSymbol.swift
index 5dbbfa07d..4c950616a 100644
--- a/Sources/LanguageServerProtocol/DocumentSymbol.swift
+++ b/Sources/LanguageServerProtocol/DocumentSymbol.swift
@@ -24,7 +24,7 @@
 /// - Returns: An array of document symbols, if any.
 public struct DocumentSymbolRequest: TextDocumentRequest, Hashable {
   public static let method: String = "textDocument/documentSymbol"
-  public typealias Response = [DocumentSymbol]?
+  public typealias Response = DocumentSymbolResponse?
 
   /// The document in which to lookup the symbol location.
   public var textDocument: TextDocumentIdentifier
@@ -34,6 +34,31 @@ public struct DocumentSymbolRequest: TextDocumentRequest, Hashable {
   }
 }
 
+public enum DocumentSymbolResponse: ResponseType, Hashable {
+  case documentSymbols([DocumentSymbol])
+  case symbolInformation([SymbolInformation])
+
+  public init(from decoder: Decoder) throws {
+    if let documentSymbols = try? [DocumentSymbol](from: decoder) {
+      self = .documentSymbols(documentSymbols)
+    } else if let symbolInformation = try? [SymbolInformation](from: decoder) {
+      self = .symbolInformation(symbolInformation)
+    } else {
+      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected [DocumentSymbol] or [SymbolInformation]")
+      throw DecodingError.dataCorrupted(context)
+    }
+  }
+
+  public func encode(to encoder: Encoder) throws {
+    switch self {
+    case .documentSymbols(let documentSymbols):
+      try documentSymbols.encode(to: encoder)
+    case .symbolInformation(let symbolInformation):
+      try symbolInformation.encode(to: encoder)
+    }
+  }
+}
+
 /// Represents programming constructs like variables, classes, interfaces etc. that appear 
 /// in a document. Document symbols can be hierarchical and they have two ranges: one that encloses
 /// its definition and one that points to its most interesting range, e.g. the range of an identifier.
@@ -70,12 +95,12 @@ public struct DocumentSymbol: Hashable, Codable, ResponseType {
 
   public init(
     name: String,
-    detail: String?, 
+    detail: String? = nil,
     kind: SymbolKind,
-    deprecated: Bool?,
+    deprecated: Bool? = nil,
     range: Range<Position>,
     selectionRange: Range<Position>,
-    children: [DocumentSymbol]?)
+    children: [DocumentSymbol]? = nil)
   {
     self.name = name
     self.detail = detail
diff --git a/Sources/LanguageServerProtocol/Hover.swift b/Sources/LanguageServerProtocol/Hover.swift
index cb82dfeb6..4c94d7a45 100644
--- a/Sources/LanguageServerProtocol/Hover.swift
+++ b/Sources/LanguageServerProtocol/Hover.swift
@@ -78,7 +78,7 @@ extension MarkedString: Codable {
     } else if let codeBlock = try? MarkdownCodeBlock(from: decoder) {
       self = .codeBlock(language: codeBlock.language, value: codeBlock.value)
     } else {
-      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "MarkedString is neither pure string nor code block")
+      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected String or MarkdownCodeBlock")
       throw DecodingError.dataCorrupted(context)
     }
   }
@@ -104,7 +104,7 @@ extension HoverResponseContents: Codable {
     } else if let value = try? MarkupContent(from: decoder) {
       self = .markupContent(value)
     } else {
-      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "HoverResponseContents is neither MarkedString, nor [MarkedString], nor MarkupContent")
+      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected MarkedString, [MarkedString], or MarkupContent")
       throw DecodingError.dataCorrupted(context)
     }
   }
diff --git a/Sources/LanguageServerProtocol/ImplementationRequest.swift b/Sources/LanguageServerProtocol/ImplementationRequest.swift
index 63f763d2b..aecfa4e7e 100644
--- a/Sources/LanguageServerProtocol/ImplementationRequest.swift
+++ b/Sources/LanguageServerProtocol/ImplementationRequest.swift
@@ -25,7 +25,7 @@
 ///            protocol conforming types, subclasses, or overrides.
 public struct ImplementationRequest: TextDocumentRequest, Hashable {
   public static let method: String = "textDocument/implementation"
-  public typealias Response = [Location]
+  public typealias Response = LocationsOrLocationLinksResponse?
 
