Auto merge of #121644 - oli-obk:unique_static_innards2, r=RalfJung,nnethercote

Ensure nested allocations in statics neither get deduplicated nor duplicated

This PR generates new `DefId`s for nested allocations in static items and feeds all the right queries to make the compiler believe these are regular `static` items. I chose this design, because all other designs are fragile and make the compiler horribly complex for such a niche use case.

At present this wrecks incremental compilation performance *in case nested allocations exist* (because any query creating a `DefId` will be recomputed and never loaded from the cache). This will be resolved later in rust-lang/rust#115613 . All other statics are unaffected by this change and will not have performance regressions (heh, famous last words)

This PR contains various smaller refactorings that can be pulled out into separate PRs. It is best reviewed commit-by-commit. The last commit is where the actual magic happens.

r? `@RalfJung` on the const interner and engine changes

fixes rust-lang/rust#79738

Author: bors

clippy_lints/src/loops/needless_range_loop.rs

@@ -273,7 +273,7 @@ impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
                     }
                     return false; // no need to walk further *on the variable*
                 },
-                Res::Def(DefKind::Static(_) | DefKind::Const, ..) => {
+                Res::Def(DefKind::Static{..} | DefKind::Const, ..) => {
                     if index_used_directly {
                         self.indexed_directly.insert(
                             seqvar.segments[0].ident.name,

clippy_lints/src/loops/while_immutable_condition.rs

@@ -101,7 +101,7 @@ impl<'a, 'tcx> VarCollectorVisitor<'a, 'tcx> {
                 Res::Local(hir_id) => {
                     self.ids.insert(hir_id);
                 },
-                Res::Def(DefKind::Static(_), def_id) => {
+                Res::Def(DefKind::Static{..}, def_id) => {
                     let mutable = self.cx.tcx.is_mutable_static(def_id);
                     self.def_ids.insert(def_id, mutable);
                 },

clippy_lints/src/methods/expect_fun_call.rs

@@ -91,7 +91,7 @@ pub(super) fn check<'tcx>(
             },
             hir::ExprKind::Path(ref p) => matches!(
                 cx.qpath_res(p, arg.hir_id),
-                hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static(_), _)
+                hir::def::Res::Def(hir::def::DefKind::Const | hir::def::DefKind::Static{..}, _)
             ),
             _ => false,
         }

clippy_lints/src/multiple_unsafe_ops_per_block.rs

@@ -109,7 +109,7 @@ fn collect_unsafe_exprs<'tcx>(
             ExprKind::Path(QPath::Resolved(
                 _,
                 hir::Path {
-                    res: Res::Def(DefKind::Static(Mutability::Mut), _),
+                    res: Res::Def(DefKind::Static{mutability:Mutability::Mut, ..}, _),
                     ..
                 },
             )) => {
@@ -149,7 +149,7 @@ fn collect_unsafe_exprs<'tcx>(
                     ExprKind::Path(QPath::Resolved(
                         _,
                         hir::Path {
-                            res: Res::Def(DefKind::Static(Mutability::Mut), _),
+                            res: Res::Def(DefKind::Static{mutability:Mutability::Mut, ..}, _),
                             ..
                         }
                     ))