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This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: Why is this implicit deref allowed?

I’m trying to figure why the following Rust snippet is allowed:

let mut a = &12;
let b = &&34;
a = b; // <- seems like &&i32 is coerced to &i32

This is a reduced version of Rust code I've seen in the wild. Here a has the inferred type &i32 and b has the inferred type &&i32. Yet, even though there not the same type, the assignment it allowed.

I can't find anything in the Rust reference explaining why this is legal. What I can find is:

• There is a coercion enabled by the Deref trait.
• The type &T implements Deref<Target = T>.
• The above two implies that &&i32 can be coerced to &i32.
• But, coercions can only occur at coercion sites and assignment expressions are not coercion sites.

In other words, I do understand why this slightly modified program is allowed:

let mut a = &12;
let b = &&34;
let c: &i32 = b; // <- allowed since annotated let is a coercion site

Am I missing something about coercions? Or is the some completely different mechanism at play here?

Thanks in advance for helping me out!

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