Highlight function definitions

[danielshahaf]

In f() {}, highlight f specially. Ditto for f g h() {} when MULTI_FUNC_DEF is in effect (that would help with a common user mistake).

The default color of f g h shall be different from the default color of the [command] style.

The first word is parsed differently from the others: it is subject to alias expansion and to must not be a reserved word. That said, using a reserved word for g or h would probably be a mistake on the user's part (so it might be useful to check for that and highlight it as unknown-token).

The first word should never be considered for the [command] and [path] highlights.

Further ideas (which might be good and might be pure feature creep):

• Highlight the syntax function f g h () {} as well?
• Highlight f differently depending on whether it shadows/overwrites an existing function, builtin, or command?

Compare #194.

[danielshahaf]

Relation to #237: in the syntaxes f g h() { ls } and function f g h { ls }, this issue is about the highlighting of f, g, and h, and that issue is about the highlighting of the { and ls.