Issue 5082. It is an error if argument to '?' is not a formal parameter

compiler/java/com/google/dart/compiler/resolver/Resolver.java

Index: compiler/java/com/google/dart/compiler/resolver/Resolver.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/Resolver.java b/compiler/java/com/google/dart/compiler/resolver/Resolver.java
index 5aad16edff76960def1fc0a93d249ce95795639a..f577e91bb62dc51d0a66e9a17bc9094bebb73ae0 100644
--- a/compiler/java/com/google/dart/compiler/resolver/Resolver.java
+++ b/compiler/java/com/google/dart/compiler/resolver/Resolver.java
@@ -1989,6 +1989,11 @@ public class Resolver {
             break;
         }
       }
+      if (node.getOperator() == Token.CONDITIONAL) {
+        if (ElementKind.of(argElement) != ElementKind.PARAMETER) {
+          onError(arg, ResolverErrorCode.FORMAL_PARAMETER_NAME_EXPECTED);
+        }
+      }
       return null;
     }