这意味着format_args!()宏可以给出编译错误,例如占位符和参数不匹配。 这也意味着它可以将字符串模板转换成一种更易于在运行时处理的表现形式。例如:[Str("Hello, "), Arg(0), Str("!\n")]。在我们的print例子中,展开format_args会得到类似这样的结果: std::io::_print(// 简化版的 format_args!()...
fmt::Arguments{pieces:&[""," "," "],placeholders:None,args:&[fmt::Argument::new(&a,Display::fmt),fmt::Argument::new(&a,Debug::fmt),fmt::Argument::new(&b,LowerHex::fmt),],} 不过,当一个参数被以相同的特性但不同的标志使用了两次时,它只会在args中出现一次。举个例子,format_args!(...
usestd::fmt;lets = fmt::format(format_args!("hello {}","world"));assert_eq!(s,format!("hello {}","world"));
("b: {b}"); | ^ `b` used here but it is possibly-uninitialized | = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to ...
EN在 rust 中，我们一开始就在使用宏，例如 println!, vec!, assert_eq! 等。看起来宏和函数在使用...
and format_args! equally affected, .to_string() is not. Only happens in debug mode, works fine in release mode. Happens with all integer types from i8 to u128, f32, f64, bool, char and fmt::Argument, but not with references to those types or str, String and raw pointers. Debug ...
文件format_args.rs定义了与格式化输出相关的结构体和枚举,主要用于将格式化字符串和参数解析为对应的数据结构进行处理。 以下是各个结构体和枚举的作用和功能: Structs: FormatArgs: 用于保存格式化字符串和对应的参数列表。可以通过其构造函数创建一个FormatArgs实例,并提供一个支持ArgumentsTrait 的闭包函数作为参数。
标签：Cannot use format_args! due to temporary value is freed at the end of this statement ...
Change formatting items to lang items (part ofMove format_args!() into AST (and expand it during AST lowering)#106745) Remove all public exports of the lang items, after the beta 1.69 bump:Remove public doc(hidden) core::fmt::rt::v1#110616 ...
= note: this error originatesinthe macro `$crate::format_args_nl` (inNightly builds, run with -Z macro-backtraceformore info) For more information about this error, try `rustc --explain E0382`. 左右滑动查看完整代码 由于Rust在let s2 = s1操作执行之后将s1的内存所有权转移给了s2,因此它认为...