   /// The document in which the given symbol is located.
   public var textDocument: TextDocumentIdentifier
diff --git a/Sources/LanguageServerProtocol/LocationLink.swift b/Sources/LanguageServerProtocol/LocationLink.swift
new file mode 100644
index 000000000..003d68554
--- /dev/null
+++ b/Sources/LanguageServerProtocol/LocationLink.swift
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 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
+//
+//===----------------------------------------------------------------------===//
+
+public struct LocationLink: Codable, Hashable {
+  /// Span of the origin of this link.
+  ///
+  /// Used as the underlined span for mouse interaction. Defaults to the word range at the mouse position.
+  @CustomCodable<PositionRange?>
+  public var originSelectionRange: Range<Position>?
+  
+  /// The target resource identifier of this link.
+  public var targetUri: DocumentURI
+  
+  /// The full target range of this link. If the target for example is a symbol then target range is the
+  /// range enclosing this symbol not including leading/trailing whitespace but everything else
+  /// like comments. This information is typically used to highlight the range in the editor.
+  @CustomCodable<PositionRange>
+  public var targetRange: Range<Position>
+  
+  /// The range that should be selected and revealed when this link is being followed, e.g the name of a function.
+  /// Must be contained by the the `targetRange`. See also `DocumentSymbol#range`
+  @CustomCodable<PositionRange>
+  public var targetSelectionRange: Range<Position>
+  
+  public init(originSelectionRange: Range<Position>? = nil,
+              targetUri: DocumentURI,
+              targetRange: Range<Position>,
+              targetSelectionRange: Range<Position>) {
+    self._originSelectionRange = CustomCodable<PositionRange?>(wrappedValue: originSelectionRange)
+    self.targetUri = targetUri
+    self._targetRange = CustomCodable<PositionRange>(wrappedValue: targetRange)
+    self._targetSelectionRange = CustomCodable<PositionRange>(wrappedValue: targetSelectionRange)
+  }
+}
diff --git a/Sources/LanguageServerProtocol/LocationsOrLocationLinksResponse.swift b/Sources/LanguageServerProtocol/LocationsOrLocationLinksResponse.swift
new file mode 100644
index 000000000..3edf18815
--- /dev/null
+++ b/Sources/LanguageServerProtocol/LocationsOrLocationLinksResponse.swift
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 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
+//
+//===----------------------------------------------------------------------===//
+
+public enum LocationsOrLocationLinksResponse: ResponseType, Hashable {
+  case locations([Location])
+  case locationLinks([LocationLink])
+
+  public init(from decoder: Decoder) throws {
+    if let locations = try? [Location](from: decoder) {
+      self = .locations(locations)
+    } else if let locationLinks = try? [LocationLink](from: decoder) {
+      self = .locationLinks(locationLinks)
+    } else if let location = try? Location(from: decoder) {
+      // Fallback: Decode single location as array with one element
+      self = .locations([location])
+    } else {
+      let context = DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Expected [Location], [LocationLink], or Location")
+      throw DecodingError.dataCorrupted(context)
+    }
+  }
+
+  public func encode(to encoder: Encoder) throws {
+    switch self {
+    case .locations(let locations):
+      try locations.encode(to: encoder)
+    case .locationLinks(let locationLinks):
+      try locationLinks.encode(to: encoder)
+    }
+  }
+}
+
diff --git a/Sources/LanguageServerProtocol/ReferencesRequest.swift b/Sources/LanguageServerProtocol/ReferencesRequest.swift
index 33168d487..6664baab8 100644
--- a/Sources/LanguageServerProtocol/ReferencesRequest.swift
+++ b/Sources/LanguageServerProtocol/ReferencesRequest.swift
@@ -33,12 +33,20 @@ public struct ReferencesRequest: RequestType, Hashable {
   /// The document location at which to lookup symbol information.
   public var position: Position
 
