e6166b7498
This PR introduces a `Reflect` marker trait which is a supertrait of `Any`. The idea is that `Reflect` is defined for all concrete types, but is not defined for type parameters unless there is a `T:Reflect` bound. This is intended to preserve the parametricity property. This allows the `Any` interface to be stabilized without committing us to unbounded reflection that is not easily detectable by the caller. The implementation of `Reflect` relies on an experimental variant of OIBIT. This variant behaves differently for objects, since it requires that all types exposed as part of the object's *interface* are `Reflect`, but isn't concerned about other types that may be closed over. In other words, you don't have to write `Foo+Reflect` in order for `Foo: Reflect` to hold (where `Foo` is a trait). Given that `Any` is slated to stabilization and hence that we are committed to some form of reflection, the goal of this PR is to leave our options open with respect to parametricity. I see the options for full stabilization as follows (I think an RFC would be an appropriate way to confirm whichever of these three routes we take): 1. We make `Reflect` a lang-item. 2. We stabilize some version of the OIBIT variation I implemented as a general mechanism that may be appropriate for other use cases. 3. We give up on preserving parametricity here and just have `impl<T> Reflect for T` instead. In that case, `Reflect` is a harmless but not especially useful trait going forward. cc @aturon cc @alexcrichton cc @glaebhoerl (this is more-or-less your proposal, as I understood it) cc @reem (this is more-or-less what we discussed on IRC at some point) cc @FlaPer87 (vaguely pertains to OIBIT) |
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| compiler-rt@58ab642c30 | ||
| compiletest | ||
| doc | ||
| driver | ||
| etc | ||
| grammar | ||
| jemalloc@e24a1a025a | ||
| liballoc | ||
| libarena | ||
| libbacktrace | ||
| libcollections | ||
| libcollectionstest | ||
| libcore | ||
| libcoretest | ||
| libflate | ||
| libfmt_macros | ||
| libgetopts | ||
| libgraphviz | ||
| liblibc | ||
| liblog | ||
| librand | ||
| librbml | ||
| librustc | ||
| librustc_back | ||
| librustc_bitflags | ||
| librustc_borrowck | ||
| librustc_driver | ||
| librustc_lint | ||
| librustc_llvm | ||
| librustc_privacy | ||
| librustc_resolve | ||
| librustc_trans | ||
| librustc_typeck | ||
| librustdoc | ||
| libserialize | ||
| libstd | ||
| libsyntax | ||
| libterm | ||
| libtest | ||
| libunicode | ||
| llvm@bff6907697 | ||
| rt | ||
| rust-installer@60fd8abfca | ||
| rustbook | ||
| rustllvm | ||
| test | ||
| snapshots.txt | ||