Toml: Clarify inline tables are immutable (and dotted keys can't "inject" into them)

[pradyunsg]

You can't "inject" into inline tables with dotted keys. This isn't clear in the specification and we should clarify.

[LongTengDao]

Also include below (if I am right):

a = {}
[a.b]

[pradyunsg]

a = {}
[a.b]

This isn't valid. This is injecting a "b" key into an inline table defined "a".

[eksortso]

That would make a good counterexample for the spec, though.

How about this?

---

Inline tables are immutable. Once they are defined, new elements and subtables cannot be added to them.

a = {}
#a.b = 1  # INVALID
#[a.b]  # INVALID

---

I would avoid saying the word "inject." "Immutable" carries plenty of weight, so making that meaning clear ought to be sufficient.

[eksortso]

I'm going to have to change the wording. We don't want anyone to think that, when TOML is loaded into a data structure in a program, that the data structure must be immutable. Granted, it's not recommended to modify a configuration in a program. But what the program does with it is outside the scope of the specification.

---

Once inline tables are defined, their values are fully set, and new elements and subtables cannot be added to them.

a = {}
#a.b = 1  # INVALID
#[a.b]  # INVALID