new inference: reject partial computation

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/IDEA119535.java

@@ -0,0 +1,44 @@
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.stream.Collector;
+
+class Stuff {
+  public enum Type { A }
+  private final int value;
+  private final Type type;
+  public Stuff(int value, Type type) {
+    this.value = value;
+    this.type = type;
+  }
+  public int getValue() {
+    return value;
+  }
+  public Type getType() {
+    return type;
+  }
+}
+
+class FakeErrors {
+  {
+
+    Collector<Stuff, ?, Map<Stuff.Type, Optional<Stuff>>> collector =
+      groupingBy(Stuff::getType,
+                 reducing((d1, d2) -> {
+                   boolean b = d1.getValue() > d2.getValue();
+                   return d1;
+                 }));
+  }
+
+  public static <T> Collector<T, ?, Optional<Stuff>> reducing(BinaryOperator<T> op) {
+    return null;
+  }
+
+  public static <T, K, A, D>
+  Collector<T, ?, Map<K, D>> groupingBy(Function<? super T, ? extends K> classifier,
+                                        Collector<? super T, A, D> downstream) {
+    return null;
+  }
+}