IDEA-221210 false positive isEmpty is always true after stream.collect with custom Collector

GitOrigin-RevId: 6b5616254c78f038380ab7f4bf017a5905ce7c9f

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/CFGBuilder.java

@@ -452,6 +452,19 @@ public class CFGBuilder {
     return add(new FlushFieldsInstruction());
   }
 
+  /**
+   * Generate instruction to flush given value if it's variable.
+   *
+   * @param value value to flush
+   * @return this builder
+   */
+  public CFGBuilder flush(DfaValue value) {
+    if (value instanceof DfaVariableValue) {
+      add(new FlushVariableInstruction((DfaVariableValue)value));
+    }
+    return this;
+  }
+
   /**
    * Generate instructions to assign top stack value to the second stack value
    * (usually pushed via {@link #pushForWrite(DfaVariableValue)}).

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/inliner/StreamChainInliner.java

@@ -600,7 +600,7 @@ public class StreamChainInliner implements CallInliner {
     void iteration(CFGBuilder builder) {
       // do nothing currently: we can emulate calling collection.add,
       // but it's unnecessary for current analysis
-      builder.pop();
+      builder.flush(SpecialField.COLLECTION_SIZE.createValue(builder.getFactory(), myResult)).pop();
     }
 
     @Override

java/java-tests/testData/inspection/dataFlow/fixture/StreamToCollectionInlining.java

@@ -0,0 +1,16 @@
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+class Main2 {
+  // IDEA-221210
+  public static void main(String[] args) {
+    List<Integer> originalList = new ArrayList<>();
+    originalList.add(1);
+    final List<Integer> newList = originalList.stream()
+      .collect(Collectors.toCollection(() -> new ArrayList<>(1)));
+
+    boolean empty = newList.isEmpty();
+  }
+
+}

java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspection8Test.java

@@ -174,6 +174,7 @@ public class DataFlowInspection8Test extends DataFlowInspectionTestCase {
   public void testStreamInlining() { doTest(); }
   public void testStreamCollectorInlining() { doTest(); }
   public void testStreamToMapInlining() { doTest(); }
+  public void testStreamToCollectionInlining() { doTest(); }
   public void testStreamComparatorInlining() { doTest(); }
   public void testStreamKnownSource() { doTest(); }
   public void testStreamTypeAnnoInlining() {