Vim uses regular expressions for syntax highlighting. Often maintaining these can become rather unwieldy. For example:
syn match goVarAssign /\v[_.[:alnum:]]+(,\s*[_.[:alnum:]]+)*\ze(\s*([-^+|^\/%&]|\*|\<\<|\>\>|\&\^)?\=[^=])/
For example Python supports comments inside regular expressions, which would make things a lot more helpful:
syn match goVarAssign /\v [_.[:alnum:]]+ " One or more valid identifier characters. (,\s*[_.[:alnum:]]+)* " Repeated one or more times separated by , \ze " Start matching here ( \s* " Any whitespace ( " ... um? [-^+|^\/%&]| \*| \<\<| \>\>| \&\^ ) ?\=[^=] " .. um? ) /
The above pseudo-example does not work, but is there any way to approach something like that in Vim?