Merge #1108

1108: Add missing unify rules for inference variables r=philberty a=philberty

Inference variables can unify with anything so this includes these
covariant types like references/slices etc. This patch is needed for more
complex type-checking in libcore and generics.


Co-authored-by: Philip Herron <[email protected]>

Author: bors[bot]

gcc/rust/typecheck/rust-tyty-rules.h

@@ -867,6 +867,18 @@ class ArrayRules : public BaseRules
 		       TyVar (base_resolved->get_ref ()));
   }
 
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
 private:
   BaseType *get_base () override { return base; }
 
@@ -896,6 +908,18 @@ class SliceRules : public BaseRules
 			      TyVar (base_resolved->get_ref ()));
   }
 
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
 private:
   BaseType *get_base () override { return base; }
 
@@ -1140,6 +1164,18 @@ class TupleRules : public BaseRules
 				    type.get_ident ().locus, fields);
   }
 
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
 private:
   BaseType *get_base () override { return base; }
 
@@ -1263,6 +1299,18 @@ class ReferenceRules : public BaseRules
 				  base->mutability ());
   }
 
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
 private:
   BaseType *get_base () override { return base; }
 
@@ -1303,6 +1351,18 @@ class PointerRules : public BaseRules
 				base->mutability ());
   }
 
+  void visit (InferType &type) override
+  {
+    if (type.get_infer_kind () != InferType::InferTypeKind::GENERAL)
+      {
+	BaseRules::visit (type);
+	return;
+      }
+
+    resolved = base->clone ();
+    resolved->set_ref (type.get_ref ());
+  }
+
 private:
   BaseType *get_base () override { return base; }