Fn::ForEach Issue - Unable to reference resources with logical IDs generated using the &{} syntax

[miguel-aws]

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Tell us about the bug

If you reference a resource that was created with the &{} syntax, the stack will fail with unresolved resource dependencies template format error:

Template format error: Unresolved resource dependencies [SNS&{TopicId}] in the Resources block of the template

Expected behavior

ForEach transform resolves the generated resource.

Observed behavior

ForEach transform does not resolve the referenced generated resource.

Test cases

Transform: 'AWS::LanguageExtensions'
Parameters:
  TopicIds:
    Type: CommaDelimitedList
    Default: us.anthropic.claude-3-5-sonnet-20241022-v2:0
Resources:
  'Fn::ForEach::Topics':
    - TopicId
    - !Ref TopicIds
    - 'SNS&{TopicId}':
        Type: "AWS::SNS::Topic"

      'ALARM&{TopicId}':
        Type: AWS::CloudWatch::Alarm
        Properties:
          ActionsEnabled: true
          OKActions:
            - !Ref
              'Fn::Sub': "SNS&{TopicId}"
          AlarmActions: 
            - !Ref
                'Fn::Sub': "SNS&{TopicId}"
          InsufficientDataActions: []
          MetricName: ModelMetric
          Namespace: CustomNamespace
          Statistic: Sum
          Dimensions:
            - Name: TopicId
              Value: !Ref TopicId
          Period: 10
          EvaluationPeriods: 1
          DatapointsToAlarm: 1
          Threshold: 0  
          ComparisonOperator: GreaterThanOrEqualToThreshold
          TreatMissingData: notBreaching

Additional context

Only workaround is not to use the &{} syntax and provide only alphanumeric identifiers:

Transform: 'AWS::LanguageExtensions'
Parameters:
  TopicIds:
    Type: CommaDelimitedList
    Default: usanthropicclaude353sonnet20241022v20
Resources:
  'Fn::ForEach::Topics':
    - TopicId
    - !Ref TopicIds
    - 'SNS${TopicId}':
        Type: "AWS::SNS::Topic"

      'ALARM${TopicId}':
        Type: AWS::CloudWatch::Alarm
        Properties:
          ActionsEnabled: true
          OKActions:
            - !Ref
              'Fn::Sub': "SNS${TopicId}"
          AlarmActions: 
            - !Ref
                'Fn::Sub': "SNS${TopicId}"
          InsufficientDataActions: []
          MetricName: ModelMetric
          Namespace: CustomNamespace
          Statistic: Sum
          Dimensions:
            - Name: TopicId
              Value: !Ref TopicId
          Period: 10
          EvaluationPeriods: 1
          DatapointsToAlarm: 1
          Threshold: 0  
          ComparisonOperator: GreaterThanOrEqualToThreshold
          TreatMissingData: notBreaching