Auto-enable file/line/function info on contracts violations + usability improvements

Thanks @MikeShah for your YouTube video here: https://youtu.be/ZslemeHsOjk?si=qPoNdJLxBoSgFh6b . I'm treating the video as a "looking over your shoulder using Cpp2" mini-UX study to make a better experience for folks coming to the syntax the first time...

Diagnose attempt to declare two things at once, e.g., `x,y : int = 5;`

Diagnose attempt to for-loop over two ranges, e.g., `for x,y do ..`

Automatically use <source_location>, including for file/line/function information on contracts checks so when using a capable compiler you get nice bounds/other violation messages out of the box that point directly to the offending source line

Remove the -add-source-info flag as no longer needed, now <source_location> is now reliable and automated (modulo a workaround in cpp2util.h for an MSVC bug where importing source_location via a module doesn't work correctly)

Author: hsutter

include/cpp2util.h

@@ -43,8 +43,10 @@
 
 //  If this implementation doesn't support source_location yet, disable it
 #include <version>
-#if !defined(_MSC_VER) && !defined(__cpp_lib_source_location)
-    #undef CPP2_USE_SOURCE_LOCATION
+
+#undef CPP2_USE_SOURCE_LOCATION
+#if defined(__cpp_lib_source_location)
+    #define CPP2_USE_SOURCE_LOCATION Yes
 #endif
 
 //  If the user requested making the entire C++ standard library available
@@ -553,15 +555,17 @@ auto pointer_eq(T const* a, T const* b) {
 //
 
 #ifdef CPP2_USE_SOURCE_LOCATION
-    #define CPP2_SOURCE_LOCATION_PARAM              , std::source_location where
-    #define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT , std::source_location where = std::source_location::current()
-    #define CPP2_SOURCE_LOCATION_PARAM_SOLO         std::source_location where
+    #define CPP2_SOURCE_LOCATION_PARAM              , [[maybe_unused]] std::source_location where
+    #define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT , [[maybe_unused]] std::source_location where = std::source_location::current()
+    #define CPP2_SOURCE_LOCATION_PARAM_SOLO         [[maybe_unused]] std::source_location where
     #define CPP2_SOURCE_LOCATION_ARG                , where
+    #define CPP2_SOURCE_LOCATION_VALUE              (cpp2::to_string(where.file_name()) + "(" + cpp2::to_string(where.line()) + ") " + where.function_name())
 #else
     #define CPP2_SOURCE_LOCATION_PARAM
     #define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT
     #define CPP2_SOURCE_LOCATION_PARAM_SOLO
     #define CPP2_SOURCE_LOCATION_ARG
+    #define CPP2_SOURCE_LOCATION_VALUE              std::string("")
 #endif
 
 //  For C++23: make this std::string_view and drop the macro
@@ -1520,8 +1524,16 @@ inline constexpr auto as() -> auto
     return cpp2::to_string(CPP2_FORWARD(x));
 }
 
+//  Work around MSVC modules bugs: source_location doesn't work correctly if imported via a module
+#if defined(_MSC_VER) && defined(CPP2_IMPORT_STD)
+    #define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT_AS
+    #define CPP2_SOURCE_LOCATION_ARG_AS
+#else
+    #define CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT_AS    CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT
+    #define CPP2_SOURCE_LOCATION_ARG_AS                   CPP2_SOURCE_LOCATION_ARG
+#endif
 template< typename C >
-auto as(auto&& x CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
+auto as(auto&& x CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT_AS) -> decltype(auto)
     //  This "requires" list may need to be tweaked further. The idea is to have
     //  this function used for all the cases it's supposed to cover, but not
     //  hide user-supplied extensions (such as the ones later in this file for
@@ -1555,7 +1567,7 @@ auto as(auto&& x CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> decltype(auto)
         const C c = static_cast<C>(CPP2_FORWARD(x));
         type_safety.enforce(   // precondition check: must be round-trippable => not lossy
             static_cast<CPP2_TYPEOF(x)>(c) == x && (c < C{}) == (x < CPP2_TYPEOF(x){}),
-            "dynamic lossy narrowing conversion attempt detected" CPP2_SOURCE_LOCATION_ARG
+            "dynamic lossy narrowing conversion attempt detected" CPP2_SOURCE_LOCATION_ARG_AS
         );
         return CPP2_COPY(c);
     }

regression-tests/mixed-lifetime-safety-and-null-contracts.cpp2

@@ -18,9 +18,17 @@ try_pointer_stuff: () = {
                 // to show -n
 }
 
-call_my_framework: (msg: * const char) = {
+auto call_my_framework(const char* msg CPP2_SOURCE_LOCATION_PARAM) {
     std::cout
         << "sending error to my framework... ["
-        << msg << "]\n";
+        << msg 
+        << "]\n";
+    auto loc = CPP2_SOURCE_LOCATION_VALUE;
+    if (!loc.empty()) {
+        std::cout
+            << "from source location: "
+            << loc
+            << "]\n";
+    }
     exit(0);
 }

regression-tests/test-results/gcc-14-c++2b/mixed-bounds-check.cpp.execution

@@ -1 +1 @@
-Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
+mixed-bounds-check.cpp2(9) int main(): Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]

regression-tests/test-results/gcc-14-c++2b/mixed-bounds-safety-with-assert.cpp.execution

