[Wasm] Introduce check and error specialized for String to reduce output size

libraries/stdlib/wasm/src/kotlin/util/PreconditionsWasm.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin
+
+import kotlin.contracts.contract
+
+// Here are functions specialized with String type to avoid marking Any.toString and its overrides as reachable in DCE.
+// Just making the declarations public is impossible since it may change the resolution in a user code. 
+// TODO: investigate other ways to achieve the same, preferably covering not stdlib only but user cases too.
+
+@PublishedApi
+@kotlin.internal.InlineOnly
+internal inline fun check(value: Boolean, lazyMessage: () -> String): Unit {
+    contract {
+        returns() implies value
+    }
+    if (!value) {
+        val message = lazyMessage()
+        throw IllegalStateException(message)
+    }
+}
+
+@PublishedApi
+@kotlin.internal.InlineOnly
+internal inline fun error(message: String): Nothing = throw IllegalStateException(message)