[clang][bytecode] Check that a ltor cast to a complex value is possible (llvm#155152)

When we get to this point, the pointer might _not_ be backed by a
primitive array, so the later code will fail.

Fixes llvm#155144

Author: tbaederr

clang/lib/AST/ByteCode/Pointer.cpp

@@ -785,8 +785,11 @@ std::optional<APValue> Pointer::toRValue(const Context &Ctx,
 
     // Complex types.
     if (const auto *CT = Ty->getAs<ComplexType>()) {
-      QualType ElemTy = CT->getElementType();
+      // Can happen via C casts.
+      if (!Ptr.getFieldDesc()->isPrimitiveArray())
+        return false;
 
+      QualType ElemTy = CT->getElementType();
       if (ElemTy->isIntegerType()) {
         OptPrimType ElemT = Ctx.classify(ElemTy);
         assert(ElemT);

clang/test/AST/ByteCode/c.c

@@ -173,6 +173,10 @@ _Static_assert(CTB3, ""); // pedantic-ref-warning {{GNU extension}} \
                           // pedantic-expected-warning {{GNU extension}}
 
 
+void nonComplexToComplexCast(void) {
+  _Complex double z = *(_Complex double *)&(struct { double r, i; }){0.0, 1.0};
+}
+
 int t1 = sizeof(int);
 void test4(void) {
   t1 = sizeof(int);