K2: support implicit integer to unsigned conversions...

with dedicated opt-in language feature and special
annotation or module capability.
Not intended for a general use, solves specific K/N
scenario with interop libs.
#KT-55902 fixed

compiler/testData/ir/irText/expressions/signedToUnsignedConversions.fir.kt.txt

@@ -0,0 +1,71 @@
+// FILE: signedToUnsignedConversions_annotation.kt
+package kotlin.internal
+
+open annotation class ImplicitIntegerCoercion : Annotation {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+}
+
+// FILE: signedToUnsignedConversions_test.kt
+
+@ImplicitIntegerCoercion
+const val IMPLICIT_INT: Int
+  field = 255
+  get
+
+@ImplicitIntegerCoercion
+const val EXPLICIT_INT: Int
+  field = 255
+  get
+
+@ImplicitIntegerCoercion
+const val LONG_CONST: Long
+  field = 255L
+  get
+
+@ImplicitIntegerCoercion
+val NON_CONST: Int
+  field = 255
+  get
+
+@ImplicitIntegerCoercion
+const val BIGGER_THAN_UBYTE: Int
+  field = 256
+  get
+
+@ImplicitIntegerCoercion
+const val UINT_CONST: UInt
+  field = 42
+  get
+
+fun takeUByte(@ImplicitIntegerCoercion u: UByte) {
+}
+
+fun takeUShort(@ImplicitIntegerCoercion u: UShort) {
+}
+
+fun takeUInt(@ImplicitIntegerCoercion u: UInt) {
+}
+
+fun takeULong(@ImplicitIntegerCoercion u: ULong) {
+}
+
+fun takeUBytes(@ImplicitIntegerCoercion vararg u: UByte) {
+}
+
+fun takeLong(@ImplicitIntegerCoercion l: Long) {
+}
+
+fun test() {
+  takeUByte(u = 255.toUByte())
+  takeUByte(u = 255.toUByte())
+  takeUShort(u = 255.toUShort())
+  takeUShort(u = 256.toUShort())
+  takeUInt(u = 255.toUInt())
+  takeULong(u = 255.toULong())
+  takeUBytes(u = [255.toUByte(), 255.toUByte(), 42B])
+}