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Richard SmithandGeoff Romer
1ec8ac7ef9
Instead of hardcoding which types are copyable, add a `Core.Copy` interface to perform copying. Move almost all the current copy support to that interface. Some remaining pieces are still using builtin logic after this PR: * For tuples and structs, builtin logic is used to perform elementwise copies. This also supports copying *adapters of* tuples and structs, which seems like it may not be desirable, especially for non-extending adapters. A `Copy` impl is provided for tuples of at most 2 elements, so that `Core.Copy` constraints are satisfied, but we can't implement this generally until we have variadics support, and don't yet have a mechanism to generalize this to structs. * For `enum` types imported from C++, builtin logic is used to perform a copy. This is temporary until we have a mechanism to identify these types from an impl in the prelude. One lowering test in `toolchain/lower/testdata/class/generic.carbon` is disabled for now, as it causes a crash in the lowering code due to an ABI mismatch between the call signature in the lowered declaration of a specific function and the call that is generated in the specific callee. Fixing this is a little involved, and will be done in a separate PR. --------- Co-authored-by: Geoff Romer <gromer@google.com>