@@ -1 +1 @@
-Bounds safety violation
+mixed-bounds-safety-with-assert.cpp2(11) void print_subrange(const auto:89&, cpp2::impl::in<int>, cpp2::impl::in<int>) [with auto:89 = std::vector<int>; cpp2::impl::in<int> = const int]: Bounds safety violation

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 | template<typename T>
+ 2100 | {
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | class c_raii {
+ 2137 | //  Speculative: RAII wrapping for the C standard library
       |                                                           ^         
 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 | template<typename T>
+ 2100 | {
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | class c_raii {
+ 2137 | //  Speculative: RAII wrapping for the C standard library
       |                                                           ^         
 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 | template<typename T>
+ 2100 | {
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | class c_raii {
+ 2137 | //  Speculative: RAII wrapping for the C standard library
       |                                                           ^         
 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 | template<typename T>
+ 2100 | {
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | class c_raii {
+ 2137 | //  Speculative: RAII wrapping for the C standard library
       |                                                           ^         
 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 | template<typename T>
+ 2100 | {
       | ^
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 | class c_raii {
+ 2137 | //  Speculative: RAII wrapping for the C standard library
       |                                                           ^         
 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

regression-tests/test-results/gcc-14-c++2b/mixed-initialization-safety-3-contract-violation.cpp.execution

@@ -1 +1 @@
-Contract violation: fill: value must contain at least count elements
+mixed-initialization-safety-3-contract-violation.cpp2(25) void fill(cpp2::impl::out<std::__cxx11::basic_string<char> >, cpp2::impl::in<std::__cxx11::basic_string<char> >, cpp2::impl::in<int>): Contract violation: fill: value must contain at least count elements

regression-tests/test-results/gcc-14-c++2b/mixed-lifetime-safety-and-null-contracts.cpp.execution

@@ -1 +1,2 @@
 sending error to my framework... [dynamic null dereference attempt detected]
+from source location: mixed-lifetime-safety-and-null-contracts.cpp2(17) void try_pointer_stuff()]

regression-tests/test-results/gcc-14-c++2b/pure2-assert-expected-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::expected has an unexpected value
+pure2-assert-expected-not-null.cpp2(15) int bad_expected_access(): Null safety violation: std::expected has an unexpected value

regression-tests/test-results/gcc-14-c++2b/pure2-assert-optional-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::optional does not contain a value
+pure2-assert-optional-not-null.cpp2(14) int bad_optional_access(): Null safety violation: std::optional does not contain a value

regression-tests/test-results/gcc-14-c++2b/pure2-assert-shared-ptr-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::shared_ptr is empty
+pure2-assert-shared-ptr-not-null.cpp2(15) int bad_shared_ptr_access(): Null safety violation: std::shared_ptr is empty

regression-tests/test-results/gcc-14-c++2b/pure2-assert-unique-ptr-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::unique_ptr is empty
+pure2-assert-unique-ptr-not-null.cpp2(15) int bad_unique_ptr_access(): Null safety violation: std::unique_ptr is empty

regression-tests/test-results/mixed-lifetime-safety-and-null-contracts.cpp

@@ -24,9 +24,23 @@
 auto null_from_cpp1() -> int* { return nullptr; }
 
 auto try_pointer_stuff() -> void;
+#line 20 "mixed-lifetime-safety-and-null-contracts.cpp2"
+
+auto call_my_framework(const char* msg CPP2_SOURCE_LOCATION_PARAM) {
+    std::cout
+        << "sending error to my framework... ["
+        << msg 
+        << "]\n";
+    auto loc = CPP2_SOURCE_LOCATION_VALUE;
+    if (!loc.empty()) {
+        std::cout
+            << "from source location: "
+            << loc
+            << "]\n";
+    }
+    exit(0);
+}
 
-#line 21 "mixed-lifetime-safety-and-null-contracts.cpp2"
-auto call_my_framework(char const* msg) -> void;
 
 //=== Cpp2 function definitions =================================================
 
@@ -46,11 +60,3 @@ auto try_pointer_stuff() -> void{
                 // to show -n
 }
 
-#line 21 "mixed-lifetime-safety-and-null-contracts.cpp2"
-auto call_my_framework(char const* msg) -> void{
-    std::cout 
-        << "sending error to my framework... [" 
-        << msg << "]\n";
-    exit(0);
-}
-

regression-tests/test-results/msvc-2022-c++latest/mixed-bounds-check.cpp.execution

@@ -1 +1 @@
-Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]
+mixed-bounds-check.cpp2(9) int __cdecl main(void): Bounds safety violation: out of bounds access attempt detected - attempted access at index 5, [min,max] range is [0,4]

regression-tests/test-results/msvc-2022-c++latest/mixed-bounds-safety-with-assert.cpp.execution

