[clang] [Clang] Consider reachability for file-scope warnings on initializers (PR #163885)

[Yanzuo Liu via cfe-commits]

================
@@ -13100,6 +13100,13 @@ namespace {
     if (isa<ParmVarDecl>(OrigDecl))
       return;
 
+    // Skip checking for file-scope constexpr variables - constant evaluation
+    // will produce appropriate errors without needing runtime diagnostics.
+    // Local constexpr should still emit runtime warnings.
+    if (auto *VD = dyn_cast<VarDecl>(OrigDecl))
+      if (VD->isConstexpr() && VD->isFileVarDecl())
----------------
zwuis wrote:

```cpp
if (auto *VD = ...;
    VD && ...)
```

https://github.com/llvm/llvm-project/pull/163885