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>

src/ast/ast.c

@@ -48,10 +48,11 @@ AstNode* ast_make_function(void* alloc, const char* name, AstNode** params, size
 }
 
 AstNode* ast_make_parameter(void* alloc, const char* name, TypeKind type,
-                             const char* struct_type_name, SourceLoc loc) {
+                             const char* struct_type_name, bool is_out, SourceLoc loc) {
     NEW(alloc, AST_PARAMETER);
     n->as.parameter.name = name; n->as.parameter.type = type;
     n->as.parameter.struct_type_name = struct_type_name;
+    n->as.parameter.is_out = is_out;
     return n;
 }
 

src/ast/ast.h

@@ -74,7 +74,7 @@ struct AstNode {
                  const char** type_params; size_t type_param_count;
                  TypeKind* multi_ret_types; const char** multi_ret_snames; size_t multi_ret_count; } function;
         // AST_PARAMETER (也用作结构体字段: name + type)
-        struct { const char* name; TypeKind type; const char* struct_type_name; } parameter;
+        struct { const char* name; TypeKind type; const char* struct_type_name; bool is_out; } parameter;
         // AST_BLOCK
         struct { struct AstNode** stmts; size_t stmt_count; } block;
         // AST_LET_STMT
@@ -150,7 +150,7 @@ AstNode* ast_make_function(void* alloc, const char* name, AstNode** params, size
                            TypeKind ret, const char* ret_struct_name, AstNode* body,
                            bool is_pub, const char** type_params, size_t tp_count,
                            SourceLoc loc);
-AstNode* ast_make_parameter(void* alloc, const char* name, TypeKind type, const char* struct_type_name, SourceLoc loc);
+AstNode* ast_make_parameter(void* alloc, const char* name, TypeKind type, const char* struct_type_name, bool is_out, SourceLoc loc);
 AstNode* ast_make_block(void* alloc, AstNode** stmts, size_t count, SourceLoc loc);
 AstNode* ast_make_let(void* alloc, const char* name, TypeKind annot_type, bool has_type_annot,
                       bool is_mut, AstNode* init, const char* struct_type_name,

src/codegen/cg_expr.c

@@ -239,8 +239,34 @@ static LLVMValueRef cg_call_impl(CgCtx* ctx, AstNode* node) {
     if (!fn) return NULL;
     LLVMValueRef args[16];
     if (node->as.call.arg_count > 16) { ctx->error = "函数参数过多(最多16)"; return NULL; }
+    FnEntry* fn_entry = find_fn_entry(ctx, node->as.call.name);
     for (size_t i = 0; i < node->as.call.arg_count; i++) {
-        args[i] = codegen_expr(ctx, node->as.call.args[i]);
+        bool is_out = fn_entry && fn_entry->out_params
+                      && i < fn_entry->pc && fn_entry->out_params[i];
+        if (is_out) {
+            // out 参数传 alloca 地址而非加载后的值
+            AstNode* arg = node->as.call.args[i];
+            if (arg->kind == AST_IDENT_EXPR) {
+                args[i] = find_var(ctx, arg->as.ident.name);
+            } else if (arg->kind == AST_INDEX_EXPR) {
+                // arr[i]: 生成 GEP 得到元素指针
+                LLVMValueRef arr_ptr = find_var(ctx, arg->as.index_expr.array->as.ident.name);
+                LLVMValueRef idx_val = codegen_expr(ctx, arg->as.index_expr.index);
+                if (!arr_ptr || !idx_val) return NULL;
+                LLVMValueRef indices[] = {
+                    LLVMConstInt(LLVMInt32TypeInContext(ctx->context), 0, false),
+                    LLVMBuildIntCast2(ctx->builder, idx_val,
+                        LLVMInt32TypeInContext(ctx->context), false, "idx32")
+                };
+                args[i] = LLVMBuildGEP2(ctx->builder,
+                    LLVMGetElementType(LLVMTypeOf(arr_ptr)),
+                    arr_ptr, indices, 2, "out_gep");
+            } else {
+                args[i] = codegen_expr(ctx, node->as.call.args[i]);
+            }
+        } else {
+            args[i] = codegen_expr(ctx, node->as.call.args[i]);
+        }
         if (!args[i]) return NULL;
     }
     LLVMTypeRef fn_ty = LLVMGlobalGetValueType(fn);

src/codegen/codegen.c

@@ -23,17 +23,24 @@ LLVMValueRef find_fn(CgCtx* ctx, const char* name) {
     return NULL;
 }
 
