gccrs: support deref cycles to resolve to trait items

Fixes #2190

gcc/rust/ChangeLog:

	* backend/rust-compile-expr.cc (HIRCompileBase::resolve_deref_adjustment):
	reuse op overload code
	* typecheck/rust-autoderef.cc (Adjuster::try_deref_type): update
	(Adjuster::try_raw_deref_type): likewise
	* typecheck/rust-autoderef.h: likewise
	* typecheck/rust-hir-dot-operator.cc (MethodResolver::select):
	improve debug loging

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2190-1.rs: New test.
	* rust/compile/issue-2190-2.rs: New test.

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

6 files changed, 106 insertions, 62 deletions

diff --git a/gcc/rust/backend/rust-compile-expr.cc b/gcc/rust/backend/rust-compile-expr.cc
index 8db52d4..b35db09 100644
--- a/gcc/rust/backend/rust-compile-expr.cc
+++ b/gcc/rust/backend/rust-compile-expr.cc
@@ -2367,15 +2367,8 @@ HIRCompileBase::resolve_deref_adjustment (Resolver::Adjustment &adjustment,
   rust_assert (adjustment.has_operator_overload ());
 
   TyTy::FnType *lookup = adjustment.get_deref_operator_fn ();
-  HIR::ImplItem *resolved_item = adjustment.get_deref_hir_item ();
-
-  tree fn_address = error_mark_node;
-  if (!lookup->has_subsititions_defined ())
-    fn_address = CompileInherentImplItem::Compile (resolved_item, ctx, nullptr,
-						   true, locus);
-  else
-    fn_address = CompileInherentImplItem::Compile (resolved_item, ctx, lookup,
-						   true, locus);
+  TyTy::BaseType *receiver = adjustment.get_actual ();
+  tree fn_address = resolve_method_address (lookup, receiver, locus);
 
   // does it need a reference to call
   tree adjusted_argument = expression;
diff --git a/gcc/rust/typecheck/rust-autoderef.cc b/gcc/rust/typecheck/rust-autoderef.cc
index 078a570..4ad0904 100644
--- a/gcc/rust/typecheck/rust-autoderef.cc
+++ b/gcc/rust/typecheck/rust-autoderef.cc
@@ -28,7 +28,7 @@ namespace Resolver {
 static bool
 resolve_operator_overload_fn (
   Analysis::RustLangItem::ItemType lang_item_type, TyTy::BaseType *ty,
-  TyTy::FnType **resolved_fn, HIR::ImplItem **impl_item,
+  TyTy::FnType **resolved_fn,
   Adjustment::AdjustmentType *requires_ref_adjustment);
 
 TyTy::BaseType *
@@ -44,19 +44,18 @@ Adjustment
 Adjuster::try_deref_type (TyTy::BaseType *ty,
 			  Analysis::RustLangItem::ItemType deref_lang_item)
 {
-  HIR::ImplItem *impl_item = nullptr;
   TyTy::FnType *fn = nullptr;
   Adjustment::AdjustmentType requires_ref_adjustment
     = Adjustment::AdjustmentType::ERROR;
   bool operator_overloaded
-    = resolve_operator_overload_fn (deref_lang_item, ty, &fn, &impl_item,
+    = resolve_operator_overload_fn (deref_lang_item, ty, &fn,
 				    &requires_ref_adjustment);
   if (!operator_overloaded)
     {
       return Adjustment::get_error ();
     }
 
-  auto resolved_base = fn->get_return_type ()->clone ();
+  auto resolved_base = fn->get_return_type ()->destructure ();
   bool is_valid_type = resolved_base->get_kind () == TyTy::TypeKind::REF;
   if (!is_valid_type)
     return Adjustment::get_error ();
@@ -81,7 +80,7 @@ Adjuster::try_deref_type (TyTy::BaseType *ty,
     }
 
   return Adjustment::get_op_overload_deref_adjustment (adjustment_type, ty,
-						       ref_base, fn, impl_item,
+						       ref_base, fn,
 						       requires_ref_adjustment);
 }
 
