IR: add IrSimpleFunction.isInfix

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/overrides/FakeOverrideCopier.kt

@@ -59,7 +59,8 @@ class FakeOverrideCopier(
             isTailrec = declaration.isTailrec,
             isSuspend = declaration.isSuspend,
             isExpect = declaration.isExpect,
-            isOperator = declaration.isOperator
+            isOperator = declaration.isOperator,
+            isInfix = declaration.isInfix
         ).apply {
             transformFunctionChildren(declaration)
         }

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/IrFileDeserializer.kt

@@ -1191,6 +1191,7 @@ abstract class IrFileDeserializer(
                     flags.isTailrec,
                     flags.isSuspend,
                     flags.isOperator,
+                    flags.isInfix,
                     flags.isExpect,
                     flags.isFakeOverride
                 )

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/encodings/BinaryFlags.kt

@@ -54,6 +54,7 @@ inline class FunctionFlags(val flags: Long) {
     val visibility: Visibility get() = ProtoEnumFlags.visibility(IrFlags.VISIBILITY.get(flags.toInt()))
 
     val isOperator: Boolean get() = IrFlags.IS_OPERATOR.get(flags.toInt())
+    val isInfix: Boolean get() = IrFlags.IS_INFIX.get(flags.toInt())
     val isInline: Boolean get() = IrFlags.IS_INLINE.get(flags.toInt())
     val isTailrec: Boolean get() = IrFlags.IS_TAILREC.get(flags.toInt())
     val isExternal: Boolean get() = IrFlags.IS_EXTERNAL_FUNCTION.get(flags.toInt())
@@ -76,7 +77,7 @@ inline class FunctionFlags(val flags: Long) {
 
                 val flags = IrFlags.getFunctionFlags(
                     hasAnnotation, visibility, modality, kind,
-                    isOperator, false, isInline, isTailrec, isExternal, isSuspend, isExpect
+                    isOperator, isInfix, isInline, isTailrec, isExternal, isSuspend, isExpect
                 )
 
                 return flags.toLong()