-void add_fn(CgCtx* ctx, const char* name, LLVMValueRef fn) {
+void add_fn(CgCtx* ctx, const char* name, LLVMValueRef fn, bool* out_params, size_t pc) {
     FnEntry* e = arena_alloc(ctx->arena, sizeof(*e));
     if (!e) return;
     e->name = name; e->fn = fn;
     e->ret = TYPE_VOID;
     e->params = NULL;
-    e->pc = 0;
+    e->out_params = out_params;
+    e->pc = pc;
     e->next = ctx->fn_table;
     ctx->fn_table = e;
 }
 
+FnEntry* find_fn_entry(CgCtx* ctx, const char* name) {
+    for (FnEntry* e = ctx->fn_table; e; e = e->next)
+        if (strcmp(e->name, name) == 0) return e;
+    return NULL;
+}
+
 // === 结构体类型表 ===
 void add_struct_type(CgCtx* ctx, const char* name, LLVMTypeRef ty, size_t fc) {
     StructTypeEntry* e = arena_alloc(ctx->arena, sizeof(*e));
@@ -379,14 +386,23 @@ LLVMModuleRef codegen_module(AstNode* ast, Arena* codegen_arena,
         AstNode* fn = ast->as.program.functions[i];
         LLVMTypeRef* ptypes = arena_alloc(ctx.arena,
             fn->as.function.param_count * sizeof(LLVMTypeRef));
+        bool* out_params = NULL;
+        if (fn->as.function.param_count > 0) {
+            out_params = arena_alloc(ctx.arena,
+                fn->as.function.param_count * sizeof(bool));
+        }
         for (size_t j = 0; j < fn->as.function.param_count; j++) {
             AstNode* param = fn->as.function.params[j];
+            bool is_out = param->as.parameter.is_out;
+            if (out_params) out_params[j] = is_out;
+            LLVMTypeRef inner_ty;
             if (param->as.parameter.type == TYPE_STRUCT &&
                 param->as.parameter.struct_type_name) {
-                ptypes[j] = find_struct_type(&ctx, param->as.parameter.struct_type_name);
+                inner_ty = find_struct_type(&ctx, param->as.parameter.struct_type_name);
             } else {
-                ptypes[j] = to_llvm_type(&ctx, param->as.parameter.type);
+                inner_ty = to_llvm_type(&ctx, param->as.parameter.type);
             }
+            ptypes[j] = is_out ? LLVMPointerType(inner_ty, 0) : inner_ty;
         }
         LLVMTypeRef ret_ty;
         if (fn->as.function.return_type == TYPE_STRUCT &&
@@ -398,7 +414,8 @@ LLVMModuleRef codegen_module(AstNode* ast, Arena* codegen_arena,
         LLVMTypeRef fty = LLVMFunctionType(ret_ty,
             ptypes, (unsigned)fn->as.function.param_count, false);
         LLVMValueRef lfn = LLVMAddFunction(ctx.module, fn->as.function.name, fty);
-        add_fn(&ctx, fn->as.function.name, lfn);
+        add_fn(&ctx, fn->as.function.name, lfn, out_params,
+               fn->as.function.param_count);
     }
 
