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Don't emit clippy::useless_conversion on type aliases #10778

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Merged
merged 2 commits into from
May 14, 2023
Merged

Don't emit clippy::useless_conversion on type aliases #10778

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1190c02
fix #10773
Centri3 May 14, 2023
a36d9a7
move `is_ty_alias` to `clippy_utils`
Centri3 May 14, 2023
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13 changes: 12 additions & 1 deletion clippy_lints/src/useless_conversion.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,8 @@ use clippy_utils::ty::{is_copy, is_type_diagnostic_item, same_type_and_consts};
use clippy_utils::{get_parent_expr, is_trait_method, match_def_path, path_to_local, paths};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{BindingAnnotation, Expr, ExprKind, HirId, MatchSource, Node, PatKind};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{BindingAnnotation, Expr, ExprKind, HirId, MatchSource, Node, PatKind, QPath, TyKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};
Expand Down Expand Up @@ -138,6 +139,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
if_chain! {
if let ExprKind::Path(ref qpath) = path.kind;
if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id();
if !is_ty_alias(qpath);
then {
let a = cx.typeck_results().expr_ty(e);
let b = cx.typeck_results().expr_ty(arg);
Expand Down Expand Up @@ -195,3 +197,12 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
}
}
}

/// `cx.qpath_res` seems to return `AssocFn` so we do this instead
fn is_ty_alias(qpath: &QPath<'_>) -> bool {
match *qpath {
QPath::Resolved(_, path) => matches!(path.res, Res::Def(DefKind::TyAlias, ..)),
QPath::TypeRelative(ty, _) if let TyKind::Path(qpath) = ty.kind => is_ty_alias(&qpath),
_ => false,
}
}
6 changes: 6 additions & 0 deletions tests/ui/useless_conversion.fixed
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Expand Up @@ -33,6 +33,11 @@ fn test_issue_3913() -> Result<(), std::io::Error> {
Ok(())
}

fn dont_lint_on_type_alias() {
type A = i32;
_ = A::from(0i32);
}

fn dont_lint_into_iter_on_immutable_local_implementing_iterator_in_expr() {
let text = "foo\r\nbar\n\nbaz\n";
let lines = text.lines();
Expand Down Expand Up @@ -106,6 +111,7 @@ fn main() {
test_questionmark().unwrap();
test_issue_3913().unwrap();

dont_lint_on_type_alias();
dont_lint_into_iter_on_immutable_local_implementing_iterator_in_expr();
lint_into_iter_on_mutable_local_implementing_iterator_in_expr();
lint_into_iter_on_expr_implementing_iterator();
Expand Down
6 changes: 6 additions & 0 deletions tests/ui/useless_conversion.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,11 @@ fn test_issue_3913() -> Result<(), std::io::Error> {
Ok(())
}

fn dont_lint_on_type_alias() {
type A = i32;
_ = A::from(0i32);
}

fn dont_lint_into_iter_on_immutable_local_implementing_iterator_in_expr() {
let text = "foo\r\nbar\n\nbaz\n";
let lines = text.lines();
Expand Down Expand Up @@ -106,6 +111,7 @@ fn main() {
test_questionmark().unwrap();
test_issue_3913().unwrap();

dont_lint_on_type_alias();
dont_lint_into_iter_on_immutable_local_implementing_iterator_in_expr();
lint_into_iter_on_mutable_local_implementing_iterator_in_expr();
lint_into_iter_on_expr_implementing_iterator();
Expand Down
32 changes: 16 additions & 16 deletions tests/ui/useless_conversion.stderr
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Expand Up @@ -23,97 +23,97 @@ LL | let _: i32 = 0i32.into();
| ^^^^^^^^^^^ help: consider removing `.into()`: `0i32`

error: useless conversion to the same type: `std::str::Lines<'_>`
--> $DIR/useless_conversion.rs:45:22
--> $DIR/useless_conversion.rs:50:22
|
LL | if Some("ok") == lines.into_iter().next() {}
| ^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `lines`

