Commit the last few evenings' changes

This is an omnibus commit of the last few evenings' changes. Primarily it was to start laying the groundwork for constructors, but it includes other fixes and closes a few issues.

Details:

- Begin infrastructure preparation for constructors

- Started creating navigation APIs to replace the low-level graph node chasing; this makes cppfront's own code cleaner and the tree easier to change if needed, but it's also a step toward a reflection API

- Extended `main:(args)` to require the name "args" for the single-parameter `main`, and to support `args.argc` and `args.argv`, further on #262 (see comment thread)

- Changed default return type for unnamed functions to be `-> void`, same as named functions, closes #257

- Disallow single-expression function body to be just `return`, closes #267

- Make `make_args` inline, closes #268

- Bug fix: emit prolog also for single-expression function body. Specifically, this enables main:(args)=expression; to work correctly. Generally, this also corrects the code gen for examples that were trying (but failing) to inject prologs in single-expression functions... in the regression tests this corrected the code gen for `pure2-forward-return.cpp2` which was missing the contract check before.

Author: hsutter

include/cpp2util.h

@@ -1419,8 +1419,17 @@ inline auto to_string(std::tuple<Ts...> const& t) -> std::string
 //
 //-----------------------------------------------------------------------
 //
-auto args(int argc, char **argv) -> std::vector<std::string_view> {
-    auto ret = std::vector<std::string_view>{(size_t)argc};
+struct args_t : std::vector<std::string_view>
+{
+    args_t(int c, char const* const* v) : vector{(size_t)c}, argc{c}, argv{v} {}
+
+    int                argc = 0;
+    char const* const* argv = nullptr;
+};
+
+inline auto make_args(int argc, char const* const* argv) -> args_t
+{
+    auto ret = args_t{argc, argv};
     for (auto i = 0; i < argc; ++i) {
         ret[i] = std::string_view{argv[i]};
     }

regression-tests/pure2-cpp1-multitoken-fundamental-types-error.cpp2

@@ -1,5 +1,5 @@
 
-main: (argc: int, argv: **char) -> int = {
+main: () -> int = {
     a: signed short int       = 1;
     b: short int signed       = 2;
     c: long long unsigned int = 3;

regression-tests/pure2-main-args.cpp2

@@ -0,0 +1,2 @@
+main: (args) =
+    std::cout << "args.argc is (args.argc)$, and args.argv[0] is (args.argv[0])$\n";

regression-tests/pure2-more-wildcards.cpp2

@@ -1,6 +1,6 @@
 
 less_than: (value:_) -> _ =
-    :(x:_) = x < value$;
+    :(x:_) -> _ = x < value$;
 
 main: () -> int
 = {

regression-tests/test-results/clang-12/pure2-main-args.cpp.execution

@@ -0,0 +1 @@
+args.argc is 1, and args.argv[0] is ./test.exe

regression-tests/test-results/clang-12/pure2-main-args.cpp.output

@@ -0,0 +1 @@
+args.argc is 1, and args.argv[0] is ./test.exe

regression-tests/test-results/gcc-10/pure2-main-args.cpp.execution

@@ -22,7 +22,7 @@ auto insert_at(cpp2::in<int> where, cpp2::in<int> val) -> void;
                "hello", "2022"}; 
 
     std::string y {"\n"}; 
-    auto callback {[_0 = (&y)](auto const& x){std::cout << x << *cpp2::assert_not_null(_0);}}; 
+    auto callback {[_0 = (&y)](auto const& x) -> void{std::cout << x << *cpp2::assert_not_null(_0);}}; 
 
     std::ranges::for_each( vec, callback );
     y = "-ish\n";

regression-tests/test-results/gcc-10/pure2-main-args.cpp.output

@@ -13,7 +13,7 @@ namespace my {
 #line 8 "mixed-fixed-type-aliases.cpp2"
 auto test(auto const& x) -> void;
 #line 15 "mixed-fixed-type-aliases.cpp2"
-[[nodiscard]] auto main(int argc, char **argv) -> int;
+[[nodiscard]] auto main(int const argc_, char const* const* const argv_) -> int;
 
 //=== Cpp2 definitions ==========================================================
 
@@ -26,8 +26,8 @@ auto test(auto const& x) -> void{
         << "\n";
 }
 
-[[nodiscard]] auto main(int argc, char **argv) -> int{
-    auto args = cpp2::args(argc, argv); 
+[[nodiscard]] auto main(int const argc_, char const* const* const argv_) -> int{
+    auto args = cpp2::make_args(argc_, argv_); 
 #line 16 "mixed-fixed-type-aliases.cpp2"
     my::u16 y {42}; 
     test(std::move(y));

regression-tests/test-results/mixed-captures-in-expressions-and-postconditions.cpp

@@ -25,11 +25,11 @@
     std::for_each(
         CPP2_UFCS_0(begin, view), 
         CPP2_UFCS_0(end, view), 
-        [](auto& x ) { return x += "-ish"; }
+        [](auto& x ) -> void { x += "-ish"; }
     );
 
