new inference: provide diagnostics on failed inference (strict subtyping constraints); don't resolve vars before incorporate - this way captures won't be opened too early

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/params/FormalParams.java

@@ -32,6 +32,6 @@ class ReturnTypeCompatibility {
     call((String i)->{ return i;});
     call(i->{ return i;});
     call(i->"");
-    call((int i)->{ return <error descr="Bad return type in lambda expression: int cannot be converted to P">i</error>;});
+    call(<error descr="no instance(s) of type variable(s)  exist so that Integer conforms to int">(int i)->{ return i;}</error>);
   }
 }