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

[Yanzuo Liu via cfe-commits]

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@@ -20544,31 +20544,40 @@ void Sema::MarkDeclarationsReferencedInExpr(Expr *E,
 }
 
 /// Emit a diagnostic when statements are reachable.
-/// FIXME: check for reachability even in expressions for which we don't build a
-///        CFG (eg, in the initializer of a global or in a constant expression).
-///        For example,
-///        namespace { auto *p = new double[3][false ? (1, 2) : 3]; }
 bool Sema::DiagIfReachable(SourceLocation Loc, ArrayRef<const Stmt *> Stmts,
                            const PartialDiagnostic &PD) {
-  if (!Stmts.empty() && getCurFunctionOrMethodDecl()) {
-    if (!FunctionScopes.empty())
-      FunctionScopes.back()->PossiblyUnreachableDiags.push_back(
-          sema::PossiblyUnreachableDiag(PD, Loc, Stmts));
-    return true;
-  }
-
   // The initializer of a constexpr variable or of the first declaration of a
   // static data member is not syntactically a constant evaluated constant,
   // but nonetheless is always required to be a constant expression, so we
   // can skip diagnosing.
-  // FIXME: Using the mangling context here is a hack.
   if (auto *VD = dyn_cast_or_null<VarDecl>(
-          ExprEvalContexts.back().ManglingContextDecl)) {
+          ExprEvalContexts.back().DeclForInitializer)) {
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zwuis wrote:

`DeclForInitializer` is `VarDecl *` now. Ditto below.

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