fixes #13577

src/vs/base/common/mime.ts

@@ -143,7 +143,7 @@ function guessMimeTypeByPath(path: string, filename: string, associations: IText
 	let patternMatch: ITextMimeAssociationItem;
 	let extensionMatch: ITextMimeAssociationItem;
 
-	for (var i = 0; i < associations.length; i++) {
+	for (let i = 0; i < associations.length; i++) {
 		let association = associations[i];
 
 		// First exact name match
@@ -243,13 +243,17 @@ export function isUnspecific(mime: string[] | string): boolean {
 }
 
 export function suggestFilename(langId: string, prefix: string): string {
-	for (var i = 0; i < registeredAssociations.length; i++) {
+	for (let i = 0; i < registeredAssociations.length; i++) {
 		let association = registeredAssociations[i];
 		if (association.userConfigured) {
 			continue; // only support registered ones
 		}
 
 		if (association.id === langId && association.extension) {
+			if (langId && langId.toLowerCase() === 'xml') {
+				return prefix + '.xml'; // https://github.com/Microsoft/vscode/issues/13577
+			}
+
 			return prefix + association.extension;
 		}
 	}

src/vs/workbench/services/textfile/electron-browser/textFileService.ts

@@ -168,7 +168,12 @@ export class TextFileService extends AbstractTextFileService {
 				return null;
 			}
 
-			const filter: IFilter = { name: languageName, extensions: extensions.slice(0, 10).map(e => strings.trim(e, '.')) };
+			let extensionEntries = extensions.slice(0, 20).map(e => strings.trim(e, '.'));
+			if (languageName.toLowerCase() === 'xml') {
+				extensionEntries.unshift('xml'); // https://github.com/Microsoft/vscode/issues/13577
+			}
+
+			const filter: IFilter = { name: languageName, extensions: extensionEntries };
 
 			if (ext && extensions.indexOf(ext) >= 0) {
 				matchingFilter = filter;