diff --git a/include/cpp2util.h b/include/cpp2util.h
index 0572a9820..d9ae3c3dd 100644
--- a/include/cpp2util.h
+++ b/include/cpp2util.h
@@ -302,6 +302,12 @@
     #include <vector>
 #endif
 
+//  cpp2util.h uses signed integer types for indices and container sizes
+//  so disable clang signed-to-unsigned conversion warnings in this header.
+#ifdef __clang__
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wsign-conversion"
+#endif
 
 //-----------------------------------------------------------------------
 //
@@ -2833,4 +2839,9 @@ using cpp2::cpp2_new;
     #define CPP2_REQUIRES_(...) requires (__VA_ARGS__)
 #endif
 
+//  Restore clang signed-to-unsigned conversion warnings
+#ifdef __clang__
+    #pragma clang diagnostic pop
 #endif
+
+#endif // CPP2_CPP2UTIL_H
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-check.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-check.cpp.execution
index 1d524e6e1..77c30fa83 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-check.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-check.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(964) decltype(auto) cpp2::impl::assert_in_bounds(auto &&, std::source_location) [arg = 5, x:auto = std::vector<int>]: Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
+../../../include/cpp2util.h(970) decltype(auto) cpp2::impl::assert_in_bounds(auto &&, std::source_location) [arg = 5, x:auto = std::vector<int>]: Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-safety-with-assert.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-safety-with-assert.cpp.execution
index 0f1269838..1284e5107 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-safety-with-assert.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/mixed-bounds-safety-with-assert.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(776) : Bounds safety violation
+../../../include/cpp2util.h(782) : Bounds safety violation
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/mixed-initialization-safety-3-contract-violation.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/mixed-initialization-safety-3-contract-violation.cpp.execution
index d4f3fe0ad..dc708ffb5 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/mixed-initialization-safety-3-contract-violation.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/mixed-initialization-safety-3-contract-violation.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(776) : Contract violation: fill: value must contain at least count elements
+../../../include/cpp2util.h(782) : Contract violation: fill: value must contain at least count elements
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/mixed-lifetime-safety-and-null-contracts.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/mixed-lifetime-safety-and-null-contracts.cpp.execution
index ec5bef9c8..ffe7899ea 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/mixed-lifetime-safety-and-null-contracts.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/mixed-lifetime-safety-and-null-contracts.cpp.execution
@@ -1,2 +1,2 @@
 sending error to my framework... [dynamic null dereference attempt detected]
-from source location: ../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = int *&]
+from source location: ../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = int *&]
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-expected-not-null.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-expected-not-null.cpp.execution
index c611b6acf..a625bdf83 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-expected-not-null.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-expected-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::expected<int, bool>]: Null safety violation: std::expected has an unexpected value
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::expected<int, bool>]: Null safety violation: std::expected has an unexpected value
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-optional-not-null.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-optional-not-null.cpp.execution
index 57dee71f2..a9d924ed2 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-optional-not-null.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-optional-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::optional<int>]: Null safety violation: std::optional does not contain a value
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::optional<int>]: Null safety violation: std::optional does not contain a value
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-shared-ptr-not-null.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-shared-ptr-not-null.cpp.execution
index 60a924d17..64d065485 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-shared-ptr-not-null.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-shared-ptr-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::shared_ptr<int>]: Null safety violation: std::shared_ptr is empty
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::shared_ptr<int>]: Null safety violation: std::shared_ptr is empty
diff --git a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-unique-ptr-not-null.cpp.execution b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-unique-ptr-not-null.cpp.execution
index f8b437704..e16aca64a 100644