     // 第二遍：生成函数体
@@ -422,10 +439,15 @@ LLVMModuleRef codegen_module(AstNode* ast, Arena* codegen_arena,
             } else {
                 param_ty = to_llvm_type(&ctx, pnode->as.parameter.type);
             }
-            LLVMValueRef alloca = LLVMBuildAlloca(ctx.builder,
-                param_ty, pnode->as.parameter.name);
-            LLVMBuildStore(ctx.builder, param, alloca);
-            add_var(&ctx, pnode->as.parameter.name, alloca, param_ty);
+            if (pnode->as.parameter.is_out) {
+                // out 参数: param 已是指向调用者变量的指针, 直接用作 alloca
+                add_var(&ctx, pnode->as.parameter.name, param, param_ty);
+            } else {
+                LLVMValueRef alloca = LLVMBuildAlloca(ctx.builder,
+                    param_ty, pnode->as.parameter.name);
+                LLVMBuildStore(ctx.builder, param, alloca);
+                add_var(&ctx, pnode->as.parameter.name, alloca, param_ty);
+            }
         }
 
         ctx.defer_count = 0;

src/codegen/codegen_internal.h

@@ -28,6 +28,7 @@ typedef struct FnEntry {
     LLVMValueRef      fn;
     TypeKind          ret;
     TypeKind*         params;
+    bool*             out_params;   // 哪些参数是 out (引用传递)
     size_t            pc;
     struct FnEntry*   next;
 } FnEntry;
@@ -71,7 +72,8 @@ LLVMValueRef coerce_int(CgCtx* ctx, LLVMValueRef val, LLVMTypeRef from_ty, LLVMT
 LLVMValueRef find_var(CgCtx* ctx, const char* name);
 void add_var(CgCtx* ctx, const char* name, LLVMValueRef alloca, LLVMTypeRef alloca_type);
 LLVMValueRef find_fn(CgCtx* ctx, const char* name);
-void add_fn(CgCtx* ctx, const char* name, LLVMValueRef fn);
+FnEntry*    find_fn_entry(CgCtx* ctx, const char* name);
+void add_fn(CgCtx* ctx, const char* name, LLVMValueRef fn, bool* out_params, size_t pc);
 void add_struct_type(CgCtx* ctx, const char* name, LLVMTypeRef ty, size_t fc);
 LLVMTypeRef find_struct_type(CgCtx* ctx, const char* name);
 

src/lexer/lexer.c

@@ -68,7 +68,7 @@ static TokenKind check_keyword(const Token* tok) {
     KW("struct", TOK_STRUCT); KW("type", TOK_TYPE);
     KW("enum", TOK_ENUM);  KW("extend", TOK_EXTEND);  KW("defer", TOK_DEFER);  KW("match", TOK_MATCH);
     KW("pub",  TOK_PUB);   KW("mod",  TOK_MOD);  KW("use",  TOK_USE);
-    KW("trait", TOK_TRAIT); KW("Self", TOK_SELF);
+    KW("trait", TOK_TRAIT); KW("Self", TOK_SELF); KW("out", TOK_OUT);
     KW("_", TOK_UNDERSCORE);
     KW("true",   TOK_TRUE);   KW("false",  TOK_FALSE);
     #undef KW

src/lexer/token.c

@@ -7,7 +7,7 @@
 static const char* NAMES[] = {
     [TOK_FN] = "fn", [TOK_LET] = "let", [TOK_VAR] = "var", [TOK_CONST] = "const", [TOK_IF] = "if", [TOK_GUARD] = "guard",
     [TOK_PUB] = "pub", [TOK_MOD] = "mod", [TOK_USE] = "use",
-    [TOK_TRAIT] = "trait", [TOK_SELF] = "Self",
+    [TOK_TRAIT] = "trait", [TOK_SELF] = "Self", [TOK_OUT] = "out",
     [TOK_ELSE] = "else", [TOK_WHILE] = "while", [TOK_FOR] = "for", [TOK_IN] = "in", [TOK_RETURN] = "return",
     [TOK_STRUCT] = "struct", [TOK_TYPE] = "type", [TOK_ENUM] = "enum", [TOK_EXTEND] = "extend",
     [TOK_DEFER] = "defer", [TOK_MATCH] = "match",

