From d1069815fa6238712f51a23dfd43d2ae6cd7c5e8 Mon Sep 17 00:00:00 2001
From: Philip Herron <philip.herron@embecosm.com>
Date: Fri, 30 Sep 2022 13:41:09 +0100
Subject: Add catch for recusive type queries

When we have a type query where by generic substitution occurs we can hit
the case where we need to Probe the bounds of the substited item to
determine whether the the bounds are compatible this can cause us to
end up querying the same type recursively.

Fixes #1550
---
 gcc/rust/typecheck/rust-hir-type-check-base.cc | 10 ++++++++++
 gcc/rust/typecheck/rust-hir-type-check.h       | 12 ++++++++++++
 gcc/rust/typecheck/rust-tyty-bounds.cc         |  5 +++--
 3 files changed, 25 insertions(+), 2 deletions(-)

(limited to 'gcc')

diff --git a/gcc/rust/typecheck/rust-hir-type-check-base.cc b/gcc/rust/typecheck/rust-hir-type-check-base.cc
index bd6a2fb..8107ef5 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-base.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-base.cc
@@ -495,14 +495,20 @@ TypeCheckBase::resolve_generic_params (
 bool
 TypeCheckBase::query_type (HirId reference, TyTy::BaseType **result)
 {
+  if (context->query_in_progress (reference))
+    return false;
+
   if (context->lookup_type (reference, result))
     return true;
 
+  context->insert_query (reference);
+
   HIR::Item *item = mappings->lookup_hir_item (reference);
   if (item != nullptr)
     {
       rust_debug_loc (item->get_locus (), "resolved item {%u} to", reference);
       *result = TypeCheckItem::Resolve (*item);
+      context->query_completed (reference);
       return true;
     }
 
@@ -520,6 +526,7 @@ TypeCheckBase::query_type (HirId reference, TyTy::BaseType **result)
 		      reference);
 
       *result = TypeCheckItem::ResolveImplItem (*impl_block, *impl_item);
+      context->query_completed (reference);
       return true;
     }
 
@@ -530,6 +537,7 @@ TypeCheckBase::query_type (HirId reference, TyTy::BaseType **result)
   if (found_impl_block_type)
     {
       *result = TypeCheckItem::ResolveImplBlockSelf (*impl_block_by_type);
+      context->query_completed (reference);
       return true;
     }
 
@@ -544,6 +552,7 @@ TypeCheckBase::query_type (HirId reference, TyTy::BaseType **result)
       rust_assert (block != nullptr);
 
       *result = TypeCheckTopLevelExternItem::Resolve (extern_item, *block);
+      context->query_completed (reference);
       return true;
     }
 
@@ -551,6 +560,7 @@ TypeCheckBase::query_type (HirId reference, TyTy::BaseType **result)
   Location possible_locus = mappings->lookup_location (reference);
   rust_debug_loc (possible_locus, "query system failed to resolve: [%u]",
 		  reference);
+  context->query_completed (reference);
 
   return false;
 }
diff --git a/gcc/rust/typecheck/rust-hir-type-check.h b/gcc/rust/typecheck/rust-hir-type-check.h
index c17db71..f85585b 100644
--- a/gcc/rust/typecheck/rust-hir-type-check.h
+++ b/gcc/rust/typecheck/rust-hir-type-check.h
@@ -372,6 +372,15 @@ public:
     return true;
   }
 
+  void insert_query (HirId id) { querys_in_progress.insert (id); }
+
+  void query_completed (HirId id) { querys_in_progress.erase (id); }
+
+  bool query_in_progress (HirId id) const
+  {
+    return querys_in_progress.find (id) != querys_in_progress.end ();
+  }
+
 private:
   TypeCheckContext ();
 
@@ -406,6 +415,9 @@ private:
 
   // predicates
   std::map<HirId, TyTy::TypeBoundPredicate> predicates;
+
+  // query context lookups
+  std::set<HirId> querys_in_progress;
 };
 
 class TypeResolution
diff --git a/gcc/rust/typecheck/rust-tyty-bounds.cc b/gcc/rust/typecheck/rust-tyty-bounds.cc
index ec4a11f..d7647b7 100644
--- a/gcc/rust/typecheck/rust-tyty-bounds.cc
+++ b/gcc/rust/typecheck/rust-tyty-bounds.cc
@@ -34,8 +34,9 @@ TypeBoundsProbe::scan ()
       if (!impl->has_trait_ref ())
 	return true;
 
-      TyTy::BaseType *impl_type = TypeCheckItem::ResolveImplBlockSelf (*impl);
-      if (impl_type->get_kind () == TyTy::TypeKind::ERROR)
+      HirId impl_ty_id = impl->get_type ()->get_mappings ().get_hirid ();
+      TyTy::BaseType *impl_type = nullptr;
+      if (!query_type (impl_ty_id, &impl_type))
 	return true;
 
       if (!receiver->can_eq (impl_type, false))
-- 
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