[clang] [LifetimeSafety] Support C Language in LifetimeSafety (PR #203270)

[Utkarsh Saxena via cfe-commits]

================
@@ -27,6 +27,11 @@ namespace clang::lifetimes {
 inline bool IsLifetimeSafetyEnabled(Sema &S, const Decl *D) {
   if (S.getLangOpts().DebugRunLifetimeSafety)
     return true;
+  // TODO: Enable ObjectiveC later when we know it's stable enough.
+  if (S.getLangOpts().ObjC)
+    return false;
----------------
usx95 wrote:

TU mode and non-TU mode should be exclusive. E.g. currently `DebugRunLifetimeSafety` would run both the modes. I think we can further absorb the remaining `EnableLifetimeSafetyTUAnalysis` check:

```cpp
inline bool IsLifetimeSafetyEnabled(Sema &S, const Decl *D) {
  // TODO: Enable ObjectiveC later when we know it's stable enough.
  if (S.getLangOpts().ObjC)
    return false;
  
  // Translation-unit mode: whole-program analysis runs once on TU.
  // Individual function analysis is disabled when TU mode is enabled.
  if (S.getLangOpts().EnableLifetimeSafetyTUAnalysis)
    return isa<TranslationUnitDecl>(D);
  
  // Per-function mode: analysis runs on each function/method individually.
  // Skip TU-level calls when per-function mode is enabled.
  if (isa<TranslationUnitDecl>(D))
    return false;
  
  // Enable per-function mode via debug flag or specific diagnostics
  if (S.getLangOpts().DebugRunLifetimeSafety)
    return true;
  // ... rest of diagnostic checks
}
```

This is complicated :) but atleast these keeps the complicated bits in one place.

You can then remove the TU check in non-TU mode.
`bool EnableLifetimeSafetyAnalysis = lifetimes::IsLifetimeSafetyEnabled(S, D);`

https://github.com/llvm/llvm-project/pull/203270