Not types added to config after upgrade to 1.16.1

[fggarcia]

This code runs correctly in 1.16.0

type customOperation struct {
	name      string
	operation string
}

func (o customOperation) Name() string {
	return o.name
}

func (o customOperation) Code() string {
	return o.operation
}

func (o customOperation) Expr() func(interface{}, interface{}) interface{} {
	return func(arg1 interface{}, arg2 interface{}) interface{} {
		a, _ := arg1.(float64)
		b, _ := arg2.(float64)
		return a * b
	}
}

func TestExprLanguage(t *testing.T) {
	exp := "263.5 * 4.63"
	operator := customOperation{name: "*", operation: "multiplyNumbers"}
	options := []expr.Option{
		expr.Operator(operator.Code(), operator.Name()),
		expr.Env(map[string]interface{}{operator.Name(): operator.Expr()}),
	}
	_, err := expr.Compile(exp, options...)
	assert.True(t, err == nil)
}

But after upgrade to 1.16.1 this expression not compile.

--- FAIL: TestExprLanguage (0.00s)
panic: function * for multiplyNumbers operator does not exist in the environment [recovered]
	panic: function * for multiplyNumbers operator does not exist in the environment

goroutine 36 [running]:
testing.tRunner.func1.2({0x10132ada0, 0x14000285a30})
	/opt/go/libexec/src/testing/testing.go:1631 +0x1c4
testing.tRunner.func1()
	/go/libexec/src/testing/testing.go:1634 +0x33c
panic({0x10132ada0?, 0x14000285a30?})
	/opt/go/libexec/src/runtime/panic.go:770 +0x124
github.com/expr-lang/expr/patcher.(*OperatorOverloading).Check(0x140002b3280)
	/vendor/github.com/expr-lang/expr/patcher/operator_override.go:109 +0x21c
github.com/expr-lang/expr/conf.(*Config).Check(0x140002fe080?)
	/vendor/github.com/expr-lang/expr/conf/config.go:88 +0x70
github.com/expr-lang/expr.Compile({0x10116a75d, 0xc}, {0x14000088f00, 0x2, 0x14000312f18?})
	/vendor/github.com/expr-lang/expr/expr.go:195 +0x1f0
github.com/melisource/rule-engine-api/src/api/expression_test.TestExprLanguage(0x140001b3d40)
	/expression/expression_test.go:1232 +0x124
testing.tRunner(0x140001b3d40, 0x101434100)
	/opt/go/libexec/src/testing/testing.go:1689 +0xec
created by testing.(*T).Run in goroutine 1
	/opt/go/libexec/src/testing/testing.go:1742 +0x318

[bizywizy]

There is a problem with your example:

options := []expr.Option{
    expr.Operator(operator.Code(), operator.Name()),  // arguments should be flipped, now you have `multiplyNumbers 
` as an operator name and `*` overriding function name
    expr.Env(map[string]interface{}{operator.Name(): operator.Expr()}), // function name, not operator name should be provided here as a key
	}

Btw error is still occurred after fixing that.

The main problem is with order of options, it works pretty well if expr.Env goes first:

options := []expr.Option{
    expr.Env(map[string]interface{}{operator.Code(): operator.Expr()}),
    expr.Operator(operator.Name(), operator.Code()),
}

@antonmedv expr.Operator in v1.6.1 depends on unitialized map .Types which may be created after calling operator options. I guess we can fix it with #606