[FIR] Add diagnostic CONFLICTING_OVERLOADS & REDECLARATION

compiler/fir/analysis-tests/testData/resolve/diagnostics/conflictingOverloads.kt

@@ -0,0 +1,68 @@
+<!CONFLICTING_OVERLOADS!>fun test(x: Int) {}<!>
+
+<!CONFLICTING_OVERLOADS!>fun test(y: Int) {}<!>
+
+fun test() {}
+
+fun test(z: Int, c: Char) {}
+
+<!REDECLARATION!>open class A {
+    open fun rest(s: String) {}
+
+    open val u = 20
+}<!>
+
+<!REDECLARATION!>class A {
+
+}<!>
+
+<!REDECLARATION!>class B : A {
+    <!CONFLICTING_OVERLOADS!>override fun rest(s: String) {}<!>
+
+    <!CONFLICTING_OVERLOADS!>fun rest(s: String) {}<!>
+
+    fun rest(l: Long) {}
+
+    override val u = 310
+}<!>
+
+<!REDECLARATION!>interface B<!>
+
+<!REDECLARATION!>enum class B<!>
+
+<!REDECLARATION!>val u = 10<!>
+<!REDECLARATION!>val u = 20<!>
+
+<!REDECLARATION!>typealias TA = A<!>
+<!REDECLARATION!>typealias TA = B<!>
+
+typealias BA = A
+
+fun <T> kek(t: T) where T : (String) -> Any?, T : Char {}
+fun <T> kek(t: T) where T : () -> Boolean, T : String {}
+fun <T : Int> kek(t: T) {}
+
+fun lol(a: Array<Int>) {}
+fun lol(a: Array<Boolean>) {}
+
+<!CONFLICTING_OVERLOADS!>fun <T> mem(t: T) where T : () -> Boolean, T : String {}<!>
+<!CONFLICTING_OVERLOADS!>fun <T> mem(t: T) where T : String, T : () -> Boolean {}<!>
+
+class M {
+    companion <!REDECLARATION!>object<!> {}
+    <!REDECLARATION!>val Companion = object : Any {}<!>
+}
+
+fun B.foo() {}
+
+class L {
+    fun B.foo() {}
+}
+
+fun mest()
+
+class mest
+
+fun() {}
+
+private fun() {}