X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=doc%2Fcommon_tools_writing_lints.md;h=828bf4cbef9481526edc8840762be8421397dbe7;hb=764dd1360f1fb1540778592a36fefe71f713ca83;hp=6c8a3dc418b1517f4156a7c58a0146f4b9ca2a0a;hpb=a98e7ab8b94485be6bd03e0c6b8682ecab5b52e6;p=rust.git

diff --git a/doc/common_tools_writing_lints.md b/doc/common_tools_writing_lints.md
index 6c8a3dc418b..828bf4cbef9 100644
--- a/doc/common_tools_writing_lints.md
+++ b/doc/common_tools_writing_lints.md
@@ -26,7 +26,7 @@ Sometimes you may want to retrieve the type `Ty` of an expression `Expr`, for ex
 - does it implement a trait?
 
 This operation is performed using the [`expr_ty()`][expr_ty] method from the [`TypeckResults`][TypeckResults] struct,
-that gives you access to the underlying structure [`TyS`][TyS].
+that gives you access to the underlying structure [`Ty`][Ty].
 
 Example of use:
 ```rust
@@ -235,7 +235,11 @@ Use the following functions to deal with macros:
    assert_eq!(in_external_macro(cx.sess(), match_span), true);
    ```
 
-- `differing_macro_contexts()`: returns true if the two given spans are not from the same context
+- `span.ctxt()`: the span's context represents whether it is from expansion, and if so, what expanded it
+
+One thing `SpanContext` is useful for is to check if two spans are in the same context. For example,
+in `a == b`, `a` and `b` have the same context. In a `macro_rules!` with `a == $b`, `$b` is expanded to some
+expression with a different context from `a`.
 
    ```rust
    macro_rules! m {
@@ -252,10 +256,10 @@ Use the following functions to deal with macros:
    // These spans are not from the same context
    // x.is_some() is from inside the macro
    // x.unwrap() is from outside the macro
-   assert_eq!(differing_macro_contexts(x_is_some_span, x_unwrap_span), true);
+   assert_eq!(x_is_some_span.ctxt(), x_unwrap_span.ctxt());
    ```
 
-[TyS]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.TyS.html
+[Ty]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.Ty.html
 [TyKind]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/enum.TyKind.html
 [TypeckResults]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.TypeckResults.html
 [expr_ty]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.TypeckResults.html#method.expr_ty