-  /// Whether to include the declaration in the list of symbols, or just the references.
-  public var includeDeclaration: Bool?
+  public var context: ReferencesContext
 
-  public init(textDocument: TextDocumentIdentifier, position: Position, includeDeclaration: Bool? = nil) {
+  public init(textDocument: TextDocumentIdentifier, position: Position, context: ReferencesContext) {
     self.textDocument = textDocument
     self.position = position
+    self.context = context
+  }
+}
+
+public struct ReferencesContext: Codable, Hashable {
+  /// Whether to include the declaration in the list of symbols, or just the references.
+  public var includeDeclaration: Bool
+
+  public init(includeDeclaration: Bool) {
     self.includeDeclaration = includeDeclaration
   }
 }
diff --git a/Sources/LanguageServerProtocol/WorkspaceSettings.swift b/Sources/LanguageServerProtocol/WorkspaceSettings.swift
index 77d2d3f2c..ceaa419f1 100644
--- a/Sources/LanguageServerProtocol/WorkspaceSettings.swift
+++ b/Sources/LanguageServerProtocol/WorkspaceSettings.swift
@@ -16,7 +16,7 @@
 public enum WorkspaceSettingsChange: Codable, Hashable {
 
   case clangd(ClangWorkspaceSettings)
-  case unknown
+  case unknown(LSPAny)
 
   public init(from decoder: Decoder) throws {
     // FIXME: doing trial deserialization only works if we have at least one non-optional unique
@@ -25,7 +25,8 @@ public enum WorkspaceSettingsChange: Codable, Hashable {
     if let settings = try? ClangWorkspaceSettings(from: decoder) {
       self = .clangd(settings)
     } else {
-      self = .unknown
+      let settings = try LSPAny(from: decoder)
+      self = .unknown(settings)
     }
   }
 
@@ -33,8 +34,8 @@ public enum WorkspaceSettingsChange: Codable, Hashable {
     switch self {
     case .clangd(let settings):
       try settings.encode(to: encoder)
-    case .unknown:
-      break // Nothing to do.
+    case .unknown(let settings):
+      try settings.encode(to: encoder)
     }
   }
 }
diff --git a/Sources/LanguageServerProtocol/WorkspaceSymbols.swift b/Sources/LanguageServerProtocol/WorkspaceSymbols.swift
index e71488420..a342b2145 100644
--- a/Sources/LanguageServerProtocol/WorkspaceSymbols.swift
+++ b/Sources/LanguageServerProtocol/WorkspaceSymbols.swift
@@ -45,7 +45,11 @@ public struct SymbolInformation: Hashable, ResponseType {
 
   public var containerName: String?
 
-  public init(name: String, kind: SymbolKind, deprecated: Bool?, location: Location, containerName: String?) {
+  public init(name: String,
+              kind: SymbolKind,
+              deprecated: Bool? = nil,
+              location: Location,
+              containerName: String? = nil) {
     self.name = name
     self.kind = kind
     self.deprecated = deprecated
diff --git a/Sources/SourceKit/SourceKitServer.swift b/Sources/SourceKit/SourceKitServer.swift
index 2dd3650ce..95a0fcc42 100644
--- a/Sources/SourceKit/SourceKitServer.swift
+++ b/Sources/SourceKit/SourceKitServer.swift
@@ -80,8 +80,8 @@ public final class SourceKitServer: LanguageServer {
     registerToolchainTextDocumentRequest(SourceKitServer.completion,
                                          CompletionList(isIncomplete: false, items: []))
     registerToolchainTextDocumentRequest(SourceKitServer.hover, nil)
-    registerToolchainTextDocumentRequest(SourceKitServer.definition, [])
-    registerToolchainTextDocumentRequest(SourceKitServer.implementation, [])
+    registerToolchainTextDocumentRequest(SourceKitServer.definition, .locations([]))
+    registerToolchainTextDocumentRequest(SourceKitServer.implementation, .locations([]))
     registerToolchainTextDocumentRequest(SourceKitServer.symbolInfo, [])
     registerToolchainTextDocumentRequest(SourceKitServer.documentSymbolHighlight, nil)
     registerToolchainTextDocumentRequest(SourceKitServer.foldingRange, nil)
@@ -574,7 +574,7 @@ extension SourceKitServer {
         if let error = result.failure {
           req.reply(.failure(error))
         } else {
-          req.reply([])
+          req.reply(.locations([]))
         }
         return
       }
@@ -582,7 +582,7 @@ extension SourceKitServer {
       let fallbackLocation = [symbol.bestLocalDeclaration].compactMap { $0 }
 
