Merge pull request #2079 from rust-lang-nursery/ptr_arg-vs-capacity

avoid linting `ptr_arg` if `.capacity()` is called.

tests/ui/ptr_arg.rs

@@ -55,3 +55,15 @@ fn str_cloned(x: &String) -> String {
              .clone();
     x.clone()
 }
+
+fn false_positive_capacity(x: &Vec<u8>, y: &String) {
+    let a = x.capacity();
+    let b = y.clone();
+    let c = y.as_str();
+}
+
+fn false_positive_capacity_too(x: &String) -> String {
+    if x.capacity() > 1024 { panic!("Too large!"); }
+    x.clone()
+}
+

tests/ui/ptr_arg.stderr

@@ -28,11 +28,11 @@ help: change this to
    |
 40 | fn cloned(x: &[u8]) -> Vec<u8> {
    |              ^^^^^
-help: change the `.clone()` to
+help: change `x.clone()` to
    |
 41 |     let e = x.to_owned();
    |             ^^^^^^^^^^^^
-help: change the `.clone()` to
+help: change `x.clone()` to
    |
 46 |     x.to_owned()
    |     ^^^^^^^^^^^^
@@ -47,18 +47,37 @@ help: change this to
    |
 49 | fn str_cloned(x: &str) -> String {
    |                  ^^^^
-help: change the `.clone` to 
+help: change `x.clone()` to
    |
 50 |     let a = x.to_string();
    |             ^^^^^^^^^^^^^
-help: change the `.clone` to 
+help: change `x.clone()` to
    |
 51 |     let b = x.to_string();
    |             ^^^^^^^^^^^^^
-help: change the `.clone` to 
+help: change `x.clone()` to
    |
 56 |     x.to_string()
    |     ^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: writing `&String` instead of `&str` involves a new object where a slice will do.
+  --> $DIR/ptr_arg.rs:59:44
+   |
+59 | fn false_positive_capacity(x: &Vec<u8>, y: &String) {
+   |                                            ^^^^^^^
+   |
+help: change this to
+   |
+59 | fn false_positive_capacity(x: &Vec<u8>, y: &str) {
+   |                                            ^^^^
+help: change `y.clone()` to
+   |
+61 |     let b = y.to_string();
+   |             ^^^^^^^^^^^^^
+help: change `y.as_str()` to
+   |
+62 |     let c = y;
+   |             ^
+
+error: aborting due to 6 previous errors