Fix default argument lowering (#1262)

There should now be enough test cases to exercise all the places you can put default arguments

Also, only emit Cpp1 lambdas as 'mutable' if there are captures (when it matters) so that pure function expressions are not 'mutable'

Closes #1235

Signed-off-by: Herb Sutter <[email protected]>

Author: hsutter

regression-tests/pure2-default-arguments.cpp2

@@ -11,19 +11,52 @@ my_function_name: (
 
 f: (x: i32 = 0) = { std::cout << x; }
 
+combine_maps:
+    < 
+        AssocContainer, 
+        Func: type = std::plus<> 
+    >
+    ( 
+        inout map1: AssocContainer, 
+              map2: AssocContainer, 
+              func: Func = () 
+    )
+= {
+    for map2 do(kv) {
+        map1[kv.first] = func(map1[kv.first], kv.second);
+    }
+}
+
+myclass: <T: type = int, N: int = 42> type = { 
+    memfunc: <TT: type = int, NN: int = 42> (MM: int = 43) = { _ = MM; }
+}
+myfunc:  <T: type = int, N: int = 42> (M: int = 43) = {
+    _ = M;
+    : <TT: type = int, NN: int = 42> (MM: int = 43) = { _ = MM; };
+}
+
 main: (args) = {
     my_function_name();
     f();
     f(1);
     f(2);
 
-    : <V: bool = gcc_clang_msvc_min_versions( 1400, 1600, 1920)> () = {
+    : <V: bool = gcc_clang_msvc_min_versions( 1400, 1600, 1920 )> () = {
         if constexpr V {
-            std::cout << "a newer compiler\n";
+            std::cout << "\na newer compiler\n";
         }
         else {
-            std::cout << "an older compiler\n";
+            std::cout << "\nan older compiler\n";
         }
     } ();
 
+    m1: std::map<int, int> = ();
+    m1[1] = 11;
+
+    m2: std::map<int, int> = ();
+    m2[1] = 22;
+
+    combine_maps( m1, m2, :(x,y) x+y+33 );
+
+    std::cout << "(m1.size())$, (m2.size())$, (m1[1])$\n";
 }

regression-tests/test-results/clang-12-c++20/mixed-bugfix-for-ufcs-non-local.cpp.output

@@ -107,7 +107,7 @@ mixed-bugfix-for-ufcs-non-local.cpp2:27:29: error: a lambda expression cannot ap
 #define CPP2_UFCS_(LAMBDADEFCAPT,SFINAE,MVFWD,QUALID,TEMPKW,...) \
                                                                  ^
 mixed-bugfix-for-ufcs-non-local.cpp2:41:84: error: lambda expression in an unevaluated operand
-  inline CPP2_CONSTEXPR bool u::c{ [](cpp2::impl::in<std::type_identity_t<decltype(CPP2_UFCS_NONLOCAL(f)(o))>> x) mutable -> auto { return x; }(true) };// Fails on Clang 12 (lambda in unevaluated context).
+  inline CPP2_CONSTEXPR bool u::c{ [](cpp2::impl::in<std::type_identity_t<decltype(CPP2_UFCS_NONLOCAL(f)(o))>> x) -> auto { return x; }(true) };// Fails on Clang 12 (lambda in unevaluated context).
                                                                                    ^
 ../../../include/cpp2util.h:2137:59: note: expanded from macro 'CPP2_UFCS_NONLOCAL'
 #define CPP2_UFCS_NONLOCAL(...)                           CPP2_UFCS_(,CPP2_UFCS_IDENTITY,CPP2_UFCS_IDENTITY,(),,__VA_ARGS__)

regression-tests/test-results/clang-12-c++20/pure2-bugfix-for-non-local-function-expression.cpp.output

@@ -1,10 +1,10 @@
 pure2-bugfix-for-non-local-function-expression.cpp2:5:34: error: lambda expression in an unevaluated operand
-template<typename T> concept v = []() mutable -> bool { return true;  }(); 
+template<typename T> concept v = []() -> bool { return true;  }(); 
                                  ^
 pure2-bugfix-for-non-local-function-expression.cpp2:7:41: error: lambda expression in an unevaluated operand
-using u = std::type_identity_t<decltype([]() mutable -> void{})>;
+using u = std::type_identity_t<decltype([]() -> void{})>;
                                         ^
 pure2-bugfix-for-non-local-function-expression.cpp2:9:47: error: lambda expression in an unevaluated operand
-class t: public std::type_identity_t<decltype([]() mutable -> void{})> {
+class t: public std::type_identity_t<decltype([]() -> void{})> {
                                               ^
 3 errors generated.