--- a/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-unique-ptr-not-null.cpp.execution
+++ b/regression-tests/test-results/apple-clang-15-c++2b/pure2-assert-unique-ptr-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::unique_ptr<int>]: Null safety violation: std::unique_ptr is empty
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::unique_ptr<int>]: Null safety violation: std::unique_ptr is empty
diff --git a/regression-tests/test-results/clang-15-c++20/mixed-bounds-check.cpp.execution b/regression-tests/test-results/clang-15-c++20/mixed-bounds-check.cpp.execution
index 1d524e6e1..77c30fa83 100644
--- a/regression-tests/test-results/clang-15-c++20/mixed-bounds-check.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/mixed-bounds-check.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(964) decltype(auto) cpp2::impl::assert_in_bounds(auto &&, std::source_location) [arg = 5, x:auto = std::vector<int>]: Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
+../../../include/cpp2util.h(970) decltype(auto) cpp2::impl::assert_in_bounds(auto &&, std::source_location) [arg = 5, x:auto = std::vector<int>]: Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
diff --git a/regression-tests/test-results/clang-15-c++20/mixed-bounds-safety-with-assert.cpp.execution b/regression-tests/test-results/clang-15-c++20/mixed-bounds-safety-with-assert.cpp.execution
index 0f1269838..1284e5107 100644
--- a/regression-tests/test-results/clang-15-c++20/mixed-bounds-safety-with-assert.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/mixed-bounds-safety-with-assert.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(776) : Bounds safety violation
+../../../include/cpp2util.h(782) : Bounds safety violation
diff --git a/regression-tests/test-results/clang-15-c++20/mixed-initialization-safety-3-contract-violation.cpp.execution b/regression-tests/test-results/clang-15-c++20/mixed-initialization-safety-3-contract-violation.cpp.execution
index d4f3fe0ad..dc708ffb5 100644
--- a/regression-tests/test-results/clang-15-c++20/mixed-initialization-safety-3-contract-violation.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/mixed-initialization-safety-3-contract-violation.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(776) : Contract violation: fill: value must contain at least count elements
+../../../include/cpp2util.h(782) : Contract violation: fill: value must contain at least count elements
diff --git a/regression-tests/test-results/clang-15-c++20/mixed-lifetime-safety-and-null-contracts.cpp.execution b/regression-tests/test-results/clang-15-c++20/mixed-lifetime-safety-and-null-contracts.cpp.execution
index ec5bef9c8..ffe7899ea 100644
--- a/regression-tests/test-results/clang-15-c++20/mixed-lifetime-safety-and-null-contracts.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/mixed-lifetime-safety-and-null-contracts.cpp.execution
@@ -1,2 +1,2 @@
 sending error to my framework... [dynamic null dereference attempt detected]
-from source location: ../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = int *&]
+from source location: ../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = int *&]
diff --git a/regression-tests/test-results/clang-15-c++20/pure2-assert-optional-not-null.cpp.execution b/regression-tests/test-results/clang-15-c++20/pure2-assert-optional-not-null.cpp.execution
index 57dee71f2..a9d924ed2 100644
--- a/regression-tests/test-results/clang-15-c++20/pure2-assert-optional-not-null.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/pure2-assert-optional-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::optional<int>]: Null safety violation: std::optional does not contain a value
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::optional<int>]: Null safety violation: std::optional does not contain a value
diff --git a/regression-tests/test-results/clang-15-c++20/pure2-assert-shared-ptr-not-null.cpp.execution b/regression-tests/test-results/clang-15-c++20/pure2-assert-shared-ptr-not-null.cpp.execution
index 60a924d17..64d065485 100644
--- a/regression-tests/test-results/clang-15-c++20/pure2-assert-shared-ptr-not-null.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/pure2-assert-shared-ptr-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::shared_ptr<int>]: Null safety violation: std::shared_ptr is empty
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::shared_ptr<int>]: Null safety violation: std::shared_ptr is empty
diff --git a/regression-tests/test-results/clang-15-c++20/pure2-assert-unique-ptr-not-null.cpp.execution b/regression-tests/test-results/clang-15-c++20/pure2-assert-unique-ptr-not-null.cpp.execution
index f8b437704..e16aca64a 100644
--- a/regression-tests/test-results/clang-15-c++20/pure2-assert-unique-ptr-not-null.cpp.execution
+++ b/regression-tests/test-results/clang-15-c++20/pure2-assert-unique-ptr-not-null.cpp.execution
@@ -1 +1 @@
-../../../include/cpp2util.h(855) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::unique_ptr<int>]: Null safety violation: std::unique_ptr is empty
+../../../include/cpp2util.h(861) decltype(auto) cpp2::impl::assert_not_null(auto &&, std::source_location) [arg:auto = std::unique_ptr<int>]: Null safety violation: std::unique_ptr is empty
diff --git a/regression-tests/test-results/gcc-13-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output b/regression-tests/test-results/gcc-13-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
