"Cannot convert error" in generated StrawberryShake code for implemented result types

[maris-jurgenbergs]

Is there an existing issue for this?

• I have searched the existing issues

Product

Strawberry Shake

Describe the bug

In a recent project encountered "cannot convert from" error in the StrawberryShake generated code. I simplified the data structure which is handled with errors in the StrawberryShake generator.

There is a base type (ParentType), that is used in one mutation result (MutationResultVariantA) and the there is a extended type (ParentVariant), which is used in the second mutation result (MutationResultVariantB).
Additional data that is inside these types were stripped for simplicity.

The generated error:
cannot convert from 'ConsoleApp1.State.IParentTypeData' to 'ConsoleApp1.State.ParentVariantData'

Steps to reproduce

1. mutations.graphql:

mutation mutationOneTest {
  testMutation {
    parent {
      someValue
    }
  }
}

mutation mutationOne {
  testMutation {
    ... on MutationResultVariantB {
      parent {
        ... on ParentVariant {
          someValue
        }
      }
    }
  }
}

2. schema.graphql:

schema {
  query: Query
  mutation: Mutation
}

type Query {
  testQuery(): MutationResult!
}

type Mutation {
  testMutation(): MutationResult!
}

interface MutationResult {
  parent: ParentType!
}

interface ParentType {
  someValue: Int!
}

type MutationResultVariantA implements MutationResult {
  parent: ParentType!
}

type MutationResultVariantB implements MutationResult {
  parent: ParentVariant!
}

type ParentVariant implements ParentType {
  someValue: Int!
}

3. .graphqlrc,json

{
    "schema": "schema.graphql",
    "documents": "**/*.graphql",
    "extensions": {
        "strawberryShake": {
            "name": "GraphQLClient",
            "dependencyInjection": true,
            "strictSchemaValidation": true,
            "hashAlgorithm": "md5",
            "useSingleFile": true,
            "requestStrategy": "Default",
            "outputDirectoryName": "Generated",
            "noStore": false,
            "emitGeneratedCode": true,
            "razorComponents": false,
            "records": {
                "inputs": false,
                "entities": false
            },
            "transportProfiles": [
                {
                    "default": "Http",
                    "subscription": "WebSocket"
                }
            ]
        }
    }
}

4. Run the generator
5. There is a repo with the bug present: https://github.com/maris-jurgenbergs/SBSGQLBug

Relevant log output

No response

Additional Context?

No response

Version

12.18.0