KT-2310: js: !! translated incorrectly (syntax ok, but logic not).

#KT-2310 Fixed

js/js.tests/test/org/jetbrains/k2js/test/semantics/MiscTest.java

@@ -148,6 +148,10 @@ public final class MiscTest extends AbstractExpressionTest {
         fooBoxTest();
     }
 
+    public void testExclExclResultIsComputedOnce() throws Exception {
+        fooBoxTest();
+    }
+
     public void testLazyPropertyGetterNotCalledOnStart() throws Exception {
         checkOutput("lazyProperty.kt", "Hello, world! Gotcha 3");
     }

js/js.translator/src/org/jetbrains/k2js/translate/operation/UnaryOperationTranslator.java

@@ -19,10 +19,11 @@ package org.jetbrains.k2js.translate.operation;
 import com.google.dart.compiler.backend.js.ast.JsBinaryOperation;
 import com.google.dart.compiler.backend.js.ast.JsConditional;
 import com.google.dart.compiler.backend.js.ast.JsExpression;
-import com.google.dart.compiler.backend.js.ast.JsNameRef;
+import com.google.dart.compiler.util.AstUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.psi.JetUnaryExpression;
 import org.jetbrains.jet.lexer.JetTokens;
+import org.jetbrains.k2js.translate.context.TemporaryVariable;
 import org.jetbrains.k2js.translate.context.TranslationContext;
 import org.jetbrains.k2js.translate.reference.CallBuilder;
 import org.jetbrains.k2js.translate.reference.CallType;
@@ -63,9 +64,10 @@ public final class UnaryOperationTranslator {
 
     @NotNull
     private static JsExpression translateExclExclOperator(@NotNull JetUnaryExpression expression, @NotNull TranslationContext context) {
-        JsNameRef cachedValue = context.declareTemporary(translateAsExpression(getBaseExpression(expression), context), true).reference();
-        JsBinaryOperation notNullCheck = notNullCheck(context, cachedValue);
-        return new JsConditional(notNullCheck, cachedValue, context.namer().throwNPEFunctionCall());
+        TemporaryVariable cachedValue = context.declareTemporary(translateAsExpression(getBaseExpression(expression), context), false);
+        JsBinaryOperation initAndCheckNotNull = AstUtil.newSequence(cachedValue.assignmentExpression(),
+                                                             notNullCheck(context, cachedValue.reference()));
+        return new JsConditional(initAndCheckNotNull, cachedValue.reference(), context.namer().throwNPEFunctionCall());
     }
 
     @NotNull

js/js.translator/testFiles/expression/misc/cases/exclExclResultIsComputedOnce.kt

@@ -0,0 +1,12 @@
+package foo
+
+var c = 0
+val a: Int?
+  get() {
+      c++
+      return 2
+  }
+
+fun box() : Boolean {
+  return c == 0 && (a!! + 3) == 5 && c == 1
+}