Introduce TypedefEntity

pkg/compiler/lib/src/common_elements.dart

Index: pkg/compiler/lib/src/common_elements.dart
diff --git a/pkg/compiler/lib/src/common_elements.dart b/pkg/compiler/lib/src/common_elements.dart
index aed124f505b7a4492a74e21f102d7d1309ee5b4a..bcbf446980afbee98c891fb880300538e439ba4a 100644
--- a/pkg/compiler/lib/src/common_elements.dart
+++ b/pkg/compiler/lib/src/common_elements.dart
@@ -1322,7 +1322,8 @@ abstract class ElementEnvironment {
   /// Returns the type of the [local] function.
   FunctionType getLocalFunctionType(Local local);
 
-  /// Returns the unaliased type of [type].
+  /// Returns the 'unaliased' type of [type]. For typedefs this is the function
+  /// type it is an alias of, for other types it is the type itself.
   ///
   /// Use this during resolution to ensure that the alias has been computed.
   // TODO(johnniwinther): Remove this when the resolver is removed.
@@ -1334,4 +1335,7 @@ abstract class ElementEnvironment {
 
   /// Returns the metadata constants declared on [member].
   Iterable<ConstantValue> getMemberMetadata(MemberEntity member);
+
+  /// Returns the function type that is an alias of a [typedef].
+  FunctionType getFunctionTypeOfTypedef(TypedefEntity typedef);
 }