Highlight closing brackets

[danielshahaf]

In the following constructs, the opening parenthesis/bracket/brace is highlighted as a reserved word, and the closing one isn't, but should be.

• (subshell) — done in c0dafd1
  • That kicked in for array assignments too (e.g., a=(foo bar)); fixed by b285c7b.
  • (pattern), part of the case syntax — punted.
• { block } — done in c0dafd1
• [[ test ]]
• (( arithmetic evaluation )) — done in a59f442
• [ test ] — note that this one is a builtin, unlike the others which are reserved words.

[danielshahaf]

a59f442 handles arithmetic evaluation, which is different from all the other cases: for every other case, the closing } or ) or ]] is its own token, but the ${(z)} splitter gives the entire (( … )) statement as a single token.

[danielshahaf]

c0dafd1 handles subshells and blocks, which are easy because ) and } tokens are special wherever they occur.

The test syntax isn't as simple, since ]] is not always special — e.g., echo ]] works and prints two closing brackets — so it will require remembering that "the current command is [[".

As mentioned above, [ is a builtin but [[ is a reserved word. That has various user-visible consequences at the language level. It also causes [[ to be highlighted in yellow and [ in green. How similarly or differently should [ and [[ statements be highlighted?