107 lines
4.3 KiB
Rust
107 lines
4.3 KiB
Rust
use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
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use clippy_utils::higher::FormatArgsExpn;
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use clippy_utils::{is_expn_of, match_function_call, paths};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// 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?
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/// Using `(e)println! is clearer and more concise
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///
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/// ### Example
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/// ```rust
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/// # use std::io::Write;
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/// # let bar = "furchtbar";
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/// // this would be clearer as `eprintln!("foo: {:?}", bar);`
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/// writeln!(&mut std::io::stderr(), "foo: {:?}", bar).unwrap();
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/// ```
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pub EXPLICIT_WRITE,
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complexity,
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"using the `write!()` family of functions instead of the `print!()` family of functions, when using the latter would work"
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}
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declare_lint_pass!(ExplicitWrite => [EXPLICIT_WRITE]);
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impl<'tcx> LateLintPass<'tcx> for ExplicitWrite {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
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// match call to unwrap
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if let ExprKind::MethodCall(unwrap_fun, _, [write_call], _) = expr.kind;
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if unwrap_fun.ident.name == sym::unwrap;
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// match call to write_fmt
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if let ExprKind::MethodCall(write_fun, _, [write_recv, write_arg], _) = write_call.kind;
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if write_fun.ident.name == sym!(write_fmt);
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// match calls to std::io::stdout() / std::io::stderr ()
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if let Some(dest_name) = if match_function_call(cx, write_recv, &paths::STDOUT).is_some() {
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Some("stdout")
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} else if match_function_call(cx, write_recv, &paths::STDERR).is_some() {
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Some("stderr")
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} else {
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None
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};
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if let Some(format_args) = FormatArgsExpn::parse(write_arg);
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then {
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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_call.span, "writeln").is_some() {
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Some("writeln")
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} else if is_expn_of(write_call.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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// We need to remove the last trailing newline from the string because the
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// underlying `fmt::write` function doesn't know whether `println!` or `print!` was
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// used.
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let (used, sugg_mac) = if let Some(macro_name) = calling_macro {
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(
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format!("{}!({}(), ...)", macro_name, dest_name),
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macro_name.replace("write", "print"),
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)
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} else {
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(
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format!("{}().write_fmt(...)", dest_name),
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"print".into(),
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)
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};
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let msg = format!("use of `{}.unwrap()`", used);
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if let [write_output] = *format_args.format_string_symbols {
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let mut write_output = write_output.to_string();
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if write_output.ends_with('\n') {
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write_output.pop();
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}
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let sugg = format!("{}{}!(\"{}\")", prefix, sugg_mac, write_output.escape_default());
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span_lint_and_sugg(
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cx,
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EXPLICIT_WRITE,
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expr.span,
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&msg,
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"try this",
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sugg,
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Applicability::MachineApplicable
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);
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} else {
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// We don't have a proper suggestion
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let help = format!("consider using `{}{}!` instead", prefix, sugg_mac);
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span_lint_and_help(cx, EXPLICIT_WRITE, expr.span, &msg, None, &help);
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}
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}
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}
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}
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}
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