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Don't suggest to_string().to_string in USELESS_FORMAT

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This commit is contained in:
mcarton 2018-10-03 20:59:59 +02:00
parent 7eebd5b20c
commit 5173ed0c03
3 changed files with 39 additions and 7 deletions
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24
clippy_lints/src/format.rs
View file

@ -57,12 +57,24 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
if check_single_piece(&args[0]);
if let Some(format_arg) = get_single_string_arg(cx, &args[1]);
if check_unformatted(&args[2]);
if let ExprKind::AddrOf(_, ref format_arg) = format_arg.node;
then {
let sugg = format!("{}.to_string()", snippet(cx, format_arg, "<arg>").into_owned());
let (message, sugg) = if_chain! {
if let ExprKind::MethodCall(ref path, ref span, ref expr) = format_arg.node;
if path.ident.as_interned_str() == "to_string";
then {
("`to_string()` is enough",
snippet(cx, format_arg.span, "<arg>").to_string())
} else {
("consider using .to_string()",
format!("{}.to_string()", snippet(cx, format_arg.span, "<arg>")))
}
};
span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |db| {
db.span_suggestion_with_applicability(
expr.span,
"consider using .to_string()",
message,
sugg,
Applicability::MachineApplicable,
);
@ -113,9 +125,9 @@ fn check_single_piece(expr: &Expr) -> bool {
/// ::std::fmt::Display::fmt)],
/// }
/// ```
/// and that type of `__arg0` is `&str` or `String`
/// then returns the span of first element of the matched tuple
fn get_single_string_arg(cx: &LateContext<'_, '_>, expr: &Expr) -> Option<Span> {
/// and that the type of `__arg0` is `&str` or `String`,
/// then returns the span of first element of the matched tuple.
fn get_single_string_arg<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<&'a Expr> {
if_chain! {
if let ExprKind::AddrOf(_, ref expr) = expr.node;
if let ExprKind::Match(ref match_expr, ref arms, _) = expr.node;
@ -134,7 +146,7 @@ fn get_single_string_arg(cx: &LateContext<'_, '_>, expr: &Expr) -> Option<Span>
let ty = walk_ptrs_ty(cx.tables.pat_ty(&pat[0]));
if ty.sty == ty::Str || match_type(cx, ty, &paths::STRING) {
if let ExprKind::Tup(ref values) = match_expr.node {
return Some(values[0].span);
return Some(&values[0]);
}
}
}

4
tests/ui/format.rs
View file

@ -52,4 +52,8 @@ fn main() {
format!("{:.10}", "foo"); // could not be "foo"[..10]
format!("{:.prec$}", "foo", prec = 1);
format!("{:.prec$}", "foo", prec = 10);
format!("{}", 42.to_string());
let x = std::path::PathBuf::from("/bar/foo/qux");
format!("{}", x.display().to_string());
}

18
tests/ui/format.stderr
View file

@ -54,5 +54,21 @@ error: useless use of `format!`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: aborting due to 7 previous errors
error: useless use of `format!`
--> $DIR/format.rs:56:5
|
56 | format!("{}", 42.to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `42.to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: useless use of `format!`
--> $DIR/format.rs:58:5
|
58 | format!("{}", x.display().to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: `to_string()` is enough: `x.display().to_string()`
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: aborting due to 9 previous errors