infer nullity: check for switch conditions (IDEA-61451)

java/java-impl/src/com/intellij/codeInspection/inferNullity/NullityInferrer.java

@@ -578,6 +578,10 @@ public class NullityInferrer {
           return true;
         }
       }
+      else if (parent instanceof PsiSwitchStatement && ((PsiSwitchStatement)parent).getExpression() == expr) {
+        registerNotNullAnnotation(parameter);
+        return true;
+      }
 
       final PsiCall call = PsiTreeUtil.getParentOfType(expr, PsiCall.class);
       if (call != null) {

java/java-tests/testData/codeInsight/nullityinferrer/afterTryEnumSwitch.java

@@ -0,0 +1,13 @@
+import org.jetbrains.annotations.*;
+
+public class Infer {
+    enum E {;
+    }
+
+    void trySwitchEnum(@NotNull E e) {
+        switch (e) {
+
+        }
+    }
+
+}

java/java-tests/testData/codeInsight/nullityinferrer/beforeTryEnumSwitch.java

@@ -0,0 +1,13 @@
+import org.jetbrains.annotations.*;
+
+public class Infer {
+    enum E {;
+    }
+
+    void trySwitchEnum(E e) {
+        switch (e) {
+
+        }
+    }
+
+}

java/java-tests/testSrc/com/intellij/codeInsight/NullityInferrerTest.java

@@ -66,6 +66,10 @@ public class NullityInferrerTest extends CodeInsightTestCase {
     doTest(true);
   }
 
+  public void testTryEnumSwitch() throws Exception {
+    doTest(true);
+  }
+
   //-----------------------fields---------------------------------------------------
   public void testFieldsAssignment() throws Exception {
     doTest(false);