Created SC2190 (markdown)

SC2190.md

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+## Elements in associative arrays need index, e.g. array=( [index]=value ) .
+
+### Problematic code:
+
+```sh
+declare -A foo
+foo=( myvalue )
+```
+
+### Correct code:
+
+```sh
+declare -A foo
+foo=( [key]=myvalue )
+```
+### Rationale:
+
+You appear to be initializing or appending an array element to an associative array without giving it an index. In an indexed array, elements will be auto-indexed by incremented characters. In associative arrays, the index must be given explicitly.
+
+This could happen because of invalid spaces or otherwise malformed index assignment, such as `array=( [key] = value )`. This should instead be `array=( [key]=value )`.
+
+### Exceptions:
+
+ShellCheck may be confused when a variable name is reused in different contexts. If shellcheck mistakenly believes the array is associated, please [[ignore]] this error.