add another test

Author: y21

tests/ui/useless_conversion.fixed

@@ -205,6 +205,16 @@ mod issue11300 {
     {
     }
 
+    trait Helper2<T> {}
+    impl Helper2<std::array::IntoIter<i32, 3>> for i32 {}
+    impl Helper2<[i32; 3]> for i32 {}
+    fn foo3<I>(_: I)
+    where
+        I: IntoIterator<Item = i32>,
+        i32: Helper2<I>,
+    {
+    }
+
     pub fn bar() {
         // This should not trigger the lint:
         // `[i32, 3]` does not satisfy the `ExactSizeIterator` bound, so the into_iter call cannot be
@@ -217,6 +227,10 @@ mod issue11300 {
         // This again should *not* lint, since X = () and I = std::array::IntoIter<i32, 3>,
         // and `[i32; 3]: Helper<()>` is not true (only `std::array::IntoIter<i32, 3>: Helper<()>` is).
         foo2::<(), _>([1, 2, 3].into_iter());
+
+        // This should lint. `I` gets substituted with `[i32; 3]`, and
+        // `i32: Helper<[i32, 3]>` is true.
+        foo3([1, 2, 3]);
     }
 }
 

tests/ui/useless_conversion.rs

@@ -205,6 +205,16 @@ mod issue11300 {
     {
     }
 
+    trait Helper2<T> {}
+    impl Helper2<std::array::IntoIter<i32, 3>> for i32 {}
+    impl Helper2<[i32; 3]> for i32 {}
+    fn foo3<I>(_: I)
+    where
+        I: IntoIterator<Item = i32>,
+        i32: Helper2<I>,
+    {
+    }
+
     pub fn bar() {
         // This should not trigger the lint:
         // `[i32, 3]` does not satisfy the `ExactSizeIterator` bound, so the into_iter call cannot be
@@ -217,6 +227,10 @@ mod issue11300 {
         // This again should *not* lint, since X = () and I = std::array::IntoIter<i32, 3>,
         // and `[i32; 3]: Helper<()>` is not true (only `std::array::IntoIter<i32, 3>: Helper<()>` is).
         foo2::<(), _>([1, 2, 3].into_iter());
+
+        // This should lint. `I` gets substituted with `[i32; 3]`, and
+        // `i32: Helper<[i32, 3]>` is true.
+        foo3([1, 2, 3].into_iter());
     }
 }
 

tests/ui/useless_conversion.stderr

@@ -179,7 +179,7 @@ LL |     fn b<T: IntoIterator<Item = i32>>(_: T) {}
    |             ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
-  --> $DIR/useless_conversion.rs:215:24
+  --> $DIR/useless_conversion.rs:225:24
    |
 LL |         foo2::<i32, _>([1, 2, 3].into_iter());
    |                        ^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `[1, 2, 3]`
@@ -190,5 +190,17 @@ note: this parameter accepts any `IntoIterator`, so you don't need to call `.int
 LL |         I: IntoIterator<Item = i32> + Helper<X>,
    |            ^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 25 previous errors
+error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
+  --> $DIR/useless_conversion.rs:233:14
+   |
+LL |         foo3([1, 2, 3].into_iter());
+   |              ^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `[1, 2, 3]`
+   |
+note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
+  --> $DIR/useless_conversion.rs:213:12
+   |
+LL |         I: IntoIterator<Item = i32>,
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 26 previous errors