Function emit_read 

pub fn emit_read(
    w: &mut CodeWriter,
    var_name: &str,
    ty: &ResolvedType,
    enc: &FieldEncoding,
    registry: &TypeRegistry,
    field_name: &str,
)

Emit code to read a field from r: &mut BitReader<'_>.

Binds the result to var_name.