add some test cases from rustc's test suite

tests/ui/needless_move.fixed

@@ -3,6 +3,9 @@
 //! any of the `move`s are removed.
 
 #![warn(clippy::needless_move)]
+#![allow(unused)]
+#![allow(clippy::useless_format)]
+#![allow(clippy::let_and_return)]
 
 #[derive(Copy, Clone)]
 struct Copy;
@@ -370,4 +373,336 @@ fn main() {
         a.non_copy = NonCopy;
         with_owned(a);
     });
+
+    // below are a few tests from rustc's testsuite that use move closures,
+    // which might uncover edge cases
+
+    // rust/$DIR/closures/2229_closure_analysis/migrations/no_migrations.rs
+
+    fn _no_migrations() {
+        // Set of test cases that don't need migrations
+
+        #![deny(rust_2021_incompatible_closure_captures)]
+
+        // Copy types as copied by the closure instead of being moved into the closure
+        // Therefore their drop order isn't tied to the closure and won't be requiring any
+        // migrations.
+        fn test1_only_copy_types() {
+            let t = (0i32, 0i32);
+
+            let c = || {
+                let _t = t.0;
+            };
+
+            c();
+        }
+
+        // Same as test1 but using a move closure
+        fn test2_only_copy_types_move_closure() {
+            let t = (0i32, 0i32);
+
+            let c = move || {
+                println!("{}", t.0);
+            };
+
+            c();
+        }
+
+        // Don't need to migrate if captured by ref
+        fn test3_only_copy_types_move_closure() {
+            let t = (String::new(), String::new());
+
+            let c = || {
+                println!("{}", t.0);
+            };
+
+            c();
+        }
+
+        // Test migration analysis in case of Insignificant Drop + Non Drop aggregates.
+        // Note in this test the closure captures a non Drop type and therefore the variable
+        // is only captured by ref.
+        fn test4_insignificant_drop_non_drop_aggregate() {
+            let t = (String::new(), 0i32);
+
+            let c = || {
+                let _t = t.1;
+            };
+
+            c();
+        }
+
+        struct Foo(i32);
+        impl Drop for Foo {
+            fn drop(&mut self) {
+                println!("{:?} dropped", self.0);
+            }
+        }
+
+        // Test migration analysis in case of Significant Drop + Non Drop aggregates.
+        // Note in this test the closure captures a non Drop type and therefore the variable
+        // is only captured by ref.
+        fn test5_significant_drop_non_drop_aggregate() {
+            let t = (Foo(0), 0i32);
+
+            let c = || {
+                let _t = t.1;
+            };
+
+            c();
+        }
+
+        fn main() {
+            test1_only_copy_types();
+            test2_only_copy_types_move_closure();
+            test3_only_copy_types_move_closure();
+            test4_insignificant_drop_non_drop_aggregate();
+            test5_significant_drop_non_drop_aggregate();
+        }
+    }
+
+    // rust/$DIR/closures/2229_closure_analysis/run_pass/issue-88476.rs
+
+    fn _issue_88476() {
+        use std::rc::Rc;
+
+        // Test that we restrict precision when moving not-`Copy` types, if any of the parent paths
+        // implement `Drop`. This is to ensure that we don't move out of a type that implements Drop.
+        pub fn test1() {
+            struct Foo(Rc<i32>);
+
+            impl Drop for Foo {
+                fn drop(self: &mut Foo) {}
+            }
+
+            let f = Foo(Rc::new(1));
+            let x = move || {
+                println!("{:?}", f.0);
+            };
+
+            x();
+        }
+
+        // Test that we don't restrict precision when moving `Copy` types(i.e. when copying),
+        // even if any of the parent paths implement `Drop`.
+        pub fn test2() {
+            struct Character {
+                hp: u32,
+                name: String,
+            }
+
+            impl Drop for Character {
+                fn drop(&mut self) {}
+            }
+
+            let character = Character {
+                hp: 100,
+                name: format!("A"),
+            };
+
+            let c = move || println!("{}", character.hp);
