feat: 类型别名 type alias (P1 #10)

- lexer: TOK_TYPE 关键字
- ast: AST_TYPE_ALIAS + AST_PROGRAM aliases数组
- parser: parse_type_expr() 抽取, type Name = Type; 解析
- sema: 别名注册+解析, 类型标注/struct字段/函数参数均支持
- 新增测试: 15_type_alias.l, 16_type_alias_struct.l

测试: 112 通过 (41+15+41+15)

test/programs/15_type_alias.l

@@ -0,0 +1,6 @@
+type Meters = i64;
+fn main() -> i64 {
+    let x: Meters = 100;
+    print_i64(x);
+    return 0;
+}

test/programs/16_type_alias_struct.l

@@ -0,0 +1,8 @@
+struct Point { x: i64, y: i64 }
+type P = Point;
+fn main() -> i64 {
+    let p: P = Point { x: 10, y: 20 };
+    print_i64(p.x);
+    print_i64(p.y);
+    return 0;
+}

test/test_codegen.c

@@ -13,7 +13,7 @@ void test_codegen_simple_function() {
     AstNode* body = ast_make_block(&a, stmts, 1, loc_at(1, 1));
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, body, loc_at(1, 1));
     AstNode* fns[] = { fn };
-    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx = NULL;
@@ -47,7 +47,7 @@ void test_codegen_if_else() {
     AstNode* body = ast_make_block(&a, stmts, 1, loc_at(1, 1));
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, body, loc_at(1, 1));
     AstNode* fns[] = { fn };
-    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx2 = NULL;
@@ -78,7 +78,7 @@ void test_codegen_binary_ops() {
     AstNode* body = ast_make_block(&a, stmts, 1, loc_at(1, 1));
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, body, loc_at(1, 1));
     AstNode* fns[] = { fn };
-    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx3 = NULL;
@@ -108,7 +108,7 @@ void test_codegen_while_loop() {
     AstNode* fn_body = ast_make_block(&a, stmts, 2, loc_at(1, 1));
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, fn_body, loc_at(1, 1));
     AstNode* fns[] = { fn };
-    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, NULL, 0, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx4 = NULL;
@@ -162,7 +162,7 @@ void test_codegen_struct_decl() {
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, body, loc_at(1, 1));
     AstNode* fns[] = { fn };
 
-    AstNode* prog = ast_make_program(&a, fns, 1, structs, 1, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, structs, 1, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx = NULL;
@@ -217,7 +217,7 @@ void test_codegen_struct_field_access() {
     AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, NULL, body, loc_at(1, 1));
     AstNode* fns[] = { fn };
 
-    AstNode* prog = ast_make_program(&a, fns, 1, structs, 1, loc_at(1, 1));
+    AstNode* prog = ast_make_program(&a, fns, 1, structs, 1, NULL, 0, loc_at(1, 1));
 
     const char* err = NULL;
     LLVMContextRef ctx = NULL;

test/test_sema.c

@@ -168,6 +168,44 @@ void test_struct_field_count_mismatch() {
     arena_destroy(&a);
 }
 
+/* === 类型别名测试 === */
+
+void test_type_alias_ok() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "type Meters = i64; fn main() { let x: Meters = 100; print_i64(x); return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ASSERT(ast->as.program.alias_count == 1);
+
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);
+    arena_destroy(&a);
+}
+
+void test_type_alias_struct() {
+    Arena a = arena_create(1);
+    size_t tc; ErrorInfo lex_err = {0};
+    Token* toks = lex(&a,
+        "struct Point { x: i64, y: i64 } type P = Point; fn main() { let p: P = Point { x: 1, y: 2 }; return; }",
+        "test", &tc, &lex_err);
+    ASSERT(toks != NULL);
+    ErrorInfo parse_err = {0};
+    AstNode* ast = parse(&a, toks, tc, "test", &parse_err);
+    ASSERT(ast != NULL);
+    ASSERT(ast->as.program.alias_count == 1);
+
+    ErrorList errors; error_init(&errors);
+    sema_analyze(ast, &errors, &a);
+    ASSERT(errors.count == 0);
+    arena_destroy(&a);
+}
+
 void test_struct_nested_type_ok() {
     Arena a = arena_create(1);
     size_t tc; ErrorInfo lex_err = {0};
@@ -197,5 +235,7 @@ int main(void) {
     TEST_RUN(test_struct_undefined);
     TEST_RUN(test_struct_field_count_mismatch);
     TEST_RUN(test_struct_nested_type_ok);
+    TEST_RUN(test_type_alias_ok);
+    TEST_RUN(test_type_alias_struct);
     return test_summary();
 }