completion for older java versions: allow boxing even to specify explicit type arguments later when needed

fixing SmartTypeCompletionTest#testIfConditionExpectedType, consequence of changing expected type for condition from boxed to primitive

java/java-impl/src/com/intellij/psi/impl/source/resolve/CompletionParameterTypeInferencePolicy.java

@@ -71,4 +71,9 @@ public class CompletionParameterTypeInferencePolicy extends ProcessCandidatePara
   public boolean inferLowerBoundForFreshVariables() {
     return true;
   }
+
+  @Override
+  public boolean requestForBoxingExplicitly() {
+    return true;
+  }
 }

java/java-psi-api/src/com/intellij/psi/impl/source/resolve/ParameterTypeInferencePolicy.java

@@ -51,4 +51,15 @@ public abstract class ParameterTypeInferencePolicy {
   public boolean inferLowerBoundForFreshVariables() {
     return false;
   }
+
+  /**
+   * Workaround for inference < 1.8. 
+   * 
+   * Boxed type is used for inference as it may be specified as type argument explicitly later for completion 
+   * {@link com.intellij.codeInsight.completion.JavaMethodCallElement#setInferenceSubstitutorFromExpectedType(com.intellij.psi.PsiElement, com.intellij.psi.PsiType)},
+   * but should not be used for normal inference due to javac bug
+   */
+  public boolean requestForBoxingExplicitly() {
+    return false;
+  }
 }

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/PsiOldInferenceHelper.java

@@ -685,6 +685,10 @@ public class PsiOldInferenceHelper implements PsiInferenceHelper {
         expectedType = methodCall instanceof PsiCallExpression ? policy.getDefaultExpectedType((PsiCallExpression)methodCall) : null;
       }
 
+      if (policy.requestForBoxingExplicitly() && TypeConversionUtil.isPrimitiveAndNotNull(expectedType)) {
+        expectedType = ((PsiPrimitiveType)expectedType).getBoxedType(typeParameter);
+      }
+
       returnType = ((PsiMethod)typeParameter.getOwner()).getReturnType();
 
       constraint =

java/java-tests/testData/codeInsight/completion/normal/ExplicitTypeArgumentsWhenParameterTypesDoNotDependOnTypeParameters_after.java

@@ -6,7 +6,7 @@ class Foo<T> {
   }
 
   static {
-    new Foo<Integer>().to(Bar.<Integer>method(<caret>))
+    new Foo<Integer>().to(Bar.method(<caret>))
   }
 }