Add in experimental support for js/ts multi-line diagnostics

From https://github.com/weswigham/vscode/commit/da48d42acc7b4be254d644b8d894e20608fa3ee3

extensions/typescript-language-features/src/typeScriptServiceClientHost.ts

@@ -8,7 +8,7 @@
  * https://github.com/Microsoft/TypeScript-Sublime-Plugin/blob/master/TypeScript%20Indent.tmPreferences
  * ------------------------------------------------------------------------------------------ */
 
-import { workspace, Memento, Diagnostic, Range, Disposable, Uri, DiagnosticSeverity, DiagnosticTag } from 'vscode';
+import { workspace, Memento, Diagnostic, Range, Disposable, Uri, DiagnosticSeverity, DiagnosticTag, DiagnosticRelatedInformation } from 'vscode';
 
 import * as Proto from './protocol';
 import * as PConst from './protocol.const';
@@ -281,6 +281,17 @@ export default class TypeScriptServiceClientHost {
 		if (diagnostic.code) {
 			converted.code = diagnostic.code;
 		}
+		// TODO: requires TS 3.0
+		const relatedInformation = (diagnostic as any).relatedInformation;
+		if (relatedInformation) {
+			converted.relatedInformation = relatedInformation.map((info: any) => {
+				let span = info.span;
+				if (!span) {
+					return undefined;
+				}
+				return new DiagnosticRelatedInformation(typeConverters.Location.fromTextSpan(this.client.toResource(span.file), span), info.message);
+			}).filter((x: any) => !!x) as DiagnosticRelatedInformation[];
+		}
 		if (diagnostic.reportsUnnecessary) {
 			converted.customTags = [DiagnosticTag.Unnecessary];
 		}