don't generate !! for array access in assignment lvalue

src/org/jetbrains/jet/j2k/ast/Expressions.kt

@@ -2,9 +2,9 @@ package org.jetbrains.jet.j2k.ast
 
 import org.jetbrains.jet.j2k.ast.types.Type
 
-public open class ArrayAccessExpression(val expression : Expression, val index : Expression) : Expression() {
+public open class ArrayAccessExpression(val expression: Expression, val index: Expression, val lvalue: Boolean) : Expression() {
     override fun toKotlin() = expression.toKotlin() +
-        (if (expression.isNullable()) "!!" else "") +
+        (if (!lvalue && expression.isNullable()) "!!" else "") +
         "[" + index.toKotlin() + "]"
 }
 

src/org/jetbrains/jet/j2k/visitors/ExpressionVisitor.kt

@@ -24,8 +24,11 @@ public open class ExpressionVisitor(converter: Converter): StatementVisitor(conv
     }
 
     public override fun visitArrayAccessExpression(expression: PsiArrayAccessExpression?): Unit {
+        val assignment = PsiTreeUtil.getParentOfType(expression, javaClass<PsiAssignmentExpression>())
+        val lvalue = assignment != null && expression == assignment.getLExpression();
         myResult = ArrayAccessExpression(getConverter().expressionToExpression(expression?.getArrayExpression()),
-                getConverter().expressionToExpression(expression?.getIndexExpression()))
+                getConverter().expressionToExpression(expression?.getIndexExpression()),
+                lvalue)
     }
 
     public override fun visitArrayInitializerExpression(expression: PsiArrayInitializerExpression?): Unit {

tests/testData/ast/for/statement/forRangeWithLE.kt

@@ -1,4 +1,4 @@
 var array : IntArray? = IntArray(10)
 for (i in 0..10) {
-array!![i] = i
+array[i] = i
 }

tests/testData/ast/for/statement/forRangeWithLT.kt

@@ -1,4 +1,4 @@
 var array : IntArray? = IntArray(10)
 for (i in 0..10 - 1) {
-array!![i] = i
+array[i] = i
 }

tests/testData/ast/for/statement/forWithBlock.kt

@@ -1,4 +1,4 @@
 var array : IntArray? = IntArray(10)
 for (i in 0..10 - 1) {
-array!![i] = i
+array[i] = i
 }