cco 0.2.0

cascading configuration
Documentation 
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use super::{Expr, ExprEvaluator};
use crate::err::*;
use crate::eval::*;

#[derive(Debug, Clone)]
pub struct VariableExpr {
    pub name: String,
}

impl Expr for VariableExpr {
    fn resolve(
        &self,
        index: Index,
        evaluation: &mut dyn ExprEvaluator,
    ) -> Result<ValueOrReference, ErrorKind> {
        evaluation.resolve_variable(index, self.name.clone())
    }

    fn traverse(
        &self,
        _evaluation: &dyn ExprEvaluator,
        expression: Index,
        _name: &Indexer,
    ) -> Result<Option<ValueOrReference>, ErrorKind> {
        Err(ErrorKind::DependenciesNotSatisfied {
            indices: vec![expression],
        })
    }
}

impl From<String> for VariableExpr {
    fn from(name: String) -> Self {
        VariableExpr { name }
    }
}

impl From<&str> for VariableExpr {
    fn from(name: &str) -> Self {
        VariableExpr {
            name: name.to_string(),
        }
    }
}