fix links (#469)

Author: tshepang

src/appendix/code-index.md

@@ -17,7 +17,7 @@ Item            |  Kind    | Short description           | Chapter            |
 `NodeId` | struct | One of four types of HIR node identifiers. Being phased out | [Identifiers in the HIR] | [src/libsyntax/ast.rs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ast/struct.NodeId.html)
 `P` | struct | An owned immutable smart pointer. By contrast, `&T` is not owned, and `Box<T>` is not immutable. | None | [src/syntax/ptr.rs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ptr/struct.P.html)
 `ParamEnv` | struct | Information about generic parameters or `Self`, useful for working with associated or generic items | [Parameter Environment] | [src/librustc/ty/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty/struct.ParamEnv.html)
-`ParseSess` | struct | This struct contains information about a parsing session | [The parser] | [src/libsyntax/parse/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/parse/struct.ParseSess.html)
+`ParseSess` | struct | This struct contains information about a parsing session | [The parser] | [src/libsyntax/parse/mod.rs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/sess/struct.ParseSess.html)
 `Query` | struct | Represents the result of query to the `Compiler` interface and allows stealing, borrowing, and returning the results of compiler passes. | [The Rustc Driver and Interface] | [src/librustc_interface/queries.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/queries/struct.Query.html)
 `Rib` | struct | Represents a single scope of names | [Name resolution] | [src/librustc_resolve/lib.rs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_resolve/late/struct.Rib.html)
 `Session` | struct | The data associated with a compilation session | [The parser], [The Rustc Driver and Interface] | [src/librustc/session/mod.html](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/session/struct.Session.html)

src/diagnostics.md

@@ -31,7 +31,7 @@ usually have names like `span_err` or `struct_span_err` or `span_warn`, etc...
 There are lots of them; they emit different types of "errors", such as
 warnings, errors, fatal errors, suggestions, etc.
 
-[parsesses]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/parse/struct.ParseSess.html
+[parsesses]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/sess/struct.ParseSess.html
 [session]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/session/struct.Session.html
 
 In general, there are two class of such methods: ones that emit an error
@@ -281,7 +281,7 @@ processed. [`Session`][sessbl] and [`ParseSess`][parsebl] both have
 system automatically takes care of handling buffered lints later.
 
 [sessbl]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/session/struct.Session.html#method.buffer_lint
-[parsebl]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/parse/struct.ParseSess.html#method.buffer_lint
+[parsebl]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/sess/struct.ParseSess.html#method.buffer_lint
 
 Thus, to define a lint that runs early in the compilation, one defines a lint
 like normal but invokes the lint with `buffer_lint`.

src/implementing_new_features.md

@@ -174,7 +174,7 @@ Once the feature is moved to `accepted.rs`, the version is changed to that night
 8. Get your PR reviewed and land it. You have now successfully
    implemented a feature in Rust!
 
-[`GatedSpans`]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/parse/struct.GatedSpans.html
+[`GatedSpans`]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/sess/struct.GatedSpans.html
 [`feature_gate::check::check_crate`]: https://doc.rust-lang.org/nightly/nightly-rustc/syntax/feature_gate/check/fn.check_crate.html
 [value the stability of Rust]: https://github.com/rust-lang/rfcs/blob/master/text/1122-language-semver.md
 [stability in code]: #stability-in-code