parser: unify item list parsing.

as a consequence, `trait X { #![attr] }` becomes legal.

src/test/pretty/trait-inner-attr.rs

@@ -0,0 +1,7 @@
+// pp-exact
+
+trait Foo {
+    #![allow(bar)]
+}
+
+fn main() { }

src/test/ui/parser/attrs-after-extern-mod.rs

@@ -1,13 +1,7 @@
-// Constants (static variables) can be used to match in patterns, but mutable
-// statics cannot. This ensures that there's some form of error if this is
-// attempted.
+// Make sure there's an error when given `extern { ... #[attr] }`.
 
-extern crate libc;
+fn main() {}
 
 extern {
-    static mut rust_dbg_static_mut: libc::c_int;
-    pub fn rust_dbg_static_mut_check_four();
     #[cfg(stage37)] //~ ERROR expected item after attributes
 }
-
-pub fn main() {}

src/test/ui/parser/attrs-after-extern-mod.stderr

@@ -1,5 +1,5 @@
 error: expected item after attributes
-  --> $DIR/attrs-after-extern-mod.rs:10:19
+  --> $DIR/attrs-after-extern-mod.rs:6:19
    |
 LL |     #[cfg(stage37)]
    |                   ^

src/test/ui/parser/doc-before-extern-rbrace.rs

@@ -1,4 +1,6 @@
+fn main() {}
+
 extern {
     /// hi
-    //~^ ERROR expected item after doc comment
+    //~^ ERROR found a documentation comment that doesn't document anything
 }

src/test/ui/parser/doc-before-extern-rbrace.stderr

@@ -1,8 +1,11 @@
-error: expected item after doc comment
-  --> $DIR/doc-before-extern-rbrace.rs:2:5
+error[E0584]: found a documentation comment that doesn't document anything
+  --> $DIR/doc-before-extern-rbrace.rs:4:5
    |
 LL |     /// hi
    |     ^^^^^^ this doc comment doesn't document anything
+   |
+   = help: doc comments must come before what they document, maybe a comment was intended with `//`?
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0584`.

src/test/ui/parser/doc-inside-trait-item.stderr

@@ -2,7 +2,7 @@ error[E0584]: found a documentation comment that doesn't document anything
   --> $DIR/doc-inside-trait-item.rs:3:5
    |
 LL |     /// empty doc
-   |     ^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^ this doc comment doesn't document anything
    |
    = help: doc comments must come before what they document, maybe a comment was intended with `//`?
 

src/test/ui/parser/duplicate-visibility.rs

@@ -1,4 +1,7 @@
 // error-pattern: expected one of `(`, `async`, `const`, `extern`, `fn`
+
+fn main() {}
+
 extern {
     pub pub fn foo();
 }

src/test/ui/parser/duplicate-visibility.stderr

@@ -1,5 +1,5 @@
 error: expected one of `(`, `async`, `const`, `extern`, `fn`, `static`, `type`, or `unsafe`, found keyword `pub`
-  --> $DIR/duplicate-visibility.rs:3:9
+  --> $DIR/duplicate-visibility.rs:6:9
    |
 LL |     pub pub fn foo();
    |         ^^^ expected one of 8 possible tokens

src/test/ui/parser/inner-attr-in-trait-def.rs

@@ -0,0 +1,9 @@
+// check-pass
+
+#![deny(non_camel_case_types)]
+
+fn main() {}
+
+trait foo_bar {
+    #![allow(non_camel_case_types)]
+}