"constants" expressions are expressions, not constants.

[drortirosh]

Constant expressions are left as expressions, not constants.

Description

a constant declared as:

bytes32 public constant EIP712DOMAIN_TYPEHASH = keccak256(
    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
);

Is re-calculated each time it is in use.

expected

the value should be converted into a constant value at compile time.

###a ctual
The expression is re-calculated each time the constant is referenced.

consequences:

• each usage of a "constant" costs ~100gas more on each access (it is still a little better than storing the result in storage, but not much..)
• since these are not real constants, they can't be referenced from a real constant environment (e.g. from assembly, or from another library )

Environment

-- solc 0.6.10
-- checked in remix, with optimization enabled.

[chriseth]

Duplicate of #4024 / #3157

[chriseth]

Ah and by the way: You could use immutables until the referenced issues are implemented, then you only pay the gas costs for the computation at deploy time.