Constructors and functions with underscore arguments should be allowed to be called, but

only if the underscore arguments are not provided but are implicit from
the default values. Same for constructing structs with private fields.

1 files changed, 33 insertions, 17 deletions

diff --git a/src/compile.c b/src/compile.c
index 6bb528a0..262608c5 100644
--- a/src/compile.c
+++ b/src/compile.c
@@ -579,7 +579,7 @@ static Text_t compile_binary_op(env_t *env, ast_t *ast) {
             DeclareMatch(fn, b->type, FunctionType);
             if (type_eq(fn->ret, rhs_t)) {
                 arg_ast_t *args = new (arg_ast_t, .value = binop.rhs, .next = new (arg_ast_t, .value = binop.lhs));
-                if (is_valid_call(env, fn->args, args, true))
+                if (is_valid_call(env, fn->args, args, (call_opts_t){.promotion = true}))
                     return Texts(b->code, "(", compile_arguments(env, ast, fn->args, args), ")");
             }
         }
@@ -589,7 +589,7 @@ static Text_t compile_binary_op(env_t *env, ast_t *ast) {
             DeclareMatch(fn, b->type, FunctionType);
             if (type_eq(fn->ret, lhs_t)) {
                 arg_ast_t *args = new (arg_ast_t, .value = binop.lhs, .next = new (arg_ast_t, .value = binop.rhs));
-                if (is_valid_call(env, fn->args, args, true))
+                if (is_valid_call(env, fn->args, args, (call_opts_t){.promotion = true}))
                     return Texts(b->code, "(", compile_arguments(env, ast, fn->args, args), ")");
             }
         }
@@ -599,7 +599,7 @@ static Text_t compile_binary_op(env_t *env, ast_t *ast) {
             DeclareMatch(fn, b->type, FunctionType);
             if (type_eq(fn->ret, lhs_t)) {
                 arg_ast_t *args = new (arg_ast_t, .value = binop.lhs, .next = new (arg_ast_t, .value = binop.rhs));
-                if (is_valid_call(env, fn->args, args, true))
+                if (is_valid_call(env, fn->args, args, (call_opts_t){.promotion = true}))
                     return Texts(b->code, "(", compile_arguments(env, ast, fn->args, args), ")");
             }
         }
@@ -609,7 +609,7 @@ static Text_t compile_binary_op(env_t *env, ast_t *ast) {
             DeclareMatch(fn, b->type, FunctionType);
             if (type_eq(fn->ret, lhs_t)) {
                 arg_ast_t *args = new (arg_ast_t, .value = binop.lhs, .next = new (arg_ast_t, .value = binop.rhs));
-                if (is_valid_call(env, fn->args, args, true))
+                if (is_valid_call(env, fn->args, args, (call_opts_t){.promotion = true}))
                     return Texts(b->code, "(", compile_arguments(env, ast, fn->args, args), ")");
             }
         }
@@ -3466,6 +3466,24 @@ Text_t compile(env_t *env, ast_t *ast) {
         type_t *fn_t = get_type(env, call->fn);
         if (fn_t->tag == FunctionType) {
             Text_t fn = compile(env, call->fn);
+            if (!is_valid_call(env, Match(fn_t, FunctionType)->args, call->args, (call_opts_t){.promotion = true})) {
+                if (is_valid_call(env, Match(fn_t, FunctionType)->args, call->args,
+                                  (call_opts_t){.promotion = true, .underscores = true})) {
+                    code_err(ast, "You can't pass underscore arguments to this function (those are private)");
+                } else {
+                    arg_t *args = NULL;
+                    for (arg_ast_t *a = call->args; a; a = a->next)
+                        args = new (arg_t, .name = a->name, .type = get_type(env, a->value), .next = args);
+                    REVERSE_LIST(args);
+                    code_err(ast,
+                             "This function's public signature doesn't match this call site.\n"
+                             "The signature is: ",
+                             type_to_text(fn_t),
+                             "\n"
+                             "But it's being called with: ",
+                             type_to_text(Type(FunctionType, .args = args)));
+                }
+            }
             return Texts(fn, "(", compile_arguments(env, ast, Match(fn_t, FunctionType)->args, call->args), ")");
         } else if (fn_t->tag == TypeInfoType) {
             type_t *t = Match(fn_t, TypeInfoType)->type;
@@ -3509,21 +3527,19 @@ Text_t compile(env_t *env, ast_t *ast) {
                              ")");
             } else if (t->tag == StructType) {
                 DeclareMatch(struct_, t, StructType);
-                if (!struct_->opaque && is_valid_call(env, struct_->fields, call->args, true)) {
-                    if (env->current_type == NULL || !type_eq(env->current_type, t)) {
-                        for (arg_t *field = struct_->fields; field; field = field->next) {
-                            if (field->name[0] == '_')
-                                code_err(ast, "This struct can't be "
-                                              "initialized directly because it "
-                                              "has private fields (starting "
-                                              "with underscore).\n"
-                                              "Use a `convert` or `func` to "
-                                              "instantiate the type "
-                                              "instead.");
-                        }
-                    }
+                if (struct_->opaque) code_err(ast, "This struct is opaque, so I don't know what's inside it!");
+
+                call_opts_t constructor_opts = {
+                    .promotion = true,
+                    .underscores = (env->current_type != NULL && type_eq(env->current_type, t)),
+                };
+                if (is_valid_call(env, struct_->fields, call->args, constructor_opts)) {
                     return Texts("((", compile_type(t), "){", compile_arguments(env, ast, struct_->fields, call->args),
                                  "})");
+                } else if (!constructor_opts.underscores
+                           && is_valid_call(env, struct_->fields, call->args,
+                                            (call_opts_t){.promotion = true, .underscores = true})) {
+                    code_err(ast, "This constructor uses private fields that are not exposed.");
                 }
             }
             code_err(ast,