new inference: teach strict subtyping constraint about intersection types (IDEA-129727)

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/StrictSubtypingConstraint.java

@@ -92,8 +92,22 @@ public class StrictSubtypingConstraint implements ConstraintFormula {
           return false;
         }
 
-        if (!(myS instanceof PsiClassType)) return false;
-        PsiClassType.ClassResolveResult SResult = ((PsiClassType)myS).resolveGenerics();
+        PsiClassType.ClassResolveResult SResult = null;
+        if (myS instanceof PsiIntersectionType) {
+          for (PsiType conjunct : ((PsiIntersectionType)myS).getConjuncts()) {
+            if (conjunct instanceof PsiClassType) {
+              final PsiClassType.ClassResolveResult conjunctResult = ((PsiClassType)conjunct).resolveGenerics();
+              if (InheritanceUtil.isInheritorOrSelf(conjunctResult.getElement(), CClass, true)) {
+                SResult = conjunctResult;
+                break;
+              }
+            }
+          }
+        } else if (myS instanceof PsiClassType) {
+          SResult = ((PsiClassType)myS).resolveGenerics();
+        }
+
+        if (SResult == null) return false;
         PsiClass SClass = SResult.getElement();
         if (((PsiClassType)myT).isRaw()) {
           return SClass != null && InheritanceUtil.isInheritorOrSelf(SClass, CClass, true);

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/constraints/IntersectionTypeStrictSubtypingConstraint.java

@@ -0,0 +1,15 @@
+import java.io.Serializable;
+import java.util.function.Supplier;
+
+class Test {
+  static class Loader<K> {
+
+    static <K> Loader<K> from(Supplier<K> supplier) {
+      return new Loader<>();
+    }
+  }
+
+  Loader loader = Loader.from((I<String> & Serializable) () -> "");
+
+  interface I<H> extends Supplier<H>{}
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/ConstraintsInferenceMiscTest.java

@@ -54,6 +54,10 @@ public class ConstraintsInferenceMiscTest extends LightDaemonAnalyzerTestCase {
     doTest(false);
   }
 
+  public void testIntersectionTypeStrictSubtypingConstraint() throws Exception {
+    doTest(false);
+  }
+
   private void doTest(final boolean checkWarnings) {
     doTest(BASE_PATH + "/" + getTestName(false) + ".java", checkWarnings, false);
   }