Auto merge of #10027 - smoelius:fix-10021, r=dswij

Fix 10021

This PR proposes a fix for #10021.

The problem is similar to the one that `@mikerite` described in #9505. The compiler is generating an empty substitution for a call, even though the type of `Self` seems to be needed for a predicate. In `@mikerite's` case, the call was to [`IntoFuture::into_future`](https://doc.rust-lang.org/std/future/trait.IntoFuture.html#tymethod.into_future). In this case, the call is to [`Try::branch`](https://doc.rust-lang.org/std/ops/trait.Try.html#tymethod.branch).

The proposed fix is to verify that the parameter whose type is changing has an index within the substitution. The strikes me as a reasonable approach, since if the check were to fail, the following code would be a no-op:

4c123a06ba/clippy_lints/src/methods/unnecessary_to_owned.rs (L420-L428)

Like `@mikerite's` original solution, this solution turns ICEs into false negatives.

changelog: fix `unnecessary_to_owned` false positive involving `Try::branch`

tests/ui/unnecessary_to_owned.fixed

@@ -454,3 +454,23 @@ mod issue_9771b {
         Key(v.to_vec())
     }
 }
+
+// This is a watered down version of the code in: https://github.com/oxigraph/rio
+// The ICE is triggered by the call to `to_owned` on this line:
+// https://github.com/oxigraph/rio/blob/66635b9ff8e5423e58932353fa40d6e64e4820f7/testsuite/src/parser_evaluator.rs#L116
+mod issue_10021 {
+    #![allow(unused)]
+
+    pub struct Iri<T>(T);
+
+    impl<T: AsRef<str>> Iri<T> {
+        pub fn parse(iri: T) -> Result<Self, ()> {
+            unimplemented!()
+        }
+    }
+
+    pub fn parse_w3c_rdf_test_file(url: &str) -> Result<(), ()> {
+        let base_iri = Iri::parse(url.to_owned())?;
+        Ok(())
+    }
+}

tests/ui/unnecessary_to_owned.rs

@@ -454,3 +454,23 @@ mod issue_9771b {
         Key(v.to_vec())
     }
 }
+
+// This is a watered down version of the code in: https://github.com/oxigraph/rio
+// The ICE is triggered by the call to `to_owned` on this line:
+// https://github.com/oxigraph/rio/blob/66635b9ff8e5423e58932353fa40d6e64e4820f7/testsuite/src/parser_evaluator.rs#L116
+mod issue_10021 {
+    #![allow(unused)]
+
+    pub struct Iri<T>(T);
+
+    impl<T: AsRef<str>> Iri<T> {
+        pub fn parse(iri: T) -> Result<Self, ()> {
+            unimplemented!()
+        }
+    }
+
+    pub fn parse_w3c_rdf_test_file(url: &str) -> Result<(), ()> {
+        let base_iri = Iri::parse(url.to_owned())?;
+        Ok(())
+    }
+}