test: fuzz gnovm/pkg/gnolang Machine.doOpEval for BasicLitExpr

Fuzzing for BasicLitExpr and equivalence comparisons
for if those values parse in Go.

Updates #3087

gnovm/pkg/gnolang/fuzz_test.go

@@ -1,11 +1,15 @@
 package gnolang
 
 import (
+	"context"
+	"encoding/json"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/cockroachdb/apd/v3"
 )
@@ -87,3 +91,79 @@ func FuzzParseFile(f *testing.F) {
 		_, _ = ParseFile("a.go", goFileContents)
 	})
 }
+
+func FuzzDoOpEvalBaseConversion(f *testing.F) {
+	if testing.Short() {
+		f.Skip("Skipping in -short mode")
+	}
+
+	// 1. Add the seeds.
+	seeds := []*BasicLitExpr{
+		{Kind: INT, Value: "9223372036854775807"},
+		{Kind: INT, Value: "0"},
+		{Kind: INT, Value: "0777"},
+		{Kind: INT, Value: "0xDEADBEEF"},
+		{Kind: INT, Value: "0o123"},
+		{Kind: INT, Value: "0b111111111111111111111111111111111111111111111111111111111111111"},
+		{Kind: FLOAT, Value: "0.00001111"},
+		{Kind: FLOAT, Value: "9999.12"},
+		{Kind: STRING, Value: `"9999.12"`},
+		{Kind: STRING, Value: `"aaaaaaaaaaa   "`},
+		{Kind: STRING, Value: `"🚨🌎"`},
+	}
+
+	for _, seed := range seeds {
+		blob, err := json.Marshal(seed)
+		if err != nil {
+			panic(err)
+		}
+		f.Add(blob)
+	}
+
+	// 2. Fuzz it.
+	f.Fuzz(func(t *testing.T, basicLitExprBlob []byte) {
+		expr := new(BasicLitExpr)
+		if err := json.Unmarshal(basicLitExprBlob, expr); err != nil {
+			return
+		}
+
+		defer func() {
+			r := recover()
+			if r == nil {
+				return
+			}
+
+			switch {
+			case strings.Contains(fmt.Sprintf("%s", r), "unexpected lit kind"):
+				return
+
+			default:
+				if !basicLitExprIsValidGoValue(t, expr) {
+					return
+				}
+				panic(r)
+			}
+		}()
+
+		m := NewMachine("test", nil)
+		m.PushExpr(expr)
+		m.doOpEval()
+		_ = m.PopValue()
+	})
+}
+
+func basicLitExprIsValidGoValue(t *testing.T, lit *BasicLitExpr) bool {
+	tempDir := t.TempDir()
+	file := filepath.Join(tempDir, "basic_lit_check.go")
+	var craftedGo = []byte(fmt.Sprintf(`package main
+var _ = %s
+func main() {}`, lit.Value))
+	if err := os.WriteFile(file, craftedGo, 0755); err != nil {
+		panic(err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	err := exec.CommandContext(ctx, "go", "run", file).Run()
+	return err == nil
+}