Avoid generating populator for the exception fields (#1501)

Some AWS services define the Message member of the exception shapes,
even though it is part of the standard AWS exception representation
already. We want to keep the message containing the full parsed
information.

Author: stof

src/Generator/CodeGenerator/PopulatorGenerator.php

@@ -177,6 +177,11 @@ private function generatePopulator(Operation $operation, StructureShape $shape,
         $nonHeaders = [];
         $body = '';
         foreach ($shape->getMembers() as $member) {
+            // Avoid conflicts with PHP properties. Those AWS members are included in the AWSError anyway.
+            if ($forException && \in_array(strtolower($member->getName()), ['code', 'message'])) {
+                continue;
+            }
+
             if ('header' !== $member->getLocation()) {
                 $nonHeaders[$member->getName()] = $member;