@@ -94,7 +93,7 @@ Adjuster::try_raw_deref_type (TyTy::BaseType *ty)
 
   const TyTy::ReferenceType *ref_base
     = static_cast<const TyTy::ReferenceType *> (ty);
-  auto infered = ref_base->get_base ()->clone ();
+  auto infered = ref_base->get_base ()->destructure ();
 
   return Adjustment (Adjustment::AdjustmentType::INDIRECTION, ty, infered);
 }
@@ -122,8 +121,8 @@ Adjuster::try_unsize_type (TyTy::BaseType *ty)
 
 static bool
 resolve_operator_overload_fn (
-  Analysis::RustLangItem::ItemType lang_item_type, TyTy::BaseType *ty,
-  TyTy::FnType **resolved_fn, HIR::ImplItem **impl_item,
+  Analysis::RustLangItem::ItemType lang_item_type, TyTy::BaseType *lhs,
+  TyTy::FnType **resolved_fn,
   Adjustment::AdjustmentType *requires_ref_adjustment)
 {
   auto context = TypeCheckContext::get ();
@@ -139,35 +138,69 @@ resolve_operator_overload_fn (
   if (!lang_item_defined)
     return false;
 
+  // we might be in a static or const context and unknown is fine
+  TypeCheckContextItem current_context = TypeCheckContextItem::get_error ();
+  if (context->have_function_context ())
+    {
+      current_context = context->peek_context ();
+    }
+
+  // this flags stops recurisve calls to try and deref when none is available
+  // which will cause an infinite loop
+  bool autoderef_flag = true;
   auto segment = HIR::PathIdentSegment (associated_item_name);
-  auto candidates
-    = MethodResolver::Probe (ty, HIR::PathIdentSegment (associated_item_name),
-			     true);
+  auto candidates = MethodResolver::Probe (lhs, segment, autoderef_flag);
+
+  // remove any recursive candidates
+  std::set<MethodCandidate> resolved_candidates;
+  for (auto &c : candidates)
+    {
+      const TyTy::BaseType *candidate_type = c.candidate.ty;
+      rust_assert (candidate_type->get_kind () == TyTy::TypeKind::FNDEF);
+
+      const TyTy::FnType &fn
+	= *static_cast<const TyTy::FnType *> (candidate_type);
 
-  bool have_implementation_for_lang_item = !candidates.empty ();
+      DefId current_fn_defid = current_context.get_defid ();
+      bool recursive_candidated = fn.get_id () == current_fn_defid;
+      if (!recursive_candidated)
+	{
+	  resolved_candidates.insert (c);
+	}
+    }
+
+  bool have_implementation_for_lang_item = resolved_candidates.size () > 0;
   if (!have_implementation_for_lang_item)
     return false;
 
-  // multiple candidates?
-  if (candidates.size () > 1)
+  if (resolved_candidates.size () > 1)
     {
-      // error out? probably not for this case
+      // no need to error out as we are just trying to see if there is a fit
       return false;
     }
 
   // Get the adjusted self
-  auto candidate = *candidates.begin ();
-  Adjuster adj (ty);
+  MethodCandidate candidate = *resolved_candidates.begin ();
+  Adjuster adj (lhs);
   TyTy::BaseType *adjusted_self = adj.adjust_type (candidate.adjustments);
 
