use acorn.isIdentifierStart and isIdentifierChar to determine validity

src/utils/isValidIdentifier.ts

@@ -0,0 +1,11 @@
+import { isIdentifierStart, isIdentifierChar } from 'acorn';
+
+export default function isValidIdentifier(str) {
+	if (!isIdentifierStart(str.charCodeAt(0), true)) return false;
+
+	for (let i = 0; i < str.length; i += 1) {
+		if (!isIdentifierChar(str.charCodeAt(i), true)) return false;
+	}
+
+	return true;
+}

src/validate/js/propValidators/computed.ts

@@ -1,6 +1,8 @@
 import checkForDupes from '../utils/checkForDupes';
 import checkForComputedKeys from '../utils/checkForComputedKeys';
-import checkForValidIdentifiers from '../utils/checkForValidIdentifiers';
+import getName from '../../../utils/getName';
+import isValidIdentifier from '../../../utils/isValidIdentifier';
+import reservedNames from '../../../utils/reservedNames';
 import { Validator } from '../../';
 import { Node } from '../../../interfaces';
 import walkThroughTopFunctionScope from '../../../utils/walkThroughTopFunctionScope';
@@ -21,9 +23,25 @@ export default function computed(validator: Validator, prop: Node) {
 
 	checkForDupes(validator, prop.value.properties);
 	checkForComputedKeys(validator, prop.value.properties);
-	checkForValidIdentifiers(validator, prop.value.properties);
 
 	prop.value.properties.forEach((computation: Node) => {
+		const name = getName(computation.key);
+
+		if (!isValidIdentifier(name)) {
+			const suggestion = name.replace(/[^_$a-z0-9]/ig, '_').replace(/^\d/, '_$&');
+			validator.error(
+				`Computed property name '${name}' is invalid — must be a valid identifier such as ${suggestion}`,
+				computation.start
+			);
+		}
+
+		if (reservedNames.has(name)) {
+			validator.error(
+				`Computed property name '${name}' is invalid — cannot be a JavaScript reserved word`,
+				computation.start
+			);
+		}
+
 		if (!isFunctionExpression.has(computation.value.type)) {
 			validator.error(
 				`Computed properties can be function expressions or arrow function expressions`,

src/validate/js/utils/checkForValidIdentifiers.ts

@@ -1,25 +0,0 @@
-import { Validator } from '../../';
-import { Node } from '../../../interfaces';
-import getName from '../../../utils/getName';
-import { parse } from 'acorn';
-
-export default function checkForValidIdentifiers(
-	validator: Validator,
-	properties: Node[]
-) {
-	properties.forEach(prop => {
-		const name = getName(prop.key);
-		const functionDefinitionString = `function ${name}() {}`;
-		try {
-			parse(functionDefinitionString);
-		} catch (exception) {
-			const invalidCharacter = functionDefinitionString[exception.pos];
-			validator.error(
-				`Computed property name "${name}" is invalid. Character '${
-					invalidCharacter
-				}' at position ${exception.pos} is illegal in function identifiers`,
-				prop.start
-			);
-		}
-	});
-}