1 files changed, 85 insertions, 0 deletions
diff --git a/src/test/ui/lint/trivial_casts.rs b/src/test/ui/lint/trivial_casts.rs
new file mode 100644
index 000000000..0a8b9de1d
--- /dev/null
+++ b/src/test/ui/lint/trivial_casts.rs
@@ -0,0 +1,85 @@
+// Test the trivial_casts and trivial_numeric_casts lints. For each error we also
+// check that the cast can be done using just coercion.
+
+#![deny(trivial_casts, trivial_numeric_casts)]
+
+trait Foo {
+    fn foo(&self) {}
+}
+
+pub struct Bar;
+
+impl Foo for Bar {}
+
+pub fn main() {
+    // Numeric
+    let _ = 42_i32 as i32; //~ ERROR trivial numeric cast: `i32` as `i32`
+    let _: i32 = 42_i32;
+
+    let _ = 42_u8 as u8; //~ ERROR trivial numeric cast: `u8` as `u8`
+    let _: u8 = 42_u8;
+
+    // & to * pointers
+    let x: &u32 = &42;
+    let _ = x as *const u32; //~ERROR trivial cast: `&u32` as `*const u32`
+    let _: *const u32 = x;
+
+    let x: &mut u32 = &mut 42;
+    let _ = x as *mut u32; //~ERROR trivial cast: `&mut u32` as `*mut u32`
+    let _: *mut u32 = x;
+
+    // unsize array
+    let x: &[u32; 3] = &[42, 43, 44];
+    let _ = x as &[u32]; //~ERROR trivial cast: `&[u32; 3]` as `&[u32]`
+    let _ = x as *const [u32]; //~ERROR trivial cast: `&[u32; 3]` as `*const [u32]`
+    let _: &[u32] = x;
+    let _: *const [u32] = x;
+
+    let x: &mut [u32; 3] = &mut [42, 43, 44];
+    let _ = x as &mut [u32]; //~ERROR trivial cast: `&mut [u32; 3]` as `&mut [u32]`
+    let _ = x as *mut [u32]; //~ERROR trivial cast: `&mut [u32; 3]` as `*mut [u32]`
+    let _: &mut [u32] = x;
+    let _: *mut [u32] = x;
+
+    let x: Box<[u32; 3]> = Box::new([42, 43, 44]);
+    let _ = x as Box<[u32]>;
+    //~^ ERROR trivial cast: `Box<[u32; 3]>` as `Box<[u32]>`
+    let x: Box<[u32; 3]> = Box::new([42, 43, 44]);
+    let _: Box<[u32]> = x;
+
+    // unsize trait
+    let x: &Bar = &Bar;
+    let _ = x as &dyn Foo; //~ERROR trivial cast: `&Bar` as `&dyn Foo`
+    let _ = x as *const dyn Foo; //~ERROR trivial cast: `&Bar` as `*const dyn Foo`
+    let _: &dyn Foo = x;
+    let _: *const dyn Foo = x;
+
+    let x: &mut Bar = &mut Bar;
+    let _ = x as &mut dyn Foo; //~ERROR trivial cast: `&mut Bar` as `&mut dyn Foo`
+    let _ = x as *mut dyn Foo; //~ERROR trivial cast: `&mut Bar` as `*mut dyn Foo`
+    let _: &mut dyn Foo = x;
+    let _: *mut dyn Foo = x;
+
+    let x: Box<Bar> = Box::new(Bar);
+    let _ = x as Box<dyn Foo>; //~ERROR `Box<Bar>` as `Box<dyn Foo>`
+    let x: Box<Bar> = Box::new(Bar);
+    let _: Box<dyn Foo> = x;
+
+    // functions
+    fn baz(_x: i32) {}
+    let _ = &baz as &dyn Fn(i32); //~ERROR `&fn(i32) {baz}` as `&dyn Fn(i32)`
+    let _: &dyn Fn(i32) = &baz;
+    let x = |_x: i32| {};
+    let _ = &x as &dyn Fn(i32); //~ERROR trivial cast
+    let _: &dyn Fn(i32) = &x;
+}
+
+// subtyping
+pub fn test_subtyping<'a, 'b: 'a>(a: &'a Bar, b: &'b Bar) {
+    let _ = a as &'a Bar; //~ERROR trivial cast
+    let _: &'a Bar = a;
+    let _ = b as &'a Bar; //~ERROR trivial cast
+    let _: &'a Bar = b;
+    let _ = b as &'b Bar; //~ERROR trivial cast
+    let _: &'b Bar = b;
+}