Auto merge of #4362 - lzutao:expect-on-cstring_as_ptr, r=flip1995

Fix lint_cstring_as_ptr for expect

Closes #4312
changelog: none

clippy_lints/src/methods/mod.rs

@@ -937,7 +937,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
             ["is_some", "position"] => lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0]),
             ["is_some", "rposition"] => lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0]),
             ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
-            ["as_ptr", "unwrap"] => lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0]),
+            ["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
+                lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
+            },
             ["nth", "iter"] => lint_iter_nth(cx, expr, arg_lists[1], false),
             ["nth", "iter_mut"] => lint_iter_nth(cx, expr, arg_lists[1], true),
             ["next", "skip"] => lint_iter_skip_next(cx, expr),

tests/ui/cstring.rs

@@ -5,4 +5,5 @@ fn temporary_cstring() {
     use std::ffi::CString;
 
     CString::new("foo").unwrap().as_ptr();
+    CString::new("foo").expect("dummy").as_ptr();
 }

tests/ui/cstring.stderr

@@ -12,5 +12,18 @@ help: assign the `CString` to a variable to extend its lifetime
 LL |     CString::new("foo").unwrap().as_ptr();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: you are getting the inner pointer of a temporary `CString`
+  --> $DIR/cstring.rs:8:5
+   |
+LL |     CString::new("foo").expect("dummy").as_ptr();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: that pointer will be invalid outside this expression
+help: assign the `CString` to a variable to extend its lifetime
+  --> $DIR/cstring.rs:8:5
+   |
+LL |     CString::new("foo").expect("dummy").as_ptr();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors