[WIP] Proposal for type hierarchy

protocol/protocol.typeHierarchy.proposed.md

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+
+#### Type Hierarchy
+
+Many language support inheritance and LSP provides retrieving the hierarchy information with the following requests.
+
+
+The `textDocument/subTypes` request is sent from the client to the server to resolve resolve the subtypes of a symbol at a given text document position. Returns the direct subtypes in no particular order.
+
+_Client Capabilities_:
+
+```ts
+  TextDocumentClientCapabilities {
+    /**
+     * Capabilities specific to the `textDocument/subTypes`
+     *  and `textDocument/superTypes
+     */
+    typeHierarchy?: {
+    /**
+     * Whether implementation supports dynamic registration.
+     */
+    dynamicRegistration?: boolean;
+  };
+```
+
+_Server Capabilities_:
+```ts
+ServerCapabilities{
+  /**
+   * The server provides type hierarchy information
+   */
+  typeHierarchyProvider?: boolean
+}
+```
+
+```ts
+/**
+ * Represents hierarchical information about programming constructs like variables, classes,
+ * interfaces etc.
+ */
+export interface SymbolNode extends SymbolInformation {
+  /**
+   * Immediate descendants of this node
+   */
+  descendants? : SymbolNode[]
+  /**
+   * true if this node has children. hasChildren can be
+   * true even when the descendants are empty. In that case
+   * the clients should do a call to retrieve the descendants.
+   */
+  hasChildren: boolean
+}
+```
+
+_Request_:
+
+method: ‘textDocument/subTypes’
+params: TextDocumentPositionParams
+
+_Response_
+
+* result: `SymbolNode[] | null`
+* error: code and message set in case an exception happens during the 'textDocument/subTypes' request
+
+
+
+The `textDocument/superTypes` request is sent from the client to the server to resolve resolve the supertypes of a symbol at a given text document position. Returns all the supertypes in bottom-up order.
+
+_Request_:
+
+method: ‘textDocument/superTypes’
+params: TextDocumentPositionParams
+
+_Response_
+
+* result: `SymbolNode[] | null`
+* error: code and message set in case an exception happens during the 'textDocument/superTypes' request
+

protocol/src/protocol.typeHierarchy.proposed.ts

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+/* --------------------------------------------------------------------------------------------
+ * Copyright (c) Red Hat Inc and others . All rights reserved.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ * ------------------------------------------------------------------------------------------ */
+'use strict';
+
+import { RequestType } from 'vscode-jsonrpc';
+import {SymbolInformation} from 'vscode-languageserver-types';
+import {TextDocumentPositionParams, TextDocumentRegistrationOptions} from './protocol'
+
+export interface TypeHierarchyClientCapabilities {
+	/**
+	 * The text document client capabilities
+	 */
+	textDocument?: {
+		/**
+		 * Capabilities specific to the `textDocument/subTypes` and `textDocument/superTypes`
+		 */
+		typeHierarchy?: {
+			/**
+			 * Whether implementation supports dynamic registration.
+			 */
+			dynamicRegistration?: boolean;
+		};
+	}
+}
+
+export interface TypeHierarchyServerCapabilities {
+	/**
+	 * The server provides type hierarchy information
+	 */
+	typeHierarchyProvider?: boolean
+}
+
+/**
+ *
+ */
+export namespace SubTypesRequest {
+  export const type = new RequestType<TextDocumentPositionParams, SymbolNode[], void, TextDocumentRegistrationOptions>('textDocument/subTypes');
+}
+
+/**
+ *
+ */
+export namespace SuperTypesRequest {
+  export const type = new RequestType<TextDocumentPositionParams, SymbolNode[], void, TextDocumentRegistrationOptions>('textDocument/superTypes');
+}
+
+
+/**
+ * Represents hierarchical information about programming constructs like variables, classes,
+ * interfaces etc.
+ */
+export interface SymbolNode extends SymbolInformation {
+  /**
+   * Immediate descendants of this node
+   */
+  descendants? : SymbolNode[]
+  /**
+   * true if this node has children. hasChildren can be
+   * true even when the descendants are empty. In that case
+   * the clients should do a call to retrieve the descendants.
+   */
+  hasChildren: boolean
+}