Code calling external contract using interface causes compilation error: Interface parameter default value not applied

[ghost]

Version Information

• vyper Version (output of vyper --version): 0.2.12
• OS: linux,ubuntu 20.*
• Python Version (output of python --version): 3.8.5
• Environment (output of pip freeze): attached as popsicle.txt
  popsicle.txt

What's your issue about?

I define an interface with a default value for one of the parameters like:

interface myInterface:
   def function1 (param1: uint256, param2: uint256=10) -> uint256:

This default value is not applied when omitting the parameter with the default value, like param2 in this example.

Please note:
I am unaware whether I can actually pass default values in the interface definition.
This is an assumption I made because I do this in python all the time. I could not figure it out using the vyper documentation.

• full output of the error you received*

pack_arguments did not return a value 
This is an unhandled internal compiler error. 

Please create an issue on Github to notify the developers. 
https://github.com/vyperlang/vyper/issues/new?template=bug.md 

Compilation of /home/ethbox/Vyper-Main/VyperTest-002/contracts/interfaceError.vy failed.

• what command you ran
  I use the tintinweb vyper extension in VScode, which calls vyper to compile. It auto compiles when saving the file

• the code that caused the failure
  in this example I omit the second argument. passing 5,10 as arguments when calling the function will result in successful compilation

# @version >=0.2.12
externalContract: address 

interface myInterface:
    def function1(param1: uint256, param2: uint256=10) -> uint256: nonpayable

@internal
def callExternalContract() : 
    externalContract: address =  ZERO_ADDRESS
    param1:uint256 = 5
    param2:uint256 = 10
    
    result: uint256 = 0

    # use the interface by passing 1 of the 2 arguments, assuming the default value "param2:uint256 = 10" will be passed
    result = myInterface(externalContract).function1(5)

edits: styling and adding a bit of info

[charles-cooper]

Note: in latest vyper (v0.3.0) this throws the following error

  File "/home/charles/.venvs/vyper/lib/python3.8/site-packages/vyper-0.3.0-py3.8.egg/vyper/old_codegen/external_call.py", line 124, in _external_call_helper
    assert len(contract_sig.args) == len(args_lll)
AssertionError

[fubuloubu]

Note: in latest vyper (v0.3.0) this throws the following error

  File "/home/charles/.venvs/vyper/lib/python3.8/site-packages/vyper-0.3.0-py3.8.egg/vyper/old_codegen/external_call.py", line 124, in _external_call_helper
    assert len(contract_sig.args) == len(args_lll)
AssertionError

Can this raise an actual compiler warning instead? Or does this indicate an issue with the compiler that should be resolved?

[charles-cooper]

compiler bug with method resolution, needs fix

[charles-cooper]

This was fixed in #2526