build failed, field 'value' in struct syntax::ast::Attribute has been removed

rustc version: rustc 1.17.0-nightly (134c4a0f0 2017-03-20)

> error: no field `value` on type `&mut syntax::ast::Attribute`
  --> src\plugins\src\lib.rs:49:76
   |
49 |         if let NameValue(Spanned { node: Str(ref mut doc, _), .. }) = attr.value.node {