Auto merge of #11301 - y21:issue11300, r=dswij
[`useless_conversion`]: don't lint if type parameter has unsatisfiable bounds for `.into_iter()` receiver Fixes #11300. Before this PR, clippy assumed that if it sees a `f(x.into_iter())` call and the type at that argument position is generic over any `IntoIterator`, then the `.into_iter()` call must be useless because `x` already implements `IntoIterator`, *however* this assumption is not right if the generic parameter has more than just the `IntoIterator` bound (because other traits can be implemented for the IntoIterator target type but not the IntoIterator implementor, as can be seen in the linked issue: `<[i32; 3] as IntoIterator>::IntoIter` satisfies `ExactSizeIterator`, but `[i32; 3]` does not). So, this PR makes it check that the type parameter only has a single `IntoIterator` bound. It *might* be possible to check if the type of `x` in `f(x.into_iter())` satisfies all the bounds on the generic type parameter as defined on the function (which would allow removing the `.into_iter()` call even with multiple bounds), however I'm not sure how to do that, and the current fix should always work. **Edit:** This PR has been changed to check if any of the bounds don't hold for the type of the `.into_iter()` receiver, so we can still lint in some cases. changelog: [`useless_conversion`]: don't lint `.into_iter()` if type parameter has multiple bounds
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commit
59636a2aa3
4 changed files with 331 additions and 31 deletions
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@ -151,6 +151,8 @@ fn main() {
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let _ = s3;
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let s4: Foo<'a'> = Foo;
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let _ = vec![s4, s4, s4].into_iter();
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issue11300::bar();
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}
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#[allow(dead_code)]
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@ -196,6 +198,95 @@ fn explicit_into_iter_fn_arg() {
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b(macro_generated!());
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}
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mod issue11300 {
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pub fn foo<I>(i: I)
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where
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I: IntoIterator<Item = i32> + ExactSizeIterator,
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{
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assert_eq!(i.len(), 3);
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}
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trait Helper<T: ?Sized> {}
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impl Helper<i32> for [i32; 3] {}
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impl Helper<i32> for std::array::IntoIter<i32, 3> {}
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impl Helper<()> for std::array::IntoIter<i32, 3> {}
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fn foo2<X: ?Sized, I>(_: I)
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where
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I: IntoIterator<Item = i32> + Helper<X>,
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{
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}
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trait Helper2<T> {}
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impl Helper2<std::array::IntoIter<i32, 3>> for i32 {}
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impl Helper2<[i32; 3]> for i32 {}
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fn foo3<I>(_: I)
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where
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I: IntoIterator<Item = i32>,
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i32: Helper2<I>,
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{
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}
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pub fn bar() {
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// This should not trigger the lint:
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// `[i32, 3]` does not satisfy the `ExactSizeIterator` bound, so the into_iter call cannot be
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// removed and is not useless.
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foo([1, 2, 3].into_iter());
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// This should trigger the lint, receiver type [i32; 3] also implements `Helper`
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foo2::<i32, _>([1, 2, 3]);
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// This again should *not* lint, since X = () and I = std::array::IntoIter<i32, 3>,
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// and `[i32; 3]: Helper<()>` is not true (only `std::array::IntoIter<i32, 3>: Helper<()>` is).
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foo2::<(), _>([1, 2, 3].into_iter());
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// This should lint. Removing the `.into_iter()` means that `I` gets substituted with `[i32; 3]`,
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// and `i32: Helper2<[i32, 3]>` is true, so this call is indeed unncessary.
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foo3([1, 2, 3]);
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}
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fn ice() {
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struct S1;
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impl S1 {
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pub fn foo<I: IntoIterator>(&self, _: I) {}
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}
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S1.foo([1, 2]);
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// ICE that occured in itertools
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trait Itertools {
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fn interleave_shortest<J>(self, other: J)
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where
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J: IntoIterator,
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Self: Sized;
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}
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impl<I: Iterator> Itertools for I {
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fn interleave_shortest<J>(self, other: J)
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where
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J: IntoIterator,
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Self: Sized,
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{
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}
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}
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let v0: Vec<i32> = vec![0, 2, 4];
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let v1: Vec<i32> = vec![1, 3, 5, 7];
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v0.into_iter().interleave_shortest(v1);
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trait TraitWithLifetime<'a> {}
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impl<'a> TraitWithLifetime<'a> for std::array::IntoIter<&'a i32, 2> {}
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struct Helper;
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impl<'a> Helper {
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fn with_lt<I>(&self, _: I)
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where
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I: IntoIterator + TraitWithLifetime<'a>,
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{
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}
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}
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Helper.with_lt([&1, &2].into_iter());
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}
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}
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#[derive(Copy, Clone)]
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struct Foo<const C: char>;
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@ -151,6 +151,8 @@ fn main() {
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let _ = Foo::<'a'>::from(s3);
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let s4: Foo<'a'> = Foo;
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let _ = vec![s4, s4, s4].into_iter().into_iter();
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issue11300::bar();
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}
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#[allow(dead_code)]
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@ -196,6 +198,95 @@ fn explicit_into_iter_fn_arg() {
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b(macro_generated!());
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}
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mod issue11300 {
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pub fn foo<I>(i: I)
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where
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I: IntoIterator<Item = i32> + ExactSizeIterator,
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{
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assert_eq!(i.len(), 3);
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}
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trait Helper<T: ?Sized> {}
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impl Helper<i32> for [i32; 3] {}
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impl Helper<i32> for std::array::IntoIter<i32, 3> {}
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impl Helper<()> for std::array::IntoIter<i32, 3> {}
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fn foo2<X: ?Sized, I>(_: I)
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where
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I: IntoIterator<Item = i32> + Helper<X>,
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{
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}
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trait Helper2<T> {}
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impl Helper2<std::array::IntoIter<i32, 3>> for i32 {}
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impl Helper2<[i32; 3]> for i32 {}
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fn foo3<I>(_: I)
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where
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I: IntoIterator<Item = i32>,
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i32: Helper2<I>,
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{
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}
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pub fn bar() {
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// This should not trigger the lint:
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// `[i32, 3]` does not satisfy the `ExactSizeIterator` bound, so the into_iter call cannot be
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// removed and is not useless.
