Can't use name of AWS managed policy in Serverless::Function anymore

[kokobd]

In 5df088e#diff-a4d1e4b9b8d4a2350c8364f894fa27ce941261df804af6a0e61095c57dfec7e7R29-R35, the type of Policies is changed from Optional (./../../Fn.dhall).CfnText to

Optional
          ( List
              < IAMPolicyDocument : (./IAMPolicyDocument.dhall).Type
              | SAMPolicyTemplate : (./SAMPolicyTemplate.dhall).Type
              >
          )

But AWS documentation says

This property accepts a single value or list of values. Allowed values include:

• AWS SAM policy templates.
• The ARN of an AWS managed policy or customer managed policy.
• The name of an AWS managed policy from the following list.
• An inline IAM policy formatted in YAML as a map.

Previously we had simple json strings in the Policies list, like Fn.renderText "AWSLambdaBasicExecutionRole". But now, given that each policy is a union, and the union doesn't have a constructor for strings, I think this usage has become impossible?

[endgame]

That will be because the code is faithfully generating from https://raw.githubusercontent.com/awslabs/goformation/master/generate/sam-2016-10-31.json . I'd file a bug against the goformation package and link it to this discussion, unless there's a true source further upstream.