Remove support for -Zast-json and -Zast-json-noexpand

compiler/rustc_ast/src/ast.rs

@@ -41,9 +41,6 @@ use std::convert::TryFrom;
 use std::fmt;
 use std::mem;
 
-#[cfg(test)]
-mod tests;
-
 /// A "Label" is an identifier of some point in sources,
 /// e.g. in the following code:
 ///

compiler/rustc_ast/src/ast/tests.rs

@@ -1,11 +0,0 @@
-use super::*;
-
-// Are ASTs encodable?
-#[test]
-fn check_asts_encodable() {
-    fn assert_encodable<
-        T: for<'a> rustc_serialize::Encodable<rustc_serialize::json::Encoder<'a>>,
-    >() {
-    }
-    assert_encodable::<Crate>();
-}