Ignore doc_markdown pedantic clippy lint in test

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:3:40
      |
    3 | //! 1. Parse the file using syn into a syn::File.
      |                                        ^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
      = note: `-W clippy::doc-markdown` implied by `-W clippy::pedantic`
      = help: to override `-W clippy::pedantic` add `#[allow(clippy::doc_markdown)]`
    help: try
      |
    3 | //! 1. Parse the file using syn into a `syn::File`.
      |                                        ~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:4:22
      |
    4 | //! 2. Extract every syn::Expr from the file.
      |                      ^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    4 | //! 2. Extract every `syn::Expr` from the file.
      |                      ~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:6:36
      |
    6 | //! 4. Parse the source code using librustc_parse into a rustc_ast::Expr.
      |                                    ^^^^^^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    6 | //! 4. Parse the source code using `librustc_parse` into a rustc_ast::Expr.
      |                                    ~~~~~~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:6:58
      |
    6 | //! 4. Parse the source code using librustc_parse into a rustc_ast::Expr.
      |                                                          ^^^^^^^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    6 | //! 4. Parse the source code using librustc_parse into a `rustc_ast::Expr`.
      |                                                          ~~~~~~~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:7:21
      |
    7 | //! 5. For both the syn::Expr and rustc_ast::Expr, crawl the syntax tree to
      |                     ^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    7 | //! 5. For both the `syn::Expr` and rustc_ast::Expr, crawl the syntax tree to
      |                     ~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:7:35
      |
    7 | //! 5. For both the syn::Expr and rustc_ast::Expr, crawl the syntax tree to
      |                                   ^^^^^^^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    7 | //! 5. For both the syn::Expr and `rustc_ast::Expr`, crawl the syntax tree to
      |                                   ~~~~~~~~~~~~~~~~~

    warning: item in documentation is missing backticks
     --> tests/test_precedence.rs:9:42
      |
    9 | //! 6. Serialize the fully parenthesized syn::Expr to a string of source code.
      |                                          ^^^^^^^^^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
      |
    9 | //! 6. Serialize the fully parenthesized `syn::Expr` to a string of source code.
      |                                          ~~~~~~~~~~~

    warning: item in documentation is missing backticks
      --> tests/test_precedence.rs:10:56
       |
    10 | //! 7. Parse the fully parenthesized source code using librustc_parse.
       |                                                        ^^^^^^^^^^^^^^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
       |
    10 | //! 7. Parse the fully parenthesized source code using `librustc_parse`.
       |                                                        ~~~~~~~~~~~~~~~~

    warning: item in documentation is missing backticks
      --> tests/test_precedence.rs:11:20
       |
    11 | //! 8. Compare the rustc_ast::Expr resulting from parenthesizing using rustc
       |                    ^^^^^^^^^^^^^^^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
    help: try
       |
    11 | //! 8. Compare the `rustc_ast::Expr` resulting from parenthesizing using rustc
       |                    ~~~~~~~~~~~~~~~~~

tests/test_precedence.rs

@@ -18,6 +18,7 @@
 #![recursion_limit = "1024"]
 #![feature(rustc_private)]
 #![allow(
+    clippy::doc_markdown,
     clippy::explicit_deref_methods,
     clippy::let_underscore_untyped,
     clippy::manual_assert,