3 use utils::{is_expn_of, match_def_path, resolve_node, span_lint};
6 /// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
7 /// replaced with `(e)print!()` / `(e)println!()`
9 /// **Why is this bad?** Using `(e)println! is clearer and more concise
11 /// **Known problems:** None.
15 /// // this would be clearer as `eprintln!("foo: {:?}", bar);`
16 /// writeln!(&mut io::stderr(), "foo: {:?}", bar).unwrap();
21 "using the `write!()` family of functions instead of the `print!()` family \
22 of functions, when using the latter would work"
25 #[derive(Copy, Clone, Debug)]
28 impl LintPass for Pass {
29 fn get_lints(&self) -> LintArray {
30 lint_array!(EXPLICIT_WRITE)
34 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
35 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
37 // match call to unwrap
38 if let ExprMethodCall(ref unwrap_fun, _, ref unwrap_args) = expr.node;
39 if unwrap_fun.name == "unwrap";
40 // match call to write_fmt
41 if unwrap_args.len() > 0;
42 if let ExprMethodCall(ref write_fun, _, ref write_args) =
44 if write_fun.name == "write_fmt";
45 // match calls to std::io::stdout() / std::io::stderr ()
46 if write_args.len() > 0;
47 if let ExprCall(ref dest_fun, _) = write_args[0].node;
48 if let ExprPath(ref qpath) = dest_fun.node;
49 if let Some(dest_fun_id) =
50 opt_def_id(resolve_node(cx, qpath, dest_fun.hir_id));
51 if let Some(dest_name) = if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stdout"]) {
53 } else if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stderr"]) {
59 let write_span = unwrap_args[0].span;
61 // ordering is important here, since `writeln!` uses `write!` internally
62 if is_expn_of(write_span, "writeln").is_some() {
64 } else if is_expn_of(write_span, "write").is_some() {
69 let prefix = if dest_name == "stderr" {
74 if let Some(macro_name) = calling_macro {
80 "use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
84 macro_name.replace("write", "print")
93 "use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead",