1 files changed, 98 insertions, 0 deletions
diff --git a/src/test/ui/rust-2021/future-prelude-collision.rs b/src/test/ui/rust-2021/future-prelude-collision.rs
new file mode 100644
index 000000000..4c7a47ffb
--- /dev/null
+++ b/src/test/ui/rust-2021/future-prelude-collision.rs
@@ -0,0 +1,98 @@
+// run-rustfix
+// edition:2018
+// check-pass
+#![warn(rust_2021_prelude_collisions)]
+
+trait TryIntoU32 {
+    fn try_into(self) -> Result<u32, ()>;
+}
+
+impl TryIntoU32 for u8 {
+    fn try_into(self) -> Result<u32, ()> {
+        Ok(self as u32)
+    }
+}
+
+// needed for autoref test
+impl TryIntoU32 for &f32 {
+    fn try_into(self) -> Result<u32, ()> {
+        Ok(*self as u32)
+    }
+}
+
+trait TryFromU8: Sized {
+    fn try_from(x: u8) -> Result<Self, ()>;
+}
+
+impl TryFromU8 for u32 {
+    fn try_from(x: u8) -> Result<Self, ()> {
+        Ok(x as u32)
+    }
+}
+
+impl TryIntoU32 for *const u16 {
+    fn try_into(self) -> Result<u32, ()> {
+        Ok(unsafe { *self } as u32)
+    }
+}
+
+trait FromByteIterator {
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: Iterator<Item = u8>;
+}
+
+impl FromByteIterator for Vec<u8> {
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: Iterator<Item = u8>,
+    {
+        iter.collect()
+    }
+}
+
+fn main() {
+    // test dot-call that will break in 2021 edition
+    let _: u32 = 3u8.try_into().unwrap();
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    // test associated function call that will break in 2021 edition
+    let _ = u32::try_from(3u8).unwrap();
+    //~^ WARNING trait-associated function `try_from` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    // test reverse turbofish too
+    let _ = <Vec<u8>>::from_iter(vec![1u8, 2, 3, 4, 5, 6].into_iter());
+    //~^ WARNING trait-associated function `from_iter` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    // negative testing lint (this line should *not* emit a warning)
+    let _: u32 = TryFromU8::try_from(3u8).unwrap();
+
+    // test type omission
+    let _: u32 = <_>::try_from(3u8).unwrap();
+    //~^ WARNING trait-associated function `try_from` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    // test autoderef
+    let _: u32 = (&3u8).try_into().unwrap();
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    // test autoref
+    let _: u32 = 3.0.try_into().unwrap();
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    let mut data = 3u16;
+    let mut_ptr = std::ptr::addr_of_mut!(data);
+    let _: u32 = mut_ptr.try_into().unwrap();
+    //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+
+    type U32Alias = u32;
+    let _ = U32Alias::try_from(3u8).unwrap();
+    //~^ WARNING trait-associated function `try_from` will become ambiguous in Rust 2021
+    //~^^ WARNING this is accepted in the current edition
+}