Use E0665 for missing `#[default]` error

Use orphaned error code for the same error it belonged to before.

```
error[E0665]: `#[derive(Default)]` on enum with no `#[default]`
  --> $DIR/macros-nonfatal-errors.rs:42:10
   |
LL |   #[derive(Default)]
   |            ^^^^^^^
LL | / enum NoDeclaredDefault {
LL | |     Foo,
LL | |     Bar,
LL | | }
   | |_- this enum needs a unit variant marked with `#[default]`
   |
   = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info)
help: make this unit variant default by placing `#[default]` on it
   |
LL |     #[default] Foo,
   |     ~~~~~~~~~~~~~~
help: make this unit variant default by placing `#[default]` on it
   |
LL |     #[default] Bar,
   |     ~~~~~~~~~~~~~~
```

1 files changed, 7 insertions, 8 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0665.md b/compiler/rustc_error_codes/src/error_codes/E0665.md
index d5fd2130840..caa94423377 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0665.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0665.md
@@ -1,10 +1,9 @@
-#### Note: this error code is no longer emitted by the compiler.
-
-The `Default` trait was derived on an enum.
+The `Default` trait was derived on an enum without specifying the default
+variant.
 
 Erroneous code example:
 
-```compile_fail
+```compile_fail,E0665
 #[derive(Default)]
 enum Food {
     Sweet,
@@ -16,8 +15,8 @@ The `Default` cannot be derived on an enum for the simple reason that the
 compiler doesn't know which value to pick by default whereas it can for a
 struct as long as all its fields implement the `Default` trait as well.
 
-For the case where the desired default variant has no data, you can annotate
-it with `#[default]` to derive it:
+For the case where the desired default variant has no payload, you can
+annotate it with `#[default]` to derive it:
 
 ```
 #[derive(Default)]
@@ -28,8 +27,8 @@ enum Food {
 }
 ```
 
-In the case where the default variant does have data, you will have to
-implement `Default` on your enum "by hand":
+In the case where the default variant does have a payload, you will have to
+implement `Default` on your enum manually:
 
 ```
 enum Food {