Fix @struct closes #426, and lay more groundwork for generative met…

…afunctions

Fix `@struct` to generate a type that's actually usable as a struct, by providing a metafunction a way to disable all member function generation

Make member initialization diagnostics clearer and more actionable, with better source location attribution

Lay more groundwork for generative metafunctions like `enum` and `flag_enum` that replace the entire type's contents, including to move more semantic checks to `sema.h` where they belong and will run later

regression-tests/test-results/msvc-2022/MSVC-version.output

@@ -1,3 +1,3 @@
-Microsoft (R) C/C++ Optimizing Compiler Version 19.35.32217.1 for x86
+Microsoft (R) C/C++ Optimizing Compiler Version 19.36.32534 for x86
 Copyright (C) Microsoft Corporation.  All rights reserved.
 

regression-tests/test-results/pure2-types-ordering-via-meta-functions.cpp

@@ -68,14 +68,6 @@ public: [[nodiscard]] auto operator<=>(person_in_family_tree const& that) const
 
 class mystruct {
     public: int val {0}; 
-    public: mystruct(mystruct const& that);
-
-public: auto operator=(mystruct const& that) -> mystruct& ;
-public: mystruct(mystruct&& that) noexcept;
-public: auto operator=(mystruct&& that) noexcept -> mystruct& ;
-public: explicit mystruct();
-
-#line 19 "pure2-types-ordering-via-meta-functions.cpp2"
 };
 
 auto main() -> int;
@@ -123,18 +115,6 @@ auto main() -> int;
     }
 
 
-    mystruct::mystruct(mystruct const& that)
-                                : val{ that.val }{}
-
-auto mystruct::operator=(mystruct const& that) -> mystruct& {
-                                val = that.val;
-                                return *this;}
-mystruct::mystruct(mystruct&& that) noexcept
-                                : val{ std::move(that).val }{}
-auto mystruct::operator=(mystruct&& that) noexcept -> mystruct& {
-                                val = std::move(that).val;
-                                return *this;}
-mystruct::mystruct(){}
 #line 21 "pure2-types-ordering-via-meta-functions.cpp2"
 auto main() -> int{
     my_integer a {1}; 

regression-tests/test-results/version

@@ -1,5 +1,5 @@
 
-cppfront compiler v0.2.1   Build 8613:1951
+cppfront compiler v0.2.1   Build 8617:0816
 Copyright(c) Herb Sutter   All rights reserved
 
 SPDX-License-Identifier: CC-BY-NC-ND-4.0

source/build.info

@@ -1 +1 @@
-"8613:1951"
+"8617:0816"

source/common.h

@@ -501,6 +501,15 @@ auto contains(
         != range.end();
 }
 
+auto contains(
+    std::string const& s,
+    auto const&        value
+)
+    -> bool
+{
+    return s.find(value);
+}
+
 
 //-----------------------------------------------------------------------
 //

source/cppfront.cpp

@@ -4488,7 +4488,8 @@ class cppfront
 
             //  We'll use this common guidance in several errors,
             //  so write it once to keep the guidance consistent
-            auto error_msg = "an operator= body must start with a series of 'member = value;' initialization statements for each of the type-scope objects in the same order they are declared";
+            assert (n.parent_declaration && n.parent_declaration->name());
+            auto error_msg = "an operator= body must start with a series of 'member = value;' initialization statements for each of the type-scope objects in the same order they are declared, or the member must have a default initializer (in type '" + n.parent_declaration->name()->to_string(true) + "')";
 
             //  If this constructor's type has data members, handle their initialization
             //      - objects is the list of this type's declarations
@@ -4519,6 +4520,9 @@ class cppfront
                 {
                     assert (*statement);
                     stmt_pos = (*statement)->position();
+                    if (stmt_pos.lineno < 0) {
+                        stmt_pos = n.position();
+                    }
 
                     auto lhs = std::string{};
                     auto rhs = std::string{};
@@ -4615,7 +4619,15 @@ class cppfront
                 {
                     errors.emplace_back(
                         stmt_pos,
-                        "expected '" + object_name + " = ...' initialization statement - " + error_msg
+                        "in operator=, expected '" + object_name + " = ...' initialization statement (because type scope object '" + object_name + "' does not have a default initializer)"
+                    );
+                    errors.emplace_back(
+                        (*object)->position(),
+                        "see declaration for '" + object_name + "' here"
+                    );
+                    errors.emplace_back(
+                        stmt_pos,
+                        error_msg
                     );
                     return;
                 }
@@ -4731,7 +4743,15 @@ class cppfront
             {
                 errors.emplace_back(
                     (*object)->position(),
-                    canonize_object_name(*object) + " was not initialized - " + error_msg
+                    canonize_object_name(*object) + " was not initialized - did you forget to write a default initializer, or assign to it in the operator= body?"
+                );
+                errors.emplace_back(
+                    (*object)->position(),
+                    "see declaration for '" + canonize_object_name(*object) + "' here"
+                );
+                errors.emplace_back(
+                    (*object)->position(),
+                    error_msg
                 );
                 return;
             }
@@ -4776,7 +4796,7 @@ class cppfront
         //  Declarations are handled in multiple passes,
         //  but we only want to do the sema checks once
         if (
-            printer.get_phase() == printer.phase1_type_defs_func_decls
+            printer.get_phase() == printer.phase2_func_defs
             && !sema.check(n)
             )
         {
@@ -5191,21 +5211,24 @@ class cppfront
                                 );
                 auto prefix = "\n" + std::string( indent, ' ' ) + "public: ";
 
-                //  If no constructor was defined, there should only be
-                //  a default constructor, so generate that
-                if (!found_constructor) {
-                    printer.print_extra( prefix + id + "() = default;" );
-                }
+                if (n.member_function_generation)
+                {
+                    //  If no constructor was defined, there should only be
+                    //  a default constructor, so generate that
+                    if (!found_constructor) {
+                        printer.print_extra( prefix + id + "() = default;" );
+                    }
 
-                //  If no 'that' constructor was defined, disable copy/move
-                //  so that Cpp1 doesn't silently generate it anyway
-                if (!found_that_constructor) {
-                    printer.print_extra( prefix + id + "(" + id + " const&) = delete; /* No 'that' constructor, suppress copy */" );
-                    printer.print_extra( prefix + "auto operator=(" + id + " const&) -> void = delete;" );
-                }
+                    //  If no 'that' constructor was defined, disable copy/move
+                    //  so that Cpp1 doesn't silently generate it anyway
+                    if (!found_that_constructor) {
+                        printer.print_extra( prefix + id + "(" + id + " const&) = delete; /* No 'that' constructor, suppress copy */" );
+                        printer.print_extra( prefix + "auto operator=(" + id + " const&) -> void = delete;" );
+                    }
 
-                if (!found_constructor || !found_that_constructor) {
-                    printer.print_extra( "\n" );
+                    if (!found_constructor || !found_that_constructor) {
+                        printer.print_extra( "\n" );
+                    }
                 }
 
                 printer.print_cpp2("};\n", compound_stmt->close_brace);