builtin int unwraps underlying int value (#611)

Author: bizywizy

builtin/builtin_test.go

@@ -612,3 +612,17 @@ func TestBuiltin_bitOpsFunc(t *testing.T) {
 		})
 	}
 }
+
+type customInt int
+
+func Test_int_unwraps_underlying_value(t *testing.T) {
+	env := map[string]any{
+		"customInt": customInt(42),
+	}
+	program, err := expr.Compile(`int(customInt) == 42`, expr.Env(env))
+	require.NoError(t, err)
+
+	out, err := expr.Run(program, env)
+	require.NoError(t, err)
+	assert.Equal(t, true, out)
+}

builtin/lib.go

@@ -209,6 +209,10 @@ func Int(x any) any {
 		}
 		return i
 	default:
+		val := reflect.ValueOf(x)
+		if val.CanConvert(integerType) {
+			return val.Convert(integerType).Interface()
+		}
 		panic(fmt.Sprintf("invalid operation: int(%T)", x))
 	}
 }