test: sema + codegen 测试补全 — 86 单元测试

- test_sema: +4 测试 (let_mut_assign_ok, assign_immutable_error, str_type_ok, str_concat_ok) → 21 tests
- test_codegen: +1 测试 (while_loop LLVMVerifyModule) → 9 tests
- 总单元测试: 86 (词法41+语法15+语义21+代码生成9)
- 基于 Codex 分析报告 §5-3 §5-4 技术债务补偿

test/test_codegen.c

@@ -88,9 +88,35 @@ void test_codegen_binary_ops() {
     arena_destroy(&a);
 }
 
+void test_codegen_while_loop() {
+    Arena a = arena_create(1);
+    // fn main() -> i64 { while true { return 0; } return 1; }
+    AstNode* while_body_stmts[] = {
+        ast_make_return(&a, ast_make_literal_i64(&a, 0, 1, 1), 1, 1)
+    };
+    AstNode* while_body = ast_make_block(&a, while_body_stmts, 1, 1, 1);
+    AstNode* while_stmt = ast_make_while(&a,
+        ast_make_literal_bool(&a, true, 1, 1), while_body, 1, 1);
+    AstNode* ret = ast_make_return(&a, ast_make_literal_i64(&a, 1, 1, 1), 1, 1);
+    AstNode* stmts[] = { while_stmt, ret };
+    AstNode* fn_body = ast_make_block(&a, stmts, 2, 1, 1);
+    AstNode* fn = ast_make_function(&a, "main", NULL, 0, TYPE_I64, fn_body, 1, 1);
+    AstNode* fns[] = { fn };
+    AstNode* prog = ast_make_program(&a, fns, 1, 1, 1);
+
+    const char* err = NULL;
+    LLVMModuleRef mod = codegen_module(prog, &a, "test_while", &err);
+    ASSERT(mod != NULL);
+    char* verify_err = NULL;
+    ASSERT(!LLVMVerifyModule(mod, LLVMReturnStatusAction, &verify_err));
+    LLVMDisposeModule(mod);
+    arena_destroy(&a);
+}
+
 int main(void) {
     TEST_RUN(test_codegen_simple_function);
     TEST_RUN(test_codegen_if_else);
     TEST_RUN(test_codegen_binary_ops);
+    TEST_RUN(test_codegen_while_loop);
     return test_summary();
 }