Specificity supported for dynamic types

compiler/testData/diagnostics/tests/dynamicTypes/overloading.kt

@@ -0,0 +1,26 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// MODULE[js]: m1
+// FILE: k.kt
+
+fun dyn(d: dynamic) {}
+
+fun foo(d: dynamic): String = ""
+fun foo(d: Int): Int = 1
+
+fun nothing(d: dynamic): Int = 1
+fun nothing(d: Nothing): String = ""
+
+fun test(d: dynamic) {
+    dyn(1)
+    dyn("")
+
+    foo(1).checkType { it : _<Int> }
+    foo("").checkType { it : _<String> }
+
+    // Checking specificity of `dynamic` vs `Nothing`
+    nothing(d).checkType { it : _<String> }
+    nothing("").checkType { it : _<Int> }
+    [suppress("UNREACHABLE_CODE")] nothing(null!!).checkType { it : _<String> }
+}

compiler/testData/diagnostics/tests/dynamicTypes/overloading.txt

@@ -0,0 +1,8 @@
+package
+
+internal fun dyn(/*0*/ d: (kotlin.Nothing..kotlin.Any?)): kotlin.Unit
+internal fun foo(/*0*/ d: (kotlin.Nothing..kotlin.Any?)): kotlin.String
+internal fun foo(/*0*/ d: kotlin.Int): kotlin.Int
+internal fun nothing(/*0*/ d: dynamic): kotlin.Int
+internal fun nothing(/*0*/ d: kotlin.Nothing): kotlin.String
+internal fun test(/*0*/ d: dynamic): kotlin.Unit