From f8aaded3180c2f8ae413763169aa20dfa635993c Mon Sep 17 00:00:00 2001
From: Philip Herron <herron.philip@googlemail.com>
Date: Sun, 3 Aug 2025 19:53:23 +0100
Subject: [PATCH] gccrs: allow unifications against non const types

When type resolving a function which returns a const generic for example
this means its unifying the ConstType vs the the specified type so this
mean unwrapping the type of the const.

gcc/rust/ChangeLog:

	* typecheck/rust-unify.cc (UnifyRules::go): unwrap the const type

Signed-off-by: Philip Herron <herron.philip@googlemail.com>
---
 gcc/rust/typecheck/rust-unify.cc | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/gcc/rust/typecheck/rust-unify.cc b/gcc/rust/typecheck/rust-unify.cc
index 841b42adca4..caecf2e1831 100644
--- a/gcc/rust/typecheck/rust-unify.cc
+++ b/gcc/rust/typecheck/rust-unify.cc
@@ -266,6 +266,21 @@ UnifyRules::go ()
 	}
     }
 
+  if ((ltype->is<TyTy::ConstType> () || rtype->is<TyTy::ConstType> ())
+      && !(ltype->is<TyTy::ConstType> () && rtype->is<TyTy::ConstType> ()))
+    {
+      if (ltype->is<TyTy::ConstType> ())
+	{
+	  auto const_type = static_cast<TyTy::ConstType *> (ltype);
+	  ltype = const_type->get_ty ();
+	}
+      else if (rtype->is<TyTy::ConstType> ())
+	{
+	  auto const_type = static_cast<TyTy::ConstType *> (rtype);
+	  rtype = const_type->get_ty ();
+	}
+    }
+
   switch (ltype->get_kind ())
     {
     case TyTy::INFER:
-- 
2.47.3