-  // is this the case we are recursive
-  // handle the case where we are within the impl block for this
-  // lang_item otherwise we end up with a recursive operator overload
-  // such as the i32 operator overload trait
-  TypeCheckContextItem fn_context = context->peek_context ();
-  if (fn_context.get_type () == TypeCheckContextItem::ItemType::IMPL_ITEM)
+  PathProbeCandidate &resolved_candidate = candidate.candidate;
+  TyTy::BaseType *lookup_tyty = candidate.candidate.ty;
+  rust_assert (lookup_tyty->get_kind () == TyTy::TypeKind::FNDEF);
+  TyTy::BaseType *lookup = lookup_tyty;
+  TyTy::FnType *fn = static_cast<TyTy::FnType *> (lookup);
+  rust_assert (fn->is_method ());
+
+  rust_debug ("is_impl_item_candidate: %s",
+	      resolved_candidate.is_impl_candidate () ? "true" : "false");
+
+  // in the case where we resolve to a trait bound we have to be careful we are
+  // able to do so there is a case where we are currently resolving the deref
+  // operator overload function which is generic and this might resolve to the
+  // trait item of deref which is not valid as its just another recursive case
+  if (current_context.get_type () == TypeCheckContextItem::ItemType::IMPL_ITEM)
     {
-      auto &impl_item = fn_context.get_impl_item ();
+      auto &impl_item = current_context.get_impl_item ();
       HIR::ImplBlock *parent = impl_item.first;
       HIR::Function *fn = impl_item.second;
 
@@ -201,24 +234,17 @@ resolve_operator_overload_fn (
 	}
     }
 
-  TyTy::BaseType *lookup_tyty = candidate.candidate.ty;
-
-  // rust only support impl item deref operator overloading ie you must have an
-  // impl block for it
-  rust_assert (candidate.candidate.type
-	       == PathProbeCandidate::CandidateType::IMPL_FUNC);
-  *impl_item = candidate.candidate.item.impl.impl_item;
-
-  rust_assert (lookup_tyty->get_kind () == TyTy::TypeKind::FNDEF);
-  TyTy::BaseType *lookup = lookup_tyty;
-  TyTy::FnType *fn = static_cast<TyTy::FnType *> (lookup);
-  rust_assert (fn->is_method ());
+  // we found a valid operator overload
+  fn->prepare_higher_ranked_bounds ();
+  rust_debug ("resolved operator overload to: {%u} {%s}",
+	      candidate.candidate.ty->get_ref (),
+	      candidate.candidate.ty->debug_str ().c_str ());
 
   if (fn->needs_substitution ())
     {
-      if (ty->get_kind () == TyTy::TypeKind::ADT)
+      if (lhs->get_kind () == TyTy::TypeKind::ADT)
 	{
-	  const TyTy::ADTType *adt = static_cast<const TyTy::ADTType *> (ty);
+	  const TyTy::ADTType *adt = static_cast<const TyTy::ADTType *> (lhs);
 
 	  auto s = fn->get_self_type ()->get_root ();
 	  rust_assert (s->can_eq (adt, false));
@@ -265,8 +291,8 @@ resolve_operator_overload_fn (
 	  rust_assert (lookup->get_kind () == TyTy::TypeKind::FNDEF);
 	  fn = static_cast<TyTy::FnType *> (lookup);
 
-	  Location unify_locus = mappings->lookup_location (ty->get_ref ());
-	  unify_site (ty->get_ref (),
+	  Location unify_locus = mappings->lookup_location (lhs->get_ref ());
+	  unify_site (lhs->get_ref (),
 		      TyTy::TyWithLocation (fn->get_self_type ()),
 		      TyTy::TyWithLocation (adjusted_self), unify_locus);
 
diff --git a/gcc/rust/typecheck/rust-autoderef.h b/gcc/rust/typecheck/rust-autoderef.h
index 1d5dacf..74e7c5f 100644
--- a/gcc/rust/typecheck/rust-autoderef.h
+++ b/gcc/rust/typecheck/rust-autoderef.h
@@ -42,18 +42,15 @@ public:
   // ctor for all adjustments except derefs
   Adjustment (AdjustmentType type, TyTy::BaseType *actual,
 	      TyTy::BaseType *expected)
-    : Adjustment (type, actual, expected, nullptr, nullptr,
-		  AdjustmentType::ERROR)
+    : Adjustment (type, actual, expected, nullptr, AdjustmentType::ERROR)
   {}
 
