Flow•4mo ago

joshua | Flow (2024-02-08)

Is it possible to borrow a contract as one of its interface types if I know the contract's name and address? like this:

        // Borrow a reference to the contract as an interface type
        let fungibleRef = getAccount(contractAddress)
            .contracts.borrow<&{FungibleToken}>(name: contractName)
            ?? panic("Could not borrow a reference to the fungible token contract")

        // Borrow a reference to the contract as an interface type
        let fungibleRef = getAccount(contractAddress)
            .contracts.borrow<&{FungibleToken}>(name: contractName)
            ?? panic("Could not borrow a reference to the fungible token contract")

I tried it and I am getting an error:

            error: cannot restrict using non-resource/structure interface type: `FungibleToken`
              --> 8a7abd15e963aff4f5c29b736ebeedac21bdbd34f5203efdecab52d7776d0570:15:32
               |
            15 |             .contracts.borrow<&{FungibleToken}>(name: contractName)
               |                                 ^^^^^^^^^^^^^
            
            error: ambiguous intersection type
              --> 8a7abd15e963aff4f5c29b736ebeedac21bdbd34f5203efdecab52d7776d0570:15:31
               |
            15 |             .contracts.borrow<&{FungibleToken}>(name: contractName)
               |

            error: cannot restrict using non-resource/structure interface type: `FungibleToken`
              --> 8a7abd15e963aff4f5c29b736ebeedac21bdbd34f5203efdecab52d7776d0570:15:32
               |
            15 |             .contracts.borrow<&{FungibleToken}>(name: contractName)
               |                                 ^^^^^^^^^^^^^
            
            error: ambiguous intersection type
              --> 8a7abd15e963aff4f5c29b736ebeedac21bdbd34f5203efdecab52d7776d0570:15:31
               |
            15 |             .contracts.borrow<&{FungibleToken}>(name: contractName)
               |

6 Replies

Needle•4mo ago

I've created a thread for your message. Please continue any relevant discussion in this thread. You can rename this thread using /title <new title> If this is a technical question that others may benefit from, considering also asking it on Stackoverflow: https://stackoverflow.com/questions/ask?tags=onflow-cadence

Unknown User•4mo ago

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joshua•4mo ago

thanks! I assumed contract interfaces had the same syntax as resource interfaces. seems weird that they don't

turbolent•4mo ago

yeah, that's not really how it's supposed to work. hmm

Unknown User•4mo ago

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turbolent•4mo ago

the "cannot restrict using non-resource/structure interface type" error is just an unnecessarily restrictive check in the type checker, not sure if 1.0 is better there https://github.com/onflow/cadence/issues/3088 https://github.com/onflow/cadence/pull/3089 https://github.com/onflow/cadence/pull/3090

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joshua | Flow (2024-02-08)