Rustc incorrectly suggests adding generic arguments to an enum that already has them when using enum-map-derive =1.0.0

Code

#[derive(enum_map_derive::Enum)]
enum ExampleEnum<T> {
    Variant(T),
}

Current output

Checking enum-generic-repro v0.1.0 (/Users/centdemeern1/Documents/RustProjects/enum-generic-repro)
error[E0425]: cannot find type `T` in this scope
 --> src/lib.rs:3:13
  |
3 |     Variant(T),
  |             ^ not found in this scope

error[E0107]: missing generics for enum `ExampleEnum`
 --> src/lib.rs:2:6
  |
2 | enum ExampleEnum<T> {
  |      ^^^^^^^^^^^ expected 1 generic argument
  |
note: enum defined here, with 1 generic parameter: `T`
 --> src/lib.rs:2:6
  |
2 | enum ExampleEnum<T> {
  |      ^^^^^^^^^^^ -
help: add missing generic argument
  |
2 | enum ExampleEnum<T><T> {
  |                 +++

Some errors have detailed explanations: E0107, E0425.
For more information about an error, try `rustc --explain E0107`.
error: could not compile `enum-generic-repro` (lib) due to 2 previous errors

Desired output

Rationale and extra context

rustc should probably not be suggesting invalid syntax. I don't know what this error should look like instead, though

Other cases

Rust Version

rustc 1.97.1 (8bab26f4f 2026-07-14)
binary: rustc
commit-hash: 8bab26f4f68e0e26f0bb7960be334d5b520ea452
commit-date: 2026-07-14
host: aarch64-apple-darwin
release: 1.97.1
LLVM version: 22.1.6

Anything else?

• enum-map-derive does not actually support generic arguments. The latest version of enum-map-derive adds a manual check, which bypasses this bug. To reproduce this bug, use =1.0.0
• I was told to report this by @estebank: https://hachyderm.io/@ekuber/117031928263200472
• Here's a repro project that uses the correct version of enum-map(-derive): enum-generic-repro.zip

Reproduce the diagnostic from the enum snippet in src/lib.rs using enum-map-derive =1.0.0 and the reported rustc version. Start by examining how rustc emits the E0107 missing-generics suggestion for this case. Done means the compiler no longer suggests invalid duplicated generic arguments, with the behavior covered by a regression test.