   static Adjustment get_op_overload_deref_adjustment (
     AdjustmentType type, TyTy::BaseType *actual, TyTy::BaseType *expected,
-    TyTy::FnType *fn, HIR::ImplItem *deref_item,
-    Adjustment::AdjustmentType requires_ref_adjustment)
+    TyTy::FnType *fn, Adjustment::AdjustmentType requires_ref_adjustment)
   {
     rust_assert (type == DEREF || type == DEREF_MUT);
-    return Adjustment (type, actual, expected, fn, deref_item,
-		       requires_ref_adjustment);
+    return Adjustment (type, actual, expected, fn, requires_ref_adjustment);
   }
 
   AdjustmentType get_type () const { return type; }
@@ -107,15 +104,12 @@ public:
     return requires_ref_adjustment;
   }
 
-  HIR::ImplItem *get_deref_hir_item () const { return deref_item; }
-
 private:
   Adjustment (AdjustmentType type, TyTy::BaseType *actual,
 	      TyTy::BaseType *expected, TyTy::FnType *deref_operator_fn,
-	      HIR::ImplItem *deref_item,
 	      Adjustment::AdjustmentType requires_ref_adjustment)
     : type (type), actual (actual), expected (expected),
-      deref_operator_fn (deref_operator_fn), deref_item (deref_item),
+      deref_operator_fn (deref_operator_fn),
       requires_ref_adjustment (requires_ref_adjustment)
   {}
 
@@ -127,7 +121,6 @@ private:
   //
   // the fn that we are calling
   TyTy::FnType *deref_operator_fn;
-  HIR::ImplItem *deref_item;
   // operator overloads can requre a reference
   Adjustment::AdjustmentType requires_ref_adjustment;
 };
diff --git a/gcc/rust/typecheck/rust-hir-dot-operator.cc b/gcc/rust/typecheck/rust-hir-dot-operator.cc
index 29c3e4c..3239029 100644
--- a/gcc/rust/typecheck/rust-hir-dot-operator.cc
+++ b/gcc/rust/typecheck/rust-hir-dot-operator.cc
@@ -66,8 +66,9 @@ MethodResolver::try_hook (const TyTy::BaseType &r)
 bool
 MethodResolver::select (TyTy::BaseType &receiver)
 {
-  rust_debug ("MethodResolver::select reciever=[%s]",
-	      receiver.debug_str ().c_str ());
+  rust_debug ("MethodResolver::select reciever=[%s] path=[%s]",
+	      receiver.debug_str ().c_str (),
+	      segment_name.as_string ().c_str ());
 
   struct impl_item_candidate
   {
diff --git a/gcc/testsuite/rust/compile/issue-2190-1.rs b/gcc/testsuite/rust/compile/issue-2190-1.rs
new file mode 100644
index 0000000..85091b2
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-2190-1.rs
@@ -0,0 +1,11 @@
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+fn foo<T: Deref<Target = i32>>(t: &T) -> i32 {
+    t.max(2)
+    // { dg-error "failed to resolve method for .max." "" { target *-*-* } .-1 }
+    // { dg-error "failed to type resolve expression" "" { target *-*-* } .-2 }
+}
diff --git a/gcc/testsuite/rust/compile/issue-2190-2.rs b/gcc/testsuite/rust/compile/issue-2190-2.rs
new file mode 100644
index 0000000..48ab72b
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-2190-2.rs
@@ -0,0 +1,20 @@
+// { dg-options "-w" }
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+fn foo<T: Deref<Target = i32>>(t: &T) -> i32 {
+    t.max(2)
+}
+
+impl i32 {
+    fn max(self, other: i32) -> i32 {
+        if self > other {
+            self
+        } else {
+            other
+        }
+    }
+}