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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::macros::{find_format_args, format_args_inputs_span};
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{is_expn_of, path_def_id};
use rustc_errors::Applicability;
use rustc_hir::def::Res;
use rustc_hir::{BindingAnnotation, Block, BlockCheckMode, Expr, ExprKind, Node, PatKind, QPath, Stmt, StmtKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::declare_lint_pass;
use rustc_span::{sym, ExpnId};
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `write!()` / `writeln()!` which can be
/// replaced with `(e)print!()` / `(e)println!()`
///
/// ### Why is this bad?
/// Using `(e)println!` is clearer and more concise
///
/// ### Example
/// ```no_run
/// # use std::io::Write;
/// # let bar = "furchtbar";
/// writeln!(&mut std::io::stderr(), "foo: {:?}", bar).unwrap();
/// writeln!(&mut std::io::stdout(), "foo: {:?}", bar).unwrap();
/// ```
///
/// Use instead:
/// ```no_run
/// # use std::io::Write;
/// # let bar = "furchtbar";
/// eprintln!("foo: {:?}", bar);
/// println!("foo: {:?}", bar);
/// ```
#[clippy::version = "pre 1.29.0"]
pub EXPLICIT_WRITE,
complexity,
"using the `write!()` family of functions instead of the `print!()` family of functions, when using the latter would work"
}
declare_lint_pass!(ExplicitWrite => [EXPLICIT_WRITE]);
impl<'tcx> LateLintPass<'tcx> for ExplicitWrite {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// match call to unwrap
if let ExprKind::MethodCall(unwrap_fun, write_call, [], _) = expr.kind
&& unwrap_fun.ident.name == sym::unwrap
// match call to write_fmt
&& let ExprKind::MethodCall(write_fun, write_recv, [write_arg], _) = *look_in_block(cx, &write_call.kind)
&& let ExprKind::Call(write_recv_path, _) = write_recv.kind
&& write_fun.ident.name == sym!(write_fmt)
&& let Some(def_id) = path_def_id(cx, write_recv_path)
{
// match calls to std::io::stdout() / std::io::stderr ()
let (dest_name, prefix) = match cx.tcx.get_diagnostic_name(def_id) {
Some(sym::io_stdout) => ("stdout", ""),
Some(sym::io_stderr) => ("stderr", "e"),
_ => return,
};
let Some(format_args) = find_format_args(cx, write_arg, ExpnId::root()) else {
return;
};
// ordering is important here, since `writeln!` uses `write!` internally
let calling_macro = if is_expn_of(write_call.span, "writeln").is_some() {
Some("writeln")
} else if is_expn_of(write_call.span, "write").is_some() {
Some("write")
} else {
None
};
// We need to remove the last trailing newline from the string because the
// underlying `fmt::write` function doesn't know whether `println!` or `print!` was
// used.
let (used, sugg_mac) = if let Some(macro_name) = calling_macro {
(
format!("{macro_name}!({dest_name}(), ...)"),
macro_name.replace("write", "print"),
)
} else {
(format!("{dest_name}().write_fmt(...)"), "print".into())
};
let mut applicability = Applicability::MachineApplicable;
let inputs_snippet =
snippet_with_applicability(cx, format_args_inputs_span(&format_args), "..", &mut applicability);
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&format!("use of `{used}.unwrap()`"),
"try",
format!("{prefix}{sugg_mac}!({inputs_snippet})"),
applicability,
);
}
}
}
/// If `kind` is a block that looks like `{ let result = $expr; result }` then
/// returns $expr. Otherwise returns `kind`.
fn look_in_block<'tcx, 'hir>(cx: &LateContext<'tcx>, kind: &'tcx ExprKind<'hir>) -> &'tcx ExprKind<'hir> {
if let ExprKind::Block(block, _label @ None) = kind
&& let Block {
stmts: [Stmt { kind: StmtKind::Local(local), .. }],
expr: Some(expr_end_of_block),
rules: BlockCheckMode::DefaultBlock,
..
} = block
// Find id of the local that expr_end_of_block resolves to
&& let ExprKind::Path(QPath::Resolved(None, expr_path)) = expr_end_of_block.kind
&& let Res::Local(expr_res) = expr_path.res
&& let Some(Node::Pat(res_pat)) = cx.tcx.opt_hir_node(expr_res)
// Find id of the local we found in the block
&& let PatKind::Binding(BindingAnnotation::NONE, local_hir_id, _ident, None) = local.pat.kind
// If those two are the same hir id
&& res_pat.hir_id == local_hir_id
&& let Some(init) = local.init
{
return &init.kind;
}
kind
}
|
