[intro.defs] Adding definition for the term "built-in type"

[ranaanoop]

Full name of submitter (unless configured in github; will be published with the issue): Anoop Rana

Reference (section label): [intro.defs]

Link to reflector thread (if any):

Issue description: Currently the C++ standard does not formally define the term built-in type while it uses that term at various places in the standard.

Suggested resolution:

Either change the term "built in type" in concepts.object#2 and concepts.object#3 to the term "fundamental type"

Or

Add a new entry in [intro.defs] saying something like:

built-in type[defns.builtin.type]

Same as fundamental type.

[JohelEGP]

Searching https://wg21.link/n4917 from the beginning, the use of "built-in" as an adjective for "type" occurs only in two consecutive notes in the library side at [concepts.object]. The language side has no such use.

[jensmaurer]

@ranaanoop , could you please list the first 5 (or so) hits for " built-in type", since you claim it's used in "various places in the standard"? I'm with @JohelEGP in finding rare non-normative uses only. Instead of introducing a synonym, it's better to replace the remaining uses with "fundamental type".

[ranaanoop]

@jensmaurer I can find 2 uses in this draft. Both are used in notes given in concepts.object.

Here is the first use.

Here is the second use

Also I agree that instead of introducing a synonym it's better(or atleast easy) to replace "built in type" with "fundamental type".
I've updated my suggested resolution accordingly.

[JohelEGP]

That's where I found them (I gave the wrong stable label). This should be an editorial issue instead.

[ranaanoop]

@JohelEGP I've made the pull request 6012.