diff --git a/.eslintrc.json b/.eslintrc.json
index 350c4751033..1a85f595bb2 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -25,13 +25,18 @@
         "no-sparse-arrays": "warn",
         "no-throw-literal": "warn",
         "no-unsafe-finally": "warn",
-        "no-unused-expressions": "off",
         "no-unused-labels": "warn",
         "no-var": "warn",
         "jsdoc/no-types": "warn",
         "semi": "off",
         "@typescript-eslint/semi": "warn",
         "@typescript-eslint/class-name-casing": "warn",
+        "code-no-unused-expressions": [
+            "warn",
+            {
+                "allowTernary": true
+            }
+        ],
         "code-translation-remind": "warn",
         "code-no-nls-in-standalone-editor": "warn",
         "code-no-standalone-editor": "warn",
diff --git a/build/lib/eslint/code-no-unused-expressions.js b/build/lib/eslint/code-no-unused-expressions.js
new file mode 100644
index 00000000000..c7b17551311
--- /dev/null
+++ b/build/lib/eslint/code-no-unused-expressions.js
@@ -0,0 +1,145 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+// FORKED FROM https://github.com/eslint/eslint/blob/b23ad0d789a909baf8d7c41a35bc53df932eaf30/lib/rules/no-unused-expressions.js
+// and added support for `OptionalCallExpression`, see https://github.com/facebook/create-react-app/issues/8107 and https://github.com/eslint/eslint/issues/12642
+
+/**
+ * @fileoverview Flag expressions in statement position that do not side effect
+ * @author Michael Ficarra
+ */
+
+'use strict';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+	meta: {
+		type: 'suggestion',
+
+		docs: {
+			description: 'disallow unused expressions',
+			category: 'Best Practices',
+			recommended: false,
+			url: 'https://eslint.org/docs/rules/no-unused-expressions'
+		},
+
+		schema: [
+			{
+				type: 'object',
+				properties: {
+					allowShortCircuit: {
+						type: 'boolean',
+						default: false
+					},
+					allowTernary: {
+						type: 'boolean',
+						default: false
+					},
+					allowTaggedTemplates: {
+						type: 'boolean',
+						default: false
+					}
+				},
+				additionalProperties: false
+			}
+		]
+	},
+
+	create(context) {
+		const config = context.options[0] || {},
+			allowShortCircuit = config.allowShortCircuit || false,
+			allowTernary = config.allowTernary || false,
+			allowTaggedTemplates = config.allowTaggedTemplates || false;
+
+		// eslint-disable-next-line jsdoc/require-description
+        /**
+         * @param {ASTNode} node any node
+         * @returns {boolean} whether the given node structurally represents a directive
+         */
+		function looksLikeDirective(node) {
+			return node.type === 'ExpressionStatement' &&
+				node.expression.type === 'Literal' && typeof node.expression.value === 'string';
+		}
+
+		// eslint-disable-next-line jsdoc/require-description
+        /**
+         * @param {Function} predicate ([a] -> Boolean) the function used to make the determination
+         * @param {a[]} list the input list
+         * @returns {a[]} the leading sequence of members in the given list that pass the given predicate
+         */
+		function takeWhile(predicate, list) {
+			for (let i = 0; i < list.length; ++i) {
+				if (!predicate(list[i])) {
+					return list.slice(0, i);
+				}
+			}
+			return list.slice();
+		}
+
+		// eslint-disable-next-line jsdoc/require-description
+        /**
+         * @param {ASTNode} node a Program or BlockStatement node
+         * @returns {ASTNode[]} the leading sequence of directive nodes in the given node's body
+         */
+		function directives(node) {
+			return takeWhile(looksLikeDirective, node.body);
+		}
+
+		// eslint-disable-next-line jsdoc/require-description
+        /**
+         * @param {ASTNode} node any node
+         * @param {ASTNode[]} ancestors the given node's ancestors
+         * @returns {boolean} whether the given node is considered a directive in its current position
+         */
+		function isDirective(node, ancestors) {
+			const parent = ancestors[ancestors.length - 1],
+				grandparent = ancestors[ancestors.length - 2];
+
+			return (parent.type === 'Program' || parent.type === 'BlockStatement' &&
+				(/Function/u.test(grandparent.type))) &&
+				directives(parent).indexOf(node) >= 0;
+		}
+
+        /**
+         * Determines whether or not a given node is a valid expression. Recurses on short circuit eval and ternary nodes if enabled by flags.
+         * @param {ASTNode} node any node
+         * @returns {boolean} whether the given node is a valid expression
+         */
+		function isValidExpression(node) {
+			if (allowTernary) {
+
+				// Recursive check for ternary and logical expressions
+				if (node.type === 'ConditionalExpression') {
+					return isValidExpression(node.consequent) && isValidExpression(node.alternate);
+				}
+			}
+
+			if (allowShortCircuit) {
+				if (node.type === 'LogicalExpression') {
+					return isValidExpression(node.right);
+				}
+			}
+
+			if (allowTaggedTemplates && node.type === 'TaggedTemplateExpression') {
+				return true;
+			}
+
+			return /^(?:Assignment|OptionalCall|Call|New|Update|Yield|Await)Expression$/u.test(node.type) ||
+				(node.type === 'UnaryExpression' && ['delete', 'void'].indexOf(node.operator) >= 0);
+		}
+
+		return {
+			ExpressionStatement(node) {
+				if (!isValidExpression(node.expression) && !isDirective(node, context.getAncestors())) {
+					context.report({ node, message: 'Expected an assignment or function call and instead saw an expression.' });
+				}
+			}
+		};
+
+	}
+};
diff --git a/src/vs/platform/log/common/fileLogService.ts b/src/vs/platform/log/common/fileLogService.ts
index 32493332bc1..20716554d04 100644
--- a/src/vs/platform/log/common/fileLogService.ts
+++ b/src/vs/platform/log/common/fileLogService.ts
@@ -173,7 +173,7 @@ export class FileLoggerService extends Disposable implements ILoggerService {
 	getLogger(resource: URI): ILogger {
 		let logger = this.loggers.get(resource.toString());
 		if (!logger) {
-			logger = new BufferLogService, this.logService.getLevel();
+			logger = new BufferLogService(this.logService.getLevel());
 			this.loggers.set(resource.toString(), logger);
 			whenProviderRegistered(resource, this.fileService).then(() => (<BufferLogService>logger).logger = this.instantiationService.createInstance(FileLogService, basename(resource), resource, this.logService.getLevel()));
 		}
diff --git a/src/vs/workbench/contrib/files/browser/editors/textFileSaveErrorHandler.ts b/src/vs/workbench/contrib/files/browser/editors/textFileSaveErrorHandler.ts
index 7de229cf583..cebc296f377 100644
--- a/src/vs/workbench/contrib/files/browser/editors/textFileSaveErrorHandler.ts
+++ b/src/vs/workbench/contrib/files/browser/editors/textFileSaveErrorHandler.ts
@@ -180,7 +180,7 @@ export class TextFileSaveErrorHandler extends Disposable implements ISaveErrorHa
 		// Show message and keep function to hide in case the file gets saved/reverted
 		const actions: INotificationActions = { primary: primaryActions, secondary: secondaryActions };
 		const handle = this.notificationService.notify({ severity: Severity.Error, message, actions });
-		Event.once(handle.onDidClose)(() => { dispose(primaryActions), dispose(secondaryActions); });
+		Event.once(handle.onDidClose)(() => { dispose(primaryActions); dispose(secondaryActions); });
 		this.messages.set(model.resource, handle);
 	}