Add ui tests for unconditional_recursion lint

tests/ui/unconditional_recursion.rs

@@ -0,0 +1,128 @@
+//@no-rustfix
+
+#![warn(clippy::unconditional_recursion)]
+
+enum Foo {
+    A,
+    B,
+}
+
+impl PartialEq for Foo {
+    fn ne(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self != other
+    }
+    fn eq(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self == other
+    }
+}
+
+enum Foo2 {
+    A,
+    B,
+}
+
+impl PartialEq for Foo2 {
+    fn ne(&self, other: &Self) -> bool {
+        self != &Foo2::B // no error here
+    }
+    fn eq(&self, other: &Self) -> bool {
+        self == &Foo2::B // no error here
+    }
+}
+
+enum Foo3 {
+    A,
+    B,
+}
+
+impl PartialEq for Foo3 {
+    fn ne(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self.ne(other)
+    }
+    fn eq(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self.eq(other)
+    }
+}
+
+enum Foo4 {
+    A,
+    B,
+}
+
+impl PartialEq for Foo4 {
+    fn ne(&self, other: &Self) -> bool {
+        self.eq(other) // no error
+    }
+    fn eq(&self, other: &Self) -> bool {
+        self.ne(other) // no error
+    }
+}
+
+enum Foo5 {
+    A,
+    B,
+}
+
+impl Foo5 {
+    fn a(&self) -> bool {
+        true
+    }
+}
+
+impl PartialEq for Foo5 {
+    fn ne(&self, other: &Self) -> bool {
+        self.a() // no error
+    }
+    fn eq(&self, other: &Self) -> bool {
+        self.a() // no error
+    }
+}
+
+struct S;
+
+// Check the order doesn't matter.
+impl PartialEq for S {
+    fn ne(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        other != self
+    }
+    fn eq(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        other == self
+    }
+}
+
+struct S2;
+
+// Check that if the same element is compared, it's also triggering the lint.
+impl PartialEq for S2 {
+    fn ne(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        other != other
+    }
+    fn eq(&self, other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        other == other
+    }
+}
+
+struct S3;
+
+impl PartialEq for S3 {
+    fn ne(&self, _other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self != self
+    }
+    fn eq(&self, _other: &Self) -> bool {
+        //~^ ERROR: function cannot return without recursing
+        self == self
+    }
+}
+
+fn main() {
+    // test code goes here
+}