JS/Inlining: minor improvements and clarifications after code review. Test whether expression without side effect does not prevent to relocate another expressions

js/js.translator/src/org/jetbrains/kotlin/js/translate/callTranslator/CallInfoExtensions.kt

@@ -77,6 +77,9 @@ fun VariableAccessInfo.constructAccessExpression(ref: JsExpression): JsExpressio
         return ref
     } else {
         return if (value !is JsEmptyExpression) {
+            // This is useful when passing AST to TemporaryAssignmentElimination. It can bring
+            // property assignment like `obj.propertyName = $tmp` to places where `$tmp` gets its value,
+            // but only when it's sure that no side effects possible.
             (ref as? HasMetadata)?.let { it.sideEffects = SideEffectKind.PURE }
             JsAstUtils.assignment(ref, value!!)
         }

js/js.translator/src/org/jetbrains/kotlin/js/translate/callTranslator/VariableCallCases.kt

@@ -75,7 +75,7 @@ object DefaultVariableAccessCase : VariableAccessCase() {
     override fun VariableAccessInfo.dispatchReceiver(): JsExpression {
         val accessor = JsNameRef(variableName, dispatchReceiver!!)
         val descriptor = callableDescriptor
-        if (descriptor is PropertyDescriptor && !JsDescriptorUtils.sideEffectsPossible(descriptor)) {
+        if (descriptor is PropertyDescriptor && !JsDescriptorUtils.sideEffectsPossibleOnRead(descriptor)) {
             accessor.sideEffects = SideEffectKind.DEPENDS_ON_STATE
         }
         return constructAccessExpression(accessor)

js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/JsDescriptorUtils.java

@@ -147,7 +147,7 @@ public final class JsDescriptorUtils {
         return accessorDescriptor == null || accessorDescriptor.isDefault();
     }
 
-    public static boolean sideEffectsPossible(@NotNull PropertyDescriptor property) {
+    public static boolean sideEffectsPossibleOnRead(@NotNull PropertyDescriptor property) {
         return !isDefaultAccessor(property.getGetter()) || ModalityKt.isOverridableOrOverrides(property) ||
                 isStaticInitializationPossible(property);
     }

js/js.translator/testData/inlineSizeReduction/cases/propertyReferenceDoesNotProduceSideEffect.kt

@@ -0,0 +1,29 @@
+// CHECK_VARS_COUNT: function=box count=1
+
+package foo
+
+var log = ""
+
+class A() {
+    var x = 23
+}
+
+fun sideEffect(): Int {
+    log += "sideEffect();"
+    return 42
+}
+
+fun bar(a: Int, b: Int) {
+    log += "bar($a, $b);"
+}
+
+inline fun test(a: Int, b: Int) {
+    bar(b, a)
+}
+
+fun box(): String {
+    val a = A()
+    test(sideEffect(), a.x)
+    assertEquals("sideEffect();bar(23, 42);", log)
+    return "OK"
+}

js/js.translator/testData/js-optimizer/temporary-assignment/ifWithoutElse.original.js

@@ -4,18 +4,18 @@ function f(x) {
 
 function box() {
     var result1, result2, $a, $b;
-    
+
     if (f(true)) {
         $a = "1";
     }
     result1 = $a;
     if (result1 !== "1") return "fail1: " + result1;
-    
+
     if (f(false)) {
         $b = "1";
     }
     result2 = $b;
     if (result2 !== void 0) return "fail2: " + result2;
-    
+
     return "OK";
 }