4

Why does this fail to compile on Solidity?

contract TestContract {
    function testFunc() {
        int256 constant testVar = 1;
    }
}

It compiles if I remove the constant keyword.

3

In Solidity only state variables can be declared as constant.

State variables can be declared as constant. In this case, they have to be assigned from an expression which is a constant at compile time

Ref: http://solidity.readthedocs.io/en/latest/contracts.html#constant-state-variables

So just move the variable in the contract scope instead of function scope and it will work.

1

Because currently Solidity only accepts constant state variables for Strings and value types like in the following example:

pragma solidity >=0.4.0 <0.7.0;

contract C {
   unit constant x= 32**22 - 8;
   string constant text = "contract";
}

here is a link explaining variables, events & functions: https://www.bitdegree.org/learn/solidity-variables

0

so apparently solidity has disallowed the use of constant in functions afte version 0.5.0 this is the documentation. i have a very similar issue to yours and trying to fix it i will leave a comment here once found https://docs.soliditylang.org/en/latest/050-breaking-changes.html this is the specific page you're looking for.

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