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https://github.com/rust-lang/rust-clippy
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Merge pull request #2131 from devonhollowood/suggest-print
Suggest print
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commit
f01e45faa4
4 changed files with 188 additions and 0 deletions
101
clippy_lints/src/explicit_write.rs
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101
clippy_lints/src/explicit_write.rs
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@ -0,0 +1,101 @@
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use rustc::hir::*;
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use rustc::lint::*;
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use utils::{is_expn_of, match_def_path, resolve_node, span_lint};
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use utils::opt_def_id;
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/// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
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/// replaced with `(e)print!()` / `(e)println!()`
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///
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/// **Why is this bad?** Using `(e)println! is clearer and more concise
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// // this would be clearer as `eprintln!("foo: {:?}", bar);`
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/// writeln!(&mut io::stderr(), "foo: {:?}", bar).unwrap();
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/// ```
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declare_lint! {
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pub EXPLICIT_WRITE,
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Warn,
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"using the `write!()` family of functions instead of the `print!()` family \
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of functions, when using the latter would work"
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}
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#[derive(Copy, Clone, Debug)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(EXPLICIT_WRITE)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if_let_chain! {[
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// match call to unwrap
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let ExprMethodCall(ref unwrap_fun, _, ref unwrap_args) = expr.node,
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unwrap_fun.name == "unwrap",
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// match call to write_fmt
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unwrap_args.len() > 0,
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let ExprMethodCall(ref write_fun, _, ref write_args) =
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unwrap_args[0].node,
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write_fun.name == "write_fmt",
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// match calls to std::io::stdout() / std::io::stderr ()
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write_args.len() > 0,
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let ExprCall(ref dest_fun, _) = write_args[0].node,
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let ExprPath(ref qpath) = dest_fun.node,
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let Some(dest_fun_id) =
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opt_def_id(resolve_node(cx, qpath, dest_fun.hir_id)),
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let Some(dest_name) = if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stdout"]) {
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Some("stdout")
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} else if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stderr"]) {
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Some("stderr")
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} else {
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None
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},
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], {
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let write_span = unwrap_args[0].span;
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let calling_macro =
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// ordering is important here, since `writeln!` uses `write!` internally
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if is_expn_of(write_span, "writeln").is_some() {
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Some("writeln")
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} else if is_expn_of(write_span, "write").is_some() {
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Some("write")
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} else {
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None
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};
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let prefix = if dest_name == "stderr" {
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"e"
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} else {
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""
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};
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if let Some(macro_name) = calling_macro {
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span_lint(
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cx,
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EXPLICIT_WRITE,
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expr.span,
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&format!(
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"use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
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macro_name,
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dest_name,
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prefix,
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macro_name.replace("write", "print")
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)
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);
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} else {
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span_lint(
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cx,
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EXPLICIT_WRITE,
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expr.span,
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&format!(
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"use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead",
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dest_name,
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prefix,
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)
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);
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}
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}}
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}
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}
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@ -146,6 +146,7 @@ pub mod serde_api;
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pub mod shadow;
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pub mod should_assert_eq;
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pub mod strings;
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pub mod explicit_write;
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pub mod swap;
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pub mod temporary_assignment;
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pub mod transmute;
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@ -327,6 +328,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
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reg.register_late_lint_pass(box unused_io_amount::UnusedIoAmount);
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reg.register_late_lint_pass(box large_enum_variant::LargeEnumVariant::new(conf.enum_variant_size_threshold));
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reg.register_late_lint_pass(box should_assert_eq::ShouldAssertEq);
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reg.register_late_lint_pass(box explicit_write::Pass);
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reg.register_late_lint_pass(box needless_pass_by_value::NeedlessPassByValue);
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reg.register_early_lint_pass(box literal_digit_grouping::LiteralDigitGrouping);
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reg.register_late_lint_pass(box use_self::UseSelf);
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@ -542,6 +544,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
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serde_api::SERDE_API_MISUSE,
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should_assert_eq::SHOULD_ASSERT_EQ,
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strings::STRING_LIT_AS_BYTES,
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explicit_write::EXPLICIT_WRITE,
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swap::ALMOST_SWAPPED,
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swap::MANUAL_SWAP,
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temporary_assignment::TEMPORARY_ASSIGNMENT,
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46
tests/ui/explicit_write.rs
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46
tests/ui/explicit_write.rs
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#![warn(explicit_write)]
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fn stdout() -> String {
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String::new()
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}
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fn stderr() -> String {
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String::new()
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}
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fn main() {
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// these should warn
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{
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use std::io::Write;
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write!(std::io::stdout(), "test").unwrap();
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write!(std::io::stderr(), "test").unwrap();
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writeln!(std::io::stdout(), "test").unwrap();
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writeln!(std::io::stderr(), "test").unwrap();
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std::io::stdout().write_fmt(format_args!("test")).unwrap();
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std::io::stderr().write_fmt(format_args!("test")).unwrap();
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}
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// these should not warn, different destination
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{
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use std::fmt::Write;
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let mut s = String::new();
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write!(s, "test").unwrap();
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write!(s, "test").unwrap();
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writeln!(s, "test").unwrap();
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writeln!(s, "test").unwrap();
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s.write_fmt(format_args!("test")).unwrap();
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s.write_fmt(format_args!("test")).unwrap();
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write!(stdout(), "test").unwrap();
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write!(stderr(), "test").unwrap();
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writeln!(stdout(), "test").unwrap();
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writeln!(stderr(), "test").unwrap();
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stdout().write_fmt(format_args!("test")).unwrap();
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stderr().write_fmt(format_args!("test")).unwrap();
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}
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// these should not warn, no unwrap
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{
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use std::io::Write;
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std::io::stdout().write_fmt(format_args!("test")).expect("no stdout");
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std::io::stderr().write_fmt(format_args!("test")).expect("no stderr");
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}
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}
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38
tests/ui/explicit_write.stderr
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38
tests/ui/explicit_write.stderr
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error: use of `write!(stdout(), ...).unwrap()`. Consider using `print!` instead
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--> $DIR/explicit_write.rs:16:9
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16 | write!(std::io::stdout(), "test").unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: `-D explicit-write` implied by `-D warnings`
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error: use of `write!(stderr(), ...).unwrap()`. Consider using `eprint!` instead
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--> $DIR/explicit_write.rs:17:9
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17 | write!(std::io::stderr(), "test").unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: use of `writeln!(stdout(), ...).unwrap()`. Consider using `println!` instead
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--> $DIR/explicit_write.rs:18:9
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18 | writeln!(std::io::stdout(), "test").unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: use of `writeln!(stderr(), ...).unwrap()`. Consider using `eprintln!` instead
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--> $DIR/explicit_write.rs:19:9
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19 | writeln!(std::io::stderr(), "test").unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: use of `stdout().write_fmt(...).unwrap()`. Consider using `print!` instead
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--> $DIR/explicit_write.rs:20:9
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20 | std::io::stdout().write_fmt(format_args!("test")).unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: use of `stderr().write_fmt(...).unwrap()`. Consider using `eprint!` instead
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--> $DIR/explicit_write.rs:21:9
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21 | std::io::stderr().write_fmt(format_args!("test")).unwrap();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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