Auto merge of #87875 - asquared31415:generic-lang-items, r=cjgillot

Improve detection of generics on lang items

Adds detection for the required generics for all lang items.  Many lang items require an exact or minimum amount of generic arguments and if they don't exist, the compiler will ICE.  This does not add any additional validation about bounds on generics or any other lang item restrictions.

Fixes one of the ICEs in #87573

cc `@FabianWolff`

1 files changed, 35 insertions, 87 deletions

diff --git a/compiler/rustc_passes/src/lang_items.rs b/compiler/rustc_passes/src/lang_items.rs
index 62f9bcfdc47..77ff8dc5b4a 100644
--- a/compiler/rustc_passes/src/lang_items.rs
+++ b/compiler/rustc_passes/src/lang_items.rs
@@ -18,7 +18,7 @@ use rustc_errors::{pluralize, struct_span_err};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
-use rustc_hir::lang_items::{extract, ITEM_REFS};
+use rustc_hir::lang_items::{extract, GenericRequirement, ITEM_REFS};
 use rustc_hir::{HirId, LangItem, LanguageItems, Target};
 use rustc_span::Span;
 
@@ -183,97 +183,39 @@ impl LanguageItemCollector<'tcx> {
     }
 
     // Like collect_item() above, but also checks whether the lang item is declared
-    // with the right number of generic arguments if it is a trait.
+    // with the right number of generic arguments.
     fn collect_item_extended(&mut self, item_index: usize, hir_id: HirId, span: Span) {
         let item_def_id = self.tcx.hir().local_def_id(hir_id).to_def_id();
         let lang_item = LangItem::from_u32(item_index as u32).unwrap();
         let name = lang_item.name();
 
-        self.collect_item(item_index, item_def_id);
-
         // Now check whether the lang_item has the expected number of generic
-        // arguments if it is a trait. Generally speaking, binary and indexing
-        // operations have one (for the RHS/index), unary operations have none,
-        // and the rest also have none except for the closure traits (one for
-        // the argument list), generators (one for the resume argument),
-        // ordering/equality relations (one for the RHS), and various conversion
-        // traits.
-
-        let expected_num = match lang_item {
-            // Binary operations
-            LangItem::Add
-            | LangItem::Sub
-            | LangItem::Mul
-            | LangItem::Div
-            | LangItem::Rem
-            | LangItem::BitXor
-            | LangItem::BitAnd
-            | LangItem::BitOr
-            | LangItem::Shl
-            | LangItem::Shr
-            | LangItem::AddAssign
-            | LangItem::SubAssign
-            | LangItem::MulAssign
-            | LangItem::DivAssign
-            | LangItem::RemAssign
-            | LangItem::BitXorAssign
-            | LangItem::BitAndAssign
-            | LangItem::BitOrAssign
-            | LangItem::ShlAssign
-            | LangItem::ShrAssign
-            | LangItem::Index
-            | LangItem::IndexMut
-
-            // Miscellaneous
-            | LangItem::Unsize
-            | LangItem::CoerceUnsized
-            | LangItem::DispatchFromDyn
-            | LangItem::Fn
-            | LangItem::FnMut
-            | LangItem::FnOnce
-            | LangItem::Generator
-            | LangItem::PartialEq
-            | LangItem::PartialOrd
-                => Some(1),
-
-            // Unary operations
-            LangItem::Neg
-            | LangItem::Not
-
-            // Miscellaneous
-            | LangItem::Deref
-            | LangItem::DerefMut
-            | LangItem::Sized
-            | LangItem::StructuralPeq
-            | LangItem::StructuralTeq
-            | LangItem::Copy
-            | LangItem::Clone
-            | LangItem::Sync
-            | LangItem::DiscriminantKind
-            | LangItem::PointeeTrait
-            | LangItem::Freeze
-            | LangItem::Drop
-            | LangItem::Receiver
-            | LangItem::Future
-            | LangItem::Unpin
-            | LangItem::Termination
-            | LangItem::Try
-                => Some(0),
+        // arguments. Generally speaking, binary and indexing operations have
+        // one (for the RHS/index), unary operations have none, the closure
+        // traits have one for the argument list, generators have one for the
+        // resume argument, and ordering/equality relations have one for the RHS
+        // Some other types like Box and various functions like drop_in_place
+        // have minimum requirements.
 
-            // Not a trait
-            _ => None,
-        };
+        if let hir::Node::Item(hir::Item { kind, span: item_span, .. }) = self.tcx.hir().get(hir_id)
+        {
+            let (actual_num, generics_span) = match kind.generics() {
+                Some(generics) => (generics.params.len(), generics.span),
+                None => (0, *item_span),
+            };
 
-        if let Some(expected_num) = expected_num {
-            let (actual_num, generics_span) = match self.tcx.hir().get(hir_id) {
-                hir::Node::Item(hir::Item {
-                    kind: hir::ItemKind::Trait(_, _, generics, ..),
-                    ..
-                }) => (generics.params.len(), generics.span),
-                _ => bug!("op/index/deref lang item target is not a trait: {:?}", lang_item),
+            let required = match lang_item.required_generics() {
+                GenericRequirement::Exact(num) if num != actual_num => {
+                    Some((format!("{}", num), pluralize!(num)))
+                }
+                GenericRequirement::Minimum(num) if actual_num < num => {
+                    Some((format!("at least {}", num), pluralize!(num)))
+                }
+                // If the number matches, or there is no requirement, handle it normally
+                _ => None,
             };
 
-            if expected_num != actual_num {
+            if let Some((range_str, pluralized)) = required {
                 // We are issuing E0718 "incorrect target" here, because while the
                 // item kind of the target is correct, the target is still wrong
                 // because of the wrong number of generic arguments.
@@ -281,23 +223,29 @@ impl LanguageItemCollector<'tcx> {
                     self.tcx.sess,
                     span,
                     E0718,
-                    "`{}` language item must be applied to a trait with {} generic argument{}",
+                    "`{}` language item must be applied to a {} with {} generic argument{}",
                     name,
-                    expected_num,
-                    pluralize!(expected_num)
+                    kind.descr(),
+                    range_str,
+                    pluralized,
                 )
                 .span_label(
                     generics_span,
                     format!(
-                        "this trait has {} generic argument{}, not {}",
+                        "this {} has {} generic argument{}",
+                        kind.descr(),
                         actual_num,
                         pluralize!(actual_num),
-                        expected_num
                     ),
                 )
                 .emit();
+
+                // return early to not collect the lang item
+                return;
             }
         }
+
+        self.collect_item(item_index, item_def_id);
     }
 }