error: useless conversion to the same type: `std::str::Lines<'_>`
--> $DIR/useless_conversion.rs:50:21
--> $DIR/useless_conversion.rs:55:21
|
LL | let mut lines = text.lines().into_iter();
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `text.lines()`

error: useless conversion to the same type: `std::str::Lines<'_>`
--> $DIR/useless_conversion.rs:56:22
--> $DIR/useless_conversion.rs:61:22
|
LL | if Some("ok") == text.lines().into_iter().next() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `text.lines()`

error: useless conversion to the same type: `std::ops::Range<i32>`
--> $DIR/useless_conversion.rs:62:13
--> $DIR/useless_conversion.rs:67:13
|
LL | let _ = NUMBERS.into_iter().next();
| ^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `NUMBERS`

error: useless conversion to the same type: `std::ops::Range<i32>`
--> $DIR/useless_conversion.rs:67:17
--> $DIR/useless_conversion.rs:72:17
|
LL | let mut n = NUMBERS.into_iter();
| ^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `NUMBERS`

error: useless conversion to the same type: `std::string::String`
--> $DIR/useless_conversion.rs:128:21
--> $DIR/useless_conversion.rs:134:21
|
LL | let _: String = "foo".to_string().into();
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `"foo".to_string()`

error: useless conversion to the same type: `std::string::String`
--> $DIR/useless_conversion.rs:129:21
--> $DIR/useless_conversion.rs:135:21
|
LL | let _: String = From::from("foo".to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `From::from()`: `"foo".to_string()`

error: useless conversion to the same type: `std::string::String`
--> $DIR/useless_conversion.rs:130:13
--> $DIR/useless_conversion.rs:136:13
|
LL | let _ = String::from("foo".to_string());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `"foo".to_string()`

error: useless conversion to the same type: `std::string::String`
--> $DIR/useless_conversion.rs:131:13
--> $DIR/useless_conversion.rs:137:13
|
LL | let _ = String::from(format!("A: {:04}", 123));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `format!("A: {:04}", 123)`

error: useless conversion to the same type: `std::str::Lines<'_>`
--> $DIR/useless_conversion.rs:132:13
--> $DIR/useless_conversion.rs:138:13
|
LL | let _ = "".lines().into_iter();
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `"".lines()`

error: useless conversion to the same type: `std::vec::IntoIter<i32>`
--> $DIR/useless_conversion.rs:133:13
--> $DIR/useless_conversion.rs:139:13
|
LL | let _ = vec![1, 2, 3].into_iter().into_iter();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![1, 2, 3].into_iter()`

error: useless conversion to the same type: `std::string::String`
--> $DIR/useless_conversion.rs:134:21
--> $DIR/useless_conversion.rs:140:21
|
LL | let _: String = format!("Hello {}", "world").into();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `format!("Hello {}", "world")`

error: useless conversion to the same type: `i32`
--> $DIR/useless_conversion.rs:139:13
--> $DIR/useless_conversion.rs:145:13
|
LL | let _ = i32::from(a + b) * 3;
| ^^^^^^^^^^^^^^^^ help: consider removing `i32::from()`: `(a + b)`

error: useless conversion to the same type: `Foo<'a'>`
--> $DIR/useless_conversion.rs:145:23
--> $DIR/useless_conversion.rs:151:23
|
LL | let _: Foo<'a'> = s2.into();
| ^^^^^^^^^ help: consider removing `.into()`: `s2`

error: useless conversion to the same type: `Foo<'a'>`
--> $DIR/useless_conversion.rs:147:13
--> $DIR/useless_conversion.rs:153:13
|
LL | let _ = Foo::<'a'>::from(s3);
| ^^^^^^^^^^^^^^^^^^^^ help: consider removing `Foo::<'a'>::from()`: `s3`

error: useless conversion to the same type: `std::vec::IntoIter<Foo<'a'>>`
--> $DIR/useless_conversion.rs:149:13
--> $DIR/useless_conversion.rs:155:13
|
LL | let _ = vec![s4, s4, s4].into_iter().into_iter();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![s4, s4, s4].into_iter()`
Expand Down