       guard let usr = symbol.usr, let index = index else {
-        return req.reply(fallbackLocation)
+        return req.reply(.locations(fallbackLocation))
       }
 
       log("performing indexed jump-to-def with usr \(usr)")
@@ -608,7 +608,7 @@ extension SourceKitServer {
         )
       }
 
-      req.reply(locations.isEmpty ? fallbackLocation : locations)
+      req.reply(.locations(locations.isEmpty ? fallbackLocation : locations))
     }
     let request = Request(symbolInfo, id: req.id, clientID: ObjectIdentifier(self),
                           cancellation: req.cancellationToken, reply: callback)
@@ -627,13 +627,13 @@ extension SourceKitServer {
         if let error = result.failure {
           req.reply(.failure(error))
         } else {
-          req.reply([])
+          req.reply(.locations([]))
         }
         return
       }
 
       guard let usr = symbol.usr, let index = index else {
-        return req.reply([])
+        return req.reply(.locations([]))
       }
 
       var occurs = index.occurrences(ofUSR: usr, roles: .baseOf)
@@ -655,7 +655,7 @@ extension SourceKitServer {
         )
       }
 
-      req.reply(locations)
+      req.reply(.locations(locations))
     }
     let request = Request(symbolInfo, id: req.id, clientID: ObjectIdentifier(self),
                           cancellation: req.cancellationToken, reply: callback)
@@ -688,7 +688,7 @@ extension SourceKitServer {
       log("performing indexed jump-to-def with usr \(usr)")
 
       var roles: SymbolRole = [.reference]
-      if req.params.includeDeclaration != false {
+      if req.params.context.includeDeclaration {
         roles.formUnion([.declaration, .definition])
       }
 
diff --git a/Sources/SourceKit/sourcekitd/SwiftLanguageServer.swift b/Sources/SourceKit/sourcekitd/SwiftLanguageServer.swift
index b625bd2e1..1a89e6a65 100644
--- a/Sources/SourceKit/sourcekitd/SwiftLanguageServer.swift
+++ b/Sources/SourceKit/sourcekitd/SwiftLanguageServer.swift
@@ -387,13 +387,13 @@ extension SwiftLanguageServer {
           let kind: sourcekitd_uid_t? = value[self.keys.kind]
           result.items.append(CompletionItem(
             label: name,
+            kind: kind?.asCompletionItemKind(self.values) ?? .value,
             detail: typeName,
             sortText: nil,
             filterText: filterName,
             textEdit: nil,
             insertText: text,
             insertTextFormat: isInsertTextSnippet ? .snippet : .plain,
-            kind: kind?.asCompletionItemKind(self.values) ?? .value,
             deprecated: nil
           ))
 
@@ -539,7 +539,7 @@ extension SwiftLanguageServer {
           return
         }
         guard let results: SKResponseArray = dict[self.keys.substructure] else {
-          return req.reply([])
+          return req.reply(.documentSymbols([]))
         }
 
         func documentSymbol(value: SKResponseDictionary) -> DocumentSymbol? {
@@ -592,7 +592,7 @@ extension SwiftLanguageServer {
           return result
         }
 
