Chore(builtins): Add output builtin check (#132)

Add output builtin check

pkg/runners/zero/zero.go

@@ -240,7 +240,8 @@ func (runner *ZeroRunner) Output() []*fp.Element {
 
 	for offset := uint64(0); offset < outputSegment.Len(); offset++ {
 		value := outputSegment.Peek(offset)
-		// todo(rodro): check if output can only contains field elements
+		// no need to check for an error here since only felts can be written
+		// to the output segment
 		valueFelt, _ := value.FieldElement()
 		output = append(output, valueFelt)
 	}

pkg/vm/builtins/output.go

@@ -2,6 +2,7 @@ package builtins
 
 import (
 	"errors"
+	"fmt"
 
 	"github.com/NethermindEth/cairo-vm-go/pkg/vm/memory"
 )
@@ -11,6 +12,9 @@ const OutputName = "output"
 type Output struct{}
 
 func (o *Output) CheckWrite(segment *memory.Segment, offset uint64, value *memory.MemoryValue) error {
+	if !value.IsFelt() {
+		return fmt.Errorf("expected a felt but got an address: %s", value)
+	}
 	return nil
 }
 

pkg/vm/builtins/output_test.go

@@ -0,0 +1,22 @@
+package builtins
+
+import (
+	"testing"
+
+	"github.com/NethermindEth/cairo-vm-go/pkg/vm/memory"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOutput(t *testing.T) {
+	output := &Output{}
+	segment := memory.EmptySegmentWithLength(5).WithBuiltinRunner(output)
+
+	mv1 := memory.MemoryValueFromInt(5)
+	err := segment.Write(0, &mv1)
+	require.NoError(t, err)
+
+	mv2 := memory.MemoryValueFromSegmentAndOffset(1, 2)
+	err = segment.Write(1, &mv2)
+	require.ErrorContains(t, err, "expected a felt but got an address")
+
+}

pkg/vm/memory/memory.go

@@ -175,7 +175,6 @@ func (segment *Segment) String() string {
 	return header
 }
 
-// todo(rodro): Check out temprary segments
 // Represents the whole VM memory divided into segments
 type Memory struct {
 	Segments []*Segment