Created SC3054 (markdown)

SC3054.md

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+## In POSIX sh, array references are undefined.
+
+(or "In dash, ... are not supported." when using `dash`)
+
+### Problematic code:
+
+```sh
+#!/bin/sh
+var=(foo bar)
+echo "${var[1]}"
+```
+
+### Correct code:
+
+The easiest solution is to switch to a shell that does support arrays, like `bash`:
+
+```sh
+#!/bin/bash
+var=(foo bar)
+echo "${var[1]}"
+```
+
+Alternatively, rewrite the logic to use e.g. indirect variable references or `set`:
+
+```sh
+#!/bin/sh
+set -- foo bar
+echo "$2"
+```
+
+### Rationale:
+
+Arrays are supported in `bash` and `ksh`, but not in `dash` or POSIX `sh`. Either switch to a shell that supports them, or rewrite your script without relying on arrays. This may not be straight forward.
+
+### Exceptions:
+
+If you only intend to target shells that supports this feature, you can change
+the shebang to a shell that guarantees support, or [[ignore]] this warning.
+
+You can use `# shellcheck disable=SC3000-SC4000` to ignore all such compatibility
+warnings.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!