Transform method for plugins has correct 'this' context

See link for more info: https://github.com/rollup/rollup/wiki/Plugins#warnings-and-errors

types/rollup/index.d.ts

@@ -133,7 +133,7 @@ export interface Plugin {
 	 */
 	resolveId?(importee: string, importer: string): string | null | undefined | false | 0 | ''
 	/** A module transformer function */
-	transform?(source: string, id: string): string | { code: string, map: SourceMap }
+	transform?(this: TransformContext, source: string, id: string): string | { code: string, map: SourceMap }
 	/** A bundle transformer function */
 	transformBundle?(source: string, options: { format: Format }): string | { code: string, map: SourceMap }
 	/** Function hook called when bundle.generate() is being executed. */
@@ -150,5 +150,13 @@ export interface Plugin {
 	footer?: string | (() => string)
 }
 
+// See https://github.com/rollup/rollup/wiki/Plugins#warnings-and-errors
+export interface TransformContext {
+	/** Emit warnings to Rollup which will be logged during bundling */
+	warn(message: string | { message: string }, pos?: number | { line: number, column: number }): void;
+	/** Emit an error, which will abort the bundling process */
+	error(message: string | { message: string }, pos?: number | { line: number, column: number }): void;
+}
+
 /** Returns a Promise that resolves with a bundle */
 export function rollup(options: Options): Promise<Bundle>

types/rollup/rollup-tests.ts

@@ -3,7 +3,19 @@ import { rollup, Bundle, Plugin } from 'rollup'
 let console: any
 
 let cache: Bundle | undefined
-let plugin: Plugin
+let plugin: Plugin = {
+    name: 'test-plugin',
+    transform(source, id) {
+        if (id === 'rxjs') {
+            this.error(new Error(`Don't import this directly`))
+        }
+        let indexOfQuote = source.indexOf('"')
+        if (indexOfQuote >= 0) {
+            this.warn(`Prefer ' over " for strings`, indexOfQuote)
+        }
+        return source
+    }
+}
 
 async function main() {
     const bundle = await rollup({