LibJS/Bytecode: Define named functions as a variable inside their scope

This allows you to recurse into a named function that is stored in a
variable. For example, this would previously print "wrong" instead of
"right":
```js
function g() { console.log("wrong") }
f = function g(i) { if (i !== 1) g(1); else console.log("right"); }
f()
```

1 files changed, 16 insertions, 0 deletions

diff --git a/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp b/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
index d0f9ce0329..27184a4106 100644
--- a/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
@@ -1010,7 +1010,23 @@ Bytecode::CodeGenerationErrorOr<void> FunctionDeclaration::generate_bytecode(Byt
 
 Bytecode::CodeGenerationErrorOr<void> FunctionExpression::generate_bytecode(Bytecode::Generator& generator) const
 {
+    bool has_name = !name().is_empty();
+    Optional<Bytecode::IdentifierTableIndex> name_identifier;
+
+    if (has_name) {
+        generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical);
+
+        name_identifier = generator.intern_identifier(name());
+        generator.emit<Bytecode::Op::CreateVariable>(*name_identifier, Bytecode::Op::EnvironmentMode::Lexical, true);
+    }
+
     generator.emit<Bytecode::Op::NewFunction>(*this);
+
+    if (has_name) {
+        generator.emit<Bytecode::Op::SetVariable>(*name_identifier, Bytecode::Op::SetVariable::InitializationMode::Initialize, Bytecode::Op::EnvironmentMode::Lexical);
+        generator.end_variable_scope();
+    }
+
     return {};
 }