Infer Null for return type of functions with empty returns.

pkg/analyzer/test/src/task/strong/checker_test.dart

Index: pkg/analyzer/test/src/task/strong/checker_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/checker_test.dart b/pkg/analyzer/test/src/task/strong/checker_test.dart
index 73fc16c5d48b058ac12fa345a192ac27da6a7e59..154ed75d4c7d8b71189b33ae6847563e3e27fe21 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -2389,12 +2389,12 @@ void ftf1(void x(int y)) {}
   void test_implicitDynamic_return() {
     addFile(r'''
 // function
-/*error:IMPLICIT_DYNAMIC_RETURN*/f0() {}
+/*error:IMPLICIT_DYNAMIC_RETURN*/f0() {return f0();}
 dynamic f1() { return 42; }
 
 // nested function
 void main() {
-  /*error:IMPLICIT_DYNAMIC_RETURN*/g0() {}
+  /*error:IMPLICIT_DYNAMIC_RETURN*/g0() {return g0();}
   dynamic g1() { return 42; }
 }
 
@@ -3246,8 +3246,10 @@ class C<T> {
     // Regression test for https://github.com/dart-lang/sdk/issues/26155
     checkFile(r'''
 void takesF(void f(int x)) {
-  takesF(/*info:INFERRED_TYPE_CLOSURE,info:INFERRED_TYPE_CLOSURE*/([x]) { bool z = x.isEven; });
-  takesF(/*info:INFERRED_TYPE_CLOSURE*/(y) { bool z = y.isEven; });
+  takesF(/*info:INFERRED_TYPE_CLOSURE,
+           info:INFERRED_TYPE_CLOSURE*/([x]) { bool z = x.isEven; });
+  takesF(/*info:INFERRED_TYPE_CLOSURE,
+           info:INFERRED_TYPE_CLOSURE*/(y) { bool z = y.isEven; });
 }
     ''');
   }