Fix support for BigInt literals when using the acorn plugin

package.json

@@ -66,6 +66,7 @@
     "@types/chokidar": "^1.7.5",
     "@types/minimist": "^1.2.0",
     "@types/pretty-ms": "^3.0.0",
+    "acorn-bigint": "^0.3.1",
     "acorn-dynamic-import": "^4.0.0",
     "acorn-import-meta": "^0.3.0",
     "acorn-jsx": "^5.0.1",

src/ast/nodes/BinaryExpression.ts

@@ -28,7 +28,8 @@ const binaryOperators: {
 	'|': (left: any, right: any) => left | right,
 	'^': (left: any, right: any) => left ^ right,
 	'&': (left: any, right: any) => left & right,
-	'**': (left: any, right: any) => Math.pow(left, right),
+	// At the moment, "**" will be transpiled to Math.pow
+	'**': (left: any, right: any) => left ** right,
 	in: () => UNKNOWN_VALUE,
 	instanceof: () => UNKNOWN_VALUE
 };

src/ast/nodes/Literal.ts

@@ -28,11 +28,15 @@ export default class Literal<T = LiteralValue> extends NodeBase {
 	private members: { [key: string]: MemberDescription };
 
 	getLiteralValueAtPath(path: ObjectPath): LiteralValueOrUnknown {
-		if (path.length > 0) {
+		if (
+			path.length > 0 ||
+			// unknown literals such as bigints can also be null but do not start with an "n"
+			(this.value === null && this.context.code.charCodeAt(this.start) !== 110) ||
+			typeof this.value === 'bigint'
+		) {
 			return UNKNOWN_VALUE;
 		}
-		// not sure why we need this type cast here
-		return <any>this.value;
+		return this.value as any;
 	}
 
 	getReturnExpressionWhenCalledAtPath(path: ObjectPath) {

test/form/samples/big-int/_config.js

@@ -0,0 +1,8 @@
+const bigInt = require('acorn-bigint');
+
+module.exports = {
+	description: 'supports bigint via acorn plugin',
+	options: {
+		acornInjectPlugins: [bigInt]
+	}
+};

test/form/samples/big-int/_expected.js

@@ -0,0 +1,20 @@
+if (1n > 0) {
+	console.log('ok');
+}
+
+if (1n + 1n > 0) {
+	console.log('ok');
+}
+
+if (1n ** 1n > 0) {
+	console.log('ok');
+}
+
+const max = 2n**64n;
+const min = -max;
+
+function isSafe (int) {
+	return min<=int && int<=max;
+}
+
+export default isSafe;

test/form/samples/big-int/main.js

@@ -0,0 +1,18 @@
+if (1n > 0) {
+	console.log('ok');
+}
+
+if (1n + 1n > 0) {
+	console.log('ok');
+}
+
+if (1n ** 1n > 0) {
+	console.log('ok');
+}
+
+const max = 2n**64n;
+const min = -max;
+
+export default function isSafe (int) {
+	return min<=int && int<=max;
+};