From dbb8a872a3aea4bb9510d109f5f7dbe5273446da Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Sat, 31 Oct 2015 05:18:05 +0530
Subject: [PATCH] Fix ptr-arg false positive for trait impls

Fixes #425
---
 src/ptr_arg.rs                | 10 ++++++++--
 tests/compile-fail/ptr_arg.rs | 15 +++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/ptr_arg.rs b/src/ptr_arg.rs
index 4baba7118..78a3c146c 100644
--- a/src/ptr_arg.rs
+++ b/src/ptr_arg.rs
@@ -5,6 +5,7 @@
 use rustc::lint::*;
 use rustc_front::hir::*;
 use rustc::middle::ty;
+use rustc::front::map::Node;
 
 use utils::{span_lint, match_type};
 use utils::{STRING_PATH, VEC_PATH};
@@ -34,6 +35,11 @@ impl LateLintPass for PtrArg {
 
     fn check_impl_item(&mut self, cx: &LateContext, item: &ImplItem) {
         if let &MethodImplItem(ref sig, _) = &item.node {
+            if let Some(Node::NodeItem(it)) = cx.tcx.map.find(cx.tcx.map.get_parent(item.id)) {
+                if let ItemImpl(_, _, _, Some(_), _, _) = it.node {
+                    return; // ignore trait impls
+                }
+            }
             check_fn(cx, &sig.decl);
         }
     }
@@ -47,8 +53,8 @@ impl LateLintPass for PtrArg {
 
 fn check_fn(cx: &LateContext, decl: &FnDecl) {
     for arg in &decl.inputs {
-        if let Some(pat_ty) = cx.tcx.pat_ty_opt(&arg.pat) {
-            if let ty::TyRef(_, ty::TypeAndMut { ty, mutbl: MutImmutable }) = pat_ty.sty {
+        if let Some(ty) = cx.tcx.ast_ty_to_ty_cache.borrow().get(&arg.ty.id) {
+            if let ty::TyRef(_, ty::TypeAndMut { ty, mutbl: MutImmutable }) = ty.sty {
                 if match_type(cx, ty, &VEC_PATH) {
                     span_lint(cx, PTR_ARG, arg.ty.span,
                               "writing `&Vec<_>` instead of `&[_]` involves one more reference \
diff --git a/tests/compile-fail/ptr_arg.rs b/tests/compile-fail/ptr_arg.rs
index d0615be49..e49712087 100755
--- a/tests/compile-fail/ptr_arg.rs
+++ b/tests/compile-fail/ptr_arg.rs
@@ -21,3 +21,18 @@ fn do_str_mut(x: &mut String) { // no error here
 
 fn main() {
 }
+
+trait Foo {
+    type Item;
+    fn do_vec(x: &Vec<i64>); //~ERROR writing `&Vec<_>`
+    fn do_item(x: &Self::Item);
+}
+
+struct Bar;
+
+// no error, in trait impl (#425)
+impl Foo for Bar {
+    type Item = Vec<u8>;
+    fn do_vec(x: &Vec<i64>) {}
+    fn do_item(x: &Vec<u8>) {}  
+}