Introduce TypedefEntity

pkg/compiler/lib/src/resolution/resolution_strategy.dart

Index: pkg/compiler/lib/src/resolution/resolution_strategy.dart
diff --git a/pkg/compiler/lib/src/resolution/resolution_strategy.dart b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
index fff581f574bbc8604248fc6f4f4f4eb6dfa0219b..98222e2b3d4407b423c6b27e680af21a11fc1b34 100644
--- a/pkg/compiler/lib/src/resolution/resolution_strategy.dart
+++ b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
@@ -678,6 +678,12 @@ class _CompilerElementEnvironment implements ElementEnvironment {
     });
     return values;
   }
+
+  @override
+  ResolutionFunctionType getFunctionTypeOfTypedef(
+      covariant TypedefElement typedef) {
+    return typedef.alias;
+  }
 }
 
 /// AST-based logic for processing annotations. These annotations are processed