diff --git a/src/librustc_mir/transform/nrvo.rs b/src/librustc_mir/transform/nrvo.rs index 941ffa94aa857..ffad1ebea005b 100644 --- a/src/librustc_mir/transform/nrvo.rs +++ b/src/librustc_mir/transform/nrvo.rs @@ -44,18 +44,6 @@ impl<'tcx> MirPass<'tcx> for RenameReturnPlace { } }; - // Sometimes, the return place is assigned a local of a different but coercable type, for - // example `&T` instead of `&mut T`. Overwriting the `LocalInfo` for the return place would - // result in it having an incorrect type. Although this doesn't seem to cause a problem in - // codegen, bail out anyways since it happens so rarely. - let ret_ty = body.local_decls[mir::RETURN_PLACE].ty; - let assigned_ty = body.local_decls[returned_local].ty; - if ret_ty != assigned_ty { - debug!("`{:?}` was eligible for NRVO but for type mismatch", src.def_id()); - debug!("typeof(_0) != typeof({:?}); {:?} != {:?}", returned_local, ret_ty, assigned_ty); - return; - } - debug!( "`{:?}` was eligible for NRVO, making {:?} the return place", src.def_id(), @@ -72,6 +60,12 @@ impl<'tcx> MirPass<'tcx> for RenameReturnPlace { // Overwrite the debuginfo of `_0` with that of the renamed local. let (renamed_decl, ret_decl) = body.local_decls.pick2_mut(returned_local, mir::RETURN_PLACE); + + // Sometimes, the return place is assigned a local of a different but coercable type, for + // example `&mut T` instead of `&T`. Overwriting the `LocalInfo` for the return place means + // its type may no longer match the return type of its function. This doesn't cause a + // problem in codegen because these two types are layout-compatible, but may be unexpected. + debug!("_0: {:?} = {:?}: {:?}", ret_decl.ty, returned_local, renamed_decl.ty); ret_decl.clone_from(renamed_decl); // The return place is always mutable.