rust: fix ICE when compiling impl block for !

We need to resolve the never type which is its own special AST node so it
doesnt magically get handled like the regular builtin type paths such as
i32.

Fixes #3035

gcc/rust/ChangeLog:

	* resolve/rust-ast-resolve-type.cc (ResolveType::visit):
	handle never type
	(ResolveTypeToCanonicalPath::visit): likewise
	* resolve/rust-ast-resolve-type.h: missing never type
	* resolve/rust-name-resolver.cc (Resolver::generate_builtins):
	track never type node_id
	(Resolver::setup_builtin): likewise
	* resolve/rust-name-resolver.h: new never type getter

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 cant handle this
	* rust/compile/issue-3035.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

gcc/rust/resolve/rust-ast-resolve-type.cc

@@ -69,7 +69,7 @@ ResolveType::visit (AST::InferredType &)
 void
 ResolveType::visit (AST::NeverType &)
 {
-  // FIXME
+  resolved_node = resolver->get_never_type_node_id ();
 }
 
 void
@@ -501,6 +501,12 @@ ResolveTypeToCanonicalPath::visit (AST::TraitObjectType &)
   rust_unreachable ();
 }
 
+void
+ResolveTypeToCanonicalPath::visit (AST::NeverType &type)
+{
+  result = CanonicalPath::new_seg (type.get_node_id (), "!");
+}
+
 ResolveTypeToCanonicalPath::ResolveTypeToCanonicalPath ()
   : ResolverBase (), result (CanonicalPath::create_empty ())
 {}

gcc/rust/resolve/rust-ast-resolve-type.h

@@ -246,6 +246,8 @@ class ResolveTypeToCanonicalPath : public ResolverBase
 
   void visit (AST::TraitObjectType &type) override;
 
+  void visit (AST::NeverType &type) override;
+
 private:
   ResolveTypeToCanonicalPath ();
 

gcc/rust/resolve/rust-name-resolver.cc

@@ -429,7 +429,10 @@ Resolver::generate_builtins ()
   setup_builtin ("isize", isize);
   setup_builtin ("char", char_tyty);
   setup_builtin ("str", str);
-  setup_builtin ("!", never);
+
+  // never type
+  NodeId never_node_id = setup_builtin ("!", never);
+  set_never_type_node_id (never_node_id);
 
   // unit type ()
   TyTy::TupleType *unit_tyty
@@ -443,7 +446,7 @@ Resolver::generate_builtins ()
   set_unit_type_node_id (unit_type->get_node_id ());
 }
 
-void
+NodeId
 Resolver::setup_builtin (const std::string &name, TyTy::BaseType *tyty)
 {
   AST::PathIdentSegment seg (name, BUILTINS_LOCATION);
@@ -459,6 +462,8 @@ Resolver::setup_builtin (const std::string &name, TyTy::BaseType *tyty)
   mappings.insert_canonical_path (
     builtin_type->get_node_id (),
     CanonicalPath::new_seg (builtin_type->get_node_id (), name));
+
+  return builtin_type->get_node_id ();
 }
 
 void

gcc/rust/resolve/rust-name-resolver.h

@@ -163,9 +163,13 @@ class Resolver
   Scope &get_macro_scope () { return macro_scope; }
 
   NodeId get_global_type_node_id () { return global_type_node_id; }
+
   void set_unit_type_node_id (NodeId id) { unit_ty_node_id = id; }
   NodeId get_unit_type_node_id () { return unit_ty_node_id; }
 
+  void set_never_type_node_id (NodeId id) { never_ty_node_id = id; }
+  NodeId get_never_type_node_id () { return never_ty_node_id; }
+
   void push_new_module_scope (NodeId module_id)
   {
     current_module_stack.push_back (module_id);
@@ -208,7 +212,7 @@ class Resolver
   Resolver ();
 
   void generate_builtins ();
-  void setup_builtin (const std::string &name, TyTy::BaseType *tyty);
+  NodeId setup_builtin (const std::string &name, TyTy::BaseType *tyty);
 
   Analysis::Mappings &mappings;
   TypeCheckContext *tyctx;
@@ -222,6 +226,7 @@ class Resolver
 
   NodeId global_type_node_id;
   NodeId unit_ty_node_id;
+  NodeId never_ty_node_id;
 
   // map a AST Node to a Rib
   std::map<NodeId, Rib *> name_ribs;

gcc/testsuite/rust/compile/issue-3035.rs

@@ -0,0 +1,25 @@
+#[lang = "sized"]
+trait Sized {}
+
+// ---- gccrs additions
+
+#[lang = "clone"]
+pub trait Clone: Sized {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use = "cloning is often expensive and is not expected to have side effects"]
+    fn clone(&self) -> Self;
+
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn clone_from(&mut self, source: &Self) {
+        *self = source.clone()
+    }
+}
+
+#[unstable(feature = "never_type", issue = "35121")]
+impl Clone for ! {
+    #[inline]
+    fn clone(&self) -> Self {
+        *self
+    }
+}

gcc/testsuite/rust/compile/nr2/exclude

@@ -291,3 +291,4 @@ unknown-associated-item.rs
 box_syntax_feature_gate.rs
 dropck_eyepatch_feature_gate.rs
 inline_asm_parse_output_operand.rs
+issue-3035.rs