Auto merge of #117703 - compiler-errors:recursive-async, r=lcnr

Support async recursive calls (as long as they have indirection)

Before #101692, we stored coroutine witness types directly inside of the coroutine. That means that a coroutine could not contain itself (as a witness field) without creating a cycle in the type representation of the coroutine, which we detected with the `OpaqueTypeExpander`, which is used to detect cycles when expanding opaque types after that are inferred to contain themselves.

After `-Zdrop-tracking-mir` was stabilized, we no longer store these generator witness fields directly, but instead behind a def-id based query. That means there is no technical obstacle in the compiler preventing coroutines from containing themselves per se, other than the fact that for a coroutine to have a non-infinite layout, it must contain itself wrapped in a layer of allocation indirection (like a `Box`).

This means that it should be valid for this code to work:

```
async fn async_fibonacci(i: u32) -> u32 {
    if i == 0 || i == 1 {
        i
    } else {
        Box::pin(async_fibonacci(i - 1)).await
          + Box::pin(async_fibonacci(i - 2)).await
    }
}
```

Whereas previously, you'd need to coerce the future to `Pin<Box<dyn Future<Output = ...>>` before `await`ing it, to prevent the async's desugared coroutine from containing itself across as await point.

This PR does two things:
1. Only report an error if an opaque expansion cycle is detected *not* through coroutine witness fields.
    * Instead, if we find an opaque cycle through coroutine witness fields, we compute the layout of the coroutine. If that results in a cycle error, we report it as a recursive async fn.
4. Reworks the way we report layout errors having to do with coroutines, to make up for the diagnostic regressions introduced by (1.). We actually do even better now, pointing out the call sites of the recursion!

Author: bors

clippy_lints/src/copies.rs

@@ -12,7 +12,6 @@ use rustc_errors::Applicability;
 use rustc_hir::def_id::DefIdSet;
 use rustc_hir::{intravisit, BinOpKind, Block, Expr, ExprKind, HirId, HirIdSet, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::query::Key;
 use rustc_session::impl_lint_pass;
 use rustc_span::hygiene::walk_chain;
 use rustc_span::source_map::SourceMap;
@@ -574,7 +573,7 @@ fn method_caller_is_mutable(cx: &LateContext<'_>, caller_expr: &Expr<'_>, ignore
     let caller_ty = cx.typeck_results().expr_ty(caller_expr);
     // Check if given type has inner mutability and was not set to ignored by the configuration
     let is_inner_mut_ty = is_interior_mut_ty(cx, caller_ty)
-        && !matches!(caller_ty.ty_adt_id(), Some(adt_id) if ignored_ty_ids.contains(&adt_id));
+        && !matches!(caller_ty.ty_adt_def(), Some(adt) if ignored_ty_ids.contains(&adt.did()));
 
     is_inner_mut_ty
         || caller_ty.is_mutable_ptr()

clippy_lints/src/methods/drain_collect.rs

@@ -6,7 +6,6 @@ use clippy_utils::ty::is_type_lang_item;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, LangItem, Path, QPath};
 use rustc_lint::LateContext;
-use rustc_middle::query::Key;
 use rustc_middle::ty;
 use rustc_middle::ty::Ty;
 use rustc_span::{sym, Symbol};
@@ -18,10 +17,10 @@ use rustc_span::{sym, Symbol};
 /// `vec![1,2].drain(..).collect::<HashSet<_>>()`
 ///  ^^^^^^^^^                     ^^^^^^^^^^  false
 fn types_match_diagnostic_item(cx: &LateContext<'_>, expr: Ty<'_>, recv: Ty<'_>, sym: Symbol) -> bool {
-    if let Some(expr_adt_did) = expr.ty_adt_id()
-        && let Some(recv_adt_did) = recv.ty_adt_id()
+    if let Some(expr_adt) = expr.ty_adt_def()
+        && let Some(recv_adt) = recv.ty_adt_def()
     {
-        cx.tcx.is_diagnostic_item(sym, expr_adt_did) && cx.tcx.is_diagnostic_item(sym, recv_adt_did)
+        cx.tcx.is_diagnostic_item(sym, expr_adt.did()) && cx.tcx.is_diagnostic_item(sym, recv_adt.did())
     } else {
         false
     }

clippy_lints/src/methods/redundant_as_str.rs

@@ -4,7 +4,6 @@ use clippy_utils::source::snippet_with_applicability;
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
-use rustc_middle::query::Key;
 use rustc_span::Span;
 
 pub(super) fn check(
@@ -14,11 +13,7 @@ pub(super) fn check(
     as_str_span: Span,
     other_method_span: Span,
 ) {
-    if cx
-        .tcx
-        .lang_items()
-        .string()
-        .is_some_and(|id| Some(id) == cx.typeck_results().expr_ty(recv).ty_adt_id())
+    if cx.typeck_results().expr_ty(recv).ty_adt_def().is_some_and(|adt| Some(adt.did()) == cx.tcx.lang_items().string())
     {
         let mut applicability = Applicability::MachineApplicable;
         span_lint_and_sugg(

clippy_lints/src/mut_key.rs

@@ -4,7 +4,6 @@ use clippy_utils::{def_path_def_ids, trait_ref_of_method};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::query::Key;
 use rustc_middle::ty::{Adt, Ty};
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::LocalDefId;
@@ -166,7 +165,7 @@ impl MutableKeyType {
             // Determines if a type contains interior mutability which would affect its implementation of
             // [`Hash`] or [`Ord`].
             if is_interior_mut_ty(cx, subst_ty)
-                && !matches!(subst_ty.ty_adt_id(), Some(adt_id) if self.ignore_mut_def_ids.contains(&adt_id))
+                && !matches!(subst_ty.ty_adt_def(), Some(adt) if self.ignore_mut_def_ids.contains(&adt.did()))
             {
                 span_lint(cx, MUTABLE_KEY_TYPE, span, "mutable key type");
             }

clippy_lints/src/non_copy_const.rs

@@ -15,7 +15,6 @@ use rustc_hir::{
 };
 use rustc_lint::{LateContext, LateLintPass, Lint};
 use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult, GlobalId};
-use rustc_middle::query::Key;
 use rustc_middle::ty::adjustment::Adjust;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::impl_lint_pass;
@@ -188,7 +187,7 @@ impl NonCopyConst {
     }
 
     fn is_ty_ignored(&self, ty: Ty<'_>) -> bool {
-        matches!(ty.ty_adt_id(), Some(adt_id) if self.ignore_mut_def_ids.contains(&adt_id))
+        matches!(ty.ty_adt_def(), Some(adt) if self.ignore_mut_def_ids.contains(&adt.did()))
     }
 
     fn is_unfrozen<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {

clippy_lints/src/transmute/transmute_int_to_non_zero.rs

@@ -4,7 +4,6 @@ use clippy_utils::sugg;
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
-use rustc_middle::query::Key;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::symbol::sym;
 
@@ -17,10 +16,10 @@ pub(super) fn check<'tcx>(
     to_ty: Ty<'tcx>,
     arg: &'tcx Expr<'_>,
 ) -> bool {
-    let (ty::Int(_) | ty::Uint(_), Some(to_ty_id)) = (&from_ty.kind(), to_ty.ty_adt_id()) else {
+    let (ty::Int(_) | ty::Uint(_), Some(to_ty_adt)) = (&from_ty.kind(), to_ty.ty_adt_def()) else {
         return false;
     };
-    let Some(to_type_sym) = cx.tcx.get_diagnostic_name(to_ty_id) else {
+    let Some(to_type_sym) = cx.tcx.get_diagnostic_name(to_ty_adt.did()) else {
         return false;
     };