Function decode_tree_with_codec 

pub fn decode_tree_with_codec(
    cx: &mut Cx,
    symbol: &Symbol,
    input: Input,
    read_policy: ReadPolicy,
    source_id: impl Into<String>,
) -> Result<LocatedExprTree>

Decode input into a full LocatedExprTree (trivia and layout retained), attributing spans to source_id, using default DecodeLimits.