Information on dict vs shape is unclear/incomplete/buried

[jwatzman]

Where is the problem?

The pages on shapes and dicts.

What is the problem?

When to use a dict and when to use a shape is a question that IME often trips up people new to the language, especially folks coming from PHP who aren't used to thinking about those use-cases as materially different. See, for example, this SO question as a recent example which prompted this report -- but I've given the same explanation to FB bootcampers many times too.

At the very very end of the page on vec, keyset, and dict, is this note:

If you want different keys to have different value types, or if you want a fixed set of keys, consider using a shape instead.

IMO, that footnote is pretty unclear and is unlikely to help anyone who isn't already familiar with this idea, and is also a bit hard to see at the bottom of an otherwise very busy page. This idea seems to deserve its own section or even page, more than that footnote?

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Please don't change anything below this point.

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• Build ID: HHVM=HHVM-4.164.0:HSL=v4.108.1:2022-07-26T17:24:38+0000:1fa47f258c6b68f8ec01899aa82fd6ffa0957109
• Page requested: /hack/arrays-and-collections/vec-keyset-and-dict
• Page requested at: Sun, 31 Jul 2022 15:07:23 +0000
• Controller: GuidePageController