Fix fallthrough warnings

src/Binder/Binder.cpp

@@ -56,6 +56,7 @@ namespace Porygon::Binder {
             case ParsedStatementKind::Bad:
                 return new BoundBadStatement();
         }
+        throw "unreachable";
     }
 
     BoundStatement *Binder::BindBlockStatement(const ParsedStatement *statement) {
@@ -355,6 +356,7 @@ namespace Porygon::Binder {
             case ParsedExpressionKind::Bad:
                 return new BoundBadExpression(expression->GetStartPosition(), expression->GetLength());
         }
+        throw;
     }
 
     BoundExpression *Binder::BindVariableExpression(const VariableExpression *expression) {