IR: make IrConst.copyWithOffsets an extension function

Co-authored-by: mcpiroman <mcpiroman@gmail.com>

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/IrConst.kt

@@ -11,8 +11,6 @@ abstract class IrConst<T> : IrExpression() {
     abstract val kind: IrConstKind<T>
     abstract val value: T
 
-    abstract fun copyWithOffsets(startOffset: Int, endOffset: Int): IrConst<T>
-
     override fun <R, D> accept(visitor: IrElementVisitor<R, D>, data: D): R =
         visitor.visitConst(this, data)
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/impl/IrConstImpl.kt

@@ -30,9 +30,6 @@ class IrConstImpl<T>(
     override val kind: IrConstKind<T>,
     override val value: T
 ) : IrConst<T>() {
-    override fun copyWithOffsets(startOffset: Int, endOffset: Int) =
-        IrConstImpl(startOffset, endOffset, type, kind, value)
-
     companion object {
         fun string(startOffset: Int, endOffset: Int, type: IrType, value: String): IrConstImpl<String> =
             IrConstImpl(startOffset, endOffset, type, IrConstKind.String, value)
@@ -86,3 +83,6 @@ class IrConstImpl<T>(
         }
     }
 }
+
+fun <T> IrConst<T>.copyWithOffsets(startOffset: Int, endOffset: Int) =
+    IrConstImpl(startOffset, endOffset, type, kind, value)