[lmi-commits] [lmi] master 3183c02 2/5: Make an operator 'consteval'

[Greg Chicares]

branch: master
commit 3183c028598fa7f1ea159bacd05a2c29012a7e89
Author: Gregory W. Chicares <gchicares@sbcglobal.net>
Commit: Gregory W. Chicares <gchicares@sbcglobal.net>

    Make an operator 'consteval'
    
    As shown in the unit test, any misuse is now a compile-time error, even
    outside a constexpr context.
    
    Incidentally simplified the error message, which can appear only at
    compile time, e.g.:
    
    in ‘constexpr’ expansion of ‘operator""_cents(9007199254740993)’
    error: expression ‘<throw-expression>’ is not a constant expression
       79 |         : throw std::domain_error("outside currency domain")
          |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    so extra code to print the value a second time is unwarranted.
---
 currency.hpp      |  8 +++-----
 currency_test.cpp | 25 ++++++-------------------
 2 files changed, 9 insertions(+), 24 deletions(-)

diff --git a/currency.hpp b/currency.hpp
index d2c6e2b..3aa2037 100644
--- a/currency.hpp
+++ b/currency.hpp
@@ -28,7 +28,6 @@
 #include <limits>
 #include <ostream>
 #include <stdexcept>                    // runtime_error
-#include <string>                       // to_string()
 #include <vector>
 
 class raw_cents {}; // Tag class.
@@ -39,7 +38,7 @@ class currency
     friend currency from_cents(double);       // private ctor
     template<typename> friend class round_to; // private ctor
     friend class round_to_test;               // currency::cents_digits
-    friend constexpr currency operator""_cents(unsigned long long int);
+    friend consteval currency operator""_cents(unsigned long long int);
 
     static constexpr int    cents_digits     = 2;
     static constexpr double cents_per_dollar = 100.0;
@@ -70,15 +69,14 @@ class currency
     data_type m_ = {};
 };
 
-inline constexpr currency operator""_cents(unsigned long long int cents)
+consteval currency operator""_cents(unsigned long long int cents)
 {
     constexpr auto mant_dig = std::numeric_limits<currency::data_type>::digits;
     constexpr unsigned long long int limit = 1ULL << mant_dig;
     return
           cents <= limit
         ? currency(static_cast<currency::data_type>(cents), raw_cents{})
-        : throw std::runtime_error
-            ("currency: " + std::to_string(cents) + " out of bounds");
+        : throw std::domain_error("outside currency domain")
         ;
 }
 
diff --git a/currency_test.cpp b/currency_test.cpp
index c0f08f2..02150dd 100644
--- a/currency_test.cpp
+++ b/currency_test.cpp
@@ -163,26 +163,13 @@ void currency_test::test_literals()
     currency const nc9007199254740992(  -9007199254740992_cents);
     LMI_TEST_EQUAL( -9007199254740992, nc9007199254740992.m_);
 
-    // These are run-time errors:
-    LMI_TEST_THROW
-        (9007199254740993_cents
-        ,std::runtime_error
-        ,"currency: 9007199254740993 out of bounds"
-        );
-    // In this error message, the positive literal is invalid, so
-    // an exception is thrown before the return value can be negated.
-    LMI_TEST_THROW
-        (-9007199254740993_cents
-        ,std::runtime_error
-        ,"currency: 9007199254740993 out of bounds"
-        );
-
-    // These are evaluated at compile time:
-    constexpr currency compile_time_constant_pos( 9007199254740992_cents);
-    constexpr currency compile_time_constant_neg(-9007199254740992_cents);
+    // These are evaluated at compile time, even though this is not
+    // a constexpr context:
+    auto compile_time_constant_pos( 9007199254740992_cents);
+    auto compile_time_constant_neg(-9007199254740992_cents);
     // These would be compile-time errors:
-//  constexpr currency error_at_compile_time_pos( 9007199254740993_cents);
-//  constexpr currency error_at_compile_time_neg(-9007199254740993_cents);
+//  auto error_at_compile_time_pos( 9007199254740993_cents);
+//  auto error_at_compile_time_neg(-9007199254740993_cents);
 }
 
 void currency_test::test_negation()