102 lines
3.7 KiB
Rust
102 lines
3.7 KiB
Rust
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_chain! {
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// match call to unwrap
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if let ExprMethodCall(ref unwrap_fun, _, ref unwrap_args) = expr.node;
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if unwrap_fun.name == "unwrap";
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// match call to write_fmt
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if unwrap_args.len() > 0;
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if let ExprMethodCall(ref write_fun, _, ref write_args) =
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unwrap_args[0].node;
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if write_fun.name == "write_fmt";
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// match calls to std::io::stdout() / std::io::stderr ()
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if write_args.len() > 0;
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if let ExprCall(ref dest_fun, _) = write_args[0].node;
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if let ExprPath(ref qpath) = dest_fun.node;
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if let Some(dest_fun_id) =
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opt_def_id(resolve_node(cx, qpath, dest_fun.hir_id));
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if 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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then {
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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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}
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