fix #26155 - optional param passed to positional was not inferred

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 43336713ecc174c0b6c2aec833c431854ca54ad0..e7d7de055ed1ccee032683a750390178711e3253 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -2977,6 +2977,16 @@ main() {
 ''');
   }
 
+  void test_optionalParams() {
+    // 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; });
+}
+    ''');
+  }
+
   void test_privateOverride() {
     addFile(
         '''