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Merge pull request #3256 from rust-lang-nursery/fix-2796
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Fix 2796 and 3020
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@oli-obk
oli-obk authored Oct 4, 2018
2 parents c47b948 + 5173ed0 commit c3e3be3
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Showing 3 changed files with 63 additions and 21 deletions.
34 changes: 24 additions & 10 deletions clippy_lints/src/format.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
return;
}
match expr.node {

// `format!("{}", foo)` expansion
ExprKind::Call(ref fun, ref args) => {
if_chain! {
Expand All @@ -58,12 +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,
);
Expand Down Expand Up @@ -114,9 +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;
Expand All @@ -135,7 +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]);
}
}
}
Expand All @@ -162,9 +173,12 @@ fn check_unformatted(expr: &Expr) -> bool {
if let ExprKind::Struct(_, ref fields, _) = exprs[0].node;
if let Some(format_field) = fields.iter().find(|f| f.ident.name == "format");
if let ExprKind::Struct(_, ref fields, _) = format_field.expr.node;
if let Some(align_field) = fields.iter().find(|f| f.ident.name == "width");
if let ExprKind::Path(ref qpath) = align_field.expr.node;
if last_path_segment(qpath).ident.name == "Implied";
if let Some(width_field) = fields.iter().find(|f| f.ident.name == "width");
if let ExprKind::Path(ref width_qpath) = width_field.expr.node;
if last_path_segment(width_qpath).ident.name == "Implied";
if let Some(precision_field) = fields.iter().find(|f| f.ident.name == "precision");
if let ExprKind::Path(ref precision_path) = precision_field.expr.node;
if last_path_segment(precision_path).ident.name == "Implied";
then {
return true;
}
Expand Down
12 changes: 12 additions & 0 deletions tests/ui/format.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ fn main() {
format!("{}", "foo");
format!("{:?}", "foo"); // don't warn about debug
format!("{:8}", "foo");
format!("{:width$}", "foo", width = 8);
format!("{:+}", "foo"); // warn when the format makes no difference
format!("{:<}", "foo"); // warn when the format makes no difference
format!("foo {}", "bar");
Expand All @@ -23,6 +24,7 @@ fn main() {
format!("{}", arg);
format!("{:?}", arg); // don't warn about debug
format!("{:8}", arg);
format!("{:width$}", arg, width = 8);
format!("{:+}", arg); // warn when the format makes no difference
format!("{:<}", arg); // warn when the format makes no difference
format!("foo {}", arg);
Expand All @@ -44,4 +46,14 @@ fn main() {

// A format! inside a macro should not trigger a warning
foo!("should not warn");

// precision on string means slicing without panicking on size:
format!("{:.1}", "foo"); // could be "foo"[..1]
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());
}
38 changes: 27 additions & 11 deletions tests/ui/format.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,44 +15,60 @@ 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: useless use of `format!`
--> $DIR/format.rs:17:5
--> $DIR/format.rs:18:5
|
17 | format!("{:+}", "foo"); // warn when the format makes no difference
18 | format!("{:+}", "foo"); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".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:18:5
--> $DIR/format.rs:19:5
|
18 | format!("{:<}", "foo"); // warn when the format makes no difference
19 | format!("{:<}", "foo"); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `"foo".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:23:5
--> $DIR/format.rs:24:5
|
23 | format!("{}", arg);
24 | format!("{}", arg);
| ^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.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:26:5
--> $DIR/format.rs:28:5
|
26 | format!("{:+}", arg); // warn when the format makes no difference
28 | format!("{:+}", arg); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.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:27:5
--> $DIR/format.rs:29:5
|
27 | format!("{:<}", arg); // warn when the format makes no difference
29 | format!("{:<}", arg); // warn when the format makes no difference
| ^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): `arg.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 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

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