feat: 数组+索引 [T;N], arr[i] (P1 #6)

- lexer: TOK_LBRACKET, TOK_RBRACKET
- type: TYPE_ARRAY + TypeInfo扩展(element_type/array_size)
- ast: AST_INDEX_EXPR, AST_ARRAY_ASSIGN_STMT
- parser: parse_type_expr()支持[T;N], Pratt加[索引], 数组元素赋值
- sema: 数组类型检查, 索引必须i64, 元素赋值类型匹配
- codegen: type_info_to_llvm(TYPE_ARRAY), GEP+load/store
- 新增集成测试: 18_array.l

测试: 136 通过 (41+15+59+21)

test/test_codegen.c

@@ -145,7 +145,7 @@ void test_codegen_struct_decl() {
     init->type.struct_name = "Point";
 
     AstNode* let_stmt = ast_make_let(&a, "p", TYPE_UNKNOWN, false, false,
-                                     init, NULL, loc_at(1, 1));
+                                     init, NULL, 0, NULL, 0, loc_at(1, 1));
 
     /* return p.x; */
     AstNode* p_ident = ast_make_ident(&a, "p", loc_at(1, 1));
@@ -200,7 +200,7 @@ void test_codegen_struct_field_access() {
     init->type.struct_name = "Point";
 
     AstNode* let_stmt = ast_make_let(&a, "p", TYPE_UNKNOWN, false, false,
-                                     init, NULL, loc_at(1, 1));
+                                     init, NULL, 0, NULL, 0, loc_at(1, 1));
 
     /* return p.y; */
     AstNode* p_ident = ast_make_ident(&a, "p", loc_at(1, 1));
@@ -251,7 +251,7 @@ void test_codegen_enum() {
     cv->type.kind = TYPE_ENUM;
 
     AstNode* let_stmt = ast_make_let(&a, "c", TYPE_UNKNOWN, false, false,
-                                      cv, NULL, loc_at(1, 1));
+                                      cv, NULL, 0, NULL, 0, loc_at(1, 1));
 
     /* print_i64(c); */
     AstNode* c_ident = ast_make_ident(&a, "c", loc_at(1, 1));
@@ -284,6 +284,70 @@ void test_codegen_enum() {
     arena_destroy(&a);
 }
 
+/* === 数组代码生成测试 === */
+
+void test_codegen_array() {
+    Arena a = arena_create(1);
+
+    /* 构造 AST:
+       fn main() -> i64 {
+           let arr: [i64; 3] = arr;
+           arr[0] = 10;
+           print_i64(arr[0]);
+           return 0;
+       }
+    */
+    // let arr: [i64; 3] = arr;
+    AstNode* arr_init = ast_make_ident(&a, "arr", loc_at(1, 1));
+    AstNode* let_stmt = ast_make_let(&a, "arr", TYPE_ARRAY, true, false,
+                                      arr_init, NULL, TYPE_I64, NULL, 3, loc_at(1, 1));
+    // 手动设置 LET_STMT 的类型（绕过 sema）
+    let_stmt->type.kind = TYPE_ARRAY;
+    let_stmt->type.element_type = TYPE_I64;
+    let_stmt->type.array_size = 3;
+
+    // arr[0] = 10;
+    AstNode* arr_assign = ast_make_array_assign(&a, "arr",
+        ast_make_literal_i64(&a, 0, loc_at(1, 1)),
+        ast_make_literal_i64(&a, 10, loc_at(1, 1)), loc_at(1, 1));
+
+    // arr[0] 表达式（print_i64 的参数）
+    AstNode* arr_ident = ast_make_ident(&a, "arr", loc_at(1, 1));
+    arr_ident->type.kind = TYPE_ARRAY;
+    arr_ident->type.element_type = TYPE_I64;
+    arr_ident->type.array_size = 3;
+    AstNode* idx_expr = ast_make_index_expr(&a, arr_ident,
+        ast_make_literal_i64(&a, 0, loc_at(1, 1)), loc_at(1, 1));
+    idx_expr->type.kind = TYPE_I64;  // 元素类型
+
+    // print_i64(arr[0]);
+    AstNode* args[] = { idx_expr };
+    AstNode* print_call = ast_make_call(&a, "print_i64", args, 1, loc_at(1, 1));
+
+    // return 0;
+    AstNode* ret = ast_make_return(&a, ast_make_literal_i64(&a, 0, loc_at(1, 1)), loc_at(1, 1));
+
+    AstNode* stmts[] = { let_stmt, arr_assign, print_call, ret };
+    AstNode* body = ast_make_block(&a, stmts, 4, 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, NULL, 0, NULL, 0, loc_at(1, 1));
+
+    const char* err = NULL;
+    LLVMContextRef ctx = NULL;
+    LLVMModuleRef mod = codegen_module(prog, &a, "test_array", &err, &ctx);
+    ASSERT(mod != NULL);
+    ASSERT(err == NULL);
+
+    char* verify_err = NULL;
+    int failed = LLVMVerifyModule(mod, LLVMReturnStatusAction, &verify_err);
+    ASSERT(!failed);
+
+    LLVMDisposeModule(mod);
+    LLVMContextDispose(ctx);
+    arena_destroy(&a);
+}
+
 int main(void) {
     TEST_RUN(test_codegen_simple_function);
     TEST_RUN(test_codegen_if_else);
@@ -292,5 +356,6 @@ int main(void) {
     TEST_RUN(test_codegen_struct_decl);
     TEST_RUN(test_codegen_struct_field_access);
     TEST_RUN(test_codegen_enum);
+    TEST_RUN(test_codegen_array);
     return test_summary();
 }