Merge pull request swiftlang#1361 from ikesyo/prefer-isempty

[gardening] Prefer `isEmpty` over `count == 0`

Author: ikesyo

Diff for: Foundation/Data.swift

@@ -866,7 +866,7 @@ public final class _DataStorage {
     }
 
     public func withInteriorPointerReference<T>(_ range: Range<Int>, _ work: (NSData) throws -> T) rethrows -> T {
-        if range.count == 0 {
+        if range.isEmpty {
             return try work(NSData()) // zero length data can be optimized as a singleton
         }
 
@@ -898,7 +898,7 @@ public final class _DataStorage {
     }
 
     public func bridgedReference(_ range: Range<Int>) -> NSData {
-        if range.count == 0 {
+        if range.isEmpty {
             return NSData() // zero length data can be optimized as a singleton
         }
 
@@ -1476,7 +1476,7 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
     /// - parameter buffer: The buffer of bytes to append. The size is calculated from `SourceType` and `buffer.count`.
     @inline(__always)
     public mutating func append<SourceType>(_ buffer : UnsafeBufferPointer<SourceType>) {
-        if buffer.count == 0 { return }
+        if buffer.isEmpty { return }
         if !isKnownUniquelyReferenced(&_backing) {
             _backing = _backing.mutableCopy(_sliceRange)
         }
@@ -1606,7 +1606,7 @@ public struct Data : ReferenceConvertible, Equatable, Hashable, RandomAccessColl
     @inline(__always)
     public func subdata(in range: Range<Index>) -> Data {
         _validateRange(range)
-        if count == 0 {
+        if isEmpty {
             return Data()
         }
         return _backing.subdata(in: range)

Diff for: Foundation/URLSession/TaskRegistry.swift

@@ -92,7 +92,7 @@ extension URLSession._TaskRegistry {
     }
 
     var isEmpty: Bool {
-        return tasks.count == 0
+        return tasks.isEmpty
     }
 }
 extension URLSession._TaskRegistry {

Diff for: Foundation/XMLParser.swift

@@ -282,7 +282,7 @@ internal func _NSXMLParserStartElementNs(_ ctx: _CFXMLInterface, localname: Unsa
         let attrLocalName = attributes[idx]!
         let attrLocalNameString = UTF8STRING(attrLocalName)!
         let attrPrefix = attributes[idx + 1]
-        if let attrPrefixString = UTF8STRING(attrPrefix), attrPrefixString.count != 0 {
+        if let attrPrefixString = UTF8STRING(attrPrefix), !attrPrefixString.isEmpty {
             attributeQName = attrPrefixString + ":" + attrLocalNameString
         } else {
             attributeQName = attrLocalNameString

Diff for: TestFoundation/TestNSString.swift

@@ -604,7 +604,7 @@ class TestNSString : XCTestCase {
             var matches: [String] = []
             let count = path.completePath(into: &outName, caseSensitive: false, matchesInto: &matches, filterTypes: nil)
             XCTAssert(outName == "", "If no matches found then outName is nil.")
-            XCTAssert(matches.count == 0 && count == 0, "If no matches found then return 0 and matches is empty.")
+            XCTAssert(matches.isEmpty && count == 0, "If no matches found then return 0 and matches is empty.")
         }
 
         do {
@@ -613,7 +613,7 @@ class TestNSString : XCTestCase {
             var matches: [String] = []
             let count = path.completePath(into: &outName, caseSensitive: false, matchesInto: &matches, filterTypes: nil)
             XCTAssert(outName == "", "If no matches found then outName is nil.")
-            XCTAssert(matches.count == 0 && count == 0, "If no matches found then return 0 and matches is empty.")
+            XCTAssert(matches.isEmpty && count == 0, "If no matches found then return 0 and matches is empty.")
         }
 
         do {