type compatibility constrain: unchecked conversion: return type is inference variable case

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

@@ -332,7 +332,8 @@ public class InferenceSession {
   private InferenceVariable shouldResolveAndInstantiate(PsiType returnType, PsiType targetType) {
     final InferenceVariable inferenceVariable = getInferenceVariable(returnType);
     if (inferenceVariable != null) {
-      if (targetType instanceof PsiPrimitiveType && hasPrimitiveWrapperBound(inferenceVariable)) {
+      if (targetType instanceof PsiPrimitiveType && hasPrimitiveWrapperBound(inferenceVariable) ||
+          targetType instanceof PsiClassType && hasUncheckedBounds(inferenceVariable, (PsiClassType)targetType)) {
         return inferenceVariable;
       }
     }
@@ -351,6 +352,21 @@ public class InferenceSession {
     return false;
   }
 
+  private static boolean hasUncheckedBounds(InferenceVariable inferenceVariable, PsiClassType targetType) {
+    if (!targetType.isRaw()) {
+      final InferenceBound[] boundTypes = {InferenceBound.EQ, InferenceBound.LOWER};
+      for (InferenceBound inferenceBound : boundTypes) {
+        final List<PsiType> bounds = inferenceVariable.getBounds(inferenceBound);
+        for (PsiType bound : bounds) {
+          if (TypeCompatibilityConstraint.isUncheckedConversion(targetType, bound)) {
+            return true;
+          }
+        }
+      }
+    }
+    return false;
+  }
+
   private PsiType getTargetType(final PsiExpression context) {
     final PsiElement parent = PsiUtil.skipParenthesizedExprUp(context.getParent());
     if (parent instanceof PsiExpressionList) {

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

@@ -19,7 +19,6 @@ import com.intellij.psi.*;
 import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession;
 import com.intellij.psi.util.PsiUtil;
 import com.intellij.psi.util.TypeConversionUtil;
-import com.intellij.psi.util.TypesDistinctProver;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
@@ -56,13 +55,16 @@ public class TypeCompatibilityConstraint implements ConstraintFormula {
       }
     }
 
-    if (isUncheckedConversion(session, myT, myS)) return true;
+    if (isUncheckedConversion(myT, myS)) {
+      session.setErased();
+      return true;
+    }
 
     constraints.add(new SubtypingConstraint(myT, myS, true));
     return true;
   }
 
-  private static boolean isUncheckedConversion(InferenceSession session, final PsiType t, final PsiType s) {
+  public static boolean isUncheckedConversion(final PsiType t, final PsiType s) {
     if (t instanceof PsiClassType && !((PsiClassType)t).isRaw() && s instanceof PsiClassType) {
       final PsiClassType.ClassResolveResult tResult = ((PsiClassType)t).resolveGenerics();
       final PsiClassType.ClassResolveResult sResult = ((PsiClassType)s).resolveGenerics();
@@ -71,13 +73,12 @@ public class TypeCompatibilityConstraint implements ConstraintFormula {
       if (tClass != null && sClass != null) {
         final PsiSubstitutor sSubstitutor = TypeConversionUtil.getClassSubstitutor(tClass, sClass, sResult.getSubstitutor());
         if (sSubstitutor != null && PsiUtil.isRawSubstitutor(tClass, sSubstitutor)) {
-          session.setErased();
           return true;
         }
       }
     } 
     else if (t instanceof PsiArrayType && t.getArrayDimensions() == s.getArrayDimensions()) {
-      return isUncheckedConversion(session, t.getDeepComponentType(), s.getDeepComponentType());
+      return isUncheckedConversion(t.getDeepComponentType(), s.getDeepComponentType());
     }
     return false;
   }

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

@@ -0,0 +1,10 @@
+public class Sample {
+  interface G<A> {}
+  interface G1 extends G {}
+
+  <B> B bar(B b) {return null;}
+
+  void f(G1 g1) {
+    G<String> l11 = bar(g1);
+  }
+}

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

@@ -38,6 +38,10 @@ public class ConstraintsInferenceMiscTest extends LightDaemonAnalyzerTestCase {
     doTest(false);
   }
 
+  public void testTypeCompatibilityUncheckedConversionReturnConstraints() throws Exception {
+    doTest(false);
+  }
+
   private void doTest(final boolean checkWarnings) {
     doTestNewInference(BASE_PATH + "/" + getTestName(false) + ".java", checkWarnings, false);
   }