Add support for tags `expr:"..."`

[antonmedv]

Add support for tags expr:"..." for names aliases.

type Env struct {
    Value int `expr:"value"`
}

And now it's will be possible to use value instead of Value in expressions.

[Reasno]

I quite like this. Why was this closed?

[antonmedv]

Let’s reopen this ;)

[marcus-orchard]

To piggyback on this enhancement I need to support sloppy expressions, so ideally I need to support "Value", "value", "VALUE", etc. as mapping to the Value field.

type Env struct {
    Value int `expr:"value, VALUE, Value"`
}

And/or

type Env struct {
    Value int `expr:"case-insensitive"`
}

I guess both would have their place, some implementations need only support specific field names, while other need to support any case insensitive variation.

[antonmedv]

If you want case insensitive expressions, use ast.Parse for it.