Add regression tests for unconditional_recursion

Author: GuillaumeGomez

tests/ui/unconditional_recursion.rs

@@ -158,6 +158,31 @@ struct S5;
 impl_partial_eq!(S5);
 //~^ ERROR: function cannot return without recursing
 
+struct S6 {
+    field: String,
+}
+
+impl PartialEq for S6 {
+    fn eq(&self, other: &Self) -> bool {
+        let mine = &self.field;
+        let theirs = &other.field;
+        mine == theirs // Should not warn!
+    }
+}
+
+struct S7<'a> {
+    field: &'a S7<'a>,
+}
+
+impl<'a> PartialEq for S7<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        let mine = &self.field;
+        let theirs = &other.field;
+        mine == theirs
+    }
+}
+
 fn main() {
     // test code goes here
 }

tests/ui/unconditional_recursion.stderr

@@ -247,5 +247,22 @@ LL | impl_partial_eq!(S5);
    | -------------------- in this macro invocation
    = note: this error originates in the macro `impl_partial_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 19 previous errors
+error: function cannot return without recursing
+  --> $DIR/unconditional_recursion.rs:178:5
+   |
+LL | /     fn eq(&self, other: &Self) -> bool {
+LL | |
+LL | |         let mine = &self.field;
+LL | |         let theirs = &other.field;
+LL | |         mine == theirs
+LL | |     }
+   | |_____^
+   |
+note: recursive call site
+  --> $DIR/unconditional_recursion.rs:182:9
+   |
+LL |         mine == theirs
+   |         ^^^^^^^^^^^^^^
+
+error: aborting due to 20 previous errors