new inference: use site substitutor during return constraints processing (red code in Collectors)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/graphInference/SiteSubstitutionForReturnConstraint.java

@@ -0,0 +1,21 @@
+import java.util.function.Function;
+import java.util.stream.Collector;
+
+class Collectors {
+
+  public static <A,R,RR> void collectingAndThen(Function<R, RR> finisher, Function<A, R> finisher1) {
+    Function<A, RR> f = finisher1.andThen(finisher);
+  }
+
+}
+
+
+class Collectors1 {
+  public static<T,A,R,RR> Collector<T,A,RR> collectingAndThen(Function<R, RR> finisher, Function<A, R> function) {
+    return factory(function.andThen(finisher));
+  }
+
+  static <Ts, As, Rs> Collector<Ts, As, Rs> factory(Function<As, Rs> f) {
+    return null;
+  }
+}