Remove path_span argument to the visit_path_segment methods.

The `visit_path_segment` method of both the AST and HIR visitors has a
`path_span` argument that isn't necessary. This commit removes it.

There are two very small and inconsequential functional changes.

- One call to `NodeCollector::insert` now is passed a path segment
  identifier span instead of a full path span. This span is only used in
a panic message printed in the case of an internal compiler bug.

- Likewise, one call to `LifetimeCollectVisitor::record_elided_anchor`
  now uses a path segment identifier span instead of a full path span.
  This span is used to make some `'_` lifetimes.

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -223,11 +223,9 @@ impl<'a> AstValidator<'a> {
                 for (i, segment) in path.segments.iter().enumerate() {
                     // Allow `impl Trait` iff we're on the final path segment
                     if i == path.segments.len() - 1 {
-                        self.visit_path_segment(path.span, segment);
+                        self.visit_path_segment(segment);
                     } else {
-                        self.with_banned_impl_trait(|this| {
-                            this.visit_path_segment(path.span, segment)
-                        });
+                        self.with_banned_impl_trait(|this| this.visit_path_segment(segment));
                     }
                 }
             }
@@ -1293,7 +1291,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 
     // Mirrors `visit::walk_generic_args`, but tracks relevant state.
-    fn visit_generic_args(&mut self, _: Span, generic_args: &'a GenericArgs) {
+    fn visit_generic_args(&mut self, generic_args: &'a GenericArgs) {
         match *generic_args {
             GenericArgs::AngleBracketed(ref data) => {
                 self.check_generic_args_before_constraints(data);

compiler/rustc_ast_passes/src/node_count.rs

@@ -115,9 +115,9 @@ impl<'ast> Visitor<'ast> for NodeCounter {
         self.count += 1;
         walk_use_tree(self, use_tree, id)
     }
-    fn visit_generic_args(&mut self, path_span: Span, generic_args: &GenericArgs) {
+    fn visit_generic_args(&mut self, generic_args: &GenericArgs) {
         self.count += 1;
-        walk_generic_args(self, path_span, generic_args)
+        walk_generic_args(self, generic_args)
     }
     fn visit_assoc_constraint(&mut self, constraint: &AssocConstraint) {
         self.count += 1;