Color indicator in gutter doesn't show for external color consts

[lukef]

Similar to #2684.

It seems like a pretty common pattern to use a file for external consts / static consts when you're trying to abstract out your color / theme definitions. However, when you use these on a color property you get no indication of what the actual color is.

For example:

It'd be great to be able to see what the color is whenever it's attached to something that is expecting a Color value.

[rafaelmanto]

Hey! I've tried to work on this issue last month as my first issue, and, although I haven't made much progress, I think I can contribute with something. First of all, sorry if I've skipped some steps on the process to contribute with flutter, I'm still learning although I've read the guides about it.

At first I tried to explore the issue #2684 since it was said here that it were similar to this one. That issue was closed, yet didn't have any related PR, therefore I searched for it on the history of the person that said that the problem has been addressed. This PR (#2783) was the one that I found. Since it's an old contribution, many files have been changed, but I learned the necessary keywords to find this solution on the current repository.

Looking for some keywords, I've found on the current repository the file ColorField.java, that I think it's the class that shows the color icon on the editor. But analyzing its implementation and the fix of the related issue, I've found that to show an Icon it uses the text of the respective code. However, to implement the solution to this issue, we need more, we need variables and their types, like an AST, in order to show the icon when there is a variable. So I got stuck on how to solve this issue.

I tried to get help on Discord without success. So, I'm here talking about my attempt to solve this issue in order to help someone in the future.

Good Luck!