Unused fields on nodes

[ncordon]

Mesages such as:

unused field(s) on node AssignmentPattern: trailingComments
unused field(s) on node AssignmentPattern: leadingComments
unused field(s) on node ImportDeclaration: importKind
unused field(s) on node RestElement: typeAnnotation

arose in the latest bblfsh logs.

Files that triggered AssignmentPattern: trailingComments

tests/binding/scope.js

Files that triggered AssignmentPattern: leadingComments

pkg/nuclide-ui/highlightOnUpdate.js
JSTests/test262/test/built-ins/Function/prototype/toString/function-declaration-non-simple-parameter-list.js

Files that triggered ImportDeclaration: importKind

JSTests/test262/test/language/module-code/eval-rqstd-order.js
JSTests/test262/test/language/module-code/eval-rqstd-once.js
JSTests/test262/test/language/module-code/eval-self-once.js
src/parser/test/esprima/ES6/import-declaration/import-named-empty.js
JSTests/test262/test/language/module-code/instn-once.js
JSTests/test262/test/language/module-code/instn-resolve-empty-import.js

Files that triggered RestElement: typeAnnotation

pkg/commons-node/observable.js
pkg/nuclide-jasmine/lib/waitsForPromise.js
tests/optional/optional_param4.js
tsrc/test/testRunner.js
pkg/nuclide-textedit/lib/main.js
pkg/commons-node/nuclideUri.js
pkg/nuclide-move-item-to-available-pane/spec/move-spec.js
tsrc/convert/convertRunner.js
tests/function/rest.js
tests/annot/issue-530.js
pkg/commons-node/redux-observable.js
pkg/commons-node/collection.js
pkg/nuclide-jasmine/lib/waitsForPromise.js
tsrc/new-test/new-testRunner.js
tests/spread/test4.js
website/docs/ref/syntax.doc.js
pkg/nuclide-file-tree/spec/helpers/BuildTempDirTree.js
pkg/nuclide-task/spec/fixtures/multiple-exports.js
pkg/nuclide-logging/spec/utils-spec.js
pkg/commons-node/observable.js
tests/destructuring/poly.js
pkg/nuclide-move-item-to-available-pane/spec/move-spec.js
pkg/nuclide-debugger/spec/Bridge-spec.js