refactor: work around string conversion warning

Author: JohelEGP

include/cpp2util.h

@@ -615,7 +615,7 @@ class out {
                 *t = T(CPP2_FORWARD(args)...);
             }
             else {
-                Default.expects(!"attempted to copy assign, but copy assignment is not available");
+                Default.expects(false, "attempted to copy assign, but copy assignment is not available");
             }
         }
         else {
@@ -625,7 +625,7 @@ class out {
                     dt->value() = T(CPP2_FORWARD(args)...);
                 }
                 else {
-                    Default.expects(!"attempted to copy assign, but copy assignment is not available");
+                    Default.expects(false, "attempted to copy assign, but copy assignment is not available");
                 }
             }
             else {
@@ -642,7 +642,7 @@ class out {
                 *t = T{CPP2_FORWARD(args)...};
             }
             else {
-                Default.expects(!"attempted to copy assign, but copy assignment is not available");
+                Default.expects(false, "attempted to copy assign, but copy assignment is not available");
             }
         }
         else {
@@ -652,7 +652,7 @@ class out {
                     dt->value() = T{CPP2_FORWARD(args)...};
                 }
                 else {
-                    Default.expects(!"attempted to copy assign, but copy assignment is not available");
+                    Default.expects(false, "attempted to copy assign, but copy assignment is not available");
                 }
             }
             else {

regression-tests/test-results/clang-16/clang-version.output

@@ -0,0 +1,4 @@
+clang version 16.0.6 (https://github.com/llvm/llvm-project.git 7cbf1a2591520c2491aa35339f227775f4d3adf6)
+Target: x86_64-pc-linux-gnu
+Thread model: posix
+InstalledDir: /home/johel/root/clang-16/bin

regression-tests/test-results/clang-16/mixed-bounds-check.cpp.execution

@@ -0,0 +1,2 @@
+Bounds safety violation: out of bounds access attempt detected
+libc++abi: terminating

regression-tests/test-results/clang-16/mixed-bounds-safety-with-assert.cpp.execution

@@ -0,0 +1,2 @@
+Bounds safety violation
+libc++abi: terminating

regression-tests/test-results/clang-16/mixed-initialization-safety-3-contract-violation.cpp.execution

@@ -0,0 +1,2 @@
+Contract violation: fill: value must contain at least count elements
+libc++abi: terminating

regression-tests/test-results/clang-16/xyzzy

@@ -0,0 +1 @@
+Hello Fred with UFCS!