Fix MSVC workaround with FMT_ENFORCE_COMPILE_STRING

include/fmt/chrono.h

@@ -769,18 +769,37 @@ template <typename Char, typename Rep, typename OutputIt,
           FMT_ENABLE_IF(std::is_integral<Rep>::value)>
 OutputIt format_duration_value(OutputIt out, Rep val, int) {
   static FMT_CONSTEXPR_DECL const Char format[] = {'{', '}', 0};
-  return format_to(out, compile_string_to_view(format), val);
+
+// Note(12/3/2020): Workaround an as-of-yet unfixed compiler error in MSVC.
+#if FMT_MSC_VER
+  return vformat_to(out, to_string_view(format),
+                    make_format_args<buffer_context<Char>>(val));
+#else
+  return format_to(out, FMT_STRING(format), val);
+#endif
 }
 
 template <typename Char, typename Rep, typename OutputIt,
           FMT_ENABLE_IF(std::is_floating_point<Rep>::value)>
 OutputIt format_duration_value(OutputIt out, Rep val, int precision) {
   static FMT_CONSTEXPR_DECL const Char pr_f[] = {'{', ':', '.', '{',
                                                  '}', 'f', '}', 0};
-  if (precision >= 0)
-    return format_to(out, compile_string_to_view(pr_f), val, precision);
+  if (precision >= 0) {
+#if FMT_MSC_VER && FMT_MSC_VER <= 1928
+    return vformat_to(out, to_string_view(pr_f),
+                      make_format_args<buffer_context<Char>>(val, precision));
+#else
+    return format_to(out, FMT_STRING(pr_f), val, precision);
+#endif
+  }
   static FMT_CONSTEXPR_DECL const Char fp_f[] = {'{', ':', 'g', '}', 0};
-  return format_to(out, compile_string_to_view(fp_f), val);
+
+#if FMT_MSC_VER && FMT_MSC_VER <= 1928
+  return vformat_to(out, to_string_view(fp_f),
+                    make_format_args<buffer_context<Char>>(val));
+#else
+  return format_to(out, FMT_STRING(fp_f), val);
+#endif
 }
 
 template <typename Char, typename OutputIt>
@@ -801,12 +820,23 @@ OutputIt format_duration_unit(OutputIt out) {
   if (const char* unit = get_units<Period>())
     return copy_unit(string_view(unit), out, Char());
   static FMT_CONSTEXPR_DECL const Char num_f[] = {'[', '{', '}', ']', 's', 0};
-  if (const_check(Period::den == 1))
-    return format_to(out, compile_string_to_view(num_f), Period::num);
+  if (const_check(Period::den == 1)) {
+#if FMT_MSC_VER
+    return vformat_to(out, to_string_view(num_f),
+                      make_format_args<buffer_context<Char>>(Period::num));
+#else
+    return format_to(out, FMT_STRING(num_f), Period::num);
+#endif
+  }
   static FMT_CONSTEXPR_DECL const Char num_def_f[] = {'[', '{', '}', '/', '{',
                                                       '}', ']', 's', 0};
-  return format_to(out, compile_string_to_view(num_def_f), Period::num,
-                   Period::den);
+#if FMT_MSC_VER
+  return vformat_to(
+      out, to_string_view(num_def_f),
+      make_format_args<buffer_context<Char>>(Period::num, Period::den));
+#else
+  return format_to(out, FMT_STRING(num_def_f), Period::num, Period::den);
+#endif
 }
 
 template <typename FormatContext, typename OutputIt, typename Rep,

test/CMakeLists.txt

@@ -106,6 +106,10 @@ add_fmt_test(printf-test)
 add_fmt_test(ranges-test)
 add_fmt_test(scan-test)
 
+
+add_fmt_test(enforce-compiletime-test)
+target_compile_definitions(enforce-compiletime-test PRIVATE "-DFMT_ENFORCE_COMPILE_STRING")
+
 if (NOT DEFINED MSVC_STATIC_RUNTIME AND MSVC)
   foreach (flag_var
 			 CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE

test/enforce-compiletime-test.cc

@@ -0,0 +1,29 @@
+// Formatting library for C++ - formatting library tests
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+
+#ifdef WIN32
+#  define _CRT_SECURE_NO_WARNINGS
+#endif
+
+#include "fmt/chrono.h"
+#include "fmt/format.h"
+
+#include "gmock.h"
+#include "gtest-extra.h"
+
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+
+TEST(ChronoTest, FormatDefault) {
+  EXPECT_EQ("42s", fmt::format(FMT_STRING("{}"), std::chrono::seconds(42)));
+}
+
+TEST(ChronoTest, FormatWide) {
+  EXPECT_EQ(L"42s", fmt::format(FMT_STRING(L"{}"), std::chrono::seconds(42)));
+}
+
+#endif  // FMT_STATIC_THOUSANDS_SEPARATOR