From c56dbb783761a1b7cb738e993beefbbd06d4f794 Mon Sep 17 00:00:00 2001
From: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Date: Mon, 10 Jun 2019 08:52:21 +0200
Subject: [PATCH] Deoptimize typeof for regular expression literals to better
 support es6-shim

---
 src/ast/nodes/Literal.ts                         |  6 ++++--
 test/form/samples/deopt-regexp-type/_config.js   |  3 +++
 test/form/samples/deopt-regexp-type/_expected.js | 10 ++++++++++
 test/form/samples/deopt-regexp-type/main.js      | 10 ++++++++++
 4 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 test/form/samples/deopt-regexp-type/_config.js
 create mode 100644 test/form/samples/deopt-regexp-type/_expected.js
 create mode 100644 test/form/samples/deopt-regexp-type/main.js

diff --git a/src/ast/nodes/Literal.ts b/src/ast/nodes/Literal.ts
index 5f423880cd1..83f61853cc0 100644
--- a/src/ast/nodes/Literal.ts
+++ b/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;
 		}
diff --git a/test/form/samples/deopt-regexp-type/_config.js b/test/form/samples/deopt-regexp-type/_config.js
new file mode 100644
index 00000000000..18ccd606be5
--- /dev/null
+++ b/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'
+};
diff --git a/test/form/samples/deopt-regexp-type/_expected.js b/test/form/samples/deopt-regexp-type/_expected.js
new file mode 100644
index 00000000000..cac206933ed
--- /dev/null
+++ b/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/));
diff --git a/test/form/samples/deopt-regexp-type/main.js b/test/form/samples/deopt-regexp-type/main.js
new file mode 100644
index 00000000000..cac206933ed
--- /dev/null
+++ b/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/));