Rollup merge of #127181 - BoxyUwU:dump_def_parents, r=compiler-errors

Introduce a `rustc_` attribute to dump all the `DefId` parents of a `DefId`

We've run into a bunch of issues with anon consts having the wrong generics and it would have been incredibly helpful to be able to quickly slap a `rustc_` attribute to check what `tcx.parent(` will return on the relevant DefIds.

I wasn't sure of a better way to make this work for anon consts than requiring the attribute to be on the enclosing item and then walking the inside of it to look for any anon consts. This particular method will honestly break at some point when we stop having a `DefId` available for anon consts in hir but that's for another day...

r? ``@compiler-errors``

compiler/rustc_feature/src/builtin_attrs.rs

@@ -1117,6 +1117,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         TEST, rustc_dump_predicates, Normal, template!(Word),
         WarnFollowing, EncodeCrossCrate::No
     ),
+    rustc_attr!(
+        TEST, rustc_dump_def_parents, Normal, template!(Word),
+        WarnFollowing, EncodeCrossCrate::No
+    ),
     rustc_attr!(
         TEST, rustc_object_lifetime_default, Normal, template!(Word),
         WarnFollowing, EncodeCrossCrate::No

compiler/rustc_hir_analysis/src/collect/dump.rs

@@ -1,5 +1,7 @@
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::CRATE_DEF_ID;
+use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
+use rustc_hir::intravisit;
+use rustc_middle::hir::nested_filter::OnlyBodies;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::sym;
 
@@ -41,3 +43,49 @@ pub(crate) fn predicates_and_item_bounds(tcx: TyCtxt<'_>) {
         }
     }
 }
+
+pub(crate) fn def_parents(tcx: TyCtxt<'_>) {
+    for did in tcx.hir().body_owners() {
+        if tcx.has_attr(did, sym::rustc_dump_def_parents) {
+            struct AnonConstFinder<'tcx> {
+                tcx: TyCtxt<'tcx>,
+                anon_consts: Vec<LocalDefId>,
+            }
+
+            impl<'tcx> intravisit::Visitor<'tcx> for AnonConstFinder<'tcx> {
+                type NestedFilter = OnlyBodies;
+
+                fn nested_visit_map(&mut self) -> Self::Map {
+                    self.tcx.hir()
+                }
+
+                fn visit_anon_const(&mut self, c: &'tcx rustc_hir::AnonConst) {
+                    self.anon_consts.push(c.def_id);
+                    intravisit::walk_anon_const(self, c)
+                }
+            }
+
+            // Look for any anon consts inside of this body owner as there is no way to apply
+            // the `rustc_dump_def_parents` attribute to the anon const so it would not be possible
+            // to see what its def parent is.
+            let mut anon_ct_finder = AnonConstFinder { tcx, anon_consts: vec![] };
+            intravisit::walk_expr(&mut anon_ct_finder, tcx.hir().body_owned_by(did).value);
+
+            for did in [did].into_iter().chain(anon_ct_finder.anon_consts) {
+                let span = tcx.def_span(did);
+
+                let mut diag = tcx.dcx().struct_span_err(
+                    span,
+                    format!("{}: {did:?}", sym::rustc_dump_def_parents.as_str()),
+                );
+
+                let mut current_did = did.to_def_id();
+                while let Some(parent_did) = tcx.opt_parent(current_did) {
+                    current_did = parent_did;
+                    diag.span_note(tcx.def_span(parent_did), format!("{parent_did:?}"));
+                }
+                diag.emit();
+            }
+        }
+    }
+}

compiler/rustc_hir_analysis/src/lib.rs

@@ -175,6 +175,7 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
         tcx.sess.time("variance_dumping", || variance::dump::variances(tcx));
         collect::dump::opaque_hidden_types(tcx);
         collect::dump::predicates_and_item_bounds(tcx);
+        collect::dump::def_parents(tcx);
     }
 
     // Make sure we evaluate all static and (non-associated) const items, even if unused.

compiler/rustc_span/src/symbol.rs

@@ -1614,6 +1614,7 @@ symbols! {
         rustc_do_not_const_check,
         rustc_doc_primitive,
         rustc_dummy,
+        rustc_dump_def_parents,
         rustc_dump_item_bounds,
         rustc_dump_predicates,
         rustc_dump_user_args,

tests/ui/attributes/dump_def_parents.rs

@@ -0,0 +1,34 @@
+//@ normalize-stderr-test "DefId\(.+?\)" -> "DefId(..)"
+#![feature(rustc_attrs)]
+
+fn bar() {
+    fn foo() {
+        fn baz() {
+            #[rustc_dump_def_parents]
+            || {
+                //~^ ERROR: rustc_dump_def_parents: DefId
+                qux::<
+                    {
+                        //~^ ERROR: rustc_dump_def_parents: DefId
+                        fn inhibits_dump() {
+                            qux::<
+                                {
+                                    "hi";
+                                    1
+                                },
+                            >();
+                        }
+
+                        qux::<{ 1 + 1 }>();
+                        //~^ ERROR: rustc_dump_def_parents: DefId
+                        1
+                    },
+                >();
+            };
+        }
+    }
+}
+
+const fn qux<const N: usize>() {}
+
+fn main() {}

tests/ui/attributes/dump_def_parents.stderr

@@ -0,0 +1,128 @@
+error: rustc_dump_def_parents: DefId(..)
+  --> $DIR/dump_def_parents.rs:8:13
+   |
+LL |             || {
+   |             ^^
+   |
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:6:9
+   |
+LL |         fn baz() {
+   |         ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:5:5
+   |
+LL |     fn foo() {
+   |     ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:4:1
+   |
+LL | fn bar() {
+   | ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:2:1
+   |
+LL | / #![feature(rustc_attrs)]
+LL | |
+LL | | fn bar() {
+LL | |     fn foo() {
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+
+error: rustc_dump_def_parents: DefId(..)
+  --> $DIR/dump_def_parents.rs:11:21
+   |
+LL | /                     {
+LL | |
+LL | |                         fn inhibits_dump() {
+LL | |                             qux::<
+...  |
+LL | |                         1
+LL | |                     },
+   | |_____________________^
+   |
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:8:13
+   |
+LL |             || {
+   |             ^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:6:9
+   |
+LL |         fn baz() {
+   |         ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:5:5
+   |
+LL |     fn foo() {
+   |     ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:4:1
+   |
+LL | fn bar() {
+   | ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:2:1
+   |
+LL | / #![feature(rustc_attrs)]
+LL | |
+LL | | fn bar() {
+LL | |     fn foo() {
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+
+error: rustc_dump_def_parents: DefId(..)
+  --> $DIR/dump_def_parents.rs:22:31
+   |
+LL |                         qux::<{ 1 + 1 }>();
+   |                               ^^^^^^^^^
+   |
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:11:21
+   |
+LL | /                     {
+LL | |
+LL | |                         fn inhibits_dump() {
+LL | |                             qux::<
+...  |
+LL | |                         1
+LL | |                     },
+   | |_____________________^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:8:13
+   |
+LL |             || {
+   |             ^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:6:9
+   |
+LL |         fn baz() {
+   |         ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:5:5
+   |
+LL |     fn foo() {
+   |     ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:4:1
+   |
+LL | fn bar() {
+   | ^^^^^^^^
+note: DefId(..)
+  --> $DIR/dump_def_parents.rs:2:1
+   |
+LL | / #![feature(rustc_attrs)]
+LL | |
+LL | | fn bar() {
+LL | |     fn foo() {
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+
+error: aborting due to 3 previous errors
+