4 files changed, 54 insertions, 31 deletions

diff --git a/gcc/rust/backend/rust-compile-type.cc b/gcc/rust/backend/rust-compile-type.cc
index 3874027..102bc0a 100644
--- a/gcc/rust/backend/rust-compile-type.cc
+++ b/gcc/rust/backend/rust-compile-type.cc
@@ -112,9 +112,15 @@ TyTyResolveCompile::visit (const TyTy::PlaceholderType &type)
 void
 TyTyResolveCompile::visit (const TyTy::ParamType &param)
 {
-  // FIXME make this reuse the same machinery from constexpr code
-  recursion_count++;
-  rust_assert (recursion_count < kDefaultRecusionLimit);
+  if (recurisve_ops++ >= rust_max_recursion_depth)
+    {
+      rust_error_at (Location (),
+		     "%<recursion depth%> count exceeds limit of %i (use "
+		     "%<frust-max-recursion-depth=%> to increase the limit)",
+		     rust_max_recursion_depth);
+      translated = error_mark_node;
+      return;
+    }
 
   param.resolve ()->accept_vis (*this);
 }
diff --git a/gcc/rust/backend/rust-compile-type.h b/gcc/rust/backend/rust-compile-type.h
index 3e1f903..262b8fc 100644
--- a/gcc/rust/backend/rust-compile-type.h
+++ b/gcc/rust/backend/rust-compile-type.h
@@ -63,16 +63,13 @@ public:
 private:
   TyTyResolveCompile (Context *ctx, bool trait_object_mode)
     : ctx (ctx), trait_object_mode (trait_object_mode),
-      translated (error_mark_node), recursion_count (0)
+      translated (error_mark_node), recurisve_ops (0)
   {}
 
   Context *ctx;
   bool trait_object_mode;
   tree translated;
-
-  // FIXME this needs to be derived from the gcc config option
-  size_t recursion_count;
-  static const size_t kDefaultRecusionLimit = 5;
+  int recurisve_ops;
 };
 
 } // namespace Compile
diff --git a/gcc/rust/lang.opt b/gcc/rust/lang.opt
index a6dabbf..58ec9a7 100644
--- a/gcc/rust/lang.opt
+++ b/gcc/rust/lang.opt
@@ -66,6 +66,10 @@ frust-dump-
 Rust Joined RejectNegative
 -frust-dump-<type>	Dump Rust frontend internal information.
 
+frust-max-recursion-depth=
+Rust RejectNegative Type(int) Var(rust_max_recursion_depth) Init(64)
+-frust-max-recursion-depth=integer
+
 frust-mangling=
 Rust Joined RejectNegative Enum(frust_mangling) Var(flag_rust_mangling)
 -frust-mangling=[legacy|v0]     Choose which version to use for name mangling
diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index d0e8b76..f03bc82 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -252,33 +252,49 @@ BaseType::get_root () const
 const BaseType *
 BaseType::destructure () const
 {
-  switch (get_kind ())
+  int recurisve_ops = 0;
+  const BaseType *x = this;
+  while (true)
     {
-      case TyTy::TypeKind::PARAM: {
-	const TyTy::ParamType *p = static_cast<const TyTy::ParamType *> (this);
-	return p->resolve ();
-      }
-      break;
-
-      case TyTy::TypeKind::PLACEHOLDER: {
-	const TyTy::PlaceholderType *p
-	  = static_cast<const TyTy::PlaceholderType *> (this);
-	rust_assert (p->can_resolve ());
-	return p->resolve ();
-      }
-      break;
-
-      case TyTy::TypeKind::PROJECTION: {
-	const TyTy::ProjectionType *p
-	  = static_cast<const TyTy::ProjectionType *> (this);
-	return p->get ();
-      }
+      if (recurisve_ops++ >= rust_max_recursion_depth)
+	{
+	  rust_error_at (
+	    Location (),
+	    "%<recursion depth%> count exceeds limit of %i (use "
+	    "%<frust-max-recursion-depth=%> to increase the limit)",
+	    rust_max_recursion_depth);
+	  return new ErrorType (get_ref ());
+	}
 
-    default:
-      return this;
+      switch (x->get_kind ())
+	{
+	  case TyTy::TypeKind::PARAM: {
+	    const TyTy::ParamType *p = static_cast<const TyTy::ParamType *> (x);
+	    x = p->resolve ();
+	  }
+	  break;
+
+	  case TyTy::TypeKind::PLACEHOLDER: {
+	    const TyTy::PlaceholderType *p
+	      = static_cast<const TyTy::PlaceholderType *> (x);
+	    rust_assert (p->can_resolve ());
+	    x = p->resolve ();
+	  }
+	  break;
+
+	  case TyTy::TypeKind::PROJECTION: {
+	    const TyTy::ProjectionType *p
+	      = static_cast<const TyTy::ProjectionType *> (x);
+	    x = p->get ();
+	  }
+	  break;
+
+	default:
+	  return x;
+	}
     }
 
-  return this;
+  return x;
 }
 
 TyVar::TyVar (HirId ref) : ref (ref)