-        req.reply(documentSymbols(array: results))
+        req.reply(.documentSymbols(documentSymbols(array: results)))
       }
       // FIXME: cancellation
       _ = handle
diff --git a/Tests/LanguageServerProtocolTests/CodingTests.swift b/Tests/LanguageServerProtocolTests/CodingTests.swift
index e0df07a8c..1f8a7ee71 100644
--- a/Tests/LanguageServerProtocolTests/CodingTests.swift
+++ b/Tests/LanguageServerProtocolTests/CodingTests.swift
@@ -265,6 +265,88 @@ final class CodingTests: XCTestCase {
         }
       }
       """)
+
+    checkCoding(CompletionList(isIncomplete: true, items: [CompletionItem(label: "abc", kind: .function)]), json: """
+      {
+        "isIncomplete" : true,
+        "items" : [
+          {
+            "kind" : 3,
+            "label" : "abc"
+          }
+        ]
+      }
+      """)
+
+    checkDecoding(json: """
+      [
+        {
+          "kind" : 3,
+          "label" : "abc"
+        }
+      ]
+      """, expected: CompletionList(isIncomplete: false, items: [CompletionItem(label: "abc", kind: .function)]))
+
+    checkCoding(CompletionItemDocumentation.markupContent(MarkupContent(kind: .markdown, value: "some **Markdown***")), json: """
+      {
+        "kind" : "markdown",
+        "value" : "some **Markdown***"
+      }
+      """)
+
+    checkCoding(CompletionItemDocumentation.string("Some documentation"), json: """
+      "Some documentation"
+      """)
+
+    checkCoding(LocationsOrLocationLinksResponse.locations([Location(uri: uri, range: range)]), json: """
+      [
+        {
+          "range" : \(rangejson.indented(4, skipFirstLine: true)),
+          "uri" : "\(urljson)"
+        }
+      ]
+      """)
+
+    checkCoding(LocationsOrLocationLinksResponse.locationLinks([LocationLink(targetUri: uri, targetRange: range, targetSelectionRange: range)]), json: """
+      [
+        {
+          "targetRange" : \(rangejson.indented(4, skipFirstLine: true)),
+          "targetSelectionRange" : \(rangejson.indented(4, skipFirstLine: true)),
+          "targetUri" : "\(urljson)"
+        }
+      ]
+      """)
+
+    checkDecoding(json: """
+      {
+        "range" : \(rangejson.indented(2, skipFirstLine: true)),
+        "uri" : "\(urljson)"
+      }
+      """, expected: LocationsOrLocationLinksResponse.locations([Location(uri: uri, range: range)]))
+
+    checkCoding(DocumentSymbolResponse.documentSymbols([DocumentSymbol(name: "mySymbol", kind: .function, range: range, selectionRange: range)]), json: """
+      [
+        {
+          "kind" : 12,
+          "name" : "mySymbol",
+          "range" : \(rangejson.indented(4, skipFirstLine: true)),
+          "selectionRange" : \(rangejson.indented(4, skipFirstLine: true))
+        }
+      ]
+      """)
+
+    checkCoding(DocumentSymbolResponse.symbolInformation([SymbolInformation(name: "mySymbol", kind: .function, location: Location(uri: uri, range: range))]), json: """
+      [
+        {
+          "kind" : 12,
+          "location" : {
+            "range" : \(rangejson.indented(6, skipFirstLine: true)),
+            "uri" : "\(urljson)"
+          },
+          "name" : "mySymbol"
+        }
+      ]
+      """)
   }
 
   func testPositionRange() {
diff --git a/Tests/SourceKitTests/DocumentSymbolTests.swift b/Tests/SourceKitTests/DocumentSymbolTests.swift
index b8ce9de37..35b0d2e4d 100644
--- a/Tests/SourceKitTests/DocumentSymbolTests.swift
+++ b/Tests/SourceKitTests/DocumentSymbolTests.swift
@@ -51,7 +51,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
     workspace = connection.server!.workspace!
   }
 
