PsiMethodReferenceUtil#getMethodReferenceReturnType: revert 07a45d1, public delegate instead

Review ID: IDEA-CR-24131

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightVisitorImpl.java

@@ -1432,7 +1432,7 @@ public class HighlightVisitorImpl extends JavaElementVisitor implements Highligh
     }
 
     if (!myHolder.hasErrorResults()) {
-      final String badReturnTypeMessage = PsiMethodReferenceUtil.checkReturnType(expression, functionalInterfaceType);
+      final String badReturnTypeMessage = PsiMethodReferenceUtil.checkReturnType(expression, result, functionalInterfaceType);
       if (badReturnTypeMessage != null) {
         HighlightInfo info =
           HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).range(expression).descriptionAndTooltip(badReturnTypeMessage).create();

java/java-psi-api/src/com/intellij/psi/PsiMethodReferenceUtil.java

@@ -16,12 +16,14 @@
 package com.intellij.psi;
 
 import com.intellij.codeInsight.PsiEquivalenceUtil;
+import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.util.Ref;
 import com.intellij.psi.util.*;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class PsiMethodReferenceUtil {
+  private static final Logger LOG = Logger.getInstance(PsiMethodReferenceUtil.class);
 
   public static boolean isSecondSearchPossible(PsiType[] parameterTypes,
                                                QualifierResolveResult qualifierResolveResult,
@@ -69,8 +71,10 @@ public class PsiMethodReferenceUtil {
     }
   }
 
-  public static boolean isReturnTypeCompatible(PsiMethodReferenceExpression expression, PsiType functionalInterfaceType) {
-    return isReturnTypeCompatible(expression, functionalInterfaceType, null);
+  public static boolean isReturnTypeCompatible(PsiMethodReferenceExpression expression,
+                                               JavaResolveResult result,
+                                               PsiType functionalInterfaceType) {
+    return isReturnTypeCompatible(expression, result, functionalInterfaceType, null);
   }
 
   /**
@@ -80,7 +84,17 @@ public class PsiMethodReferenceUtil {
    * @return an actual method reference return type
    */
   public static PsiType getMethodReferenceReturnType(PsiMethodReferenceExpression expression) {
-    JavaResolveResult result = expression.advancedResolve(false);
+    return getMethodReferenceReturnType(expression, expression.advancedResolve(false));
+  }
+
+  /**
+   * Returns actual return type of method reference (not the expected one)
+   *
+   * @param expression a method reference to get the return type of
+   * @param result the result of method reference resolution
+   * @return an actual method reference return type
+   */
+  private static PsiType getMethodReferenceReturnType(PsiMethodReferenceExpression expression, JavaResolveResult result) {
     PsiSubstitutor subst = result.getSubstitutor();
 
     PsiType methodReturnType = null;
@@ -123,6 +137,7 @@ public class PsiMethodReferenceUtil {
   }
 
   private static boolean isReturnTypeCompatible(PsiMethodReferenceExpression expression,
+                                                JavaResolveResult result,
                                                 PsiType functionalInterfaceType,
                                                 Ref<String> errorMessage) {
     final PsiClassType.ClassResolveResult resolveResult = PsiUtil.resolveGenericsClassInType(functionalInterfaceType);
@@ -134,7 +149,7 @@ public class PsiMethodReferenceUtil {
         return true;
       }
 
-      PsiType methodReturnType = getMethodReferenceReturnType(expression);
+      PsiType methodReturnType = getMethodReferenceReturnType(expression, result);
       if (methodReturnType == null || PsiType.VOID.equals(methodReturnType)) {
         return false;
       }
@@ -357,9 +372,9 @@ public class PsiMethodReferenceUtil {
     return null;
   }
 
-  public static String checkReturnType(PsiMethodReferenceExpression expression, PsiType functionalInterfaceType) {
+  public static String checkReturnType(PsiMethodReferenceExpression expression, JavaResolveResult result, PsiType functionalInterfaceType) {
     final Ref<String> errorMessage = Ref.create();
-    if (!isReturnTypeCompatible(expression, functionalInterfaceType, errorMessage)) {
+    if (!isReturnTypeCompatible(expression, result, functionalInterfaceType, errorMessage)) {
       return errorMessage.get();
     }
     return null;

java/java-psi-impl/src/com/intellij/psi/impl/source/tree/java/PsiMethodReferenceExpressionImpl.java

@@ -430,7 +430,7 @@ public class PsiMethodReferenceExpressionImpl extends JavaStubPsiElement<Functio
       return false;
     }
 
-    return PsiMethodReferenceUtil.isReturnTypeCompatible(this, left);
+    return PsiMethodReferenceUtil.isReturnTypeCompatible(this, result, left);
   }
 
   @Nullable