+
+            c();
+
+            println!("{}", character.name);
+        }
+
+        fn main() {}
+    }
+
+    // rust/$DIR/closures/2229_closure_analysis/preserve_field_drop_order2.rs
+
+    fn _preserve_field_drop_order2() {
+        #[derive(Debug)]
+        struct Dropable(&'static str);
+
+        impl Drop for Dropable {
+            fn drop(&mut self) {
+                println!("Dropping {}", self.0)
+            }
+        }
+
+        #[derive(Debug)]
+        struct A {
+            x: Dropable,
+            y: Dropable,
+        }
+
+        #[derive(Debug)]
+        struct B {
+            c: A,
+            d: A,
+        }
+
+        #[derive(Debug)]
+        struct R<'a> {
+            c: &'a A,
+            d: &'a A,
+        }
+
+        fn main() {
+            let a = A {
+                x: Dropable("x"),
+                y: Dropable("y"),
+            };
+
+            let c = move || println!("{:?} {:?}", a.y, a.x);
+
+            c();
+
+            let b = B {
+                c: A {
+                    x: Dropable("b.c.x"),
+                    y: Dropable("b.c.y"),
+                },
+                d: A {
+                    x: Dropable("b.d.x"),
+                    y: Dropable("b.d.y"),
+                },
+            };
+
+            let d = move || println!("{:?} {:?} {:?} {:?}", b.d.y, b.d.x, b.c.y, b.c.x);
+
+            d();
+
+            let r = R {
+                c: &A {
+                    x: Dropable("r.c.x"),
+                    y: Dropable("r.c.y"),
+                },
+                d: &A {
+                    x: Dropable("r.d.x"),
+                    y: Dropable("r.d.y"),
+                },
+            };
+
+            let e = move || println!("{:?} {:?} {:?} {:?}", r.d.y, r.d.x, r.c.y, r.c.x);
+
+            e();
+        }
+    }
+
+    // rust/$DIR/closures/issue-72408-nested-closures-exponential.rs
+
+    fn _issue_72408_nested_closures_exponential() {
+
+        /*
+        // commented out because it takes forever to run with this
+
+        // Closures include captured types twice in a type tree.
+        //
+        // Wrapping one closure with another leads to doubling
+        // the amount of types in the type tree.
+        //
+        // This test ensures that rust can handle
+        // deeply nested type trees with a lot
+        // of duplicated subtrees.
+
+        fn dup(f: impl Fn(i32) -> i32) -> impl Fn(i32) -> i32 {
+            move |a| f(a * 2)
+        }
+
+        fn main() {
+            let f = |a| a;
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            // Compiler dies around here if it tries
+            // to walk the tree exhaustively.
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+            let f = dup(f);
+
+            println!("Type size was at least {}", f(1));
+        }
+
+        */
+    }
+
+    // rust/$DIR/closures/issue-97607.rs
+
+    fn _issue_97607() {
+        #[allow(unused)]
+
+        fn test<T, F, U>(f: F) -> Box<dyn Fn(T) -> U + 'static>
+        where
+            F: 'static + Fn(T) -> U,
+            for<'a> U: 'a, // < This is the problematic line, see #97607
+        {
+            Box::new(f)
+        }
+
+        fn main() {}
+    }
+
+    // rust/$DIR/closures/once-move-out-on-heap.rs
+
+    fn _once_move_out_on_heap() {
+        // Testing guarantees provided by once functions.
+
+        use std::sync::Arc;
+
+        fn foo<F: FnOnce()>(blk: F) {
+            blk();
+        }
+
+        pub fn main() {
+            let x = Arc::new(true);
+            foo(|| {
+                assert!(*x);
+                drop(x);
+            });
+        }
+    }
+
+    // rust/$DIR/closures/supertrait-hint-references-assoc-ty.rs
+
+    fn _supertrait_hint_references_assoc_ty() {
+        pub trait Fn0: Fn(i32) -> Self::Out {
+            type Out;
+        }
+
+        impl<F: Fn(i32)> Fn0 for F {
+            type Out = ();
+        }
+
+        pub fn closure_typer(_: impl Fn0) {}
+
+        fn main() {
+            closure_typer(|x| {
+                let _: i64 = x.into();
+            });
+        }
+    }
 }