src/lexer/token.h

@@ -8,7 +8,7 @@ typedef enum {
     // 关键字
     TOK_FN, TOK_LET, TOK_VAR, TOK_CONST, TOK_IF, TOK_ELSE, TOK_WHILE, TOK_FOR, TOK_IN, TOK_RETURN, TOK_GUARD,
     TOK_STRUCT, TOK_TYPE, TOK_ENUM, TOK_EXTEND, TOK_DEFER, TOK_MATCH, TOK_PUB, TOK_MOD, TOK_USE,
-    TOK_TRAIT, TOK_SELF,
+    TOK_TRAIT, TOK_SELF, TOK_OUT,
     // 类型关键字
     TOK_I32, TOK_I64, TOK_U64, TOK_F64, TOK_BOOL, TOK_CHAR, TOK_STR, TOK_VOID,
     // 字面量

src/parser/parser.c

@@ -27,7 +27,7 @@ AstNode* parse_struct_decl(Parser* p, ErrorInfo* error) {
         }
         fields[fcount++] = ast_make_parameter(p->arena,
             arena_strdup_impl(p->arena, fname->start, fname->length),
-            fti.kind, fti.struct_name, tok_loc(fname));
+            fti.kind, fti.struct_name, false, tok_loc(fname));
         if (peek(p)->kind == TOK_COMMA) advance(p);
         else break;
     }
@@ -348,6 +348,7 @@ AstNode* parse_function(Parser* p, bool is_pub, ErrorInfo* error) {
     AstNode* params[64]; int pcount = 0;
     while (peek(p)->kind != TOK_RPAREN && !error->message) {
         if (pcount >= 64) { error->message = "函数参数过多 (最多64)"; error->filename = p->filename; error->line = peek(p)->line; error->col = peek(p)->col; return NULL; }
+        bool is_out = match(p, TOK_OUT);
         const Token* pname = expect(p, TOK_IDENT, error, "参数名");
         if (!pname) return NULL;
         if (!expect(p, TOK_COLON, error, "缺少 ':'")) return NULL;
@@ -355,7 +356,7 @@ AstNode* parse_function(Parser* p, bool is_pub, ErrorInfo* error) {
         if (pti.kind == TYPE_ERROR) return NULL;
         params[pcount++] = ast_make_parameter(p->arena,
             arena_strdup_impl(p->arena, pname->start, pname->length),
-            pti.kind, pti.struct_name, tok_loc(pname));
+            pti.kind, pti.struct_name, is_out, tok_loc(pname));
         if (match(p, TOK_COMMA)) continue;
         else break;
     }
@@ -699,7 +700,7 @@ AstNode* parse(Arena* a, const Token* tokens, size_t count,
                         arena_strdup_impl(p.arena, fbuf, strlen(fbuf)),
                         fn->as.function.multi_ret_types[i],
                         fn->as.function.multi_ret_snames[i],
-                        tok_loc(peek(&p)));
+                        false, tok_loc(peek(&p)));
                 }
                 if (struct_count >= 64) { error->message = "结构体过多"; return NULL; }
                 structs[struct_count++] = ast_make_struct_decl(p.arena,

src/sema/sema.c

@@ -159,7 +159,8 @@ void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena* a) {
             Scope* fn_scope = scope_new(a, scope);
             for (size_t j = 0; j < mono_fn->as.function.param_count; j++) {
                 AstNode* p = mono_fn->as.function.params[j];
-                scope_insert(fn_scope, a, p->as.parameter.name, SYM_PARAMETER, p->as.parameter.type);
+                Symbol* ps = scope_insert(fn_scope, a, p->as.parameter.name, SYM_PARAMETER, p->as.parameter.type);
+                if (ps && p->as.parameter.is_out) { ps->kind = SYM_VARIABLE; ps->is_mut = true; }
             }
             // 分析函数体
             current_return_type = mono_fn->as.function.return_type;
@@ -197,6 +198,7 @@ void analyze_node(AstNode* node, Scope* scope, ErrorList* errors, Arena* a) {
                 }
             }
             Symbol* sym = scope_insert(fn_scope, a, p->as.parameter.name, SYM_PARAMETER, pt);
+            if (sym && p->as.parameter.is_out) { sym->kind = SYM_VARIABLE; sym->is_mut = true; }
             if (sym && pt == TYPE_STRUCT && psn) {
                 sym->struct_type_name = psn;
             }

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();
 }