addressed some Coverity nits

src/Expr.cc

@@ -2793,7 +2793,7 @@ void FieldExpr::Assign(Frame* f, ValPtr v) {
     if ( IsError() )
         return;
 
-    Assign(op->Eval(f), v);
+    Assign(op->Eval(f), std::move(v));
 }
 
 void FieldExpr::Assign(ValPtr lhs, ValPtr rhs) {
@@ -2807,7 +2807,7 @@ ValPtr FieldExpr::Delete(Frame* f) {
         return nullptr;
 
     auto former = op_v->AsRecordVal()->GetField(field);
-    Assign(op_v, nullptr);
+    Assign(std::move(op_v), nullptr);
     // In the future we could return a value, such as former, here.
     return nullptr;
 }

src/script_opt/Reduce.cc

@@ -384,7 +384,7 @@ NameExprPtr Reducer::GetRetVar(TypePtr type) {
         return nullptr;
 
     IDPtr ret_id = install_ID("@retvar", "<internal>", false, false);
-    ret_id->SetType(type);
+    ret_id->SetType(std::move(type));
     ret_id->GetOptInfo()->SetTemp();
 
     ret_vars.insert(ret_id.get());

src/script_opt/ZAM/Compile.h

@@ -321,7 +321,7 @@ private:
 
     // Returns a handle to state associated with building
     // up a list of values.
-    OpaqueVals* BuildVals(const ListExprPtr&);
+    std::unique_ptr<OpaqueVals> BuildVals(const ListExprPtr&);
 
     // "stride" is how many slots each element of l will consume.
     ZInstAux* InternalBuildVals(const ListExpr* l, int stride = 1);

src/script_opt/ZAM/Expr.cc

@@ -101,7 +101,7 @@ const ZAMStmt ZAMCompiler::CompileAdd(const AggrAddExpr* e) {
             return AddStmt1VC(aggr, e1->AsConstExpr());
     }
 
-    return AddStmtVO(aggr, BuildVals(indices));
+    return AddStmtVO(aggr, BuildVals(indices).get());
 }
 
 const ZAMStmt ZAMCompiler::CompileDel(const AggrDelExpr* e) {
@@ -128,7 +128,7 @@ const ZAMStmt ZAMCompiler::CompileDel(const AggrDelExpr* e) {
     if ( index_list->Tag() != EXPR_LIST )
         reporter->InternalError("non-list in \"delete\"");
 
-    auto internal_ind = std::unique_ptr<OpaqueVals>(BuildVals(index_list->AsListExprPtr()));
+    auto internal_ind = BuildVals(index_list->AsListExprPtr());
     return DelTableVO(aggr, internal_ind.get());
 }
 

src/script_opt/ZAM/Low-Level.cc

@@ -24,7 +24,9 @@ const ZAMStmt ZAMCompiler::LastInst() { return ZAMStmt(insts1.size() - 1); }
 
 const ZAMStmt ZAMCompiler::ErrorStmt() { return ZAMStmt(0); }
 
-OpaqueVals* ZAMCompiler::BuildVals(const ListExprPtr& l) { return new OpaqueVals(InternalBuildVals(l.get())); }
+std::unique_ptr<OpaqueVals> ZAMCompiler::BuildVals(const ListExprPtr& l) {
+    return std::make_unique<OpaqueVals>(InternalBuildVals(l.get()));
+}
 
 ZInstAux* ZAMCompiler::InternalBuildVals(const ListExpr* l, int stride) {
     auto exprs = l->Exprs();

src/script_opt/ZAM/OPs/ZAM.op

@@ -2414,7 +2414,7 @@ internal-op Subnet-To-Addr
 type VV
 eval	auto addr_v = make_intrusive<AddrVal>(frame[z.v2].subnet_val->Prefix());
 	Unref(frame[z.v1].addr_val);
-	frame[z.v1] = ZVal(addr_v);
+	frame[z.v1] = ZVal(std::move(addr_v));
 
 internal-op Sub-Bytes
 type VVVV

src/script_opt/ZAM/Stmt.cc

@@ -78,7 +78,7 @@ const ZAMStmt ZAMCompiler::CompilePrint(const PrintStmt* ps) {
             return Print1C(e0->AsConstExpr());
     }
 
-    return PrintO(BuildVals(l));
+    return PrintO(BuildVals(l).get());
 }
 
 const ZAMStmt ZAMCompiler::CompileExpr(const ExprStmt* es) {