add explanation for E0429 (self use declaration must use brace syntax)

[zackmdavis]

This is an item under #32777.

r? @GuillaumeGomez

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[GuillaumeGomez]

This paragraph should just be the description of the error, not how to fix it. Put this paragraph just after the erroneous code example and replace it here by the error description (I think I repeated myself a lot in here haha).

[zackmdavis]

Right. Better?

[GuillaumeGomez]

I liked the original explanation, it was more complete than the actual one. Could you re-use it or expand the current one please?

[zackmdavis]

@GuillaumeGomez

I liked the original explanation, it was more complete than the actual one. Could you re-use it

Unfortunately, I'm not sure I understand what you mean; both my initial submission and the revision would seem to cover the same information:

• self can't be used alone (second sentence as of a2b7dfa, first sentence as of 06ebda8)
• to import a namespace as well as some members, self can be used in braces (first and last sentences as of a2b7dfa; sentence after the erroneous snippet as of 06ebda8)
• if you just want to use the namespace, you don't need to bother with self (first sentence after the erroneous snippet as of a2b7dfa; last sentence as of 06ebda8)

What made the first one (a2b7dfa) feel more complete to you?

In that, initial, draft, my outline was "start with a context-setting 'topic sentence' explaining what this brace-syntax feature is about, then explain the error, then point out how to just use the namespace itself, then have an example of the typical ::{self, OtherImport} usage". After you pointed out that we want to start with a description of the error itself (without excessive contextualization), it seemed more parsimonious to combine the explanation of the brace syntax with the sentence introducing the typical-usage-of-brace-syntax snippet.

[GuillaumeGomez]

Hum... I see your point. Then I have nothing to add. Thanks!

@bors: r+ rollup

[bors]

📌 Commit 06ebda8 has been approved by GuillaumeGomez