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Make useless_format recognize format!("")

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Closes #7796
This commit is contained in:
Nixon Enraght-Moony 2021-10-11 01:03:11 +01:00
parent 91496c2ac6
commit 081d0f82f4
4 changed files with 46 additions and 20 deletions
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34
clippy_lints/src/format.rs
View File

@ -49,15 +49,19 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
let mut applicability = Applicability::MachineApplicable;
if format_args.value_args.is_empty() {
if_chain! {
if let [e] = &*format_args.format_string_parts;
if let ExprKind::Lit(lit) = &e.kind;
if let Some(s_src) = snippet_opt(cx, lit.span);
then {
// Simulate macro expansion, converting {{ and }} to { and }.
let s_expand = s_src.replace("{{", "{").replace("}}", "}");
let sugg = format!("{}.to_string()", s_expand);
span_useless_format(cx, call_site, sugg, applicability);
if format_args.format_string_parts.is_empty() {
span_useless_format_empty(cx, call_site, "String::new()".to_owned(), applicability);
} else {
if_chain! {
if let [e] = &*format_args.format_string_parts;
if let ExprKind::Lit(lit) = &e.kind;
if let Some(s_src) = snippet_opt(cx, lit.span);
then {
// Simulate macro expansion, converting {{ and }} to { and }.
let s_expand = s_src.replace("{{", "{").replace("}}", "}");
let sugg = format!("{}.to_string()", s_expand);
span_useless_format(cx, call_site, sugg, applicability);
}
}
}
} else if let [value] = *format_args.value_args {
@ -89,6 +93,18 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
}
}
fn span_useless_format_empty(cx: &LateContext<'_>, span: Span, sugg: String, applicability: Applicability) {
span_lint_and_sugg(
cx,
USELESS_FORMAT,
span,
"useless use of `format!`",
"consider using `String::new()`",
sugg,
applicability,
);
}
fn span_useless_format(cx: &LateContext<'_>, span: Span, sugg: String, applicability: Applicability) {
span_lint_and_sugg(
cx,

2
tests/ui/format.fixed
View File

@ -16,6 +16,8 @@ fn main() {
r##"foo {}
" bar"##.to_string();
let _ = String::new();
"foo".to_string();
format!("{:?}", "foo"); // Don't warn about `Debug`.
format!("{:8}", "foo");

2
tests/ui/format.rs
View File

@ -18,6 +18,8 @@ fn main() {
" bar"##
);
let _ = format!("");
format!("{}", "foo");
format!("{:?}", "foo"); // Don't warn about `Debug`.
format!("{:8}", "foo");

28
tests/ui/format.stderr
View File

@ -34,64 +34,70 @@ LL ~ " bar"##.to_string();
|
error: useless use of `format!`
--> $DIR/format.rs:21:5
--> $DIR/format.rs:21:13
|
LL | let _ = format!("");
| ^^^^^^^^^^^ help: consider using `String::new()`: `String::new()`
error: useless use of `format!`
--> $DIR/format.rs:23:5
|
LL | format!("{}", "foo");
| ^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `"foo".to_string()`
error: useless use of `format!`
--> $DIR/format.rs:25:5
--> $DIR/format.rs:27:5
|
LL | format!("{:+}", "foo"); // Warn when the format makes no difference.
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `"foo".to_string()`
error: useless use of `format!`
--> $DIR/format.rs:26:5
--> $DIR/format.rs:28:5
|
LL | format!("{:<}", "foo"); // Warn when the format makes no difference.
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `"foo".to_string()`
error: useless use of `format!`
--> $DIR/format.rs:31:5
--> $DIR/format.rs:33:5
|
LL | format!("{}", arg);
| ^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `arg.to_string()`
error: useless use of `format!`
--> $DIR/format.rs:35:5
--> $DIR/format.rs:37:5
|
LL | format!("{:+}", arg); // Warn when the format makes no difference.
| ^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `arg.to_string()`
error: useless use of `format!`
--> $DIR/format.rs:36:5
--> $DIR/format.rs:38:5
|
LL | format!("{:<}", arg); // Warn when the format makes no difference.
| ^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `arg.to_string()`
error: useless use of `format!`
--> $DIR/format.rs:63:5
--> $DIR/format.rs:65:5
|
LL | format!("{}", 42.to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `42.to_string()`
error: useless use of `format!`
--> $DIR/format.rs:65:5
--> $DIR/format.rs:67:5
|
LL | format!("{}", x.display().to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `x.display().to_string()`
error: useless use of `format!`
--> $DIR/format.rs:69:18
--> $DIR/format.rs:71:18
|
LL | let _ = Some(format!("{}", a + "bar"));
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `a + "bar"`
error: useless use of `format!`
--> $DIR/format.rs:73:22
--> $DIR/format.rs:75:22
|
LL | let _s: String = format!("{}", &*v.join("/n"));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `(&*v.join("/n")).to_string()`
error: aborting due to 14 previous errors
error: aborting due to 15 previous errors