From 4749c3a99b861ac18cf210dadb22dbdb9793b770 Mon Sep 17 00:00:00 2001
From: 0x7D2B <0x7D2B@protonmail.com>
Date: Wed, 17 Mar 2021 17:20:27 +0000
Subject: [PATCH] Handle different declaration types

---
 boa/src/syntax/ast/node/declaration/mod.rs | 34 ++++++++++++++--------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/boa/src/syntax/ast/node/declaration/mod.rs b/boa/src/syntax/ast/node/declaration/mod.rs
index 51ba04b3f32..f96f5d9b5fc 100644
--- a/boa/src/syntax/ast/node/declaration/mod.rs
+++ b/boa/src/syntax/ast/node/declaration/mod.rs
@@ -61,18 +61,28 @@ impl Executable for DeclarationList {
                 (_, Some(init)) => init.run(context)?,
                 (_, None) => Value::undefined(),
             };
-            context
-                .realm_mut()
-                .environment
-                .create_mutable_binding(
-                    decl.name().to_owned(),
-                    false,
-                    match &self.declaration_type {
-                        Var => VariableScope::Function,
-                        _ => VariableScope::Block,
-                    },
-                )
-                .map_err(|e| e.to_error(context))?;
+
+            let environment = &mut context.realm_mut().environment;
+
+            if self.declaration_type == Var && environment.has_binding(decl.name()) {
+                environment
+                    .set_mutable_binding(decl.name(), val, true)
+                    .map_err(|e| e.to_error(context))?;
+                return Ok(Value::undefined());
+            }
+
+            match &self.declaration_type {
+                Const => environment
+                    .create_immutable_binding(decl.name().to_owned(), false, VariableScope::Block)
+                    .map_err(|e| e.to_error(context))?,
+                Let => environment
+                    .create_mutable_binding(decl.name().to_owned(), false, VariableScope::Block)
+                    .map_err(|e| e.to_error(context))?,
+                Var => environment
+                    .create_mutable_binding(decl.name().to_owned(), false, VariableScope::Function)
+                    .map_err(|e| e.to_error(context))?,
+            }
+
             context
                 .realm_mut()
                 .environment