From fb0401871cdd5613500a45493ea697adaf6fa1df Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Mon, 30 Mar 2020 13:41:17 +0100
Subject: [PATCH] LibJS: Throw TypeError when calling non-function object

We now have "undefined is not a function" :^)
---
 Libraries/LibJS/AST.cpp                     |  5 ++--
 Libraries/LibJS/Tests/function-TypeError.js | 31 +++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 Libraries/LibJS/Tests/function-TypeError.js

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index b3daa4eb3b..a20b90d028 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/Libraries/LibJS/AST.cpp
@@ -66,8 +66,9 @@ Value CallExpression::execute(Interpreter& interpreter) const
     if (interpreter.exception())
         return {};
 
-    ASSERT(callee.is_object());
-    ASSERT(callee.as_object()->is_function());
+    if (!callee.is_object() || !callee.as_object()->is_function())
+        return interpreter.throw_exception<Error>("TypeError", String::format("%s is not a function", callee.to_string().characters()));
+
     auto* function = static_cast<Function*>(callee.as_object());
 
     auto& call_frame = interpreter.push_call_frame();
diff --git a/Libraries/LibJS/Tests/function-TypeError.js b/Libraries/LibJS/Tests/function-TypeError.js
new file mode 100644
index 0000000000..90cae589a4
--- /dev/null
+++ b/Libraries/LibJS/Tests/function-TypeError.js
@@ -0,0 +1,31 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    try {
+        var b = true;
+        b();
+    } catch(e) {
+        assert(e.name === "TypeError");
+        assert(e.message === "true is not a function");
+    }
+
+    try {
+        var n = 100 + 20 + 3;
+        n();
+    } catch(e) {
+        assert(e.name === "TypeError");
+        assert(e.message === "123 is not a function");
+    }
+
+    try {
+        var o = {};
+        o.a();
+    } catch(e) {
+        assert(e.name === "TypeError");
+        assert(e.message === "undefined is not a function");
+    }
+
+    console.log("PASS");
+} catch(e) {
+    console.log("FAIL: " + e);
+}