[java-dfa] Flush mutable values from stack on call

GitOrigin-RevId: 64af8932d62f74966222a24cdb87472091f8a661

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/java/inst/MethodCallInstruction.java

@@ -239,8 +239,16 @@ public class MethodCallInstruction extends ExpressionPushingInstruction {
     DfaValue[] args = callArguments.toArray();
     for (DfaMemoryState state : finalStates) {
       ContractValue.flushContractTempVariables(state);
+      boolean keepNonFlushed = state.peek() instanceof DfaVariableValue;
+      DfaValue tos = null;
+      if (keepNonFlushed) {
+        tos = state.pop();
+      }
       callArguments.flush(state, factory, realMethod);
-      pushResult(interpreter, state, state.pop(), args);
+      if (!keepNonFlushed) {
+        tos = state.pop();
+      }
+      pushResult(interpreter, state, tos, args);
       result[i++] = nextState(interpreter, state);
     }
     return result;

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

@@ -6,6 +6,10 @@ class Doo {
   @Nullable
   Object getMethod() {return null;}
 
+  @Nullable
+  @Contract(pure=true)
+  Object getMethodPure() {return null;}
+
   boolean isSomething() { return false;}
 
   @Contract(pure=true)
@@ -24,7 +28,16 @@ class Doo {
     if (getMethod() == null && !pureSomething()) {
       return;
     } else {
-      System.out.println(getMethod().<warning descr="Method invocation 'hashCode' may produce 'NullPointerException'">hashCode</warning>());
+      // still not sure about nullability as getMethod() is not pure
+      System.out.println(getMethod().hashCode());
+    }
+  }
+
+  public void main4() {
+    if (getMethodPure() == null && !pureSomething()) {
+      return;
+    } else {
+      System.out.println(getMethodPure().<warning descr="Method invocation 'hashCode' may produce 'NullPointerException'">hashCode</warning>());
     }
   }
 

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

@@ -3,6 +3,7 @@ import java.util.*;
 
 public class PrimitiveGetters {
   interface Xyz {
+    @Contract(pure = true)
     boolean isFoo();
   }
 

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

@@ -0,0 +1,11 @@
+public class StringBuilderLengthReturn {
+  private static StringBuilder update(StringBuilder sb) {
+    sb.append("xyz");
+    return sb;
+  }
+
+  void test(StringBuilder sb) {
+    // No 'always zero' warning
+    int diff = sb.length() - update(sb).length();
+  }
+}

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

@@ -714,4 +714,5 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
   public void testEnumOrdinal() { doTest(); }
   public void testThisInEnumSubclass() { doTest(); }
   public void testVarargConstructorNoArgs() { doTest(); }
+  public void testStringBuilderLengthReturn() { doTest(); }
 }

platform/analysis-impl/src/com/intellij/codeInspection/dataFlow/memory/DfaMemoryStateImpl.java

@@ -1322,6 +1322,9 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
                                                              !dv.isStable() && qualifierStatusMap.shouldFlush(val, dv.isCall()))) {
         return myFactory.fromDfType(type.getBasicType());
       }
+      if (val instanceof DfaVariableValue && qualifierStatusMap.shouldFlush((DfaVariableValue)val)) {
+        return myFactory.fromDfType(type);
+      }
       return val;
     });
   }