RFC: Remove cross borrowing entirely

Author: pcwalton

active/0000-remove-cross-borrowing-entirely.md

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+- Start Date: 2014-06-25
+- RFC PR #: (leave this empty)
+- Rust Issue #: #10504
+
+# Summary
+
+Remove the coercion from `Box<T>` to `&T` from the language.
+
+# Motivation
+
+The coercion between `Box<T>` to `&T` is not replicable by user-defined smart pointers and has been found to be rarely used [1]. We already removed the coercion between `Box<T>` and `&mut T` in RFC 33.
+
+# Detailed design
+
+The coercion between `Box<T>` and `&T` should be removed.
+
+Note that methods that take `&self` can still be called on values of type `Box<T>` without any special referencing or dereferencing. That is because the semantics of auto-deref and auto-ref conspire to make it work: the types unify after one autoderef followed by one autoref.
+
+# Drawbacks
+
+Borrowing from `Box<T>` to `&T` may be convenient.
+
+# Alternatives
+
+The impact of not doing this is that the coercion will remain.
+
+# Unresolved questions
+
+None.
+
+[1]: https://github.com/rust-lang/rust/pull/15171