fix propagated type of lambdas in strong mode

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 0b1a115f888b909cd7ed4a1af220ed2e8c020b0f..915f308e3dc0b8b6dd97f9b14627685084bb2979 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -1917,6 +1917,11 @@ main() {
     check(implicitCasts: false);
   }
 
+  void test_implicitCasts_genericMethods() {
+    addFile('var x = <String>[].map((x) => "");');
+    check(implicitCasts: false);
+  }
+
   void test_implicitDynamic_field() {
     addFile(r'''
 class C {