constants replaced before folding is finished

[ptrcarta]

Version Information

• vyper Version (output of vyper --version): 0.3.6+commit.4a2124d0
• OS: osx
• Python Version (output of python --version): Python 3.9.13

What's your issue about?

Right now the following two contracts fail to compile:

#@version 0.3.6

a:constant(uint256) = as_wei_value(2*3, 'kwei')

@external
def foo() -> uint256:
    return a

#@version 0.3.6

a:constant(uint256[4]) = [as_wei_value(2*3, 'kwei'),1,2,3]

@external
def foo() -> uint256:
    return a[3]

full output of the error you received

traceback is similar for both contracts:

% vyper --verbose pietro/folding_eager_call.vy
Error compiling: pietro/folding_eager_call.vy
Traceback (most recent call last):
  File "/Users/pietro/dev/vyper/vyper_venv/bin/vyper", line 8, in <module>
    sys.exit(_parse_cli_args())
  File "/Users/pietro/dev/vyper/vyper/cli/vyper_compile.py", line 56, in _parse_cli_args
    return _parse_args(sys.argv[1:])
  File "/Users/pietro/dev/vyper/vyper/cli/vyper_compile.py", line 150, in _parse_args
    compiled = compile_files(
  File "/Users/pietro/dev/vyper/vyper/cli/vyper_compile.py", line 288, in compile_files
    compiler_data = vyper.compile_codes(
  File "/Users/pietro/dev/vyper/vyper/evm/opcodes.py", line 224, in _wrapper
    return fn(*args, **kwargs)
  File "/Users/pietro/dev/vyper/vyper/compiler/__init__.py", line 137, in compile_codes
    exc_handler(contract_name, exc)
  File "/Users/pietro/dev/vyper/vyper/cli/vyper_compile.py", line 184, in exc_handler
    raise exception
  File "/Users/pietro/dev/vyper/vyper/compiler/__init__.py", line 134, in compile_codes
    out[contract_name][output_format] = OUTPUT_FORMATS[output_format](compiler_data)
  File "/Users/pietro/dev/vyper/vyper/compiler/output.py", line 243, in build_bytecode_output
    return f"0x{compiler_data.bytecode.hex()}"
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/functools.py", line 993, in __get__
    val = self.func(instance)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 145, in bytecode
    return generate_bytecode(self.assembly, is_runtime=False)
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/functools.py", line 993, in __get__
    val = self.func(instance)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 137, in assembly
    return generate_assembly(self.ir_nodes, self.no_optimize)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 122, in ir_nodes
    ir, ir_runtime, sigs = self._ir_output
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/functools.py", line 993, in __get__
    val = self.func(instance)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 118, in _ir_output
    return generate_ir_nodes(self.global_ctx, self.no_optimize)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 113, in global_ctx
    return generate_global_context(self.vyper_module_folded, self.interface_codes)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 103, in vyper_module_folded
    module, storage_layout = self._folded_module
  File "/opt/homebrew/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/functools.py", line 993, in __get__
    val = self.func(instance)
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 97, in _folded_module
    return generate_folded_ast(
  File "/Users/pietro/dev/vyper/vyper/compiler/phases.py", line 220, in generate_folded_ast
    vy_ast.folding.fold(vyper_module_folded)
  File "/Users/pietro/dev/vyper/vyper/ast/folding.py", line 41, in fold
    changed_nodes += replace_literal_ops(vyper_module)
  File "/Users/pietro/dev/vyper/vyper/ast/folding.py", line 71, in replace_literal_ops
    vyper_module.replace_in_tree(node, new_node)
  File "/Users/pietro/dev/vyper/vyper/ast/nodes.py", line 606, in replace_in_tree
    raise CompilerPanic("Node to be replaced does not exist within parent children")
vyper.exceptions.CompilerPanic: Node to be replaced does not exist within parent children

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

How can it be fixed?

This is caused by constant folding replacing constant names with the value of the constant definition before the folding for that constant is finished. so a constant value is used even if it is of type vy_ast.Call and not a constant structure. There's a check in folding.py for is_struct but I don't think it is in the right place.

I've prepared a small pr for this issue. It manages to get these examples to compile but I'm not sure it will not introduce other issues, so double check. I didn't remove the old is_struct code in replace_constant, maybe it's there for a reason, but I don't think it's working.

[charles-cooper]

fixed as of #3669