[WIP] mgca: Add ConstArg representation for const items #139558

camelid · 2025-04-08T21:49:58Z

camelid · 2025-04-28T22:07:35Z

compiler/rustc_ast_lowering/src/item.rs

+                        let ty = this
+                            .lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy));
+                        let body =
+                            this.lower_const_item(span, body_id.unwrap(), expr.as_deref().unwrap());


These new unwraps should be correct in theory since an error should've already been emitted, but they might ICE if the compiler didn't stop earlier. It might be a good idea to add ConstArgKind::Err and use delayed_span_bug.

bors · 2025-05-21T23:47:42Z

☔ The latest upstream changes (presumably #141343) made this pull request unmergeable. Please resolve the merge conflicts.

BoxyUwU · 2025-05-22T12:46:32Z

compiler/rustc_resolve/src/def_collector.rs

+                    // HACK(mgca): see lower_const_item in ast_lowering
+                    ItemKind::Const(box ConstItem { body_id: Some(body_id), .. }) => {
+                        this.create_def(body_id, None, DefKind::AnonConst, i.span);
+                    }


Shouldn't need to be changing def collector, it should just handle anon consts in the AST correctly already. Just need to change ast::ConstItem to store an AnonConst instead of NodeId/Expr as separate fields. This should also fix some of the ICEs you've been encountering

BoxyUwU · 2025-05-22T14:05:05Z

compiler/rustc_hir_analysis/src/lib.rs

-            DefKind::Const if tcx.generics_of(item_def_id).is_empty() => {
-                let instance = ty::Instance::new_raw(item_def_id.into(), ty::GenericArgs::empty());
-                let cid = GlobalId { instance, promoted: None };
-                let typing_env = ty::TypingEnv::fully_monomorphized();
-                tcx.ensure_ok().eval_to_const_value_raw(typing_env.as_query_input(cid));
-            }


We should properly handle this before landing 🤔 don't need to care too much rn while everything is still ICEing. I expect we'll just want to update fn check_associated_item and fn check_item in wfcheck.rs to handle const aliases like we do type aliases and then get rid of this codepath

rustbot assigned BoxyUwU Apr 8, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Apr 8, 2025

camelid added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 8, 2025