tree 7126a3429ceb0e584cdcca8b7b75ecaaebf88d02
parent de362d88ea17ab23ca2483cb798bc7aeb81a48f5
parent 19801b12c950f727a4e6938a87b0b2fdece73c07
author bors <bors@rust-lang.org> 1582188077 +0000
committer bors <bors@rust-lang.org> 1582188077 +0000

Auto merge of #68847 - ecstatic-morse:const-impl, r=oli-obk

Allow trait methods to be called on concrete types in a const context

This partially implements [RFC 2632](https://github.com/rust-lang/rfcs/pull/2632) by const-checking methods inside an `impl const` block and allowing those methods to be called on concrete types. Calling trait methods on type parameters in a const context is not yet allowed. Implementing this will require much more work. Since we are only concerned with methods on concrete types, we are able to take advantage of the machinery in `Instance::resolve`, which is doing most of the work.

This also propagates `#[rustc_const_unstable]` from parent items to child items, making that attribute behave like `#[stable]` and `#[unstable]` do. This allows trait methods to be marked as unstably const.

cc #67792 #57563
cc @rust-lang/wg-const-eval
r? @oli-obk