regression-tests/test-results/clang-12-c++20/pure2-last-use.cpp.output

@@ -1,4 +1,4 @@
 pure2-last-use.cpp2:945:44: error: a lambda expression cannot appear in this context
-    static_cast<void>([_0 = std::array<int,[](auto const& x) mutable -> auto { return identity(x); }(0)>()]() mutable -> auto { return _0;  });// Fails on Clang 12 (lambda in unevaluated context).
+    static_cast<void>([_0 = std::array<int,[](auto const& x) -> auto { return identity(x); }(0)>()]() mutable -> auto { return _0;  });// Fails on Clang 12 (lambda in unevaluated context).
                                            ^
 1 error generated.

regression-tests/test-results/gcc-14-c++2b/pure2-default-arguments.cpp.execution

@@ -1,2 +1,4 @@
 calling: int main(int, char**)
-012an older compiler
+012
+a newer compiler
+1, 1, 66

regression-tests/test-results/mixed-bugfix-for-ufcs-non-local.cpp

@@ -95,7 +95,7 @@ auto g() -> void{
 
 #line 40 "mixed-bugfix-for-ufcs-non-local.cpp2"
   inline CPP2_CONSTEXPR bool u::b{ CPP2_UFCS_NONLOCAL(f)(o) };
-  inline CPP2_CONSTEXPR bool u::c{ [](cpp2::impl::in<std::type_identity_t<decltype(CPP2_UFCS_NONLOCAL(f)(o))>> x) mutable -> auto { return x; }(true) };// Fails on Clang 12 (lambda in unevaluated context).
+  inline CPP2_CONSTEXPR bool u::c{ [](cpp2::impl::in<std::type_identity_t<decltype(CPP2_UFCS_NONLOCAL(f)(o))>> x) -> auto { return x; }(true) };// Fails on Clang 12 (lambda in unevaluated context).
   auto u::g(auto const& s, auto const& sz) -> void{
                                   if (cpp2::cpp2_default.is_active() && !(CPP2_UFCS(sz)(s) != 0) ) { cpp2::cpp2_default.report_violation(""); }}
 

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

@@ -32,11 +32,11 @@
     //  Passing a function expression
     std::ranges::for_each(
         vec, 
-        [](auto& x) mutable -> void { x += "-ish";  }
+        [](auto& x) -> void { x += "-ish";  }
     );
 
     //  Initializing from a function expression
-    auto callback {[](auto& x) mutable -> void { x += " maybe";  }}; 
+    auto callback {[](auto& x) -> void { x += " maybe";  }}; 
     std::ranges::for_each(
         vec, 
         cpp2::move(callback)

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

@@ -34,7 +34,7 @@
     std::ranges::for_each
         (vec, [_0 = cpp2::move(y)](auto const& x) mutable -> void { std::cout << x << _0;  });
 
-    auto callback {[](auto& x) mutable -> void { x += "-ish";  }}; 
+    auto callback {[](auto& x) -> void { x += "-ish";  }}; 
     std::ranges::for_each(vec, cpp2::move(callback));
 
     for ( auto const& str : cpp2::move(vec) ) 

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

@@ -31,9 +31,9 @@
             "hello", "2022"}; 
 
     std::ranges::for_each
-        (vec, [](auto const& x) mutable -> void { std::cout << x << "\n";  });
+        (vec, [](auto const& x) -> void { std::cout << x << "\n";  });
 
-    auto callback {[](auto& x) mutable -> void { x += "-ish";  }}; 
+    auto callback {[](auto& x) -> void { x += "-ish";  }}; 
     std::ranges::for_each(vec, cpp2::move(callback));
 
     for ( auto const& str : cpp2::move(vec) ) 

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

@@ -35,7 +35,7 @@
         std::cout << CPP2_UFCS(c_str)((*cpp2::impl::assert_not_null(_0))) << x << *cpp2::impl::assert_not_null(_0);  }
     );
 
-    auto callback {[](auto& x) mutable -> void { x += "-ish";  }}; 
+    auto callback {[](auto& x) -> void { x += "-ish";  }}; 
     std::ranges::for_each(vec, cpp2::move(callback));
 
     for ( auto const& str : cpp2::move(vec) )