feat(Escaped Identifiers): add ability to use any symbol wrapped in back ticks.

compiler/testData/codegen/box/classes/quotedClassName.kt

@@ -1,8 +1,5 @@
-// IGNORE_BACKEND: WASM
-// WASM_MUTE_REASON: IGNORED_IN_JS
-// IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
 // IGNORE_BACKEND: JS
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
 
 // Exclamation marks are not valid in names in the dex file format.
 // Therefore, do not attempt to dex this file as it will fail.

compiler/testData/codegen/box/localClasses/nameWithWhitespace.kt

@@ -1,8 +1,5 @@
-// IGNORE_BACKEND: WASM
-// WASM_MUTE_REASON: IGNORED_IN_JS
-// IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
 // IGNORE_BACKEND: JS
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
 
 // Names with spaces are not valid according to the dex specification
 // before DEX version 040. Therefore, do not attempt to dex the resulting

compiler/testData/codegen/box/mangling/parentheses.kt

@@ -1,8 +1,6 @@
-// IGNORE_BACKEND: WASM
-// WASM_MUTE_REASON: IGNORED_IN_JS
 // !SANITIZE_PARENTHESES
-// IGNORE_BACKEND: JS, JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
+// IGNORE_BACKEND: JS
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
 
 // Sanitization is needed here because DxChecker reports ParseException on parentheses in names.
 

compiler/testData/diagnostics/testsWithJsStdLib/name/illegalNameIR.kt

@@ -0,0 +1,29 @@
+// SKIP_TXT
+// IGNORE_BACKEND: JS
+// !LANGUAGE: +JsAllowInvalidCharsIdentifiersEscaping
+
+private fun ` .private `(): String = TODO("")
+
+fun ` .public `(): String = TODO("")
+
+@JsName("  __  ")
+fun foo(): String = TODO("")
+
+@JsName("  ___  ")
+private fun bar(): String = TODO("")
+
+@JsName("validName")
+private fun ` .private with @JsName `(): String = TODO("")
+
+private class ` .private class ` {
+    val ` .field. ` = ""
+}
+
+val x: Int
+    @JsName(".")
+    get() = TODO("")
+
+fun box(x: dynamic) {
+    x.`foo-bar`()
+    x.`ba-z`
+}