Deoptimize typeof for regular expression literals to better support e…

…s6-shim (#2916)

src/ast/nodes/Literal.ts

@@ -26,9 +26,11 @@ export default class Literal<T = LiteralValue> extends NodeBase {
 	getLiteralValueAtPath(path: ObjectPath): LiteralValueOrUnknown {
 		if (
 			path.length > 0 ||
-			// unknown literals such as bigints can also be null but do not start with an "n"
+			// unknown literals 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'
+			typeof this.value === 'bigint' ||
+			// to support shims for regular expressions
+			this.context.code.charCodeAt(this.start) === 47
 		) {
 			return UNKNOWN_VALUE;
 		}

test/form/samples/deopt-regexp-type/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'deoptimizes typeof for regular expressions to better support es6-sim'
+};

test/form/samples/deopt-regexp-type/_expected.js

@@ -0,0 +1,10 @@
+const isCallable =
+	typeof /abc/ === 'function'
+		? function IsCallableSlow(x) {
+				return typeof x === 'function' && _toString(x) === '[object Function]';
+		  }
+		: function IsCallableFast(x) {
+				return typeof x === 'function';
+		  };
+
+console.log(isCallable(/x/));

test/form/samples/deopt-regexp-type/main.js

@@ -0,0 +1,10 @@
+const isCallable =
+	typeof /abc/ === 'function'
+		? function IsCallableSlow(x) {
+				return typeof x === 'function' && _toString(x) === '[object Function]';
+		  }
+		: function IsCallableFast(x) {
+				return typeof x === 'function';
+		  };
+
+console.log(isCallable(/x/));