fix(cpp1): support assignment from expression list (#487)

* fix(cpp1): support assignment from expression list

* Update cppfront.cpp

Added size check so we don't add `{` `}` around single-element lists

Signed-off-by: Herb Sutter <herb.sutter@gmail.com>

* Update cppfront.cpp

`std::ssize` for consistency, and `!= 1` so we still emit `{` `}` around empty lists.

Signed-off-by: Herb Sutter <herb.sutter@gmail.com>

* Update cppfront.cpp

Signed-off-by: Herb Sutter <herb.sutter@gmail.com>

---------

Signed-off-by: Herb Sutter <herb.sutter@gmail.com>
Co-authored-by: Herb Sutter <herb.sutter@gmail.com>

Author: JohelEGP

regression-tests/pure2-bugfix-for-assign-expression-list.cpp2

@@ -0,0 +1,10 @@
+main: () = {
+  vec: type == std::vector<int>;
+  v: vec              = (0);
+  v                   = ();
+  [[assert: v == :vec = ()]]
+  v                   = (1);
+  [[assert: v == :vec = (1)]]
+  v                   = (2, 3);
+  [[assert: v == :vec = (2, 3)]]
+}

regression-tests/test-results/gcc-13/pure2-bugfix-for-assign-expression-list.cpp.execution

@@ -0,0 +1,30 @@
+
+#define CPP2_USE_MODULES         Yes
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "pure2-bugfix-for-assign-expression-list.cpp2"
+auto main() -> int;
+  
+
+//=== Cpp2 function definitions =================================================
+
+#line 1 "pure2-bugfix-for-assign-expression-list.cpp2"
+auto main() -> int{
+  using vec = std::vector<int>;
+  vec v {0}; 
+  v                   = {  };
+  cpp2::Default.expects(v==vec{}, "");
+  v                   = { 1 };
+  cpp2::Default.expects(v==vec{1}, "");
+  v                   = { 2, 3 };
+  cpp2::Default.expects(std::move(v)==vec{2, 3}, "");
+}
+

regression-tests/test-results/gcc-13/pure2-bugfix-for-assign-expression-list.cpp.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-assign-expression-list.cpp2... ok (all Cpp2, passes safety checks)
+

regression-tests/test-results/pure2-bugfix-for-assign-expression-list.cpp

@@ -143,7 +143,7 @@ auto main() -> int{
     CPP2_UFCS(print, z, "   cp-assign     ", " <- ");
     CPP2_UFCS(print, y, "", "\n");
 
-    z = std::move(y);
+    z = { std::move(y) };
     CPP2_UFCS(print, std::move(z), "   mv-assign     ", " <- ");
     CPP2_UFCS(print, std::move(y), "", "\n");
 }

regression-tests/test-results/pure2-bugfix-for-assign-expression-list.cpp2.output

@@ -148,7 +148,7 @@ auto main() -> int{
     CPP2_UFCS(print, z, "   cp-assign     ", " <- ");
     CPP2_UFCS(print, y, "", "\n");
 
-    z = std::move(y);
+    z = { std::move(y) };
     CPP2_UFCS(print, std::move(z), "   mv-assign     ", " <- ");
     CPP2_UFCS(print, std::move(y), "", "\n");
 }

regression-tests/test-results/pure2-types-smf-and-that-1-provide-everything.cpp

@@ -147,7 +147,7 @@ auto main() -> int{
     CPP2_UFCS(print, z, "   cp-assign     ", " <- ");
     CPP2_UFCS(print, y, "", "\n");
 
-    z = std::move(y);
+    z = { std::move(y) };
     CPP2_UFCS(print, std::move(z), "   mv-assign     ", " <- ");
     CPP2_UFCS(print, std::move(y), "", "\n");
 }

regression-tests/test-results/pure2-types-smf-and-that-2-provide-mvconstruct-and-cpassign.cpp

@@ -147,7 +147,7 @@ auto main() -> int{
     CPP2_UFCS(print, z, "   cp-assign     ", " <- ");
     CPP2_UFCS(print, y, "", "\n");
 
-    z = std::move(y);
+    z = { std::move(y) };
     CPP2_UFCS(print, std::move(z), "   mv-assign     ", " <- ");
     CPP2_UFCS(print, std::move(y), "", "\n");
 }

regression-tests/test-results/pure2-types-smf-and-that-3-provide-mvconstruct-and-mvassign.cpp

@@ -153,7 +153,7 @@ auto main() -> int{
     CPP2_UFCS(print, z, "   cp-assign     ", " <- ");
     CPP2_UFCS(print, y, "", "\n");
 
-    z = std::move(y);
+    z = { std::move(y) };
     CPP2_UFCS(print, std::move(z), "   mv-assign     ", " <- ");
     CPP2_UFCS(print, std::move(y), "", "\n");
 }