[TS] Add and refactor ops

usvm-ts/src/main/kotlin/org/usvm/api/TsTest.kt

@@ -33,7 +33,13 @@ sealed interface TsTestValue {
     data object TsException : TsTestValue
 
     data class TsBoolean(val value: Boolean) : TsTestValue
-    data class TsString(val value: String) : TsTestValue
+
+    data class TsString(val value: String) : TsTestValue {
+        override fun toString(): String {
+            return "${this::class.simpleName}(value=\"$value\")"
+        }
+    }
+
     data class TsBigInt(val value: String) : TsTestValue
 
     sealed interface TsNumber : TsTestValue {

usvm-ts/src/main/kotlin/org/usvm/machine/expr/CallApproximations.kt

@@ -72,6 +72,11 @@ fun TsExprResolver.tryApproximateInstanceCall(
         }
     }
 
+    // Handle 'Boolean' constructor calls
+    if (expr.callee.enclosingClass.name == "Boolean" && expr.callee.name == CONSTRUCTOR_NAME) {
+        return from(handleBooleanConstructor(expr))
+    }
+
     // Handle `Promise` constructor calls
     if (expr.callee.enclosingClass.name == "Promise" && expr.callee.name == CONSTRUCTOR_NAME) {
         return from(handlePromiseConstructor(expr))
@@ -194,6 +199,15 @@ private fun TsExprResolver.handleNumberIsNaN(expr: EtsInstanceCallExpr): UBoolEx
     }
 }
 
+private fun TsExprResolver.handleBooleanConstructor(expr: EtsInstanceCallExpr): UExpr<*>? = with(ctx) {
+    check(expr.args.size == 1) {
+        "Boolean constructor should have exactly one argument, but got ${expr.args.size}"
+    }
+    val arg = resolve(expr.args.single()) ?: return null
+
+    mkTruthyExpr(arg, scope)
+}
+
 private fun TsExprResolver.handlePromiseConstructor(expr: EtsInstanceCallExpr): UExpr<*>? = with(ctx) {
     val instance = resolve(expr.instance) ?: return null
     val promise = instance.asExpr(addressSort)

usvm-ts/src/main/kotlin/org/usvm/machine/expr/ExprUtil.kt

@@ -149,3 +149,36 @@ fun TsContext.mkNumericExpr(
         )
     )
 }
+
+fun TsContext.mkNullishExpr(
+    expr: UExpr<out USort>,
+    scope: TsStepScope,
+): UBoolExpr {
+    // Handle fake objects specially
+    if (expr.isFakeObject()) {
+        val fakeType = expr.getFakeType(scope)
+        val ref = expr.extractRef(scope)
+        // Only check for nullish if the fake object represents a reference type.
+        // If it represents a primitive type (bool/number), it's never nullish.
+        return mkIte(
+            condition = fakeType.refTypeExpr,
+            trueBranch = mkOr(
+                mkHeapRefEq(ref, mkTsNullValue()),
+                mkHeapRefEq(ref, mkUndefinedValue())
+            ),
+            falseBranch = mkFalse(),
+        )
+    }
+
+    // Regular reference is nullish if it is either null or undefined
+    if (expr.sort == addressSort) {
+        val ref = expr.asExpr(addressSort)
+        return mkOr(
+            mkHeapRefEq(ref, mkTsNullValue()),
+            mkHeapRefEq(ref, mkUndefinedValue())
+        )
+    }
+
+    // Non-reference types (numbers, booleans, strings) are never nullish
+    return mkFalse()
+}