bad code green: reject return type constraint if unchecked conversion was applied during applicability check and return type is type parameter

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

@@ -689,6 +689,12 @@ public class InferenceSession {
   public void registerReturnTypeConstraints(PsiType returnType, PsiType targetType) {
     returnType = substituteWithInferenceVariables(returnType);
     if (myErased) {
+      final InferenceVariable inferenceVariable = getInferenceVariable(returnType);
+      if (inferenceVariable != null) {
+        final PsiSubstitutor substitutor = resolveSubset(Collections.singletonList(inferenceVariable), mySiteSubstitutor);
+        returnType = substitutor.substitute(inferenceVariable);
+        if (returnType == null) return;
+      }
       addConstraint(new TypeCompatibilityConstraint(targetType, TypeConversionUtil.erasure(returnType)));
     }
     else if (FunctionalInterfaceParameterizationUtil.isWildcardParameterized(returnType)) {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/IDEA56754.java

@@ -1,5 +1,5 @@
 class Foo<T extends Enum> {
   public T bar(Class<? extends T> type, String str) {
-    <error descr="Incompatible types. Found: 'java.lang.Enum', required: 'T'">return Enum.valueOf(type, str);</error>
+    return Enum.valueOf(<error descr="'valueOf(java.lang.Class<T>, java.lang.String)' in 'java.lang.Enum' cannot be applied to '(java.lang.Class<capture<? extends T>>, java.lang.String)'">type</error>, str);
   }
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/UncheckedWarningsInsideIncorporationPhase.java

@@ -4,7 +4,7 @@ abstract class Group {
   }
 
   public <T extends Category> T get(Key<T> key) {
-    <error descr="Incompatible types. Found: 'Category', required: 'T'">return getCategory(key);</error>
+    return getCategory<error descr="'getCategory(Key<R>)' in 'Group' cannot be applied to '(Key<T>)'">(key)</error>;
   }
 
   public abstract <R extends Category<R>> R getCategory(Key<R> key);

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/graphInference/PrimitiveTypeInReturnConstraintWithUncheckedConversion.java

@@ -0,0 +1,12 @@
+import java.util.List;
+
+class Test {
+  <T> T foo(List<T> l) {
+    return l.get(0);
+  }
+
+  void m(List l){
+    <error descr="Incompatible types. Found: 'java.lang.Object', required: 'boolean'">boolean foo = foo(l);</error>
+    <error descr="Incompatible types. Found: 'java.lang.Object', required: 'java.lang.String'">String s = foo(l);</error>
+  }
+}

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

@@ -429,6 +429,10 @@ public class GraphInferenceHighlightingTest extends LightDaemonAnalyzerTestCase
     doTest();
   }
 
+  public void testPrimitiveTypeInReturnConstraintWithUncheckedConversion() throws Exception {
+    doTest();
+  }
+
   public void testVariableNamesOfNestedCalls() throws Exception {
     IdeaTestUtil.setTestVersion(JavaSdkVersion.JDK_1_8, getModule(), getTestRootDisposable());
     String filePath = BASE_PATH + "/" + getTestName(false) + ".java";