small error formatting improvements

[ungaro]

Motivation

Consider this program:

// The 'leo_errors' program.
program leo_errors.aleo {

    struct VoteAggregate {
        proposal_id: field;
        proposal_some: field;
    }

    struct SomeStruct {
        proposal_id: boolean;
    }

    transition main() -> field {
        let st:VoteAggregate = VoteAggregate{
            proposal_id: 0field,
            proposal_some: 0field,
        };

        let ss:SomeStruct = SomeStruct{
            proposal_id: true,
            
        };

        return st.proposal_something;
        
    }
}

The output of this program is:

After this PR :

Test Plan

Run the program above.

[ungaro]

some small improvements to error outputs.
fyi @d0cd

[ungaro]

I'm looking into why the tests are failing. These changes prevent some programs from building. The tests fail after compilation.

[ungaro]

rolled back boolean to bool change, as the error comes from snarkVM; this PR only changes
Variable {} is not a member of struct struct {}
to
Variable {} is not a member of struct {}

a very small change @d0cd

[d0cd]

LGTM!