diff --git a/codon/parser/ast/types/class.cpp b/codon/parser/ast/types/class.cpp
index 264fb047..304f35ae 100644
--- a/codon/parser/ast/types/class.cpp
+++ b/codon/parser/ast/types/class.cpp
@@ -101,6 +101,8 @@ bool ClassType::canRealize() const {
     if (!hasUnbounds())
       return true; // always true!
   }
+  if (name == "unrealized_type")
+    return generics[0].type->getClass() != nullptr;
   return std::all_of(generics.begin(), generics.end(),
                      [](auto &t) { return !t.type || t.type->canRealize(); }) &&
          std::all_of(hiddenGenerics.begin(), hiddenGenerics.end(),
diff --git a/codon/parser/visitors/typecheck/infer.cpp b/codon/parser/visitors/typecheck/infer.cpp
index 721c9857..cfb0b137 100644
--- a/codon/parser/visitors/typecheck/infer.cpp
+++ b/codon/parser/visitors/typecheck/infer.cpp
@@ -138,13 +138,8 @@ types::TypePtr TypecheckVisitor::realize(types::TypePtr typ) {
         realizeType(ret->getClass().get());
         // Needed for return type unification
         unify(f->getRetType(), ret->getClass()->generics[1].type);
-        // return unify(ret, typ); // Needed for return type unification
         return ret;
       }
-    } else if (auto p = typ->getPartial()) {
-      TypePtr t = realizeType(p.get());
-      t = std::make_shared<PartialType>(t->getClass().get(), p->func);
-      return t;
     } else if (auto c = typ->getClass()) {
       auto t = realizeType(c.get());
       return t;
@@ -209,9 +204,6 @@ types::TypePtr TypecheckVisitor::realizeType(types::ClassType *type) {
     return (*r)->type->getClass();
   }
 
-  if (type->getPartial())
-    LOG("");
-
   auto realized = type->getClass();
   if (auto s = type->getStatic())
     realized = ctx->getType(s->name)->getClass();
@@ -222,10 +214,13 @@ types::TypePtr TypecheckVisitor::realizeType(types::ClassType *type) {
   }
 
   // Realize generics
-  for (auto &e : realized->generics) {
-    if (!realize(e.type))
-      return nullptr;
-  }
+  if (type->is("unrealized_type"))
+    type->generics[0].type->generalize(ctx->typecheckLevel);
+  else
+    for (auto &e : realized->generics) {
+      if (!realize(e.type))
+        return nullptr;
+    }
 
   // LOG("[realize] T {} -> {}", realized->debugString(2), realized->realizedName());
 
@@ -274,16 +269,6 @@ types::TypePtr TypecheckVisitor::realizeType(types::ClassType *type) {
     }
   }
 
-  // Fix for partial types
-  // if (auto p = type->getPartial()) {
-  //   auto pt = std::make_shared<PartialType>(realized.get(), p->func);
-  //   auto val =
-  //       std::make_shared<TypecheckItem>(pt->realizedName(), "", ctx->getModule(), pt);
-  //   ctx->addAlwaysVisible(val);
-  //   ctx->cache->classes[pt->name].realizations[pt->realizedName()] =
-  //       ctx->cache->classes[realized->name].realizations[realized->realizedName()];
-  // }
-
   return realized;
 }
 
@@ -685,11 +670,15 @@ ir::types::Type *TypecheckVisitor::makeIRType(types::ClassType *t) {
   // Prepare generics and statics
   std::vector<ir::types::Type *> types;
   std::vector<types::StaticTypePtr> statics;
-  for (auto &m : t->generics) {
-    if (auto s = m.type->getStatic())
-      statics.push_back(s);
-    types.push_back(forceFindIRType(m.type));
-  }
+  if (t->is("unrealized_type"))
+      types.push_back(nullptr);
+  else
+    for (auto &m : t->generics) {
+      if (auto s = m.type->getStatic())
+        statics.push_back(s);
+      else
+        types.push_back(forceFindIRType(m.type));
+    }
 
   // Get the IR type
   auto *module = ctx->cache->module;
diff --git a/stdlib/internal/core.codon b/stdlib/internal/core.codon
index b509f9a3..dbf846d5 100644
--- a/stdlib/internal/core.codon
+++ b/stdlib/internal/core.codon
@@ -11,6 +11,11 @@ class type[T]:
     # __doc__
     pass
 
+@tuple
+@__internal__
+class unrealized_type[T]:
+    pass
+
 @__internal__
 class __internal__:
     pass
@@ -263,17 +268,17 @@ class NamedTuple:
         s = ', '.join(f"{keys[i]}: {values[i]}" for i in range(len(keys)))
         return f"({s})"
 
-
 @__internal__
 @tuple
 class Partial:
     args: T  # format: (arg1, arg2, ..., (star_args...))
     kwargs: K
 
-    # Function argument is handled in Codon
     M: Static[str] # mask
     T: type # Tuple
     K: type # NamedTuple
+    # F: type # generic function; handled specially in Codon
+    # def __new__(args: T, kwargs: K, M: Static[str], T: type, K: type, F: type) -> Partial[M, T, K, F]:
 
     @llvm
     def __new__(args: T, kwargs: K, M: Static[str], T: type, K: type) -> Partial[M, T, K]: