[clang] [clang][ExprConst] Support virtual bases in C++26 (PR #204289)

[via cfe-commits]

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@@ -110,10 +112,30 @@ static bool CheckFieldsInitialized(InterpState &S, SourceLocation Loc,
       }
       return false;
     }
-    Result &= CheckFieldsInitialized(S, Loc, P, B.R);
+    Result &= CheckFieldsInitialized(S, Loc, P, B.R, false);
+  }
+
+  if (Toplevel) {
+    for (auto [I, B] : llvm::enumerate(R->virtual_bases())) {
+      PtrView P = BasePtr.atField(B.Offset);
+      if (!P.isInitialized()) {
+        const Descriptor *Desc = BasePtr.getDeclDesc();
+        if (const auto *CD = dyn_cast_if_present<CXXRecordDecl>(R->getDecl())) {
+          const auto &BS = *std::next(CD->bases_begin(), I);
+          SourceLocation TypeBeginLoc = BS.getBaseTypeLoc();
+          S.FFDiag(TypeBeginLoc, diag::note_constexpr_uninitialized_base)
+              << B.Desc->getType() << SourceRange(TypeBeginLoc, BS.getEndLoc());
+        } else {
+          S.FFDiag(Desc->getLocation(), diag::note_constexpr_uninitialized_base)
+              << B.Desc->getType();
+        }
+        return false;
+      }
+
+      Result &= CheckFieldsInitialized(S, Loc, P, B.R, false);
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Sirraide wrote:

Can you factor (some of) this out into a lambda instead of duplicating it from above?

https://github.com/llvm/llvm-project/pull/204289