Fix: checker to correctly expect type cast with As*() modifiers

Author: antonmedv

checker/checker.go

@@ -32,13 +32,19 @@ func Check(tree *parser.Tree, config *conf.Config) (t reflect.Type, err error) {
 	if v.config.Expect != reflect.Invalid {
 		switch v.config.Expect {
 		case reflect.Int, reflect.Int64, reflect.Float64:
-			if !isNumber(t) {
+			if !isNumber(t) && !isAny(t) {
 				return nil, fmt.Errorf("expected %v, but got %v", v.config.Expect, t)
 			}
 		default:
-			if t == nil || t.Kind() != v.config.Expect {
-				return nil, fmt.Errorf("expected %v, but got %v", v.config.Expect, t)
+			if t != nil {
+				if t.Kind() == reflect.Interface {
+					t = t.Elem()
+				}
+				if t.Kind() == v.config.Expect {
+					return t, nil
+				}
 			}
+			return nil, fmt.Errorf("expected %v, but got %v", v.config.Expect, t)
 		}
 	}
 

checker/checker_test.go

@@ -745,3 +745,35 @@ func TestCheck_works_with_nil_types(t *testing.T) {
 	_, err = checker.Check(tree, conf.New(env))
 	require.NoError(t, err)
 }
+
+func TestCheck_cast_to_expected_works_with_interface(t *testing.T) {
+	t.Run("float64", func(t *testing.T) {
+		type Env struct {
+			Any interface{}
+		}
+
+		tree, err := parser.Parse("Any")
+		require.NoError(t, err)
+
+		config := conf.New(Env{})
+		expr.AsFloat64()(config)
+
+		_, err = checker.Check(tree, config)
+		require.NoError(t, err)
+	})
+
+	t.Run("kind", func(t *testing.T) {
+		env := map[string]interface{}{
+			"Any": interface{}("foo"),
+		}
+
+		tree, err := parser.Parse("Any")
+		require.NoError(t, err)
+
+		config := conf.New(env)
+		expr.AsKind(reflect.String)(config)
+
+		_, err = checker.Check(tree, config)
+		require.NoError(t, err)
+	})
+}