index a62e6b086..4b53cb8e1 100644
--- a/regression-tests/test-results/gcc-13-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
+++ b/regression-tests/test-results/gcc-13-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
@@ -1,41 +1,41 @@
 In file included from mixed-bugfix-for-ufcs-non-local.cpp:6:
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:13:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:13:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:21:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:31:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:31:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:33:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:33:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:21:36: error: template argument 1 is invalid
diff --git a/regression-tests/test-results/gcc-14-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output b/regression-tests/test-results/gcc-14-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
index a62e6b086..4b53cb8e1 100644
--- a/regression-tests/test-results/gcc-14-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
+++ b/regression-tests/test-results/gcc-14-c++2b/mixed-bugfix-for-ufcs-non-local.cpp.output
@@ -1,41 +1,41 @@
 In file included from mixed-bugfix-for-ufcs-non-local.cpp:6:
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:13:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:13:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:21:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:31:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:31:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:33:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:33:36: error: template argument 1 is invalid
 ../../../include/cpp2util.h:2100:1: error: lambda-expression in template parameter type
- 2100 | constexpr auto is( X const& x ) -> bool
+ 2100 |     requires (std::is_same_v<X,std::any> && !std::is_same_v<T,std::any> && !std::is_same_v<T,empty>)
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | 
+ 2137 |     { return std::any_cast<T>( x ); }
       |                                                           ^         
 mixed-bugfix-for-ufcs-non-local.cpp2:21:12: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 mixed-bugfix-for-ufcs-non-local.cpp2:21:36: error: template argument 1 is invalid
diff --git a/regression-tests/test-results/msvc-2022-c++20/pure2-assert-expected-not-null.cpp.output b/regression-tests/test-results/msvc-2022-c++20/pure2-assert-expected-not-null.cpp.output
index a05de73b4..e43c7c890 100644
--- a/regression-tests/test-results/msvc-2022-c++20/pure2-assert-expected-not-null.cpp.output
+++ b/regression-tests/test-results/msvc-2022-c++20/pure2-assert-expected-not-null.cpp.output
@@ -6,7 +6,7 @@ pure2-assert-expected-not-null.cpp2(7): error C2143: syntax error: missing ';' b
 pure2-assert-expected-not-null.cpp2(7): error C2143: syntax error: missing ';' before '}'
 pure2-assert-expected-not-null.cpp2(9): error C2065: 'ex': undeclared identifier
 pure2-assert-expected-not-null.cpp2(9): error C2672: 'cpp2::impl::assert_not_null': no matching overloaded function found
-D:\a\cppfront\cppfront\include\cpp2util.h(855): note: could be 'decltype(auto) cpp2::impl::assert_not_null(_T0 &&,std::source_location)'
+D:\a\cppfront\cppfront\include\cpp2util.h(861): note: could be 'decltype(auto) cpp2::impl::assert_not_null(_T0 &&,std::source_location)'
 pure2-assert-expected-not-null.cpp2(14): error C2039: 'expected': is not a member of 'std'
 predefined C++ types (compiler internal)(347): note: see declaration of 'std'
 pure2-assert-expected-not-null.cpp2(14): error C2062: type 'int' unexpected
@@ -19,4 +19,4 @@ pure2-assert-expected-not-null.cpp2(14): note: while trying to match the argumen
 pure2-assert-expected-not-null.cpp2(14): error C2143: syntax error: missing ';' before '}'
 pure2-assert-expected-not-null.cpp2(15): error C2065: 'ex': undeclared identifier
 pure2-assert-expected-not-null.cpp2(15): error C2672: 'cpp2::impl::assert_not_null': no matching overloaded function found
-D:\a\cppfront\cppfront\include\cpp2util.h(855): note: could be 'decltype(auto) cpp2::impl::assert_not_null(_T0 &&,std::source_location)'
+D:\a\cppfront\cppfront\include\cpp2util.h(861): note: could be 'decltype(auto) cpp2::impl::assert_not_null(_T0 &&,std::source_location)'
diff --git a/regression-tests/test-results/msvc-2022-c++latest/pure2-regex_10_escapes.cpp.execution b/regression-tests/test-results/msvc-2022-c++latest/pure2-regex_10_escapes.cpp.execution
index fe6e6efc9..14d06c270 100644
--- a/regression-tests/test-results/msvc-2022-c++latest/pure2-regex_10_escapes.cpp.execution
+++ b/regression-tests/test-results/msvc-2022-c++latest/pure2-regex_10_escapes.cpp.execution
@@ -9,26 +9,26 @@ Running tests_10_escapes:
 08_y: OK regex: foo(\h)bar parsed_regex: foo(\h)bar str: foo	bar result_expr: $1 expected_results 	
 09_y: OK regex: (\H)(\h) parsed_regex: (\H)(\h) str: foo	bar result_expr: $1-$2 expected_results o-	
 10_y: OK regex: (\h)(\H) parsed_regex: (\h)(\H) str: foo	bar result_expr: $1-$2 expected_results 	-b
-11_y: OK regex: foo(\v+)bar parsed_regex: foo(\v+)bar str: foo
+11_y: OK regex: foo(\v+)bar parsed_regex: foo(\v+)bar str: foo
+
 
