2 files changed, 36 insertions, 4 deletions
diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index fb6795d516..779783106d 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -2748,18 +2748,49 @@ bool Parser::match_export_or_import() const
         || type == TokenType::Import;
 }
 
-bool Parser::match_declaration() const
+bool Parser::match_declaration()
 {
     auto type = m_state.current_token.type();
+
+    if (type == TokenType::Let && !m_state.strict_mode) {
+        return try_match_let_declaration();
+    }
+
     return type == TokenType::Function
         || type == TokenType::Class
         || type == TokenType::Const
         || type == TokenType::Let;
 }
 
-bool Parser::match_variable_declaration() const
+bool Parser::try_match_let_declaration()
+{
+    VERIFY(m_state.current_token.type() == TokenType::Let);
+
+    save_state();
+
+    ScopeGuard state_rollback = [&] {
+        load_state();
+    };
+
+    consume(TokenType::Let);
+
+    if (match_identifier_name() && m_state.current_token.value() != "in"sv)
+        return true;
+
+    if (match(TokenType::CurlyOpen) || match(TokenType::BracketOpen))
+        return true;
+
+    return false;
+}
+
+bool Parser::match_variable_declaration()
 {
     auto type = m_state.current_token.type();
+
+    if (type == TokenType::Let && !m_state.strict_mode) {
+        return try_match_let_declaration();
+    }
+
     return type == TokenType::Var
         || type == TokenType::Let
         || type == TokenType::Const;
diff --git a/Userland/Libraries/LibJS/Parser.h b/Userland/Libraries/LibJS/Parser.h
index 97036c8de6..eaf9df0a94 100644
--- a/Userland/Libraries/LibJS/Parser.h
+++ b/Userland/Libraries/LibJS/Parser.h
@@ -159,8 +159,9 @@ private:
     bool match_secondary_expression(const Vector<TokenType>& forbidden = {}) const;
     bool match_statement() const;
     bool match_export_or_import() const;
-    bool match_declaration() const;
-    bool match_variable_declaration() const;
+    bool match_declaration();
+    bool try_match_let_declaration();
+    bool match_variable_declaration();
     bool match_identifier() const;
     bool match_identifier_name() const;
     bool match_property_key() const;