Enable extra warnings required by rust-lang/rust

crates/base-db/src/lib.rs

@@ -1,4 +1,7 @@
 //! base_db defines basic database traits. The concrete DB is defined by ide.
+
+#![warn(rust_2018_idioms, unused_lifetimes, semicolon_in_expressions_from_macros)]
+
 mod input;
 mod change;
 pub mod fixture;