[clang][bytecode] Fix contains check using llvm::find

clang/lib/AST/ByteCode/Interp.cpp

@@ -575,7 +575,8 @@ bool CheckConst(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
 
   // The This pointer is writable in constructors and destructors,
   // even if isConst() returns true.
-  if (llvm::find(S.InitializingBlocks, Ptr.block()))
+  if (llvm::find(S.InitializingBlocks, Ptr.block()) !=
+      S.InitializingBlocks.end())
     return true;
 
   const QualType Ty = Ptr.getType();

clang/test/AST/ByteCode/placement-new.cpp

@@ -486,3 +486,11 @@ namespace bitcast {
   }
   static_assert(foo() == 0);
 }
+
+constexpr int modify_const_variable() {
+  const int a = 10;
+  new ((int *)&a) int(12); // both-note {{modification of object of const-qualified type 'const int' is not allowed in a constant expression}}
+  return a;
+}
+static_assert(modify_const_variable()); // both-error {{not an integral constant expression}} \
+                                        // both-note {{in call to}}

clang/test/SemaCXX/cxx2c-constexpr-placement-new.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -std=c++2c -verify %s
+// RUN: %clang_cc1 -std=c++2c -verify %s -fexperimental-new-constant-interpreter
 
 
 namespace std {