Supported variable is value pattern matching.

translator/src/org/jetbrains/k2js/translate/PatternTranslator.java

@@ -1,19 +1,15 @@
 package org.jetbrains.k2js.translate;
 
-import com.google.dart.compiler.backend.js.ast.JsExpression;
-import com.google.dart.compiler.backend.js.ast.JsName;
-import com.google.dart.compiler.backend.js.ast.JsNameRef;
+import com.google.dart.compiler.backend.js.ast.*;
 import com.google.dart.compiler.util.AstUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
-import org.jetbrains.jet.lang.psi.JetIsExpression;
-import org.jetbrains.jet.lang.psi.JetPattern;
-import org.jetbrains.jet.lang.psi.JetTypePattern;
-import org.jetbrains.jet.lang.psi.JetTypeReference;
+import org.jetbrains.jet.lang.psi.*;
 
 /**
  * @author Talanov Pavel
  */
+//TODO: fix members order
 public final class PatternTranslator extends AbstractTranslator {
 
     @NotNull
@@ -56,9 +52,22 @@ public final class PatternTranslator extends AbstractTranslator {
         if (pattern instanceof JetTypePattern) {
             return translateTypePattern(expressionToMatch, (JetTypePattern) pattern);
         }
+        if (pattern instanceof JetExpressionPattern) {
+            return translateExpressionPattern(expressionToMatch, (JetExpressionPattern) pattern);
+        }
         throw new AssertionError("Unsupported pattern type " + pattern.getClass());
     }
 
+    @NotNull
+    private JsExpression translateExpressionPattern(JsExpression expressionToMatch, JetExpressionPattern pattern) {
+        JetExpression patternExpression = pattern.getExpression();
+        assert patternExpression != null : "Expression patter should have an expression.";
+        JsExpression expressionToMatchAgainst =
+                Translation.translateAsExpression(patternExpression, translationContext());
+        //TODO: should call equals method here
+        return new JsBinaryOperation(JsBinaryOperator.REF_EQ, expressionToMatch, expressionToMatchAgainst);
+    }
+
     @NotNull
     private JetPattern getPattern(@NotNull JetIsExpression expression) {
         JetPattern pattern = expression.getPattern();

translator/src/org/jetbrains/k2js/translate/WhenTranslator.java

@@ -11,6 +11,7 @@ import java.util.List;
 /**
  * @author Talanov Pavel
  */
+//TODO: fix members order
 public class WhenTranslator extends AbstractTranslator {
 
     @NotNull

translator/test/org/jetbrains/k2js/test/PatternMatchingTest.java

@@ -29,4 +29,9 @@ public final class PatternMatchingTest extends IncludeLibraryTest {
         testFooBoxIsTrue("whenExecutesOnlyOnce.kt");
     }
 
+    @Test
+    public void whenValue() throws Exception {
+        testFooBoxIsTrue("whenValue.kt");
+    }
+
 }

translator/testFiles/patternMatching/cases/whenValue.kt

@@ -0,0 +1,10 @@
+namespace foo
+
+fun box() : Boolean {
+  var a = 4
+  when(a) {
+    is 3 => a = 10;
+    is 4 => a = 20;
+  }
+  return (a == 20)
+}