red code is green: impossible to have 2 signatures with same signature and different primitive return types (IDEA-102866)

(cherry picked from commit c4093d0e8a1021f80fafb3c6b1fc35388da46ac6)

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

@@ -1061,10 +1061,13 @@ public class HighlightMethodUtil {
       if (otherSuperReturnType == null || currentType == null || otherSuperReturnType.equals(currentType)) continue;
 
       if (PsiUtil.isLanguageLevel5OrHigher(currentMethod)) {
-        if (otherSuperReturnType.isAssignableFrom(currentType)) continue;
-        if (currentType.isAssignableFrom(otherSuperReturnType)) {
-          returnTypeSubstitutable = otherSuperSignature;
-          continue;
+        //http://docs.oracle.com/javase/specs/jls/se7/html/jls-8.html#jls-8.4.8 Example 8.1.5-3
+        if (!(otherSuperReturnType instanceof PsiPrimitiveType || currentType instanceof PsiPrimitiveType)) {
+          if (otherSuperReturnType.isAssignableFrom(currentType)) continue;
+          if (currentType.isAssignableFrom(otherSuperReturnType)) {
+            returnTypeSubstitutable = otherSuperSignature;
+            continue;
+          }
         }
       }
       return createIncompatibleReturnTypeMessage(currentMethod, currentMethod, otherSuperMethod, false, otherSuperReturnType,

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/MethodReturnTypeSubstitutability.java

@@ -0,0 +1,17 @@
+
+interface X4 { Integer m(); }
+interface Y4 { Number m(); }
+interface Z4 extends X4, Y4 {}
+
+interface X1 { long m(); }
+interface Y1 { Number m(); }
+<error descr="'m()' in 'Y1' clashes with 'm()' in 'X1'; methods have unrelated return types">interface Z1 extends X1, Y1</error> {}
+
+interface X2 { long m(); }
+interface Y2 { int m(); }
+<error descr="'m()' in 'X2' clashes with 'm()' in 'Y2'; methods have unrelated return types">interface Z2 extends X2, Y2</error> {}
+
+interface X3 { String m(); }
+interface Y3 { Integer m(); }
+<error descr="'m()' in 'Y3' clashes with 'm()' in 'X3'; methods have unrelated return types">interface Z3 extends X3, Y3</error> {}
+

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingJdk6Test.java

@@ -58,4 +58,5 @@ public class LightAdvHighlightingJdk6Test extends LightDaemonAnalyzerTestCase {
   }
 
   public void testJavacQuirks() throws Exception { setLanguageLevel(LanguageLevel.JDK_1_6); doTest(true, false); }
+  public void testMethodReturnTypeSubstitutability() throws Exception { setLanguageLevel(LanguageLevel.JDK_1_6); doTest(true, false); }
 }