CONTRIBUTING

CONTRIBUTING.md

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+# Contributing to rust-clippy
+
+Hello fellow Rustacean! Great to see your interest in compiler internals and lints!
+
+## Getting started
+
+All issues on Clippy are mentored, if you want help with a bug just ask @Manishearth or @llogiq.
+
+Some issues are easier than others. The [E-easy](https://github.com/Manishearth/rust-clippy/labels/E-easy)
+label can be used to find the easy issues. If you want to work on an issue, please leave a comment
+so that we can assign it to you!
+
+Issues marked [T-AST](https://github.com/Manishearth/rust-clippy/labels/T-AST) involve simple
+matching of the syntax tree structure, and are generally easier than
+[T-middle](https://github.com/Manishearth/rust-clippy/labels/T-middle) issues, which involve types
+and resolved paths.
+
+Issues marked [E-medium](https://github.com/Manishearth/rust-clippy/labels/E-medium) are generally
+pretty easy too, though it's recommended you work on an E-easy issue first.
+
+[Llogiq's blog post on lints](https://llogiq.github.io/2015/06/04/workflows.html) is a nice primer
+to lint-writing, though it does get into advanced stuff. Most lints consist of an implementation of
+`LintPass` with one or more of its default methods overridden. See the existing lints for examples
+of this.
+
+T-AST issues will generally need you to match against a predefined syntax structure. To figure out
+how this syntax structure is encoded in the AST, it is recommended to run `rustc -Z ast-json` on an
+example of the structure and compare with the
+[nodes in the AST docs](http://manishearth.github.io/rust-internals-docs/syntax/ast/). Usually
+the lint will end up to be a nested series of matches and ifs,
+[like so](https://github.com/Manishearth/rust-clippy/blob/de5ccdfab68a5e37689f3c950ed1532ba9d652a0/src/misc.rs#L34)
+
+T-middle issues can be more involved and require verifying types. The
+[`middle::ty`](http://manishearth.github.io/rust-internals-docs/rustc/middle/ty) module contains a
+lot of methods that are useful, though one of the most useful would be `expr_ty` (gives the type of
+an AST expression). `match_def_path()` in Clippy's `utils` module can also be useful.
+
+## Contributions
+
+Clippy welcomes contributions from everyone.
+
+Contributions to Clippy should be made in the form of GitHub pull requests. Each pull request will
+be reviewed by a core contributor (someone with permission to land patches) and either landed in the
+main tree or given feedback for changes that would be required.
+
+## Conduct
+
+We follow the [Rust Code of Conduct](http://www.rust-lang.org/conduct.html).
+
+
+<! -- adapted from https://github.com/servo/servo/blob/master/CONTRIBUTING.md -->