Added test for EA-53340.

compiler/testData/diagnostics/tests/regressions/ea53340.kt

@@ -0,0 +1,7 @@
+class A : Function0<Int> {
+    override fun invoke(): Int = 1
+}
+
+fun main(args : Array<String>) {
+    A()()
+}

compiler/testData/diagnostics/tests/regressions/ea53340.txt

@@ -0,0 +1,11 @@
+package
+
+internal fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit
+
+internal final class A : () -> kotlin.Int {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ fun invoke(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}