Extract not-null expression

java/ql/test/kotlin/library-tests/exprs/exprs.expected

@@ -534,6 +534,9 @@
 | exprs.kt:193:31:193:37 | ... + ... | exprs.kt:192:16:194:9 | <obinit> | AddExpr |
 | exprs.kt:193:36:193:37 | a2 | exprs.kt:192:16:194:9 | <obinit> | VarAccess |
 | exprs.kt:193:40:193:49 | toString(...) | exprs.kt:192:16:194:9 | <obinit> | MethodAccess |
+| exprs.kt:199:5:199:20 | y | exprs.kt:198:1:200:1 | notNullAssertion | LocalVariableDeclExpr |
+| exprs.kt:199:18:199:18 | x | exprs.kt:198:1:200:1 | notNullAssertion | VarAccess |
+| exprs.kt:199:19:199:20 | ...!! | exprs.kt:198:1:200:1 | notNullAssertion | NotNullExpr |
 | file://:0:0:0:0 | C | exprs.kt:146:5:146:33 | foo | TypeAccess |
 | file://:0:0:0:0 | Color | exprs.kt:175:6:179:1 | Color | TypeAccess |
 | file://:0:0:0:0 | Direction | exprs.kt:171:6:173:1 | Direction | TypeAccess |

java/ql/test/kotlin/library-tests/exprs/exprs.kt

@@ -194,3 +194,7 @@ class Class1 {
         }
     }
 }
+
+fun notNullAssertion(x: Any?) {
+    val y: Any = x!!
+}

java/ql/test/kotlin/library-tests/exprs/unaryOp.expected

@@ -0,0 +1 @@
+| exprs.kt:199:19:199:20 | ...!! | exprs.kt:199:18:199:18 | x |

java/ql/test/kotlin/library-tests/exprs/unaryOp.ql

@@ -0,0 +1,36 @@
+import java
+
+newtype TMaybeElement =
+  TElement(Element e) or
+  TNoElement()
+
+class MaybeElement extends TMaybeElement {
+  abstract string toString();
+
+  abstract Location getLocation();
+}
+
+class YesMaybeElement extends MaybeElement {
+  Element e;
+
+  YesMaybeElement() { this = TElement(e) }
+
+  override string toString() { result = e.toString() }
+
+  override Location getLocation() { result = e.getLocation() }
+}
+
+class NoMaybeElement extends MaybeElement {
+  NoMaybeElement() { this = TNoElement() }
+
+  override string toString() { result = "<none>" }
+
+  override Location getLocation() { none() }
+}
+
+MaybeElement op(UnaryExpr e) {
+  if exists(e.getExpr()) then result = TElement(e.getExpr()) else result = TNoElement()
+}
+
+from Expr e
+select e, op(e)