Add test for method on unbounded type parameter receiver

tests/ui/traits/method-on-unbounded-type-param.rs

@@ -0,0 +1,15 @@
+fn f<T>(a: T, b: T) -> std::cmp::Ordering {
+    a.cmp(&b) //~ ERROR E0599
+}
+fn g<T>(a: T, b: T) -> std::cmp::Ordering {
+    (&a).cmp(&b) //~ ERROR E0599
+}
+fn h<T>(a: &T, b: T) -> std::cmp::Ordering {
+    a.cmp(&b) //~ ERROR E0599
+}
+trait T {}
+impl<X: std::cmp::Ord> T for X {}
+fn main() {
+    let x: Box<dyn T> = Box::new(0);
+    x.cmp(&x); //~ ERROR E0599
+}

tests/ui/traits/method-on-unbounded-type-param.stderr

@@ -0,0 +1,83 @@
+error[E0599]: `T` is not an iterator
+  --> $DIR/method-on-unbounded-type-param.rs:2:7
+   |
+LL | fn f<T>(a: T, b: T) -> std::cmp::Ordering {
+   |      - method `cmp` not found for this type parameter
+LL |     a.cmp(&b)
+   |       ^^^ `T` is not an iterator
+   |
+   = note: the following trait bounds were not satisfied:
+           `T: Iterator`
+           which is required by `&mut T: Iterator`
+help: consider restricting the type parameter to satisfy the trait bound
+   |
+LL | fn f<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator {
+   |                                           +++++++++++++++++
+
+error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
+  --> $DIR/method-on-unbounded-type-param.rs:5:10
+   |
+LL |     (&a).cmp(&b)
+   |          ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
+   |
+   = note: the following trait bounds were not satisfied:
+           `T: Ord`
+           which is required by `&T: Ord`
+           `&T: Iterator`
+           which is required by `&mut &T: Iterator`
+           `T: Iterator`
+           which is required by `&mut T: Iterator`
+help: consider restricting the type parameters to satisfy the trait bounds
+   |
+LL | fn g<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
+   |                                           +++++++++++++++++++++++++
+
+error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
+  --> $DIR/method-on-unbounded-type-param.rs:8:7
+   |
+LL |     a.cmp(&b)
+   |       ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
+   |
+   = note: the following trait bounds were not satisfied:
+           `T: Ord`
+           which is required by `&T: Ord`
+           `&T: Iterator`
+           which is required by `&mut &T: Iterator`
+           `T: Iterator`
+           which is required by `&mut T: Iterator`
+help: consider restricting the type parameters to satisfy the trait bounds
+   |
+LL | fn h<T>(a: &T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
+   |                                            +++++++++++++++++++++++++
+
+error[E0599]: the method `cmp` exists for struct `Box<dyn T>`, but its trait bounds were not satisfied
+  --> $DIR/method-on-unbounded-type-param.rs:14:7
+   |
+LL |   trait T {}
+   |   -------
+   |   |
+   |   doesn't satisfy `dyn T: Iterator`
+   |   doesn't satisfy `dyn T: Ord`
+...
+LL |       x.cmp(&x);
+   |         ^^^ method cannot be called on `Box<dyn T>` due to unsatisfied trait bounds
+  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+  ::: $SRC_DIR/alloc/src/boxed.rs:LL:COL
+   |
+   = note: doesn't satisfy `Box<dyn T>: Iterator`
+   |
+   = note: doesn't satisfy `Box<dyn T>: Ord`
+   |
+   = note: the following trait bounds were not satisfied:
+           `dyn T: Iterator`
+           which is required by `Box<dyn T>: Iterator`
+           `dyn T: Ord`
+           which is required by `Box<dyn T>: Ord`
+           `Box<dyn T>: Iterator`
+           which is required by `&mut Box<dyn T>: Iterator`
+           `dyn T: Iterator`
+           which is required by `&mut dyn T: Iterator`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0599`.