-  func performDocumentSymbolRequest(text: String) -> [DocumentSymbol] {
+  func performDocumentSymbolRequest(text: String) -> DocumentSymbolResponse {
     let url = URL(fileURLWithPath: "/a.swift")
 
     sk.send(DidOpenTextDocument(textDocument: TextDocumentItem(
@@ -77,7 +77,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
 
     let text = ""
     let symbols = performDocumentSymbolRequest(text: text)
-    XCTAssertEqual(symbols, [])
+    XCTAssertEqual(symbols, .documentSymbols([]))
   }
 
   func testStruct() {
@@ -89,7 +89,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
     """
     let symbols = performDocumentSymbolRequest(text: text)
 
-    XCTAssertEqual(symbols, [
+    XCTAssertEqual(symbols, .documentSymbols([
       DocumentSymbol(
         name: "Foo",
         detail: nil,
@@ -99,7 +99,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
         selectionRange: range(from: (0, 7), to: (0, 10)),
         children: []
       ),
-    ])
+    ]))
   }
 
   func testUnicode() {
@@ -118,7 +118,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
     // but cake is two utf-16 code units
     let cakeRange = range(from: (1, 0), to: (1, 13))
     let cakeSelectionRange = range(from: (1, 7), to: (1, 9))
-    XCTAssertEqual(symbols, [
+    XCTAssertEqual(symbols, .documentSymbols([
       DocumentSymbol(
         name: "Żółć",
         detail: nil,
@@ -137,7 +137,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
         selectionRange: cakeSelectionRange,
         children: []
       ),
-    ])
+    ]))
   }
 
   func testEnum() {
@@ -159,7 +159,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
     """
     let symbols = performDocumentSymbolRequest(text: text)
 
-    XCTAssertEqual(symbols, [
+    XCTAssertEqual(symbols, .documentSymbols([
       DocumentSymbol(
         name: "Foo",
         detail: nil,
@@ -288,7 +288,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
           )
         ]
       )
-    ])
+    ]))
   }
 
   func testAll() {
@@ -333,7 +333,7 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
     """
     let symbols = performDocumentSymbolRequest(text: text)
 
-    XCTAssertEqual(symbols, [
+    XCTAssertEqual(symbols, .documentSymbols([
       DocumentSymbol(
         name: "Int",
         detail: nil,
@@ -646,6 +646,6 @@ func initialize(capabilities: DocumentSymbolCapabilities) {
           )
         ]
       )
-    ])
+    ]))
   }
 }
diff --git a/Tests/SourceKitTests/ImplementationTests.swift b/Tests/SourceKitTests/ImplementationTests.swift
index 71cf76123..6d04d0709 100644
--- a/Tests/SourceKitTests/ImplementationTests.swift
+++ b/Tests/SourceKitTests/ImplementationTests.swift
@@ -25,7 +25,11 @@ final class ImplementationTests: XCTestCase {
     func impls(at testLoc: TestLocation) throws -> Set<Location> {
       let textDocument = testLoc.docIdentifier
       let request = ImplementationRequest(textDocument: textDocument, position: Position(testLoc))
-      let implementations = try ws.sk.sendSync(request)
+      let response = try ws.sk.sendSync(request)
+      guard case .locations(let implementations) = response else {
+        XCTFail("Response was not locations")
+        return []
+      }
       return Set(implementations)
     }
     func testLoc(_ name: String) -> TestLocation {
diff --git a/Tests/SourceKitTests/SourceKitTests.swift b/Tests/SourceKitTests/SourceKitTests.swift
index 047c6d7fe..f5827d18d 100644
--- a/Tests/SourceKitTests/SourceKitTests.swift
+++ b/Tests/SourceKitTests/SourceKitTests.swift
@@ -66,9 +66,13 @@ final class SKTests: XCTestCase {
 
