`needless_pass_by_value`: reference the innermost `Option` content

If types such as `Option<Option<String>>` are not used by value, then
`Option<Option<&String>>` will be suggested, instead of
`Option<&Option<String>>`.

2 files changed, 55 insertions, 2 deletions

diff --git a/tests/ui/needless_pass_by_value.rs b/tests/ui/needless_pass_by_value.rs
index adea373fd55..aef7fff2870 100644
--- a/tests/ui/needless_pass_by_value.rs
+++ b/tests/ui/needless_pass_by_value.rs
@@ -196,6 +196,35 @@ fn option_inner_ref(x: Option<String>) {
     assert!(x.is_some());
 }
 
+mod non_standard {
+    #[derive(Debug)]
+    pub struct Option<T>(T);
+}
+
+fn non_standard_option(x: non_standard::Option<String>) {
+    //~^ needless_pass_by_value
+    dbg!(&x);
+}
+
+fn option_by_name(x: Option<std::option::Option<core::option::Option<non_standard::Option<String>>>>) {
+    //~^ needless_pass_by_value
+    dbg!(&x);
+}
+
+type OptStr = Option<String>;
+
+fn non_option(x: OptStr) {
+    //~^ needless_pass_by_value
+    dbg!(&x);
+}
+
+type Opt<T> = Option<T>;
+
+fn non_option_either(x: Opt<String>) {
+    //~^ needless_pass_by_value
+    dbg!(&x);
+}
+
 fn main() {
     // This should not cause an ICE either
     // https://github.com/rust-lang/rust-clippy/issues/3144
diff --git a/tests/ui/needless_pass_by_value.stderr b/tests/ui/needless_pass_by_value.stderr
index 987bfc4affc..fc67e06ca42 100644
--- a/tests/ui/needless_pass_by_value.stderr
+++ b/tests/ui/needless_pass_by_value.stderr
@@ -29,7 +29,7 @@ error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:58:18
    |
 LL | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
-   |                  ^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<&Option<String>>`
+   |                  ^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<Option<&String>>`
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:73:24
@@ -185,5 +185,29 @@ error: this argument is passed by value, but not consumed in the function body
 LL | fn option_inner_ref(x: Option<String>) {
    |                        ^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<&String>`
 
-error: aborting due to 23 previous errors
+error: this argument is passed by value, but not consumed in the function body
+  --> tests/ui/needless_pass_by_value.rs:204:27
+   |
+LL | fn non_standard_option(x: non_standard::Option<String>) {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&non_standard::Option<String>`
+
+error: this argument is passed by value, but not consumed in the function body
+  --> tests/ui/needless_pass_by_value.rs:209:22
+   |
+LL | fn option_by_name(x: Option<std::option::Option<core::option::Option<non_standard::Option<String>>>>) {
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<std::option::Option<core::option::Option<&non_standard::Option<String>>>>`
+
+error: this argument is passed by value, but not consumed in the function body
+  --> tests/ui/needless_pass_by_value.rs:216:18
+   |
+LL | fn non_option(x: OptStr) {
+   |                  ^^^^^^ help: consider taking a reference instead: `&OptStr`
+
+error: this argument is passed by value, but not consumed in the function body
+  --> tests/ui/needless_pass_by_value.rs:223:25
+   |
+LL | fn non_option_either(x: Opt<String>) {
+   |                         ^^^^^^^^^^^ help: consider taking a reference instead: `&Opt<String>`
+
+error: aborting due to 27 previous errors