Access future incompatibility information directly

Avoid querying LintStore when not necessary

src/librustc/lint/context.rs

@@ -203,10 +203,6 @@ impl LintStore {
         }
     }
 
-    pub fn future_incompatible(&self, id: LintId) -> Option<FutureIncompatibleInfo> {
-        id.lint.future_incompatible
-    }
-
     pub fn register_group_alias(
         &mut self,
         lint_name: &'static str,

src/librustc/lint/mod.rs

@@ -672,9 +672,8 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
     };
 
     // Check for future incompatibility lints and issue a stronger warning.
-    let lints = sess.lint_store.borrow();
     let lint_id = LintId::of(lint);
-    let future_incompatible = lints.future_incompatible(lint_id);
+    let future_incompatible = lint.future_incompatible;
 
     // If this code originates in a foreign macro, aka something that this crate
     // did not itself author, then it's likely that there's nothing this crate