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Annotating rules that preserve definedness #2260

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28 changes: 15 additions & 13 deletions kevm-pyk/src/kevm_pyk/kproj/evm-semantics/evm.md
Original file line number Diff line number Diff line change
Expand Up @@ -748,10 +748,23 @@ These are just used by the other operators for shuffling local execution state a
```k
syntax InternalOp ::= "#newAccount" Int
| "#newExistingAccount" Int
| "#newFreshAccount" Int
// --------------------------------------------
rule <k> #newAccount ACCT => #newExistingAccount ACCT ... </k> <account> <acctID> ACCT </acctID> ... </account>
rule <k> #newAccount ACCT => #newFreshAccount ACCT ... </k> [owise]
rule <k> #newAccount ACCT => . ... </k>
<accounts>
( .Bag
=>
<account>
<acctID> ACCT </acctID>
<balance> 0 </balance>
<code> .Bytes:AccountCode </code>
<storage> .Map </storage>
<origStorage> .Map </origStorage>
<nonce> 0 </nonce>
</account>
)
...
</accounts> [owise, preserves-definedness]
Comment on lines +754 to +768
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By moving this account creation here, the [owise] guarantees that ACCT is not in the <accounts> map, and the rule preserves definedness. Previosly, with the account creation isolated inside #newFreshAccount, which could be in principle called from anywhere, this would not hold.


rule <k> #newExistingAccount ACCT => #end EVMC_ACCOUNT_ALREADY_EXISTS ... </k>
<account>
Expand All @@ -772,17 +785,6 @@ These are just used by the other operators for shuffling local execution state a
...
</account>
requires lengthBytes(CODE) ==Int 0

rule <k> #newFreshAccount ACCT => . ... </k>
<accounts>
( .Bag
=> <account>
<acctID> ACCT </acctID>
...
</account>
)
...
</accounts>
```

- `#transferFunds` moves money from one account into another, creating the destination account if it doesn't exist.
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