[clang-tools-extra] [clang-tidy] Add AllowReferencedInitialValues to `readability-enum-initial-value` (PR #189459)

[Baranov Victor via cfe-commits]

=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>,
=?utf-8?q?Björn?= Svensson <bjorn.a.svensson at est.tech>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/189459 at github.com>


================
@@ -26,6 +26,32 @@ enum ESeqRef {
   ESeqRef_alias = ESeqRef_a,
 };
 
+// Error: sequential + multiple self-refs, should still warn and suggest
+// removing the sequential values but not the self-refs.
+enum ESeqMultiRef {
+  // CHECK-MESSAGES: :[[@LINE-1]]:1: warning: sequential initial value in 'ESeqMultiRef' can be ignored
+  ESeqMultiRef_a = 1,
+  ESeqMultiRef_b = 2,
+  // CHECK-FIXES: ESeqMultiRef_b ,
+  ESeqMultiRef_c = 3,
+  // CHECK-FIXES: ESeqMultiRef_c ,
+  ESeqMultiRef_alias = ESeqMultiRef_a,
+  ESeqMultiRef_alias2 = ESeqMultiRef_b,
+};
+
+// Error: sequential + self-refs interleaved with the sequence, should still
+// warn and suggest removing the sequential values but not the self-refs.
+enum ESeqInterRef {
+  // CHECK-MESSAGES: :[[@LINE-1]]:1: warning: sequential initial value in 'ESeqInterRef' can be ignored
+  ESeqInterRef_a = 1,
+  ESeqInterRef_alias = ESeqInterRef_a,
+  ESeqInterRef_b = 2,
+  // CHECK-FIXES: ESeqInterRef_b ,
+  ESeqInterRef_c = 3,
+  // CHECK-FIXES: ESeqInterRef_c ,
+  ESeqInterRef_alias2 = ESeqInterRef_b,
----------------
vbvictor wrote:

After thinking a bit more about such fixes, can we add test:

```cpp
enum ESeqInterRef {
  ESeqInterRef_a = 1,
  ESeqInterRef_alias = ESeqInterRef_a,
  ESeqInterRef_b = 2,
  ESeqInterRef_c = 3,
  ESeqInterRef_alias2 = ESeqInterRef_b,
  ESeqInterRef_d = 4,
};
```

If we remove `4` from `ESeqInterRef_d` we would get different value (3):
https://godbolt.org/z/aef46j9YG.
This seems like a bug.

https://github.com/llvm/llvm-project/pull/189459