feat: in/out 参数 — out 关键字引用传递

fn swap(out x: i64, out y: i64) 声明 out 参数，codegen 层面
函数签名变为 T* 指针，调用点自动传 &variable 地址。
in 是默认行为（值传递），无需显式标注。

Token → Parser → Sema → Codegen 全流水线:
- TOK_OUT + "out" 关键字注册
- AST parameter.is_out 字段
- parse_function 解析 out 前缀
- Sema: out 参数注册为 SYM_VARIABLE+is_mut（可赋值）
- Codegen: LLVM 函数签名使用 T*，调用点传 alloca

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

test/programs/42_out_param.l

@@ -0,0 +1,22 @@
+// out 参数测试 — 引用传递
+fn swap(out x: i64, out y: i64) -> void {
+    let t = x;
+    x = y;
+    y = t;
+}
+
+fn increment(out x: i64) -> void {
+    x = x + 1;
+}
+
+fn main() -> void {
+    let a = 10;
+    let b = 20;
+    print_i64(a);
+    print_i64(b);
+    swap(a, b);
+    print_i64(a);
+    print_i64(b);
+    increment(a);
+    print_i64(a);
+}

test/programs/43_out_param_struct.l

@@ -0,0 +1,22 @@
+// out 参数 + 结构体测试
+struct Point { x: i64, y: i64 }
+
+fn init_point(out p: Point) -> void {
+    p = Point { x: 100, y: 200 };
+}
+
+fn offset_point(out p: Point) -> void {
+    p = Point { x: p.x + 50, y: p.y + 100 };
+}
+
+fn main() -> void {
+    let p = Point { x: 0, y: 0 };
+    print_i64(p.x);
+    print_i64(p.y);
+    init_point(p);
+    print_i64(p.x);
+    print_i64(p.y);
+    offset_point(p);
+    print_i64(p.x);
+    print_i64(p.y);
+}

test/test_codegen.c

@@ -129,8 +129,8 @@ void test_codegen_struct_decl() {
 
     /* 构造 AST: struct Point { x: i64, y: i64 } */
     AstNode* fields[2];
-    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, loc_at(1, 1));
-    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, loc_at(1, 1));
+    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, false, loc_at(1, 1));
+    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, false, loc_at(1, 1));
     AstNode* struct_decl = ast_make_struct_decl(&a, "Point", fields, 2, loc_at(1, 1));
     AstNode* structs[] = { struct_decl };
 
@@ -185,8 +185,8 @@ void test_codegen_struct_field_access() {
 
     /* 构造 AST: struct Point { x: i64, y: i64 } */
     AstNode* fields[2];
-    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, loc_at(1, 1));
-    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, loc_at(1, 1));
+    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, false, loc_at(1, 1));
+    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, false, loc_at(1, 1));
     AstNode* struct_decl = ast_make_struct_decl(&a, "Point", fields, 2, loc_at(1, 1));
     AstNode* structs[] = { struct_decl };
 
@@ -356,13 +356,13 @@ void test_codegen_method_call() {
 
     /* struct Point { x: i64, y: i64 } */
     AstNode* fields[2];
-    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, loc_at(1, 1));
-    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, loc_at(1, 1));
+    fields[0] = ast_make_parameter(&a, "x", TYPE_I64, NULL, false, loc_at(1, 1));
+    fields[1] = ast_make_parameter(&a, "y", TYPE_I64, NULL, false, loc_at(1, 1));
     AstNode* struct_decl = ast_make_struct_decl(&a, "Point", fields, 2, loc_at(1, 1));
     AstNode* structs[] = { struct_decl };
 
     /* fn Point$get_x(self: Point) -> i64 { return self.x; } */
-    AstNode* self_param = ast_make_parameter(&a, "self", TYPE_STRUCT, "Point", loc_at(1, 1));
+    AstNode* self_param = ast_make_parameter(&a, "self", TYPE_STRUCT, "Point", false, loc_at(1, 1));
     AstNode* params[] = { self_param };
     AstNode* self_ident = ast_make_ident(&a, "self", loc_at(1, 1));
     self_ident->type.kind = TYPE_STRUCT;

test/test_sema.c

@@ -418,6 +418,40 @@ void test_match_wildcard_only_sema_ok() {
     arena_destroy(&a);
 }
 
+void test_out_param_assign_ok() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn swap(out x: i64, out y: i64) -> void { let t = x; x = y; y = t; return; }"
+        "fn main() -> void { let a = 10; let b = 20; swap(a, b); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors, &a);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);  // out 参数赋值不应报错
+    arena_destroy(&a);
+}
+
+void test_in_param_assign_error() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "fn bad(x: i64) -> void { x = 42; return; }"
+        "fn main() -> void { bad(10); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ErrorList errors; error_init(&errors, &a);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count > 0);  // 非 out 参数赋值应报错
+    arena_destroy(&a);
+}
+
 int main(void) {
     TEST_RUN(test_type_error);
     TEST_RUN(test_undefined_var);
@@ -443,5 +477,7 @@ int main(void) {
     TEST_RUN(test_match_enum_sema_ok);
     TEST_RUN(test_match_int_sema_ok);
     TEST_RUN(test_match_wildcard_only_sema_ok);
+    TEST_RUN(test_out_param_assign_ok);
+    TEST_RUN(test_in_param_assign_error);
     return test_summary();
 }