Pin to older beta

https://github.com/rust-lang/rust/issues/56128

.travis.yml

@@ -9,7 +9,7 @@ env:
 
 build: &rust_build
   language: rust
-  rust: beta
+  rust: beta-2018-11-19
   script:
     - cargo gen-tests --verify
     - cargo gen-syntax --verify

crates/tools/src/lib.rs

@@ -17,7 +17,7 @@ pub type Result<T> = ::std::result::Result<T, failure::Error>;
 pub const GRAMMAR: &str = "crates/ra_syntax/src/grammar.ron";
 pub const SYNTAX_KINDS: &str = "crates/ra_syntax/src/syntax_kinds/generated.rs.tera";
 pub const AST: &str = "crates/ra_syntax/src/ast/generated.rs.tera";
-const TOOLCHAIN: &str = "beta-2018-10-30";
+const TOOLCHAIN: &str = "beta-2018-11-19";
 
 #[derive(Debug)]
 pub struct Test {