Fixes #890

Author: outkaj

src/attribute/crate.md

@@ -4,6 +4,11 @@ The `crate_type` attribute can be used to tell the compiler whether a crate is
 a binary or a library (and even which type of library), and the `crate_name`
 attribute can be used to set the name of the crate.
 
+However, it is important to note that the `crate_type` attribute has **no**
+effect whatsoever when using Cargo, the Rust package manager. Since Cargo is
+used for the majority of Rust projects, this means real-world uses of
+`crate-type` are relatively limited.
+
 ```rust,editable
 // This crate is a library
 #![crate_type = "lib"]