Improve illegal pattern error for accidental map associations

[jchristgit]

Given a module such as this:

-module(test).
-export([pattern/1]).

pattern(#{foo => bar}) -> ok.

We presently report an error as:

test.erl:4:15: illegal pattern
%    4| pattern(#{foo => bar}) -> ok.
%     |               ^

Since we have information in erl_lint on the bad pattern being a map field update, we can be a bit more helpful by extending the error with a hint instructing the user that := is most likely wanted instead:

test.erl:4:15: illegal pattern, did you mean to use `:=`?
%    4| pattern(#{foo => bar}) -> ok.
%     |               ^

[github-actions]

CT Test Results

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[kikofernandez]

Hi! @jchristgit this is a good improvement. Given that you have previously suggested new improvements (#7383), do you have more ideas to add to this PR for better error messages?
Just checking if there are more places that could benefits from your suggestions :)

[kikofernandez]

BTW, can you rebase this on maint, so that changes these improvements are available on the next patch of OTP 27?

[jchristgit]

@kikofernandez thanks for the feedback!
I usually try to make PRs for things I catch on the fly - the last PR was from my own confusion, this one from a user of a library I maintain :-) I had a quick look around an "illegal expression" stood out but I'm unsure if 1. the illegal expression is always of the form atom:atom (as seen in the test case) 2. we should assume that an existing function is being called and suggest to call it. I've also never encountered it personally before, but in case somebody expects that functions can be called directly (without ()) it might help. What do you think?
I also rebased the branch on maint.

[kikofernandez]

I think we should let that be for now. Thanks!