+bar result_expr: $1 expected_results 
+
 
-bar result_expr: $1 expected_results 
 
+12_y: OK regex: (\V+)(\v) parsed_regex: (\V+)(\v) str: foo
+
 
+bar result_expr: $1-$2 expected_results foo-
+13_y: OK regex: (\v+)(\V) parsed_regex: (\v+)(\V) str: foo
+
 
-12_y: OK regex: (\V+)(\v) parsed_regex: (\V+)(\v) str: foo
-
-
-bar result_expr: $1-$2 expected_results foo-
-13_y: OK regex: (\v+)(\V) parsed_regex: (\v+)(\V) str: foo
-
-
-bar result_expr: $1-$2 expected_results 
-
+bar result_expr: $1-$2 expected_results 
+
 
 -b
-14_y: OK regex: foo(\v)bar parsed_regex: foo(\v)bar str: foo
bar result_expr: $1 expected_results 
-15_y: OK regex: (\V)(\v) parsed_regex: (\V)(\v) str: foo
bar result_expr: $1-$2 expected_results o-
+14_y: OK regex: foo(\v)bar parsed_regex: foo(\v)bar str: foo
bar result_expr: $1 expected_results 
+15_y: OK regex: (\V)(\v) parsed_regex: (\V)(\v) str: foo
bar result_expr: $1-$2 expected_results o-
 16_y: OK regex: (\v)(\V) parsed_regex: (\v)(\V) str: foo
bar result_expr: $1-$2 expected_results 
-b
 17_y: OK regex: foo\t\n\r\f\a\ebar parsed_regex: foo\t\n\r\f\a\ebar str: foo	
 
bar result_expr: $& expected_results foo	
diff --git a/source/common.h b/source/common.h
index cf1d6e488..844900f8e 100644
--- a/source/common.h
+++ b/source/common.h
@@ -20,6 +20,15 @@
     #pragma GCC diagnostic ignored "-Wdangling-reference"
 #endif
 
+//  Disable some clang conversion warnings:
+//      cppfront uses signed integer types for indices and container sizes.
+//  Note: We don't pop the diagnostic because we want them disabled in the
+//  entire cppfront translation unit.
+#ifdef __clang__
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wsign-conversion"
+#endif
+
 #include "cpp2util.h"
 
 
@@ -97,7 +106,7 @@ struct source_line
         break;case category::cpp1:          return "/* 1 */ ";
         break;case category::cpp2:          return "/* 2 */ ";
         break;case category::rawstring:     return "/* R */ ";
-        break;default: assert(!"illegal category"); abort();
+        break;default: assert(false && "ICE: illegal category"); abort();
         }
     }
 };
diff --git a/source/cppfront.cpp b/source/cppfront.cpp
index 3e28e46ae..a5dbb00ca 100644
--- a/source/cppfront.cpp
+++ b/source/cppfront.cpp
@@ -113,10 +113,10 @@ auto main(
                     auto total = count.cpp1_lines + count.cpp2_lines;
                     auto total_lines = print_with_thousands(total);
                     out << "   Cpp1  "
-                        << std::right << std::setw(total_lines.size())
+                        << std::right << std::setw(unsafe_narrow<int>(total_lines.size()))
                         << print_with_thousands(count.cpp1_lines) << " line" << (count.cpp1_lines != 1 ? "s" : "");
                     out << "\n   Cpp2  "
-                        << std::right << std::setw(total_lines.size())
+                        << std::right << std::setw(unsafe_narrow<int>(total_lines.size()))
                         << print_with_thousands(count.cpp2_lines) << " line" << (count.cpp2_lines != 1 ? "s" : "");
                     if (total > 0) {
                         out << " (";
@@ -145,7 +145,7 @@ auto main(
                     for (auto [elapsed, name] : sorted_timers) {
                         std::cout
                             << "\n         "
-                            << std::right << std::setw(total_time.size())
+                            << std::right << std::setw(unsafe_narrow<int>(total_time.size()))
                             << print_with_thousands(elapsed) << " ms" << " in " << name;
                     }
                 }
diff --git a/source/parse.h b/source/parse.h
index 3c3ca960b..ea07039e3 100644
--- a/source/parse.h
+++ b/source/parse.h
@@ -1414,7 +1414,7 @@ struct type_id_node
         break;case keyword:
             return std::get<keyword>(id)->to_string() + suffix;
         break;default:
-            assert(!"ICE: invalid type_id state");
+            assert(false && "ICE: invalid type_id state");
         }
         // else
         return {};
@@ -1435,7 +1435,7 @@ struct type_id_node
         break;case keyword:
             return get<keyword>(id);
         break;default:
-            assert(!"ICE: invalid type_id state");
+            assert(false && "ICE: invalid type_id state");
         }
         // else
         return {};
@@ -1501,7 +1501,7 @@ auto template_argument::to_string() const
     break;case type_id:
         return std::get<type_id>(arg)->to_string();
     break;default:
-        assert(!"ICE: invalid template_argument state");
+        assert(false && "ICE: invalid template_argument state");
     }
     // else
     return {};
@@ -4353,7 +4353,7 @@ auto primary_expression_node::position() const
     }
 
