rustc: Add some more checks to the stability lint

This catches uses of unstable traits in

```
trait Foo: UnstableTrait { }
```

and

```
impl UnstableTrait for Foo { }
```

src/librustc/lint/builtin.rs

@@ -1581,6 +1581,36 @@ impl Stability {
 
         cx.span_lint(lint, span, msg.as_slice());
     }
+
+    fn is_internal(&self, cx: &Context, span: Span) -> bool {
+        // first, check if the given expression was generated by a macro or not
+        // we need to go back the expn_info tree to check only the arguments
+        // of the initial macro call, not the nested ones.
+        let mut expnid = span.expn_id;
+        let mut is_internal = false;
+        while cx.tcx.sess.codemap().with_expn_info(expnid, |expninfo| {
+            match expninfo {
+                Some(ref info) => {
+                    // save the parent expn_id for next loop iteration
+                    expnid = info.call_site.expn_id;
+                    if info.callee.span.is_none() {
+                        // it's a compiler built-in, we *really* don't want to mess with it
+                        // so we skip it, unless it was called by a regular macro, in which case
+                        // we will handle the caller macro next turn
+                        is_internal = true;
+                        true // continue looping
+                    } else {
+                        // was this expression from the current macro arguments ?
+                        is_internal = !( span.lo > info.call_site.lo &&
+                                         span.hi < info.call_site.hi );
+                        true // continue looping
+                    }
+                },
+                _ => false // stop looping
+            }
+        }) { /* empty while loop body */ }
+        return is_internal;
+    }
 }
 
 impl LintPass for Stability {
@@ -1605,33 +1635,7 @@ impl LintPass for Stability {
     }
 
     fn check_expr(&mut self, cx: &Context, e: &ast::Expr) {
-        // first, check if the given expression was generated by a macro or not
-        // we need to go back the expn_info tree to check only the arguments
-        // of the initial macro call, not the nested ones.
-        let mut expnid = e.span.expn_id;
-        let mut is_internal = false;
-        while cx.tcx.sess.codemap().with_expn_info(expnid, |expninfo| {
-            match expninfo {
-                Some(ref info) => {
-                    // save the parent expn_id for next loop iteration
-                    expnid = info.call_site.expn_id;
-                    if info.callee.span.is_none() {
-                        // it's a compiler built-in, we *really* don't want to mess with it
-                        // so we skip it, unless it was called by a regular macro, in which case
-                        // we will handle the caller macro next turn
-                        is_internal = true;
-                        true // continue looping
-                    } else {
-                        // was this expression from the current macro arguments ?
-                        is_internal = !( e.span.lo > info.call_site.lo &&
-                                         e.span.hi < info.call_site.hi );
-                        true // continue looping
-                    }
-                },
-                _ => false // stop looping
-            }
-        }) { /* empty while loop body */ }
-        if is_internal { return; }
+        if self.is_internal(cx, e.span) { return; }
 
         let mut span = e.span;
 
@@ -1677,6 +1681,29 @@ impl LintPass for Stability {
         };
         self.lint(cx, id, span);
     }
+
+    fn check_item(&mut self, cx: &Context, item: &ast::Item) {
+        if self.is_internal(cx, item.span) { return }
+
+        match item.node {
+            ast::ItemTrait(_, _, ref supertraits, _) => {
+                for t in supertraits.iter() {
+                    match *t {
+                        ast::TraitTyParamBound(ref t) => {
+                            let id = ty::trait_ref_to_def_id(cx.tcx, t);
+                            self.lint(cx, id, t.path.span);
+                        }
+                        _ => (/* pass */)
+                    }
+                }
+            }
+            ast::ItemImpl(_, Some(ref t), _, _) => {
+                let id = ty::trait_ref_to_def_id(cx.tcx, t);
+                self.lint(cx, id, t.path.span);
+            }
+            _ => (/* pass */)
+        }
+    }
 }
 
 declare_lint!(pub UNUSED_IMPORTS, Warn,

src/test/auxiliary/lint_stability.rs

@@ -118,6 +118,9 @@ pub trait Trait {
 
 impl Trait for MethodTester {}
 
+#[experimental]
+pub trait ExperimentalTrait {}
+
 #[deprecated]
 pub struct DeprecatedStruct { pub i: int }
 #[experimental]

src/test/compile-fail/lint-stability.rs

@@ -141,6 +141,12 @@ mod cross_crate {
         foo.trait_unmarked(); //~ ERROR use of unmarked item
         foo.trait_stable();
     }
+
+    struct S;
+
+    impl ExperimentalTrait for S { } //~ ERROR use of experimental item
+
+    trait LocalTrait : ExperimentalTrait { } //~ ERROR use of experimental item
 }
 
 mod inheritance {
@@ -444,6 +450,15 @@ mod this_crate {
         foo.trait_unmarked();
         foo.trait_stable();
     }
+
+    #[deprecated]
+    pub trait DeprecatedTrait {}
+
+    struct S;
+
+    impl DeprecatedTrait for S { } //~ ERROR use of deprecated item
+
+    trait LocalTrait : DeprecatedTrait { } //~ ERROR use of deprecated item
 }
 
 fn main() {}