     //  Initializating from a function expression
-    auto callback {[](auto& x) { return x += " maybe"; }}; 
+    auto callback {[](auto& x) -> void { x += " maybe"; }}; 
     std::for_each(
         CPP2_UFCS_0(begin, view), 
         CPP2_UFCS_0(end, view), 

regression-tests/test-results/mixed-fixed-type-aliases.cpp

@@ -24,9 +24,9 @@
 
     auto y {"\n"}; 
     std::ranges::for_each
-        ( view, [_0 = std::move(y)](auto const& x){std::cout << x << _0;});
+        ( view, [_0 = std::move(y)](auto const& x) -> void{std::cout << x << _0;});
 
-    auto callback {[](auto& x) { return x += "-ish"; }}; 
+    auto callback {[](auto& x) -> void { x += "-ish"; }}; 
     std::ranges::for_each( view, std::move(callback));
 
     for ( auto const& cpp2_range = view;  auto const& str : cpp2_range ) 

regression-tests/test-results/mixed-function-expression-and-std-for-each.cpp

@@ -23,9 +23,9 @@
     std::span view {vec}; 
 
     std::ranges::for_each
-        ( view, [](auto const& x){std::cout << x << "\n";});
+        ( view, [](auto const& x) -> void{std::cout << x << "\n";});
 
-    auto callback {[](auto& x) { return x += "-ish"; }}; 
+    auto callback {[](auto& x) -> void { x += "-ish"; }}; 
     std::ranges::for_each( view, std::move(callback));
 
     for ( auto const& cpp2_range = view;  auto const& str : cpp2_range ) 

regression-tests/test-results/mixed-function-expression-and-std-ranges-for-each-with-capture.cpp

@@ -23,11 +23,11 @@
     std::span view {vec}; 
 
     std::string y {"\n"}; 
-    std::ranges::for_each( view, [_0 = (&y)](auto const& x){
+    std::ranges::for_each( view, [_0 = (&y)](auto const& x) -> void{
         std::cout << CPP2_UFCS_0(c_str, (*cpp2::assert_not_null((_0)))) << x << *cpp2::assert_not_null(_0);
     } );
 
-    auto callback {[](auto& x) { return x += "-ish"; }}; 
+    auto callback {[](auto& x) -> void { x += "-ish"; }}; 
     std::ranges::for_each( view, std::move(callback));
 
     for ( auto const& cpp2_range = view;  auto const& str : cpp2_range ) 

regression-tests/test-results/mixed-function-expression-and-std-ranges-for-each.cpp

@@ -24,9 +24,9 @@
 
     auto y {"\n"}; 
     std::ranges::for_each
-        ( view, [_0 = std::move(y)](auto const& x){std::cout << _0 << x << _0;});
+        ( view, [_0 = std::move(y)](auto const& x) -> void{std::cout << _0 << x << _0;});
 
-    auto callback {[](auto& x) { return x += "-ish"; }}; 
+    auto callback {[](auto& x) -> void { x += "-ish"; }}; 
     std::ranges::for_each( view, std::move(callback));
 
     for ( auto const& cpp2_range = view;  auto const& str : cpp2_range ) 

regression-tests/test-results/mixed-function-expression-with-pointer-capture.cpp

@@ -0,0 +1 @@
+args.argc is 1, and args.argv[0] is test.exe

regression-tests/test-results/mixed-function-expression-with-repeated-capture.cpp

@@ -0,0 +1 @@
+pure2-main-args.cpp

regression-tests/test-results/msvc-2022/pure2-main-args.cpp.execution

@@ -17,6 +17,8 @@
 #line 1 "pure2-forward-return.cpp2"
 
 [[nodiscard]] auto first(auto&& rng) -> decltype(auto) { 
+   cpp2::Bounds.expects(!(std::empty(rng)), "");
+#line 3 "pure2-forward-return.cpp2"
 
 
     return *cpp2::assert_not_null(std::begin(CPP2_FORWARD(rng))); }

regression-tests/test-results/msvc-2022/pure2-main-args.cpp.output

@@ -0,0 +1,17 @@
+
+#define CPP2_USE_MODULES         Yes
+
+#include "cpp2util.h"
+
+
+#line 1 "pure2-main-args.cpp2"
+auto main(int const argc_, char const* const* const argv_) -> int;
+
+//=== Cpp2 definitions ==========================================================
+
+#line 1 "pure2-main-args.cpp2"
+auto main(int const argc_, char const* const* const argv_) -> int { 
+   auto args = cpp2::make_args(argc_, argv_); 
+#line 2 "pure2-main-args.cpp2"
+    std::cout << "args.argc is " + cpp2::to_string(args.argc) + ", and args.argv[0] is " + cpp2::to_string(cpp2::assert_in_bounds(args.argv, 0)) + "\n"; }
+

regression-tests/test-results/pure2-forward-return.cpp

@@ -0,0 +1,2 @@
+pure2-main-args.cpp2... ok (all Cpp2, passes safety checks)
+

regression-tests/test-results/pure2-main-args.cpp

@@ -14,7 +14,7 @@
 #line 1 "pure2-more-wildcards.cpp2"
 
 [[nodiscard]] auto less_than(auto const& value) -> auto { 
-    return [_0 = value](auto const& x) { return cpp2::cmp_less(x,_0); }; }
+    return [_0 = value](auto const& x) -> auto { return cpp2::cmp_less(x,_0); }; }
 
 [[nodiscard]] auto main() -> int
 {