message: Issue Validate Collation Expressions
  Check that the collation in a CollateExpression is valid during binding.
diff: @@ -17,6 +17,8 @@ BindResult ExpressionBinder::BindExpression(CollateExpression &expr, idx_t depth
  if (child.expr->return_type.id() != LogicalTypeId::VARCHAR) {
  throw BinderException("collations are only supported for type varchar");
  }
  + // Validate the collation, but don't use it
  + PushCollation(context, child.expr->Copy(), expr.collation, false);
  child.expr->return_type = LogicalType::VARCHAR_COLLATION(expr.collation);
  return BindResult(move(child.expr));
  }
  