Implement type inference for named function expressions.

pkg/front_end/testcases/regress/issue_29979.dart.strong.expect

Index: pkg/front_end/testcases/regress/issue_29979.dart.strong.expect
diff --git a/pkg/front_end/testcases/regress/issue_29979.dart.strong.expect b/pkg/front_end/testcases/regress/issue_29979.dart.strong.expect
index 4087641188eba99692c8480d7c3cede395d91bb6..a33d2e09c69a717c979349bd9cec5f903e4e12fe 100644
--- a/pkg/front_end/testcases/regress/issue_29979.dart.strong.expect
+++ b/pkg/front_end/testcases/regress/issue_29979.dart.strong.expect
@@ -1,7 +1,8 @@
 library;
 import self as self;
+import "dart:core" as core;
 
 const field dynamic #errors = const <dynamic>["pkg/front_end/testcases/regress/issue_29979.dart:6:4: Error: A function expression can't have a name.\n  (f() {})();\n   ^"]/* from null */;
 static method main() → dynamic {
-  (let final dynamic f = () → dynamic {} in f).call();
+  (let final () → core::Null f = () → core::Null {} in f).call();
 }