Auto merge of #76028 - aticu:improve_e0118, r=estebank,jyn514,GuillaumeGomez

Improve E0118

- Changes the "base type" terminology to "nominal type" (according to the [reference](https://doc.rust-lang.org/stable/reference/items/implementations.html#inherent-implementations)).
- Suggests removing a reference, if one is present on the type.
- Clarify what is meant by a "nominal type".

closes #69392

This is my first not-entirely-trivial PR, so please let me know if I missed anything or if something could be improved. Though I probably won't be able to fix anything in the upcoming week.

1 files changed, 24 insertions, 3 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0118.md b/compiler/rustc_error_codes/src/error_codes/E0118.md
index 5cb5f506e0a..345ec341c3f 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0118.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0118.md
@@ -1,10 +1,10 @@
-An inherent implementation was defined for something which isn't a struct nor
-an enum.
+An inherent implementation was defined for something which isn't a struct,
+enum, union, or trait object.
 
 Erroneous code example:
 
 ```compile_fail,E0118
-impl (u8, u8) { // error: no base type found for inherent implementation
+impl (u8, u8) { // error: no nominal type found for inherent implementation
     fn get_state(&self) -> String {
         // ...
     }
@@ -41,3 +41,24 @@ impl TypeWrapper {
     }
 }
 ```
+
+Instead of defining an inherent implementation on a reference, you could also
+move the reference inside the implementation:
+
+```compile_fail,E0118
+struct Foo;
+
+impl &Foo { // error: no nominal type found for inherent implementation
+    fn bar(self, other: Self) {}
+}
+```
+
+becomes
+
+```
+struct Foo;
+
+impl Foo {
+    fn bar(&self, other: &Self) {}
+}
+```