     break;default:
-        assert (!"illegal primary_expression_node state");
+        assert (false && "ICE: illegal primary_expression_node state");
         return { 0, 0 };
     }
 }
@@ -4476,7 +4476,7 @@ auto statement_node::position() const
     }
 
     break;default:
-        assert (!"illegal statement_node state");
+        assert (false && "ICE: illegal statement_node state");
         return { 0, 0 };
     }
 }
@@ -6300,7 +6300,7 @@ class parser
 
                 //  And it shouldn't be anything else
                 else {
-                    assert (!"ICE: validate_op should take one token and return bool, or two tokens and return token const* ");
+                    assert (false && "ICE: validate_op should take one token and return bool, or two tokens and return token const* ");
                 }
 
                 //  At this point we may have a valid t.op, so try to parse the next term...
@@ -7480,7 +7480,7 @@ class parser
             return n;
         }
 
-        assert(!"compiler bug: unexpected case");
+        assert(false && "ICE: unexpected case");
         return {};
     }
 
@@ -8102,7 +8102,7 @@ class parser
             break;case passing_style::forward:
                 error( "a 'forward' parameter shouldn't be const, because it passes along the argument's actual const-ness (and actual value category)", false );
             break;default:
-                assert (!"ICE: missing case");
+                assert (false && "ICE: missing case");
             }
             return {};
         }
@@ -9254,7 +9254,7 @@ class parser
 
         //  Anything else shouldn't be possible
         else {
-            assert(!"ICE: should be unreachable - invalid alias declaration");
+            assert(false && "ICE: should be unreachable - invalid alias declaration");
             return {};
         }
 
diff --git a/source/sema.h b/source/sema.h
index 8c54f3b0e..46e2c509d 100644
--- a/source/sema.h
+++ b/source/sema.h
@@ -253,7 +253,7 @@ struct symbol {
         }
 
         break;default:
-            assert (!"illegal symbol state");
+            assert (false && "ICE: illegal symbol state");
             return { 0, 0 };
         }
     }
@@ -284,7 +284,7 @@ struct symbol {
         }
 
         break;default:
-            assert (!"illegal symbol state");
+            assert (false && "ICE: illegal symbol state");
             return nullptr;
         }
     }
@@ -1443,7 +1443,7 @@ class sema
             }
 
             break;default:
-                assert (!"illegal symbol");
+                assert (false && "ICE: illegal symbol");
             }
 
         }
diff --git a/source/to_cpp1.h b/source/to_cpp1.h
index 011a1e0ac..880d8cb52 100644
--- a/source/to_cpp1.h
+++ b/source/to_cpp1.h
@@ -257,7 +257,7 @@ class positional_printer
         switch (phase) {
         break;case phase0_type_decls          : phase = phase1_type_defs_func_decls;
         break;case phase1_type_defs_func_decls: phase = phase2_func_defs;
-        break;default                         : assert(!"ICE: invalid lowering phase");
+        break;default                         : assert(false && "ICE: invalid lowering phase");
         }
         curr_pos     = {};
         next_comment = 0;   // start over with the comments
@@ -2349,7 +2349,7 @@ class cppfront
         }
 
         else {
-            assert(!"ICE: unexpected case");
+            assert(false && "ICE: unexpected case");
         }
 
         assert (iteration_statements.back().stmt);
@@ -5833,7 +5833,7 @@ class cppfront
                 }
 
                 else {
-                    assert(!"ICE: should be unreachable - invalid alias");
+                    assert(false && "ICE: should be unreachable - invalid alias");
                 }
 
                 return;