functional type erasure: check if resulted type functional (IDEA-142341)

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/overloadResolution/FunctionalExpressionTypeErasure.java

@@ -0,0 +1,39 @@
+interface Functional {
+  void a(String s);
+}
+
+interface NonFunctional {
+  void b(String s);
+  void c();
+}
+
+interface P<<warning descr="Type parameter 'T' is never used">T</warning>> {
+  void subscribe(Functional f);
+  void subscribe(NonFunctional nf);
+}
+
+class Test {
+  void foo(P p) {
+    p.subscribe(s -> {});
+  }
+}
+
+interface FunctionalExact {
+  void a();
+}
+
+interface NonFunctionalExact {
+  void b();
+  void c();
+}
+
+interface PExact<<warning descr="Type parameter 'T' is never used">T</warning>> {
+  void subscribe(FunctionalExact f);
+  void subscribe(NonFunctionalExact nf);
+}
+
+class TestExact {
+  void foo(PExact p) {
+    p.subscribe(() -> {});
+  }
+}