[clang] [clang][bytecode] Fix a crash in InvalidCast op (PR #230420)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/230420

Since we have stuff like LocOverride, we can't rely on the expression we emitted the InvalidCast op for to be a CastExpr.

>From 7ed8bdaf77e2caab5baedd4d205c5f1fc4938e10 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Fri, 9 Oct 2026 11:06:53 +0200
Subject: [PATCH] [clang][bytecode] Fix a crash in InvalidCast op

Since we have stuff like LocOverride, we can't rely on the expression we
emitted the InvalidCast op for to be a CastExpr.
---
 clang/lib/AST/ByteCode/Interp.cpp |  7 ++++---
 clang/test/AST/ByteCode/cxx17.cpp | 11 +++++++++++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index d7a6d160228b92..21e5d3e617fe78 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -3342,10 +3342,11 @@ bool InvalidCast(InterpState &S, CodePtr OpPC, CastKind Kind, bool Fatal) {
     return !Fatal;
   case CastKind::Volatile:
     if (!S.checkingPotentialConstantExpression()) {
-      const auto *E = cast<CastExpr>(S.Current->getExpr(OpPC));
-      if (S.getLangOpts().CPlusPlus)
+      const auto *E = S.Current->getExpr(OpPC);
+      const auto *CE = dyn_cast<CastExpr>(E);
+      if (CE && S.getLangOpts().CPlusPlus)
         S.FFDiag(E, diag::note_constexpr_access_volatile_type)
-            << AK_Read << E->getSubExpr()->getType();
+            << AK_Read << CE->getSubExpr()->getType();
       else
         S.FFDiag(E);
     }
diff --git a/clang/test/AST/ByteCode/cxx17.cpp b/clang/test/AST/ByteCode/cxx17.cpp
index 9168f0d34d872f..c4927f675d28ea 100644
--- a/clang/test/AST/ByteCode/cxx17.cpp
+++ b/clang/test/AST/ByteCode/cxx17.cpp
@@ -194,3 +194,14 @@ namespace InitListBaseInit {
   static_assert(b.a.m == 43);
   static_assert(b.i == 0);
 }
+
+namespace NonCastExprInvalidCast {
+  struct S1 {
+    volatile unsigned int x : 16;
+    volatile unsigned int y : 16;
+  };
+  void fS1() {
+    S1 s1;
+    auto [a, b] = s1;
+  }
+}