@@ -1 +1 @@
-Bounds safety violation
+mixed-bounds-safety-with-assert.cpp2(11) void __cdecl print_subrange<class std::vector<int,class std::allocator<int> >>(const class std::vector<int,class std::allocator<int> > &,const int,const int): Bounds safety violation

regression-tests/test-results/msvc-2022-c++latest/mixed-initialization-safety-3-contract-violation.cpp.execution

@@ -1 +1 @@
-Contract violation: fill: value must contain at least count elements
+mixed-initialization-safety-3-contract-violation.cpp2(25) void __cdecl fill(class cpp2::impl::out<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,const class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &,const int): Contract violation: fill: value must contain at least count elements

regression-tests/test-results/msvc-2022-c++latest/mixed-lifetime-safety-and-null-contracts.cpp.execution

@@ -1 +1,2 @@
 sending error to my framework... [dynamic null dereference attempt detected]
+from source location: mixed-lifetime-safety-and-null-contracts.cpp2(17) void __cdecl try_pointer_stuff(void)]

regression-tests/test-results/msvc-2022-c++latest/pure2-assert-expected-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::expected has an unexpected value
+pure2-assert-expected-not-null.cpp2(15) int __cdecl bad_expected_access(void): Null safety violation: std::expected has an unexpected value

regression-tests/test-results/msvc-2022-c++latest/pure2-assert-optional-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::optional does not contain a value
+pure2-assert-optional-not-null.cpp2(14) int __cdecl bad_optional_access(void): Null safety violation: std::optional does not contain a value

regression-tests/test-results/msvc-2022-c++latest/pure2-assert-shared-ptr-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::shared_ptr is empty
+pure2-assert-shared-ptr-not-null.cpp2(15) int __cdecl bad_shared_ptr_access(void): Null safety violation: std::shared_ptr is empty

regression-tests/test-results/msvc-2022-c++latest/pure2-assert-unique-ptr-not-null.cpp.execution

@@ -1 +1 @@
-Null safety violation: std::unique_ptr is empty
+pure2-assert-unique-ptr-not-null.cpp2(15) int __cdecl bad_unique_ptr_access(void): Null safety violation: std::unique_ptr is empty

regression-tests/test-results/pure2-statement-parse-error.cpp2.output

@@ -1,3 +1,3 @@
 pure2-statement-parse-error.cpp2...
-pure2-statement-parse-error.cpp2(3,9): error: invalid statement encountered inside a compound-statement (at 'b')
+pure2-statement-parse-error.cpp2(3,5): error: invalid statement encountered inside a compound-statement (at 'int')
 

regression-tests/test-results/version

@@ -1,5 +1,5 @@
 
-cppfront compiler v0.7.0   Build 9712:1020
+cppfront compiler v0.7.1   Build 9713:1156
 Copyright(c) Herb Sutter   All rights reserved
 
 SPDX-License-Identifier: CC-BY-NC-ND-4.0

source/build.info

@@ -1 +1 @@
-"9712:1020"
+"9713:1156"

source/parse.h

@@ -6960,6 +6960,9 @@ class parser
         expression_statement_node::current_expression_statements.push_back(n.get());
         auto guard = finally([&]{ expression_statement_node::current_expression_statements.pop_back(); });
 
+        //  Remember current position, in case this isn't a valid expression-statement
+        auto start_pos = pos;
+
         if (!(n->expr = expression(true, true))) {
             return {};
         }
@@ -6978,6 +6981,7 @@ class parser
                 //  it doesn't destabilize any regression tests
             )
         {
+            pos = start_pos;    // backtrack
             return {};
         }
         if (
@@ -7248,6 +7252,10 @@ class parser
                 return {};
             }
 
+            if (curr().type() == lexeme::Comma) {
+                error("iterating over multiple ranges at once is not currently supported");
+            }
+
             if (!handle_optional_next_clause()) { return {}; }
 
             if (
@@ -7671,6 +7679,15 @@ class parser
         }
 
         else {
+            if (
+                curr().type() == lexeme::Identifier
+                && peek(1)
+                && peek(1)->type() == lexeme::Comma
+                )
+            {
+                next();
+                error("declaring multiple names at once is not currently supported");
+            }
             return {};
         }
     }

source/to_cpp1.h

@@ -147,14 +147,6 @@ static cmdline_processor::register_flag cmd_safe_comparisons(
     []{ flag_safe_comparisons = false; }
 );
 
-static auto flag_use_source_location = false;
-static cmdline_processor::register_flag cmd_enable_source_info(
-    2,
-    "add-source-info",
-    "Enable source_location information for contract checks",
-    []{ flag_use_source_location = true; }
-);
-
 static auto flag_cpp1_filename = std::string{};
 static cmdline_processor::register_flag cmd_cpp1_filename(
     8,
@@ -1309,10 +1301,6 @@ class cppfront
                 printer.print_extra( "#define " + cpp1_FILENAME+"_CPP2" + "\n\n" );
             }
 
-            if (flag_use_source_location) {
-                printer.print_extra( "#define CPP2_USE_SOURCE_LOCATION Yes\n" );
-            }
-
             if (flag_include_std) {
                 printer.print_extra( "#define CPP2_INCLUDE_STD         Yes\n" );
             }

source/version.info

@@ -1 +1 @@
-"v0.7.0"
+"v0.7.1"