E0223 should not be given in contexts where ::Thing cannot be an associated type

[sgrif]

Specifically, when there is code in the form of SomeEnum::MissingVariant { field: () }, we should be receiving E0599, behaving the same as if we had written SomeEnum::MissingVariant(()).

Example to reproduce: https://play.rust-lang.org/?gist=5fd6bb1d589b9e27b7b9ba0cd8d6cb50&version=stable

[estebank]

Current output:

error: no variant `Baz` in enum `Foo`
 --> src/main.rs:6:18
  |
1 | enum Foo {
  | -------- variant `Baz` not found here
...
6 |     let x = Foo::Baz { id: 1 };
  |                  ^^^ help: there is a variant with a similar name: `Bar`

error[E0599]: no variant or associated item named `Baz` found for type `Foo` in the current scope
 --> src/main.rs:6:18
  |
1 | enum Foo {
  | -------- variant or associated item `Baz` not found here
...
6 |     let x = Foo::Baz(());
  |                  ^^^
  |                  |
  |                  variant or associated item not found in `Foo`
  |                  help: there is a variant with a similar name: `Bar`

error[E0599]: no variant or associated item named `Baz` found for type `Foo` in the current scope
 --> src/main.rs:6:18
  |
1 | enum Foo {
  | -------- variant or associated item `Baz` not found here
...
6 |     let x = Foo::Baz;
  |                  ^^^
  |                  |
  |                  variant or associated item not found in `Foo`
  |                  help: there is a variant with a similar name: `Bar`

It is close enough, but it needs to be turned into a E0599 instead of a codeless error.