[clang][Interp] Bail out on value dependent variable initializers

Author: tbaederr

clang/lib/AST/Interp/Compiler.cpp

@@ -3683,6 +3683,9 @@ VarCreationState Compiler<Emitter>::visitVarDecl(const VarDecl *VD, bool Topleve
   const Expr *Init = VD->getInit();
   std::optional<PrimType> VarT = classify(VD->getType());
 
+  if (Init && Init->isValueDependent())
+    return false;
+
   if (Context::shouldBeGloballyIndexed(VD)) {
     auto checkDecl = [&]() -> bool {
       bool NeedsOp = !Toplevel && VD->isLocalVarDecl() && VD->isStaticLocal();

clang/test/AST/Interp/literals.cpp

@@ -1307,3 +1307,15 @@ namespace VolatileReads {
   static_assert(b, ""); // both-error {{not an integral constant expression}} \
                         // both-note {{read of volatile-qualified type 'const volatile int' is not allowed in a constant expression}}
 }
+#if __cplusplus >= 201703L
+namespace {
+  struct C {
+    int x;
+  };
+
+  template <const C *p> void f() {
+    const auto &[c] = *p;
+    &c; // both-warning {{expression result unused}}
+  }
+}
+#endif