Fix link reference

AndiDog · web-flow · commit 4fb67dcf8f51 · 2017-06-28T10:55:57.000+02:00
diff --git a/src/doc/unstable-book/src/language-features/compile-error.md b/src/doc/unstable-book/src/language-features/compile-error.md
@@ -2,7 +2,7 @@
 
 The tracking issue for this feature is: [#40872]
 
-[#29599]: https://github.com/rust-lang/rust/issues/40872
+[#40872]: https://github.com/rust-lang/rust/issues/40872
 
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