move cstring tests

Author: Cameron Steffen

tests/ui/cstring.rs

@@ -0,0 +1,8 @@
+fn main() {}
+
+#[allow(result_unwrap_used)]
+fn temporary_cstring() {
+    use std::ffi::CString;
+
+    CString::new("foo").unwrap().as_ptr();
+}

tests/ui/cstring.stderr

@@ -0,0 +1,22 @@
+error: function is never used: `temporary_cstring`
+ --> $DIR/cstring.rs:4:1
+  |
+4 | fn temporary_cstring() {
+  | ^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: `-D dead-code` implied by `-D warnings`
+
+error: you are getting the inner pointer of a temporary `CString`
+ --> $DIR/cstring.rs:7:5
+  |
+7 |     CString::new("foo").unwrap().as_ptr();
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: `-D temporary-cstring-as-ptr` implied by `-D warnings`
+  = note: that pointer will be invalid outside this expression
+help: assign the `CString` to a variable to extend its lifetime
+ --> $DIR/cstring.rs:7:5
+  |
+7 |     CString::new("foo").unwrap().as_ptr();
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+

tests/ui/methods.rs

@@ -453,10 +453,3 @@ fn str_extend_chars() {
     let f = HasChars;
     s.extend(f.chars());
 }
-
-#[allow(result_unwrap_used)]
-fn temporary_cstring() {
-    use std::ffi::CString;
-
-    CString::new("foo").unwrap().as_ptr();
-}

tests/ui/methods.stderr

@@ -567,17 +567,3 @@ error: calling `.extend(_.chars())`
 447 |     s.extend(def.chars());
     |     ^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.push_str(&def)`
 
-error: you are getting the inner pointer of a temporary `CString`
-   --> $DIR/methods.rs:461:5
-    |
-461 |     CString::new("foo").unwrap().as_ptr();
-    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-    |
-    = note: `-D temporary-cstring-as-ptr` implied by `-D warnings`
-    = note: that pointer will be invalid outside this expression
-help: assign the `CString` to a variable to extend its lifetime
-   --> $DIR/methods.rs:461:5
-    |
-461 |     CString::new("foo").unwrap().as_ptr();
-    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-