Bug 1728121 - Use std::is_same_v in unified intl; r=platform-i18n-reviewers,gregtatum

Differential Revision: https://phabricator.services.mozilla.com/D131262

intl/components/src/DateTimeFormat.h

@@ -316,14 +316,14 @@ class DateTimeFormat final {
   template <typename B>
   ICUResult TryFormat(double aUnixEpoch, B& aBuffer) const {
     static_assert(
-        std::is_same<typename B::CharType, unsigned char>::value ||
-            std::is_same<typename B::CharType, char>::value ||
-            std::is_same<typename B::CharType, char16_t>::value,
+        std::is_same_v<typename B::CharType, unsigned char> ||
+            std::is_same_v<typename B::CharType, char> ||
+            std::is_same_v<typename B::CharType, char16_t>,
         "The only buffer CharTypes supported by DateTimeFormat are char "
         "(for UTF-8 support) and char16_t (for UTF-16 support).");
 
-    if constexpr (std::is_same<typename B::CharType, char>::value ||
-                  std::is_same<typename B::CharType, unsigned char>::value) {
+    if constexpr (std::is_same_v<typename B::CharType, char> ||
+                  std::is_same_v<typename B::CharType, unsigned char>) {
       // The output buffer is UTF-8, but ICU uses UTF-16 internally.
 
       // Write the formatted date into the u16Buffer.
@@ -344,7 +344,7 @@ class DateTimeFormat final {
       }
       return Ok{};
     } else {
-      static_assert(std::is_same<typename B::CharType, char16_t>::value);
+      static_assert(std::is_same_v<typename B::CharType, char16_t>);
 
       // The output buffer is UTF-16. ICU can output directly into this buffer.
       return FillBufferWithICUCall(
@@ -370,7 +370,7 @@ class DateTimeFormat final {
   template <typename B>
   ICUResult TryFormatToParts(double aUnixEpoch, B& aBuffer,
                              DateTimePartVector& aParts) const {
-    static_assert(std::is_same<typename B::CharType, char16_t>::value,
+    static_assert(std::is_same_v<typename B::CharType, char16_t>,
                   "Only char16_t is supported (for UTF-16 support) now.");
 
     UErrorCode status = U_ZERO_ERROR;

intl/components/src/NumberFormat.h

@@ -396,12 +396,11 @@ class NumberFormat final {
   template <typename C, typename B>
   Result<Ok, ICUError> formatResult(B& buffer) const {
     // We only support buffers with char or char16_t.
-    static_assert(std::is_same<C, char>::value ||
-                  std::is_same<C, char16_t>::value);
+    static_assert(std::is_same_v<C, char> || std::is_same_v<C, char16_t>);
 
     return formatResult().andThen(
         [&buffer](std::u16string_view result) -> Result<Ok, ICUError> {
-          if constexpr (std::is_same<C, char>::value) {
+          if constexpr (std::is_same_v<C, char>) {
             if (!FillBuffer(Span(result.data(), result.size()), buffer)) {
               return Err(ICUError::OutOfMemory);
             }

intl/components/src/RelativeTimeFormat.h

@@ -88,7 +88,7 @@ class RelativeTimeFormat final {
                    ? ureldatefmt_format
                    : ureldatefmt_formatNumeric;
 
-    if constexpr (std::is_same<typename B::CharType, char>::value) {
+    if constexpr (std::is_same_v<typename B::CharType, char>) {
       mozilla::Vector<char16_t, StackU16VectorSize> u16Vec;
 
       MOZ_TRY(FillBufferWithICUCall(