Mandatory variable cannot be used for optional argument since apollo-compiler 0.9.0

[yanns]

Description

Since the update to apollo-compiler 0.9.0, we have new validation errors that do not seem valid.

Steps to reproduce

Considering the schema like:

type Query {
  category(
    "Queries with specified ID"
    id: String,

    "Queries with specified key"
    key: String): Category
}

The following query:

          query CategoryByKey($key: String!){
            category(key: $key) {
              id, key, name(locale:"en")
            }
          }

with the key as variable is not valid anymore.
It fails with variable keycannot be used for argumentkey as their types mismatch

Changing the query to:

          query CategoryByKey($key: String){
            category(key: $key) {
              id, key, name(locale:"en")
            }
          }

works.

Expected result

Not 100% sure, but a mandatory variable can be used for an optional argument.

[lrlna]

yeppp looks like a bug! thanks for reporting