add tests for format string compile-time checks

test/compile-error-test/CMakeLists.txt

@@ -18,7 +18,6 @@ set(non_error_test_content "")
 #  * adds a code segment as separate function to `non_error_test_content`
 function (expect_compile name code_fragment)
   cmake_parse_arguments(EXPECT_COMPILE "ERROR" "" "" ${ARGN})
-
   string(MAKE_C_IDENTIFIER "${name}" test_name)
 
   if (EXPECT_COMPILE_ERROR)
@@ -169,5 +168,37 @@ expect_compile(udl-check "
   #endif
 ")
 
+if (CMAKE_CXX_STANDARD GREATER_EQUAL 20)
+  # Compile-time argument type check
+  expect_compile(format-string-number-spec "
+    #ifdef FMT_HAS_CONSTEVAL
+      fmt::format(\"{:d}\", 42);
+    #endif
+  ")
+  expect_compile(format-string-number-spec-error "
+    #ifdef FMT_HAS_CONSTEVAL
+      fmt::format(\"{:d}\", \"I am not a number\");
+    #else
+      #error
+    #endif
+  " ERROR)
+
+  # Compile-time argument name check
+  expect_compile(format-string-name "
+    #if defined(FMT_HAS_CONSTEVAL) && FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
+      using namespace fmt::literals;
+      fmt::print(\"{foo}\", \"foo\"_a=42);
+    #endif
+  ")
+  expect_compile(format-string-name-error "
+    #if defined(FMT_HAS_CONSTEVAL) && FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
+      using namespace fmt::literals;
+      fmt::print(\"{foo}\", \"bar\"_a=42);
+    #else
+      #error
+    #endif
+  " ERROR)
+endif ()
+
 # Run all tests
 run_tests()