fix: generate default-value array expressions using is_inline_array flag s…

[kevinclancy]

Notes

Previously, running slither on the following program caused an assertion failure

contract DefaultValueCrashTest {
    struct S {
        uint f;
        uint8[2] g;
    }

    function debug() internal {
        S memory v;
    }
}

This was because the default value generation code produced tuples instead of arrays, causing a list to appear where an rvalue was expected. This PR fixes the default value generation code, so that it correctly produces array expressions (TupleExpressions with the is_inline_array flag set to true) to initialize array fields.

Testing

See this companion PR for testing instructions.

Related Issue

https://github.com/CertiKProject/slither-task/issues/381

[duckki]

The change makes sense. Thanks.