convert to guard statements for readability

SignalServiceKit/src/Contacts/PhoneNumber.m

@@ -324,33 +324,36 @@ static NSString *const RPDefaultsKeyPhoneNumberCanonical = @"RPDefaultsKeyPhoneN
 
     // Order matters; better results should appear first so prefer
     // matches with the same country code as this client's phone number.
-    OWSAssertDebug(clientPhoneNumber.length > 0);
+    if (clientPhoneNumber.length == 0) {
-    if (clientPhoneNumber.length > 0) {
+        OWSFailDebug(@"clientPhoneNumber had unexpected length");
-        // Note that NBPhoneNumber uses "country code" to refer to what we call a
+        return result;
-        // "calling code" (i.e. 44 in +44123123).  Within SSK we use "country code"
+    }
-        // (and sometimes "region code") to refer to a country's ISO 2-letter code
+
-        // (ISO 3166-1 alpha-2).
+    // Note that NBPhoneNumber uses "country code" to refer to what we call a
-        NSNumber *callingCodeForLocalNumber = [[PhoneNumber phoneNumberFromE164:clientPhoneNumber] getCountryCode];
+    // "calling code" (i.e. 44 in +44123123).  Within SSK we use "country code"
-        if (callingCodeForLocalNumber != nil) {
+    // (and sometimes "region code") to refer to a country's ISO 2-letter code
-            NSString *callingCodePrefix = [NSString stringWithFormat:@"+%@", callingCodeForLocalNumber];
+    // (ISO 3166-1 alpha-2).
-
+    NSNumber *callingCodeForLocalNumber = [[PhoneNumber phoneNumberFromE164:clientPhoneNumber] getCountryCode];
-            tryParsingWithCountryCode(
+    if (callingCodeForLocalNumber == nil) {
-                [callingCodePrefix stringByAppendingString:sanitizedString], [self defaultCountryCode]);
+        OWSFailDebug(@"callingCodeForLocalNumber was unexpectedly nil");
-
+        return result;
-            // Try to determine what the country code is for the local phone number
+    }
-            // and also try parsing the phone number using that country code if it
+
-            // differs from the device's region code.
+    NSString *callingCodePrefix = [NSString stringWithFormat:@"+%@", callingCodeForLocalNumber];
-            //
+
-            // For example, a French person living in Italy might have an
+    tryParsingWithCountryCode([callingCodePrefix stringByAppendingString:sanitizedString], [self defaultCountryCode]);
-            // Italian phone number but use French region/language for their
+
-            // phone. They're likely to have both Italian and French contacts.
+    // Try to determine what the country code is for the local phone number
-            NSString *localCountryCode =
+    // and also try parsing the phone number using that country code if it
-                [PhoneNumberUtil.sharedThreadLocal probableCountryCodeForCallingCode:callingCodePrefix];
+    // differs from the device's region code.
-            if (localCountryCode && ![localCountryCode isEqualToString:[self defaultCountryCode]]) {
+    //
-                tryParsingWithCountryCode(
+    // For example, a French person living in Italy might have an
-                    [callingCodePrefix stringByAppendingString:sanitizedString], localCountryCode);
+    // Italian phone number but use French region/language for their
-            }
+    // phone. They're likely to have both Italian and French contacts.
-        }
+    NSString *localCountryCode =
+        [PhoneNumberUtil.sharedThreadLocal probableCountryCodeForCallingCode:callingCodePrefix];
+    if (localCountryCode && ![localCountryCode isEqualToString:[self defaultCountryCode]]) {
+        tryParsingWithCountryCode([callingCodePrefix stringByAppendingString:sanitizedString], localCountryCode);
     }
 
     return result;