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foo([1, 2, 3].into_iter());
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// This should trigger the lint, receiver type [i32; 3] also implements `Helper`
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foo2::<i32, _>([1, 2, 3].into_iter());
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// This again should *not* lint, since X = () and I = std::array::IntoIter<i32, 3>,
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// and `[i32; 3]: Helper<()>` is not true (only `std::array::IntoIter<i32, 3>: Helper<()>` is).
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foo2::<(), _>([1, 2, 3].into_iter());
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// This should lint. Removing the `.into_iter()` means that `I` gets substituted with `[i32; 3]`,
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// and `i32: Helper2<[i32, 3]>` is true, so this call is indeed unncessary.
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foo3([1, 2, 3].into_iter());
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}
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fn ice() {
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struct S1;
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impl S1 {
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pub fn foo<I: IntoIterator>(&self, _: I) {}
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}
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S1.foo([1, 2].into_iter());
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// ICE that occured in itertools
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trait Itertools {
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fn interleave_shortest<J>(self, other: J)
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where
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J: IntoIterator,
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Self: Sized;
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}
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impl<I: Iterator> Itertools for I {
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fn interleave_shortest<J>(self, other: J)
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where
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J: IntoIterator,
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Self: Sized,
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{
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}
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}
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let v0: Vec<i32> = vec![0, 2, 4];
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let v1: Vec<i32> = vec![1, 3, 5, 7];
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v0.into_iter().interleave_shortest(v1.into_iter());
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trait TraitWithLifetime<'a> {}
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impl<'a> TraitWithLifetime<'a> for std::array::IntoIter<&'a i32, 2> {}
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struct Helper;
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impl<'a> Helper {
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fn with_lt<I>(&self, _: I)
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where
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I: IntoIterator + TraitWithLifetime<'a>,
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{
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}
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}
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Helper.with_lt([&1, &2].into_iter());
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}
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}
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#[derive(Copy, Clone)]
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struct Foo<const C: char>;
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@ -119,64 +119,112 @@ LL | let _ = vec![s4, s4, s4].into_iter().into_iter();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![s4, s4, s4].into_iter()`
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:183:7
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--> $DIR/useless_conversion.rs:185:7
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LL | b(vec![1, 2].into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `vec![1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:173:13
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--> $DIR/useless_conversion.rs:175:13
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LL | fn b<T: IntoIterator<Item = i32>>(_: T) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:184:7
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--> $DIR/useless_conversion.rs:186:7
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LL | c(vec![1, 2].into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `vec![1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:174:18
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--> $DIR/useless_conversion.rs:176:18
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LL | fn c(_: impl IntoIterator<Item = i32>) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:185:7
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--> $DIR/useless_conversion.rs:187:7
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LL | d(vec![1, 2].into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `vec![1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:177:12
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--> $DIR/useless_conversion.rs:179:12
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LL | T: IntoIterator<Item = i32>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:188:7
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--> $DIR/useless_conversion.rs:190:7
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LL | b(vec![1, 2].into_iter().into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`s: `vec![1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:173:13
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--> $DIR/useless_conversion.rs:175:13
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LL | fn b<T: IntoIterator<Item = i32>>(_: T) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:189:7
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--> $DIR/useless_conversion.rs:191:7
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LL | b(vec![1, 2].into_iter().into_iter().into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`s: `vec![1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:173:13
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--> $DIR/useless_conversion.rs:175:13
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LL | fn b<T: IntoIterator<Item = i32>>(_: T) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 24 previous errors
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:237:24
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LL | foo2::<i32, _>([1, 2, 3].into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `[1, 2, 3]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:216:12
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LL | I: IntoIterator<Item = i32> + Helper<X>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:245:14
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LL | foo3([1, 2, 3].into_iter());
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| ^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `[1, 2, 3]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:225:12
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LL | I: IntoIterator<Item = i32>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:254:16
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LL | S1.foo([1, 2].into_iter());
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| ^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `[1, 2]`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:251:27
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LL | pub fn foo<I: IntoIterator>(&self, _: I) {}
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| ^^^^^^^^^^^^
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error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
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--> $DIR/useless_conversion.rs:273:44
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LL | v0.into_iter().interleave_shortest(v1.into_iter());
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| ^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `v1`
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note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
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--> $DIR/useless_conversion.rs:260:20
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LL | J: IntoIterator,
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| ^^^^^^^^^^^^
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error: aborting due to 28 previous errors
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