     // MARK: Jump to definition
 
-    let jump = try ws.sk.sendSync(DefinitionRequest(
+    let response = try ws.sk.sendSync(DefinitionRequest(
       textDocument: locRef.docIdentifier,
       position: locRef.position))
+    guard case .locations(let jump) = response else {
+      XCTFail("Response is not locations")
+      return
+    }
 
     XCTAssertEqual(jump.count, 1)
     XCTAssertEqual(jump.first?.uri, DocumentURI(locDef.url))
@@ -78,7 +82,8 @@ final class SKTests: XCTestCase {
 
     let refs = try ws.sk.sendSync(ReferencesRequest(
       textDocument: locDef.docIdentifier,
-      position: locDef.position))
+      position: locDef.position,
+      context: ReferencesContext(includeDeclaration: true)))
 
     XCTAssertEqual(Set(refs), [
       Location(locDef),
@@ -110,9 +115,13 @@ final class SKTests: XCTestCase {
       let locDef = ws.testLoc("aaa:def")
       let locRef = ws.testLoc("aaa:call:c")
       try ws.openDocument(locRef.url, language: .swift)
-      let jump = try ws.sk.sendSync(DefinitionRequest(
+      let response = try ws.sk.sendSync(DefinitionRequest(
         textDocument: locRef.docIdentifier,
         position: locRef.position))
+      guard case .locations(let jump) = response else {
+        XCTFail("Response is not locations")
+        return nil
+      }
       XCTAssertEqual(jump.count, 1)
       XCTAssertEqual(jump.first?.uri, DocumentURI(locDef.url))
       XCTAssertEqual(jump.first?.range.lowerBound, locDef.position)
@@ -153,23 +162,23 @@ final class SKTests: XCTestCase {
     XCTAssertEqual(results, CompletionList(isIncomplete: false, items: [
       CompletionItem(
         label: "method(a: Int)",
+        kind: .method,
         detail: "Void",
         sortText: nil,
         filterText: "method(a:)",
         textEdit: nil,
         insertText: "method(a: )",
         insertTextFormat: .plain,
-        kind: .method,
         deprecated: nil),
       CompletionItem(
         label: "self",
+        kind: .keyword,
         detail: "A",
         sortText: nil,
         filterText: "self",
         textEdit: nil,
         insertText: "self",
         insertTextFormat: .plain,
-        kind: .keyword,
         deprecated: nil),
     ]))
   }
diff --git a/Tests/SourceKitTests/SwiftPMIntegration.swift b/Tests/SourceKitTests/SwiftPMIntegration.swift
index f9c6daca9..5ce138944 100644
--- a/Tests/SourceKitTests/SwiftPMIntegration.swift
+++ b/Tests/SourceKitTests/SwiftPMIntegration.swift
@@ -22,7 +22,7 @@ final class SwiftPMIntegrationTests: XCTestCase {
     let call = ws.testLoc("Lib.foo:call")
     let def = ws.testLoc("Lib.foo:def")
     try ws.openDocument(call.url, language: .swift)
-    let refs = try ws.sk.sendSync(ReferencesRequest(textDocument: call.docIdentifier, position: call.position))
+    let refs = try ws.sk.sendSync(ReferencesRequest(textDocument: call.docIdentifier, position: call.position, context: ReferencesContext(includeDeclaration: true)))
 
     XCTAssertEqual(Set(refs), [
       Location(call),
@@ -34,23 +34,23 @@ final class SwiftPMIntegrationTests: XCTestCase {
     XCTAssertEqual(completions, CompletionList(isIncomplete: false, items: [
       CompletionItem(
         label: "foo()",
+        kind: .method,
         detail: "Void",
         sortText: nil,
         filterText: "foo()",
         textEdit: nil,
         insertText: "foo()",
         insertTextFormat: .plain,
-        kind: .method,
         deprecated: nil),
       CompletionItem(
         label: "self",
+        kind: .keyword,
         detail: "Lib",
         sortText: nil,
         filterText: "self",
         textEdit: nil,
         insertText: "self",
         insertTextFormat: .plain,
-        kind: .keyword,
         deprecated: nil),
     ]))
   }