gccrs: bug-fix implicit inference checks

When generating implicit inference variables we can miss cases where the
other side might be another inference variable too but it runs the risk of
generating unending inference cycles needing more info but if they other
side is a non general inference variables like <integer> or <float> this
is safe to do so and allows us to infer mroe cases.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>
gcc/rust/ChangeLog:

	* typecheck/rust-unify.cc (UnifyRules::go): fix inference check

diff --git a/gcc/rust/typecheck/rust-unify.cc b/gcc/rust/typecheck/rust-unify.cc
index e76b362aa0c4fd1142fc9ce843a4ad7bf03995ae..fb7b5d4bd6f07d53e5519f4a5cce492ac45dbfe9 100644 (file)
--- a/gcc/rust/typecheck/rust-unify.cc
+++ b/gcc/rust/typecheck/rust-unify.cc
@@ -153,12 +153,22 @@ UnifyRules::go ()
     {
       bool rgot_param = rtype->get_kind () == TyTy::TypeKind::PARAM;
       bool lhs_is_infer_var = ltype->get_kind () == TyTy::TypeKind::INFER;
-      bool expected_is_concrete = ltype->is_concrete () && !lhs_is_infer_var;
+      bool lhs_is_general_infer_var
+       = lhs_is_infer_var
+         && static_cast<TyTy::InferType *> (ltype)->get_infer_kind ()
+              == TyTy::InferType::GENERAL;
+      bool expected_is_concrete
+       = ltype->is_concrete () && !lhs_is_general_infer_var;
       bool rneeds_infer = expected_is_concrete && rgot_param;
 
       bool lgot_param = ltype->get_kind () == TyTy::TypeKind::PARAM;
       bool rhs_is_infer_var = rtype->get_kind () == TyTy::TypeKind::INFER;
-      bool receiver_is_concrete = rtype->is_concrete () && !rhs_is_infer_var;
+      bool rhs_is_general_infer_var
+       = rhs_is_infer_var
+         && static_cast<TyTy::InferType *> (rtype)->get_infer_kind ()
+              == TyTy::InferType::GENERAL;
+      bool receiver_is_concrete
+       = rtype->is_concrete () && !rhs_is_general_infer_var;
       bool lneeds_infer = receiver_is_concrete && lgot_param;
 
       if (rneeds_infer)