Make AsAny the new default

expr.go

@@ -65,34 +65,49 @@ func AsAny() Option {
 func AsKind(kind reflect.Kind) Option {
 	return func(c *conf.Config) {
 		c.Expect = kind
+		c.ExpectAny = true
 	}
 }
 
 // AsBool tells the compiler to expect a boolean result.
 func AsBool() Option {
 	return func(c *conf.Config) {
 		c.Expect = reflect.Bool
+		c.ExpectAny = true
 	}
 }
 
 // AsInt tells the compiler to expect an int result.
 func AsInt() Option {
 	return func(c *conf.Config) {
 		c.Expect = reflect.Int
+		c.ExpectAny = true
 	}
 }
 
 // AsInt64 tells the compiler to expect an int64 result.
 func AsInt64() Option {
 	return func(c *conf.Config) {
 		c.Expect = reflect.Int64
+		c.ExpectAny = true
 	}
 }
 
 // AsFloat64 tells the compiler to expect a float64 result.
 func AsFloat64() Option {
 	return func(c *conf.Config) {
 		c.Expect = reflect.Float64
+		c.ExpectAny = true
+	}
+}
+
+// WarnOnAny tells the compiler to warn if expression return any type.
+func WarnOnAny() Option {
+	return func(c *conf.Config) {
+		if c.Expect == reflect.Invalid {
+			panic("WarnOnAny() works only with combination with AsInt(), AsBool(), etc. options")
+		}
+		c.ExpectAny = false
 	}
 }
 

expr_test.go

@@ -257,6 +257,17 @@ func ExampleAsFloat64_error() {
 	// Output: expected float64, but got bool
 }
 
+func ExampleWarnOnAny() {
+	// Arrays always have []any type. The expression return type is any.
+	// AsInt() instructs compiler to expect int or any, and cast to int,
+	// if possible. WarnOnAny() instructs to return an error on any type.
+	_, err := expr.Compile(`[42, true, "yes"][0]`, expr.AsInt(), expr.WarnOnAny())
+
+	fmt.Printf("%v", err)
+
+	// Output: expected int, but got interface {}
+}
+
 func ExampleOperator() {
 	code := `
 		Now() > CreatedAt &&