Merge pull request #133 from modocache/se-0099

Fix warnings introduced by SE-0099
diff --git a/Sources/XCTest/Private/TestListing.swift b/Sources/XCTest/Private/TestListing.swift
index bd1a2a1..f131c52 100644
--- a/Sources/XCTest/Private/TestListing.swift
+++ b/Sources/XCTest/Private/TestListing.swift
@@ -63,7 +63,7 @@
     }
 
     private var listingName: String {
-        if let childTestCase = tests.first as? XCTestCase where name == String(childTestCase.dynamicType) {
+        if let childTestCase = tests.first as? XCTestCase, name == String(childTestCase.dynamicType) {
             return "\(moduleName(value: childTestCase)).\(name)"
         } else {
             return name
diff --git a/Sources/XCTest/Public/XCTestCase+Performance.swift b/Sources/XCTest/Public/XCTestCase+Performance.swift
index 388c347..fde3d63 100644
--- a/Sources/XCTest/Public/XCTestCase+Performance.swift
+++ b/Sources/XCTest/Public/XCTestCase+Performance.swift
@@ -126,7 +126,7 @@
     ///   ensure compatibility of tests between swift-corelibs-xctest and Apple
     ///   XCTest, it is not recommended to pass explicit values for `file` and `line`.
     func startMeasuring(file: StaticString = #file, line: UInt = #line) {
-        guard let performanceMeter = _performanceMeter where !performanceMeter.didFinishMeasuring else {
+        guard let performanceMeter = _performanceMeter, !performanceMeter.didFinishMeasuring else {
             return recordAPIViolation(description: "Cannot start measuring. startMeasuring() is only supported from a block passed to measureMetrics(...).", file: file, line: line)
         }
         performanceMeter.startMeasuring(file: file, line: line)
@@ -141,7 +141,7 @@
     ///   ensure compatibility of tests between swift-corelibs-xctest and Apple
     ///   XCTest, it is not recommended to pass explicit values for `file` and `line`.
     func stopMeasuring(file: StaticString = #file, line: UInt = #line) {
-        guard let performanceMeter = _performanceMeter where !performanceMeter.didFinishMeasuring else {
+        guard let performanceMeter = _performanceMeter, !performanceMeter.didFinishMeasuring else {
             return recordAPIViolation(description: "Cannot stop measuring. stopMeasuring() is only supported from a block passed to measureMetrics(...).", file: file, line: line)
         }
         performanceMeter.stopMeasuring(file: file, line: line)
diff --git a/Sources/XCTest/Public/XCTestRun.swift b/Sources/XCTest/Public/XCTestRun.swift
index fb42f86..47fcd85 100644
--- a/Sources/XCTest/Public/XCTestRun.swift
+++ b/Sources/XCTest/Public/XCTestRun.swift
@@ -33,7 +33,7 @@
     /// The number of seconds that elapsed between when the run was started and
     /// when it was stopped.
     public var totalDuration: TimeInterval {
-        if let stop = stopDate, start = startDate {
+        if let stop = stopDate, let start = startDate {
             return stop.timeIntervalSince(start)
         } else {
             return 0.0