method reference: registry option to skip unsound capture conversion specified in the spec but ignored by the javac, to be changed in the next spec version (IDEA-171488)

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

@@ -16,6 +16,7 @@
 package com.intellij.psi.impl.source.resolve.graphInference.constraints;
 
 import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.openapi.util.registry.Registry;
 import com.intellij.psi.*;
 import com.intellij.psi.impl.source.resolve.graphInference.FunctionalInterfaceParameterizationUtil;
 import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession;
@@ -125,8 +126,10 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
         }
 
         if (applicableMethodReturnType != null) {
-          final PsiType capturedReturnType = PsiUtil.captureToplevelWildcards(psiSubstitutor.substitute(applicableMethodReturnType), myExpression);
-          constraints.add(new TypeCompatibilityConstraint(returnType, session.substituteWithInferenceVariables(capturedReturnType)));
+          applicableMethodReturnType = psiSubstitutor.substitute(applicableMethodReturnType);
+          applicableMethodReturnType = Registry.is("unsound.capture.conversion.java.spec.change") ? applicableMethodReturnType
+                                                                                                  : PsiUtil.captureToplevelWildcards(applicableMethodReturnType, myExpression);
+          constraints.add(new TypeCompatibilityConstraint(returnType, session.substituteWithInferenceVariables(applicableMethodReturnType)));
         }
       }
       return true;
@@ -164,7 +167,7 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
 
     if (element instanceof PsiMethod) {
       final PsiMethod method = (PsiMethod)element;
-      final PsiType referencedMethodReturnType;
+      PsiType referencedMethodReturnType;
       final PsiClass containingClass = method.getContainingClass();
       LOG.assertTrue(containingClass != null, method);
       PsiSubstitutor psiSubstitutor = getSubstitutor(signature, qualifierResolveResult, method, containingClass, myExpression);
@@ -211,8 +214,10 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
         session.initBounds(myExpression, containingClass.getTypeParameters());
       }
 
-      final PsiType capturedReturnType = PsiUtil.captureToplevelWildcards(psiSubstitutor.substitute(referencedMethodReturnType), myExpression);
-      constraints.add(new TypeCompatibilityConstraint(returnType, session.substituteWithInferenceVariables(capturedReturnType)));
+      referencedMethodReturnType = psiSubstitutor.substitute(referencedMethodReturnType);
+      referencedMethodReturnType = Registry.is("unsound.capture.conversion.java.spec.change") ? referencedMethodReturnType
+                                                                                              : PsiUtil.captureToplevelWildcards(referencedMethodReturnType, myExpression);
+      constraints.add(new TypeCompatibilityConstraint(returnType, session.substituteWithInferenceVariables(referencedMethodReturnType)));
     }
     
     return true;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newMethodRef/RegistryOptionToSkipUnsoundCaptureConversionInMethodReferenceReturnType.java

@@ -0,0 +1,15 @@
+import java.util.Optional;
+import java.util.function.Function;
+
+abstract class View {
+  {
+    foo(View::returnType).orElse(void.class);
+  }
+
+  abstract <H> Optional<H> foo(Function<View, H> f);
+
+  public Class<?> returnType() {
+    return null;
+  }
+}
+

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

@@ -156,6 +156,7 @@ public class NewMethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
   public void testGetClassReturnTypeInMethodReference() { doTest(); }
   public void testCaptureTypeOfNewArrayExpression() { doTest(); }
   public void testIDEA152659() { doTest(); }
+  public void testRegistryOptionToSkipUnsoundCaptureConversionInMethodReferenceReturnType() { doTest(); }
   public void testFreshVariableLowerBoundsDuringSuperTypeChecks() { doTest(); }
   public void testTypeParameterInstantiation() { doTest(); }
   public void testIgnoreForeignVariables() { doTest(); }

platform/util/resources/misc/registry.properties

@@ -809,6 +809,9 @@ javac.fresh.variables.for.captured.wildcards.only=true
 javac.fresh.variables.for.captured.wildcards.only.description=JLS 18.5.2: if R \u03B8 is a parameterized type, G<A1, ..., An>, and one of A1, ..., An is a wildcard, then, for fresh inference variables \u03B21, ..., \u03B2n ... \
   Javac creates fresh variables only for i: Ai is a wildcard
 
+unsound.capture.conversion.java.spec.change=true
+unsound.capture.conversion.java.spec.change.description=Capture in method reference return type is unsound and the spec would be changed, see https://bugs.openjdk.java.net/browse/JDK-8170887
+
 check.power.supply.for.mbp=false
 check.power.supply.for.mbp.description=Check for discrete video card and power supply on MBPs