parser: unify item list parsing.

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

Author: Centril

src/librustc_ast_pretty/pprust.rs

@@ -1269,6 +1269,7 @@ impl<'a> State<'a> {
                 self.print_where_clause(&generics.where_clause);
                 self.s.word(" ");
                 self.bopen();
+                self.print_inner_attributes(&item.attrs);
                 for trait_item in trait_items {
                     self.print_assoc_item(trait_item);
                 }

src/librustc_expand/expand.rs

@@ -867,7 +867,7 @@ pub fn parse_ast_fragment<'a>(
         AstFragmentKind::ForeignItems => {
             let mut items = SmallVec::new();
             while this.token != token::Eof {
-                items.push(this.parse_foreign_item()?);
+                items.push(this.parse_foreign_item(&mut false)?);
             }
             AstFragment::ForeignItems(items)
         }

src/librustc_parse/parser/item.rs

@@ -515,7 +515,7 @@ impl<'a> Parser<'a> {
 
         generics.where_clause = self.parse_where_clause()?;
 
-        let (impl_items, attrs) = self.parse_impl_body()?;
+        let (impl_items, attrs) = self.parse_item_list(|p, at_end| p.parse_impl_item(at_end))?;
 
         let item_kind = match ty_second {
             Some(ty_second) => {
@@ -571,15 +571,21 @@ impl<'a> Parser<'a> {
         Ok((Ident::invalid(), item_kind, Some(attrs)))
     }
 
-    fn parse_impl_body(&mut self) -> PResult<'a, (Vec<P<AssocItem>>, Vec<Attribute>)> {
+    fn parse_item_list<T>(
+        &mut self,
+        mut parse_item: impl FnMut(&mut Parser<'a>, &mut bool) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, Vec<Attribute>)> {
         self.expect(&token::OpenDelim(token::Brace))?;
         let attrs = self.parse_inner_attributes()?;
 
-        let mut impl_items = Vec::new();
+        let mut items = Vec::new();
         while !self.eat(&token::CloseDelim(token::Brace)) {
+            if self.recover_doc_comment_before_brace() {
+                continue;
+            }
             let mut at_end = false;
-            match self.parse_impl_item(&mut at_end) {
-                Ok(impl_item) => impl_items.push(impl_item),
+            match parse_item(self, &mut at_end) {
+                Ok(item) => items.push(item),
                 Err(mut err) => {
                     err.emit();
                     if !at_end {
@@ -589,7 +595,30 @@ impl<'a> Parser<'a> {
                 }
             }
         }
-        Ok((impl_items, attrs))
+        Ok((items, attrs))
+    }
+
+    /// Recover on a doc comment before `}`.
+    fn recover_doc_comment_before_brace(&mut self) -> bool {
+        if let token::DocComment(_) = self.token.kind {
+            if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
+                struct_span_err!(
+                    self.diagnostic(),
+                    self.token.span,
+                    E0584,
+                    "found a documentation comment that doesn't document anything",
+                )
+                .span_label(self.token.span, "this doc comment doesn't document anything")
+                .help(
+                    "doc comments must come before what they document, maybe a \
+                    comment was intended with `//`?",
+                )
+                .emit();
+                self.bump();
+                return true;
+            }
+        }
+        false
     }
 
     /// Parses defaultness (i.e., `default` or nothing).
@@ -660,39 +689,8 @@ impl<'a> Parser<'a> {
         } else {
             // It's a normal trait.
             tps.where_clause = self.parse_where_clause()?;
-            self.expect(&token::OpenDelim(token::Brace))?;
-            let mut trait_items = vec![];
-            while !self.eat(&token::CloseDelim(token::Brace)) {
-                if let token::DocComment(_) = self.token.kind {
-                    if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
-                        struct_span_err!(
-                            self.diagnostic(),
-                            self.token.span,
-                            E0584,
-                            "found a documentation comment that doesn't document anything",
-                        )
-                        .help(
-                            "doc comments must come before what they document, maybe a \
-                            comment was intended with `//`?",
-                        )
-                        .emit();
-                        self.bump();
-                        continue;
-                    }
-                }
-                let mut at_end = false;
-                match self.parse_trait_item(&mut at_end) {
-                    Ok(item) => trait_items.push(item),
-                    Err(mut e) => {
-                        e.emit();
-                        if !at_end {
-                            self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
-                            break;
-                        }
-                    }
-                }
-            }
-            Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
+            let (items, attrs) = self.parse_item_list(|p, at_end| p.parse_trait_item(at_end))?;
+            Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, items), Some(attrs)))
         }
     }
 
@@ -942,26 +940,18 @@ impl<'a> Parser<'a> {
         &mut self,
         lo: Span,
         abi: Option<StrLit>,
-        visibility: Visibility,
+        vis: Visibility,
         mut attrs: Vec<Attribute>,
     ) -> PResult<'a, P<Item>> {
-        self.expect(&token::OpenDelim(token::Brace))?;
-
-        attrs.extend(self.parse_inner_attributes()?);
-
-        let mut foreign_items = vec![];
-        while !self.eat(&token::CloseDelim(token::Brace)) {
-            foreign_items.push(self.parse_foreign_item()?);
-        }
-
-        let prev_span = self.prev_span;
-        let m = ast::ForeignMod { abi, items: foreign_items };
-        let invalid = Ident::invalid();
-        Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
+        let (items, iattrs) = self.parse_item_list(|p, at_end| p.parse_foreign_item(at_end))?;
+        attrs.extend(iattrs);
+        let span = lo.to(self.prev_span);
+        let m = ast::ForeignMod { abi, items };
+        Ok(self.mk_item(span, Ident::invalid(), ItemKind::ForeignMod(m), vis, attrs))
     }
 
     /// Parses a foreign item (one in an `extern { ... }` block).
-    pub fn parse_foreign_item(&mut self) -> PResult<'a, P<ForeignItem>> {
+    pub fn parse_foreign_item(&mut self, at_end: &mut bool) -> PResult<'a, P<ForeignItem>> {
         maybe_whole!(self, NtForeignItem, |ni| ni);
 
         let mut attrs = self.parse_outer_attributes()?;
@@ -973,7 +963,7 @@ impl<'a> Parser<'a> {
             self.parse_item_foreign_type()?
         } else if self.check_fn_front_matter() {
             // FOREIGN FUNCTION ITEM
-            let (ident, sig, generics, body) = self.parse_fn(&mut false, &mut attrs, |_| true)?;
+            let (ident, sig, generics, body) = self.parse_fn(at_end, &mut attrs, |_| true)?;
             (ident, ForeignItemKind::Fn(sig, generics, body))
         } else if self.is_static_global() {
             // FOREIGN STATIC ITEM
@@ -991,7 +981,7 @@ impl<'a> Parser<'a> {
                 )
                 .emit();
             self.parse_item_foreign_static()?
-        } else if let Some(mac) = self.parse_assoc_macro_invoc("extern", Some(&vis), &mut false)? {
+        } else if let Some(mac) = self.parse_assoc_macro_invoc("extern", Some(&vis), at_end)? {
             (Ident::invalid(), ForeignItemKind::Macro(mac))
         } else {
             if !attrs.is_empty() {

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();
 }