erasure of method call expression type if method is not generics but unchecked conversion was needed to check the applicability (IDEA-157223)

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

@@ -15,6 +15,7 @@
  */
 package com.intellij.psi.impl.source.tree.java;
 
+import com.intellij.codeInsight.daemon.impl.analysis.JavaGenericsUtil;
 import com.intellij.lang.ASTNode;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.projectRoots.JavaSdkVersion;
@@ -254,14 +255,18 @@ public class PsiMethodCallExpressionImpl extends ExpressionPsiElement implements
     // If unchecked conversion was necessary for the method to be applicable, 
     // the parameter types of the invocation type are the parameter types of the method's type,
     // and the return type and thrown types are given by the erasures of the return type and thrown types of the method's type.
-    if (!languageLevel.isAtLeast(LanguageLevel.JDK_1_8) && 
-        (method.hasTypeParameters() || JavaVersionService.getInstance().isAtLeast(call, JavaSdkVersion.JDK_1_8)) &&
+    if ((!languageLevel.isAtLeast(LanguageLevel.JDK_1_8) && method.hasTypeParameters() ||
+         !method.hasTypeParameters() && JavaVersionService.getInstance().isAtLeast(call, JavaSdkVersion.JDK_1_8)) &&
         result instanceof MethodCandidateInfo && ((MethodCandidateInfo)result).isApplicable()) {
       final PsiType[] args = call.getArgumentList().getExpressionTypes();
-      final boolean allowUncheckedConversion = false;
-      final int applicabilityLevel = PsiUtil.getApplicabilityLevel(method, substitutor, args, languageLevel, allowUncheckedConversion, true);
-      if (applicabilityLevel == MethodCandidateInfo.ApplicabilityLevel.NOT_APPLICABLE) {
-        return TypeConversionUtil.erasure(substitutedReturnType);
+      final PsiParameter[] parameters = method.getParameterList().getParameters();
+      final boolean varargs = ((MethodCandidateInfo)result).getApplicabilityLevel() == MethodCandidateInfo.ApplicabilityLevel.VARARGS;
+      for (int i = 0; i < args.length; i++) {
+        final PsiType parameterType = substitutor.substitute(PsiTypesUtil.getParameterType(parameters, i, varargs));
+        final PsiType expressionType = args[i];
+        if (expressionType != null && parameterType != null && JavaGenericsUtil.isRawToGeneric(parameterType, expressionType)) {
+          return TypeConversionUtil.erasure(substitutedReturnType);
+        }
       }
     }
 

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

@@ -0,0 +1,19 @@
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+class Test {
+  public static <Om> List<Om> sort(Comparator comp, Stream<Om> stream) {
+    <error descr="Incompatible types. Found: 'java.lang.Object', required: 'java.util.List<Om>'">return stream.sorted(comp).collect(Collectors.toList());</error>
+  }
+
+  //accept unbounded wildcards
+  List<String> get(List<?> lists) {
+    return null;
+  }
+
+  void foo(List l) {
+    String p = get(l).get(0);
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/GenericsHighlighting8Test.java

@@ -994,4 +994,8 @@ public class GenericsHighlighting8Test extends LightDaemonAnalyzerTestCase {
   public void testNestedCaptures() throws Exception {
     doTest();
   }
+
+  public void testErasureOfReturnTypeOfNonGenericMethod() throws Exception {
+    doTest();
+  }
 }