feat: support stringer and error as source

conversion.go

@@ -43,6 +43,10 @@ func Convert[NumOut Number](orig any) (converted NumOut, err error) {
 			return NumOut(1), nil
 		}
 		return NumOut(0), nil
+	case fmt.Stringer:
+		return convertFromString[NumOut](v.String())
+	case error:
+		return convertFromString[NumOut](v.Error())
 	case string:
 		return convertFromString[NumOut](v)
 	}

conversion_test.go

@@ -14,6 +14,18 @@ import (
 	"github.com/ccoveille/go-safecast"
 )
 
+type anyStringer struct{}
+
+func (anyStringer) String() string {
+	return "42"
+}
+
+type anyError struct{}
+
+func (anyError) Error() string {
+	return "42"
+}
+
 func TestToInt8(t *testing.T) {
 	t.Run("from int", func(t *testing.T) {
 		assertInt8OK(t, []caseInt8[int]{
@@ -1552,6 +1564,8 @@ func TestConvert(t *testing.T) {
 			"positive string within range": {input: "42", want: 42},
 			"negative string within range": {input: "-42", want: -42},
 			"float string within range":    {input: "100.0", want: 100},
+			"stringer":                     {input: anyStringer{}, want: 42},
+			"error":                        {input: anyError{}, want: 42},
 		} {
 			t.Run(name, func(t *testing.T) {
 				got, err := safecast.Convert[int8](tt.input)