Add E0537 error explanation

diff --git a/src/libsyntax/diagnostic_list.rs b/src/libsyntax/diagnostic_list.rs
index dfec5a43cdeed62257bbb64c18b158327cc48408..d19fd300886cd714d4d2a97a5d3c2d6e742ee6d2 100644 (file)
--- a/src/libsyntax/diagnostic_list.rs
+++ b/src/libsyntax/diagnostic_list.rs
@@ -128,10 +128,40 @@ pub fn main() {}
 https://doc.rust-lang.org/reference.html#conditional-compilation
 "##,
 
+E0537: r##"
+A unknown predicate was used inside the cfg attribute.
+
+Erroneous code example:
+
+```compile_fail,E0537
+#[cfg(unknown())] // error: invalid predicate `unknown`
+pub fn something() {}
+
+pub fn main() {}
+```
+
+There are only three predicates for the cfg attribute:
+
+ * any
+ * all
+ * not
+
+Example:
+
+```
+#[cfg(not(target_os = "linux"))] // ok!
+pub fn something() {}
+
+pub fn main() {}
+```
+
+For more information about the cfg attribute, take a look here:
+https://doc.rust-lang.org/reference.html#conditional-compilation
+"##,
+
 }
 
 register_diagnostics! {
-    E0537, // invalid predicate
     E0538, // multiple [same] items
     E0539, // incorrect meta item
     E0540, // multiple rustc_deprecated attributes