dfa: support contracts with no args (IDEA-127768)

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

@@ -89,10 +89,16 @@ public class MethodContract {
         throw new ParseException("A contract clause must be in form arg1, ..., argN -> return-value");
       }
 
-      String[] argStrings = clause.substring(0, arrowIndex).split(",");
-      ValueConstraint[] args = new ValueConstraint[argStrings.length];
-      for (int i = 0; i < args.length; i++) {
-        args[i] = parseConstraint(argStrings[i]);
+      String beforeArrow = clause.substring(0, arrowIndex);
+      ValueConstraint[] args;
+      if (StringUtil.isNotEmpty(beforeArrow)) {
+        String[] argStrings = beforeArrow.split(",");
+        args = new ValueConstraint[argStrings.length];
+        for (int i = 0; i < args.length; i++) {
+          args[i] = parseConstraint(argStrings[i]);
+        }
+      } else {
+        args = new ValueConstraint[0];
       }
       result.add(new MethodContract(args, parseConstraint(clause.substring(arrowIndex + arrow.length()))));
     }

java/java-tests/testData/inspection/dataFlow/CheckedExceptionDominance/src/Test.java

@@ -19,6 +19,6 @@
    }
 
    public static void bar() throws CheckedException {
-     throw new CheckedException();
+     if (new Random().nextInt() > 2) throw new CheckedException();
    }
  }

java/java-tests/testData/inspection/dataFlow/IDEADEV10489/expected.xml

@@ -7,7 +7,7 @@
   </problem>
   <problem>
     <file>IDEADEV10489.java</file>
-    <line>12</line>
+    <line>8</line>
     <description>Method invocation 's.length()' may produce NullPointerException</description>
   </problem>
 </problems>

java/java-tests/testData/inspection/dataFlow/IDEADEV10489/src/IDEADEV10489.java

@@ -1,7 +1,5 @@
 class IDEADEV10489 {
-    static String getS() {
-        return null;
-    }
+    static native String getS();
 
     static void f() {
         String s = getS();
@@ -17,7 +15,5 @@ class IDEADEV10489 {
         }
     }
 
-    private static boolean foo() {
-      return false;
-    }
+    private static native boolean foo();
 }

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

@@ -18,7 +18,5 @@ class Test {
     }
   }
 
-  private static @NotNull String createString() {
-    throw new NullPointerException();
-  }
+  private static native @NotNull String createString();
 }

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

@@ -1,3 +1,5 @@
+import java.util.Random;
+
 class BrokenAlignment {
 
   public static void main(String[] args) {
@@ -20,7 +22,7 @@ class BrokenAlignment {
   }
 
   public static void doSomething() {
-    throw new RuntimeException("dummy");
+    if (new Random().nextInt() > 2) throw new RuntimeException("dummy");
   }
 
 }

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

@@ -0,0 +1,24 @@
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+class Doo {
+
+  @NotNull
+  public String doSomething() {
+    String s = getSomeString();
+    if (s == null) {
+      throwSomeError();
+    }
+    return s;
+  }
+
+  private static void throwSomeError() {
+    throw new RuntimeException();
+  }
+
+  @Nullable
+  public String getSomeString() {
+    return Math.random() > 0.5 ? null : "Yeah";
+  }
+
+}

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

@@ -252,6 +252,7 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testRootThrowableCause() { doTest(); }
 
   public void testUseInferredContracts() { doTest(); }
+  public void testContractWithNoArgs() { doTest(); }
   public void testContractInferenceBewareOverriding() { doTest(); }
 
   public void testNumberComparisonsWhenValueIsKnown() { doTest(); }