[JS FIR] Add JS_NAME_CLASH tests for constructors

^KT-64867 Related

js/js.translator/testData/box/export/topLevelAndClassCtrNameClash.kt

@@ -0,0 +1,62 @@
+// IGNORE_BACKEND_K1: JS_IR, JS_IR_ES6
+// K1 reports a name clash error between top-level declarations and constructors. It seems relevant for legacy JS BE;
+// however, this is not applicable to JS IR BE because in the generated JS code, there is no name clash.
+// K2 doesn't report anything and works correctly with JS IR BE.
+
+// RUN_PLAIN_BOX_FUNCTION
+// MODULE: lib
+// FILE: lib.kt
+@JsExport
+class ClassA {
+    val a: String
+
+    @JsName("createFromString")
+    constructor(y: String) {
+        a = "ClassA:fromString:$y"
+    }
+
+    @JsName("createFromInt")
+    constructor(y: Int) {
+        a = "ClassA:fromInt:$y"
+    }
+}
+
+@JsExport
+class ClassB {
+    val b: String
+
+    @JsName("createFromString")
+    constructor(y: String) {
+        b = "ClassB:fromString:$y"
+    }
+
+    @JsName("createFromInt")
+    constructor(y: Int) {
+        b = "ClassB:fromInt:$y"
+    }
+}
+
+@JsExport
+fun createFromString(y: String) = "fromString:$y";
+
+@JsExport
+fun createFromInt(y: Int) = "fromInt:$y";
+
+// FILE: main.js
+function box() {
+    var a1 = this.lib.ClassA.createFromString("A1");
+    var a2 = this.lib.ClassA.createFromInt(2);
+    var b3 = this.lib.ClassB.createFromString("B3");
+    var b4 = this.lib.ClassB.createFromInt(4);
+    var x5 = this.lib.createFromString("X5");
+    var x6 = this.lib.createFromInt(6);
+
+    if (a1.a !== "ClassA:fromString:A1") return "Error: '" + a1.a + "' !== 'ClassA:fromString:A1'"
+    if (a2.a !== "ClassA:fromInt:2") return "Error: '" + a2.a + "' !== 'ClassA:fromInt:2'"
+    if (b3.b !== "ClassB:fromString:B3") return "Error: '" + b3.b + "' !== 'ClassB:fromString:B3'"
+    if (b4.b !== "ClassB:fromInt:4") return "Error: '" + b4.b + "' !== 'ClassB:fromInt:4'"
+    if (x5 !== "fromString:X5") return "Error: '" + x5 + "' !== 'fromString:X5'"
+    if (x6 !== "fromInt:6") return "Error: '" + x6 + "' !== 'fromInt:6'"
+
+    return "OK"
+}