Reword Range*/[Range*]: Iterator E0277 messages

Author: estebank

src/libcore/iter/iterator.rs

@@ -40,13 +40,16 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item=()>) {}
         _Self="[std::ops::RangeFrom<Idx>; 1]",
         label="if you meant to iterate from a value onwards, remove the square brackets",
         note="`[start..]` is an array of one `RangeFrom`; you might have meant to have a \
-              `RangeFrom` without the brackets: `start..`"
+              `RangeFrom` without the brackets: `start..`, keeping in mind that iterating over an \
+              unbounded iterator will run forever unless you `break` or `return` from within the \
+              loop"
     ),
     on(
         _Self="[std::ops::RangeTo<Idx>; 1]",
-        label="if you meant to iterate until a value, remove the square brackets",
-        note="`[..end]` is an array of one `RangeTo`; you might have meant to have a \
-              `RangeTo` without the brackets: `..end`"
+        label="if you meant to iterate until a value, remove the square brackets and add a \
+               starting value",
+        note="`[..end]` is an array of one `RangeTo`; you might have meant to have a bounded \
+              `Range` without the brackets: `0..end`"
     ),
     on(
         _Self="[std::ops::RangeInclusive<Idx>; 1]",
@@ -56,9 +59,22 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item=()>) {}
     ),
     on(
         _Self="[std::ops::RangeToInclusive<Idx>; 1]",
-        label="if you meant to iterate until a value, remove the square brackets",
+        label="if you meant to iterate until a value (including it), remove the square brackets \
+               and add a starting value",
         note="`[..=end]` is an array of one `RangeToInclusive`; you might have meant to have a \
-              `RangeToInclusive` without the brackets: `..=end`"
+              bounded `RangeInclusive` without the brackets: `0..=end`"
+    ),
+    on(
+        _Self="std::ops::RangeTo<Idx>",
+        label="if you meant to iterate until a value, add a starting value",
+        note="`..end` is a `RangeTo`, which cannot be iterated on; you might have meant to have a \
+              bounded `Range`: `0..end`"
+    ),
+    on(
+        _Self="std::ops::RangeToInclusive<Idx>",
+        label="if you meant to iterate until a value (including it), add a starting value",
+        note="`..=end` is a `RangeToInclusive`, which cannot be iterated on; you might have meant \
+              to have a bounded `RangeInclusive`: `0..=end`"
     ),
     on(
         _Self="&str",

src/test/ui/iterators/array-of-ranges.rs

@@ -1,9 +1,14 @@
 fn main() {
     for _ in [0..1] {}
+    for _ in [0..=1] {}
+    for _ in [0..] {}
+    for _ in [..1] {}
+    for _ in [..=1] {}
     let start = 0;
     let end = 0;
     for _ in [start..end] {}
     let array_of_range = [start..end];
     for _ in array_of_range {}
     for _ in [0..1, 2..3] {}
+    for _ in [0..=1] {}
 }

src/test/ui/iterators/array-of-ranges.stderr

@@ -8,9 +8,49 @@ LL |     for _ in [0..1] {}
    = note: `[start..end]` is an array of one `Range`; you might have meant to have a `Range` without the brackets: `start..end`
    = note: required by `std::iter::IntoIterator::into_iter`
 
