Rollup merge of rust-lang#33854 - petrochenkov:prefvis, r=eddyb

Apply visit_path to import prefixes by default

Overriding `visit_path` is not enough to visit all paths, some import prefixes are not visited and `visit_path_list_item` need to be overridden as well. This PR removes this catch, it should be less error prone this way. Also, the prefix is visited once now, not repeatedly for each path list item.

r? @eddyb

Author: Manishearth

src/librustc/hir/intravisit.rs

@@ -280,12 +280,9 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
                     visitor.visit_path(path, item.id);
                 }
                 ViewPathList(ref prefix, ref list) => {
-                    if !list.is_empty() {
-                        for item in list {
-                            visitor.visit_path_list_item(prefix, item)
-                        }
-                    } else {
-                        visitor.visit_path(prefix, item.id);
+                    visitor.visit_path(prefix, item.id);
+                    for item in list {
+                        visitor.visit_path_list_item(prefix, item)
                     }
                 }
             }
@@ -419,12 +416,8 @@ pub fn walk_path<'v, V: Visitor<'v>>(visitor: &mut V, path: &'v Path) {
 }
 
 pub fn walk_path_list_item<'v, V: Visitor<'v>>(visitor: &mut V,
-                                               prefix: &'v Path,
+                                               _prefix: &'v Path,
                                                item: &'v PathListItem) {
-    for segment in &prefix.segments {
-        visitor.visit_path_segment(prefix.span, segment);
-    }
-
     walk_opt_name(visitor, item.span, item.node.name());
     walk_opt_name(visitor, item.span, item.node.rename());
 }

src/librustc_incremental/calculate_svh.rs

@@ -401,10 +401,6 @@ mod svh_visitor {
             SawPath.hash(self.st); visit::walk_path(self, path)
         }
 
-        fn visit_path_list_item(&mut self, prefix: &'a Path, item: &'a PathListItem) {
-            SawPath.hash(self.st); visit::walk_path_list_item(self, prefix, item)
-        }
-
         fn visit_block(&mut self, b: &'a Block) {
             SawBlock.hash(self.st); visit::walk_block(self, b)
         }

src/libsyntax/visit.rs

@@ -233,12 +233,9 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
                     visitor.visit_path(path, item.id);
                 }
                 ViewPathList(ref prefix, ref list) => {
-                    if !list.is_empty() {
-                        for item in list {
-                            visitor.visit_path_list_item(prefix, item)
-                        }
-                    } else {
-                        visitor.visit_path(prefix, item.id);
+                    visitor.visit_path(prefix, item.id);
+                    for item in list {
+                        visitor.visit_path_list_item(prefix, item)
                     }
                 }
             }
@@ -368,12 +365,8 @@ pub fn walk_path<'v, V: Visitor<'v>>(visitor: &mut V, path: &'v Path) {
     }
 }
 
-pub fn walk_path_list_item<'v, V: Visitor<'v>>(visitor: &mut V, prefix: &'v Path,
+pub fn walk_path_list_item<'v, V: Visitor<'v>>(visitor: &mut V, _prefix: &'v Path,
                                                item: &'v PathListItem) {
-    for segment in &prefix.segments {
-        visitor.visit_path_segment(prefix.span, segment);
-    }
-
     walk_opt_ident(visitor, item.span, item.node.name());
     walk_opt_ident(visitor, item.span, item.node.rename());
 }