message: Remove DefaultKey trait
  We no longer use `.get` function directly, so DefaultKey does not make
  much sense
diff: @@ -174,14 +174,6 @@ where
  })
  }
  - /// Equivalent to `of(DefaultKey::default_key())`
  - pub fn read(&self) -> Q::Value
  - where
  - Q::Key: DefaultKey,
  - {
  - self.get(DefaultKey::default_key())
  - }
  -
  /// Assign a value to an "input queries". Must be used outside of
  /// an active query computation.
  pub fn set(&self, key: Q::Key, value: Q::Value)
  @@ -218,20 +210,6 @@ where
  }
  }
  -/// A variant of the `Default` trait used for query keys that are
  -/// either singletons (e.g., `()`) or have some overwhelming default.
  -/// In this case, you can write `query.my_query().read()` as a
  -/// convenient shorthand.
  -pub trait DefaultKey {
  - fn default_key() -> Self;
  -}
  -
  -impl DefaultKey for () {
  - fn default_key() -> Self {
  - ()
  - }
  -}
  -
  /// A macro that helps in defining the "context trait" of a given
  /// module. This is a trait that defines everything that a block of
  /// queries need to execute, as well as defining the queries
  