stream: clone stream before execution

internal/expr/logical.go

@@ -18,6 +18,12 @@ func And(a, b Expr) Expr {
 	return &AndOp{&simpleOperator{a, b, scanner.AND}}
 }
 
+func (op *AndOp) Clone() Expr {
+	return &AndOp{
+		simpleOperator: op.simpleOperator.Clone(),
+	}
+}
+
 // Eval implements the Expr interface. It evaluates a and b and returns true if both evaluate
 // to true.
 func (op *AndOp) Eval(env *environment.Environment) (types.Value, error) {
@@ -52,6 +58,12 @@ func Or(a, b Expr) Expr {
 	return &OrOp{&simpleOperator{a, b, scanner.OR}}
 }
 
+func (op *OrOp) Clone() Expr {
+	return &OrOp{
+		simpleOperator: op.simpleOperator.Clone(),
+	}
+}
+
 // Eval implements the Expr interface. It evaluates a and b and returns true if a or b evalutate
 // to true.
 func (op *OrOp) Eval(env *environment.Environment) (types.Value, error) {
@@ -92,6 +104,12 @@ func Not(e Expr) Expr {
 	return &NotOp{&simpleOperator{a: e}}
 }
 
+func (op *NotOp) Clone() Expr {
+	return &NotOp{
+		simpleOperator: op.simpleOperator.Clone(),
+	}
+}
+
 // Eval implements the Expr interface. It evaluates e and returns true if b is falsy
 func (op *NotOp) Eval(env *environment.Environment) (types.Value, error) {
 	s, err := op.a.Eval(env)