ConeTypeIntersector: inline flatIntersectionTypes

compiler/fir/providers/src/org/jetbrains/kotlin/fir/types/ConeTypeIntersector.kt

@@ -17,8 +17,15 @@ object ConeTypeIntersector {
             1 -> return types.single()
         }
 
-        val inputTypes = mutableListOf<ConeKotlinType>()
-        flatIntersectionTypes(types, inputTypes)
+        val inputTypes = mutableListOf<ConeKotlinType>().apply {
+            for (inputType in types) {
+                if (inputType is ConeIntersectionType) {
+                    addAll(inputType.intersectedTypes)
+                } else {
+                    add(inputType)
+                }
+            }
+        }
 
         /**
          * resultNullability. Value description:
@@ -85,21 +92,6 @@ object ConeTypeIntersector {
         }
     }
 
-    private fun flatIntersectionTypes(
-        inputTypes: List<ConeKotlinType>,
-        typeCollector: MutableList<ConeKotlinType>
-    ) {
-        for (inputType in inputTypes) {
-            if (inputType is ConeIntersectionType) {
-                for (type in inputType.intersectedTypes) {
-                    typeCollector += type
-                }
-            } else {
-                typeCollector += inputType
-            }
-        }
-    }
-
     private fun ConeKotlinType.isStrictSubtypeOf(context: ConeTypeContext, supertype: ConeKotlinType): Boolean =
         AbstractTypeChecker.isSubtypeOf(context, this, supertype) && !AbstractTypeChecker.isSubtypeOf(context, supertype, this)