actorstatesmultisig: out parameter cannot be assigned cached value

[iand]

Describe the bug:

During a walk the following errors were encountered:

error found for height 1231152: 
[
	{
		"Code":"bafkqadtgnfwc6njpnv2wy5djonuwo",
		"Name":"fil/5/multisig",
		"Head":"bafy2bzaceaip2d4rfkxlydzzijclyqr6hr3hfah6de73ojqmphym2lvza5vpy",
		"Address":"f028589",
		"Error":"failed to extract parsed actor state: loading current multisig state at head bafy2bzaceaip2d4rfkxlydzzijclyqr6hr3hfah6de73ojqmphym2lvza5vpy: out parameter cannot be assigned cached value"
	},
	{
		"Code":"bafkqadtgnfwc6njpnv2wy5djonuwo",
		"Name":"fil/5/multisig",
		"Head":"bafy2bzaced7qwvfu5d5rpnlcy6nccq76u5gfzei2vc5ugnfvrihga2ol5sv2o",
		"Address":"f027174",
		"Error":"failed to extract parsed actor state: loading current multisig state at head bafy2bzaced7qwvfu5d5rpnlcy6nccq76u5gfzei2vc5ugnfvrihga2ol5sv2o: out parameter cannot be assigned cached value"
	}
]
{"task": "actorstatesmultisig"}

Looks like this is reported by the experimental state cache

Steps to Reproduce:

Run actorstatesmultisig task at height 1231152 on mainnet

Lily Version: branch with statecache

[iand]

Pretty sure this is caused by the state cache #766

[frrist]

@iand did this get addressed by the changed in #766?

[frrist]

Currently hitting this with the miner actor (extended the error a bit)

actor returned with error       {"height": 1563061, "actor": "fil/6/storageminer", "address": "f01457108", "error": "failed to extract parsed actor state: extracting miner sector changes: diffing miner precommits and sectors: loading previous root: out parameter (internal.Root) cannot be assigned cached value (internal.Root)"}

[frrist]

best guess on the type is: https://github.com/filecoin-project/go-amt-ipld/blob/master/internal/internal.go#L73

[frrist]

via #885