From 0f0f32320b5569c472e75b5827adf31813ebfe12 Mon Sep 17 00:00:00 2001
From: Chip Hogg <chogg@aurora.tech>
Date: Sat, 9 Mar 2024 15:54:06 -0500
Subject: [PATCH] Delete `ForbidsComposingWith` mixin

It causes problems with Apple Clang version 9, apparently.  I think this
compiler technically falls outside of our support window.  However, an
actual user is having issues with it, and I think `ForbidsComposingWith`
is adding only very marginal value anyway.  I tried deleting it and the
error messages became a couple of lines shorter, although perhaps less
direct (no more reference to "explicitly deleted").

Amusingly, I'm keeping the unit test for it around, because it's one of
those unfortunate "uncomment to test" deals, and the tests _will_ still
pass.  (We'll get compiler errors for doing unsupported operations.)
---
 au/constant.hh                |  2 --
 au/wrapper_operations.hh      | 25 -------------------------
 au/wrapper_operations_test.cc |  2 --
 3 files changed, 29 deletions(-)

diff --git a/au/constant.hh b/au/constant.hh
index 7d4d5325..4f4b03ac 100644
--- a/au/constant.hh
+++ b/au/constant.hh
@@ -40,8 +40,6 @@ struct Constant : detail::MakesQuantityFromNumber<Constant, Unit>,
                   detail::ComposesWith<Constant, Unit, Constant, Constant>,
                   detail::ComposesWith<Constant, Unit, QuantityMaker, QuantityMaker>,
                   detail::ComposesWith<Constant, Unit, SingularNameFor, SingularNameFor>,
-                  detail::ForbidsComposingWith<Constant, Unit, QuantityPointMaker>,
-                  detail::ForbidsComposingWith<Constant, Unit, QuantityPoint>,
                   detail::CanScaleByMagnitude<Constant, Unit> {
     // Convert this constant to a Quantity of the given rep.
     template <typename T>
diff --git a/au/wrapper_operations.hh b/au/wrapper_operations.hh
index b6b2c472..62bd25f6 100644
--- a/au/wrapper_operations.hh
+++ b/au/wrapper_operations.hh
@@ -217,30 +217,5 @@ struct CanScaleByMagnitude {
     }
 };
 
-//
-// A mixin to explicitly delete operations that we want to forbid.
-//
-template <template <typename U> class UnitWrapper,
-          typename Unit,
-          template <typename... Us>
-          class OtherWrapper>
-struct ForbidsComposingWith {
-    // (W * O), for wrapper W and wrapper O.
-    template <typename... Us>
-    friend constexpr void operator*(UnitWrapper<Unit>, OtherWrapper<Us...>) = delete;
-
-    // (W / O), for wrapper W and wrapper O.
-    template <typename... Us>
-    friend constexpr void operator/(UnitWrapper<Unit>, OtherWrapper<Us...>) = delete;
-
-    // (O * W), for wrapper W and wrapper O.
-    template <typename... Us>
-    friend constexpr void operator*(OtherWrapper<Us...>, UnitWrapper<Unit>) = delete;
-
-    // (O / W), for wrapper W and wrapper O.
-    template <typename... Us>
-    friend constexpr void operator/(OtherWrapper<Us...>, UnitWrapper<Unit>) = delete;
-};
-
 }  // namespace detail
 }  // namespace au
diff --git a/au/wrapper_operations_test.cc b/au/wrapper_operations_test.cc
index 190d0aae..cac07e08 100644
--- a/au/wrapper_operations_test.cc
+++ b/au/wrapper_operations_test.cc
@@ -31,8 +31,6 @@ struct UnitWrapper : MakesQuantityFromNumber<UnitWrapper, Unit>,
                      ScalesQuantity<UnitWrapper, Unit>,
                      ComposesWith<UnitWrapper, Unit, UnitWrapper, UnitWrapper>,
                      ComposesWith<UnitWrapper, Unit, QuantityMaker, QuantityMaker>,
-                     ForbidsComposingWith<UnitWrapper, Unit, QuantityPointMaker>,
-                     ForbidsComposingWith<UnitWrapper, Unit, QuantityPoint>,
                      CanScaleByMagnitude<UnitWrapper, Unit> {};
 
 TEST(MakesQuantityFromNumber, MakesQuantityWhenPostMultiplyingNumericValue) {