Auto merge of #1039 - RalfJung:dyn-tests, r=RalfJung

More tests for dyn trait (in particular, unsized receivers)

So far we only tested them indirectly through `dyn FnOnce`; this also adds some self-contained tests from the rustc test suite.

Author: bors

tests/run-pass/box_box_trait.rs

@@ -40,10 +40,21 @@ fn fn_once_closure_with_multiple_args() -> i64 {
     }
 }
 
-fn boxed(f: Box<dyn FnOnce() -> i32>) -> i32 {
+fn boxed_fn_once(f: Box<dyn FnOnce() -> i32>) -> i32 {
     f()
 }
 
+fn box_dyn() {
+    let x: Box<dyn Fn(i32) -> i32> = Box::new(|x| x * 2);
+    assert_eq!(x(21), 42);
+    let mut i = 5;
+    {
+        let mut x: Box<dyn FnMut()> = Box::new(|| i *= 2);
+        x(); x();
+    }
+    assert_eq!(i, 20);
+}
+
 fn fn_item_as_closure_trait_object() {
     fn foo() {}
     let f: &dyn Fn() = &foo;
@@ -96,8 +107,9 @@ fn main() {
     assert_eq!(crazy_closure(), (84, 10, 10));
     assert_eq!(closure_arg_adjustment_problem(), 3);
     assert_eq!(fn_once_closure_with_multiple_args(), 6);
-    assert_eq!(boxed(Box::new({let x = 13; move || x})), 13);
+    assert_eq!(boxed_fn_once(Box::new({let x = 13; move || x})), 13);
 
+    box_dyn();
     fn_item_as_closure_trait_object();
     fn_item_with_args_as_closure_trait_object();
     fn_item_with_multiple_args_as_closure_trait_object();

tests/run-pass/closures.rs

@@ -0,0 +1,136 @@
+#![feature(unsized_locals)]
+
+fn ref_box_dyn() {
+    struct Struct(i32);
+
+    trait Trait {
+        fn method(&self);
+    }
+
+    impl Trait for Struct {
+        fn method(&self) {
+            assert_eq!(self.0, 42);
+        }
+    }
+
+    struct Foo<T: ?Sized>(T);
+
+    let y: &dyn Trait = &Struct(42);
+    y.method();
+
+    let x: Foo<Struct> = Foo(Struct(42));
+    let y: &Foo<dyn Trait> = &x;
+    y.0.method();
+
+    let y: Box<dyn Trait> = Box::new(Struct(42));
+    y.method();
+
+    let y = &y;
+    y.method();
+}
+
+
+fn box_box_trait() {
+    struct DroppableStruct;
+
+    static mut DROPPED: bool = false;
+
+    impl Drop for DroppableStruct {
+        fn drop(&mut self) {
+            unsafe { DROPPED = true; }
+        }
+    }
+
+    trait MyTrait { fn dummy(&self) { } }
+    impl MyTrait for Box<DroppableStruct> {}
+
+    struct Whatever { w: Box<dyn MyTrait+'static> }
+
+    impl  Whatever {
+        fn new(w: Box<dyn MyTrait+'static>) -> Whatever {
+            Whatever { w: w }
+        }
+    }
+
+    {
+        let f = Box::new(DroppableStruct);
+        let a = Whatever::new(Box::new(f) as Box<dyn MyTrait>);
+        a.w.dummy();
+    }
+    assert!(unsafe { DROPPED });
+}
+
+fn unsized_dyn() {
+    pub trait Foo {
+        fn foo(self) -> String;
+    }
+
+    struct A;
+
+    impl Foo for A {
+        fn foo(self) -> String {
+            format!("hello")
+        }
+    }
+
+    let x = *(Box::new(A) as Box<dyn Foo>);
+    assert_eq!(x.foo(), format!("hello"));
+
+    // I'm not sure whether we want this to work
+    let x = Box::new(A) as Box<dyn Foo>;
+    assert_eq!(x.foo(), format!("hello"));
+}
+
+fn unsized_dyn_autoderef() {
+    pub trait Foo {
+        fn foo(self) -> String;
+    }
+
+    impl Foo for [char] {
+        fn foo(self) -> String {
+            self.iter().collect()
+        }
+    }
+
+    impl Foo for str {
+        fn foo(self) -> String {
+            self.to_owned()
+        }
+    }
+
+    impl Foo for dyn FnMut() -> String {
+        fn foo(mut self) -> String {
+            self()
+        }
+    }
+
+    let x = *(Box::new(['h', 'e', 'l', 'l', 'o']) as Box<[char]>);
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = Box::new(['h', 'e', 'l', 'l', 'o']) as Box<[char]>;
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = "hello".to_owned().into_boxed_str();
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = *("hello".to_owned().into_boxed_str());
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = "hello".to_owned().into_boxed_str();
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = *(Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>);
+    assert_eq!(&x.foo() as &str, "hello");
+
+    let x = Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>;
+    assert_eq!(&x.foo() as &str, "hello");
+}
+
+fn main() {
+    ref_box_dyn();
+    box_box_trait();
+
+    // "exotic" receivers
+    unsized_dyn();
+    unsized_dyn_autoderef();
+}