-error[E0277]: `[std::ops::Range<{integer}>; 1]` is not an iterator
+error[E0277]: `[std::ops::RangeInclusive<{integer}>; 1]` is not an iterator
+  --> $DIR/array-of-ranges.rs:3:14
+   |
+LL |     for _ in [0..=1] {}
+   |              ^^^^^^^ if you meant to iterate between two values, remove the square brackets
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::RangeInclusive<{integer}>; 1]`
+   = note: `[start..=end]` is an array of one `RangeInclusive`; you might have meant to have a `RangeInclusive` without the brackets: `start..=end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `[std::ops::RangeFrom<{integer}>; 1]` is not an iterator
+  --> $DIR/array-of-ranges.rs:4:14
+   |
+LL |     for _ in [0..] {}
+   |              ^^^^^ if you meant to iterate from a value onwards, remove the square brackets
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::RangeFrom<{integer}>; 1]`
+   = note: `[start..]` is an array of one `RangeFrom`; you might have meant to have a `RangeFrom` without the brackets: `start..`, keeping in mind that iterating over an unbounded iterator will run forever unless you `break` or `return` from within the loop
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `[std::ops::RangeTo<{integer}>; 1]` is not an iterator
   --> $DIR/array-of-ranges.rs:5:14
    |
+LL |     for _ in [..1] {}
+   |              ^^^^^ if you meant to iterate until a value, remove the square brackets and add a starting value
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::RangeTo<{integer}>; 1]`
+   = note: `[..end]` is an array of one `RangeTo`; you might have meant to have a bounded `Range` without the brackets: `0..end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `[std::ops::RangeToInclusive<{integer}>; 1]` is not an iterator
+  --> $DIR/array-of-ranges.rs:6:14
+   |
+LL |     for _ in [..=1] {}
+   |              ^^^^^^ if you meant to iterate until a value (including it), remove the square brackets and add a starting value
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::RangeToInclusive<{integer}>; 1]`
+   = note: `[..=end]` is an array of one `RangeToInclusive`; you might have meant to have a bounded `RangeInclusive` without the brackets: `0..=end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `[std::ops::Range<{integer}>; 1]` is not an iterator
+  --> $DIR/array-of-ranges.rs:9:14
+   |
 LL |     for _ in [start..end] {}
    |              ^^^^^^^^^^^^ if you meant to iterate between two values, remove the square brackets
    |
@@ -19,7 +59,7 @@ LL |     for _ in [start..end] {}
    = note: required by `std::iter::IntoIterator::into_iter`
 
 error[E0277]: `[std::ops::Range<{integer}>; 1]` is not an iterator
-  --> $DIR/array-of-ranges.rs:7:14
+  --> $DIR/array-of-ranges.rs:11:14
    |
 LL |     for _ in array_of_range {}
    |              ^^^^^^^^^^^^^^ if you meant to iterate between two values, remove the square brackets
@@ -29,7 +69,7 @@ LL |     for _ in array_of_range {}
    = note: required by `std::iter::IntoIterator::into_iter`
 
 error[E0277]: `[std::ops::Range<{integer}>; 2]` is not an iterator
-  --> $DIR/array-of-ranges.rs:8:14
+  --> $DIR/array-of-ranges.rs:12:14
    |
 LL |     for _ in [0..1, 2..3] {}
    |              ^^^^^^^^^^^^ borrow the array with `&` or call `.iter()` on it to iterate over it
@@ -38,6 +78,16 @@ LL |     for _ in [0..1, 2..3] {}
    = note: arrays are not an iterators, but slices like the following are: `&[1, 2, 3]`
    = note: required by `std::iter::IntoIterator::into_iter`
 
-error: aborting due to 4 previous errors
+error[E0277]: `[std::ops::RangeInclusive<{integer}>; 1]` is not an iterator
+  --> $DIR/array-of-ranges.rs:13:14
+   |
+LL |     for _ in [0..=1] {}
+   |              ^^^^^^^ if you meant to iterate between two values, remove the square brackets
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::RangeInclusive<{integer}>; 1]`
+   = note: `[start..=end]` is an array of one `RangeInclusive`; you might have meant to have a `RangeInclusive` without the brackets: `start..=end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error: aborting due to 9 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/iterators/ranges.rs

@@ -0,0 +1,9 @@
+fn main() {
+    for _ in ..10 {}
+    //~^ ERROR E0277
+    for _ in ..=10 {}
+    //~^ ERROR E0277
+    for _ in 0..10 {}
+    for _ in 0..=10 {}
+    for _ in 0.. {}
+}

src/test/ui/iterators/ranges.stderr

@@ -0,0 +1,23 @@
+error[E0277]: `std::ops::RangeTo<{integer}>` is not an iterator
+  --> $DIR/ranges.rs:2:14
+   |
+LL |     for _ in ..10 {}
+   |              ^^^^ if you meant to iterate until a value, add a starting value
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `std::ops::RangeTo<{integer}>`
+   = note: `..end` is a `RangeTo`, which cannot be iterated on; you might have meant to have a bounded `Range`: `0..end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `std::ops::RangeToInclusive<{integer}>` is not an iterator
+  --> $DIR/ranges.rs:4:14
+   |
+LL |     for _ in ..=10 {}
+   |              ^^^^^ if you meant to iterate until a value (including it), add a starting value
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `std::ops::RangeToInclusive<{integer}>`
+   = note: `..=end` is a `RangeToInclusive`, which cannot be iterated on; you might have meant to have a bounded `RangeInclusive`: `0..=end`
+   = note: required by `std::iter::IntoIterator::into_iter`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.