move completion suggestions before lambda only when they really match specific expected type (IDEA-183592)

java/java-impl/src/com/intellij/codeInsight/completion/PreferByKindWeigher.java

@@ -255,7 +255,15 @@ public class PreferByKindWeigher extends LookupElementWeigher {
   private boolean isExpectedTypeItem(@NotNull LookupElement item) {
     TypedLookupItem typed = item.as(TypedLookupItem.CLASS_CONDITION_KEY);
     PsiType itemType = typed == null ? null : typed.getType();
-    return itemType != null && Arrays.stream(myExpectedTypes).anyMatch(info -> info.getType().isAssignableFrom(itemType));
+    return itemType != null &&
+           Arrays.stream(myExpectedTypes)
+             .map(ExpectedTypeInfo::getType)
+             .anyMatch(type -> !isTooGeneric(type) && type.isAssignableFrom(itemType));
+  }
+
+  private static boolean isTooGeneric(PsiType type) {
+    PsiType erasure = TypeConversionUtil.erasure(type);
+    return erasure == null || erasure.equalsToText(CommonClassNames.JAVA_LANG_OBJECT);
   }
 
   @NotNull
@@ -278,7 +286,7 @@ public class PreferByKindWeigher extends LookupElementWeigher {
       if (myCompletionType == CompletionType.SMART) {
         boolean inReturn = psiElement().withParents(PsiReferenceExpression.class, PsiReturnStatement.class).accepts(myPosition);
         return inReturn ? ThreeState.YES : ThreeState.UNSURE;
-      } else if (Arrays.stream(myExpectedTypes).anyMatch(info -> PsiType.BOOLEAN.isConvertibleFrom(info.getDefaultType())) &&
+      } else if (Arrays.stream(myExpectedTypes).anyMatch(info -> PsiType.BOOLEAN.isAssignableFrom(info.getDefaultType())) &&
           PsiTreeUtil.getParentOfType(myPosition, PsiIfStatement.class, true, PsiStatement.class, PsiMember.class) == null) {
         return ThreeState.YES;
       }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/completion/normal/PreferLambdaToTooGenericLocalVariables.java

@@ -0,0 +1,5 @@
+class Foo {
+  void foo(java.util.stream.Stream<Foo> s, int local, StringBuilder local2) {
+    s.reduce(<caret>)
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/completion/Normal8CompletionTest.groovy

@@ -310,6 +310,11 @@ class Test88 {
     myFixture.assertPreferredCompletionItems 0, '() -> ', 'AbstractMethodError::new'
   }
 
+  void testPreferLambdaToTooGenericLocalVariables() {
+    configureByTestName()
+    myFixture.assertPreferredCompletionItems 0, '(foo, foo2) -> '
+  }
+
   private checkResultByFileName() {
     checkResultByFile(getTestName(false) + "_after.java")
   }