[feature request] [longshot] Smart pattern search

Hello! My guess is this is probably the most appropriate GitHub project to suggest this to. Thought I'd throw this idea in here.

Say I'm working on a codebase with hundreds if not thousands of patterns being matched for very complex type structures, as one might find in a programming language project with a complex AST and type-checker.

I'd like to be able to provide a complex value (something nested, and maybe with placeholders like TypeT (_, AnnotT (_, _, OpenT (_, _))) and find all occurrences of patterns that would match it, either in a function, a file, or maybe even the whole project.

This would be very useful for debugging complex values flowing through many layers of functions, and possible branchings that might not be obvious at first.

Although I've used merlin I'm not at all familiar with the scope of the project and its structure. Is this out of scope for merlin? Is there a plugin architecture to add this as optional functionality? Is it possible with the amount of knowledge merlin has of the codebase at any given time? Would anyone have any pointers to resources that could help me implement this?

The issue names no files, tests, or entry points. Start by reviewing Merlin's architecture and whether it exposes plugin or extension points for project-wide analysis. Before implementation, define the supported pattern syntax, search scope, and how matches are reported; the issue currently leaves these outcomes open.