Auto merge of #10934 - Centri3:single_range_in_vec_init, r=giraffate

new lint [`single_range_in_vec_init`]

Lints on `vec![0..200]` (or `[0..200]`), suggesting either `(0..200).collect::<Vec<i32>>()` or `[0; 200]`.

Haven't tested it with anything that isn't primitive. Probably should!

Closes #10932

changelog: new lint [`single_range_in_vec_init`]

12 files changed, 393 insertions, 33 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35b1075ff01..218bca40cb0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5164,6 +5164,7 @@ Released 2018-09-13
 [`single_element_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_element_loop
 [`single_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match
 [`single_match_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_match_else
+[`single_range_in_vec_init`]: https://rust-lang.github.io/rust-clippy/master/index.html#single_range_in_vec_init
 [`size_of_in_element_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_in_element_count
 [`size_of_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_ref
 [`skip_while_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#skip_while_next
diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index 62317dc60eb..9509e6d016a 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/clippy_lints/src/declared_lints.rs
@@ -570,6 +570,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::significant_drop_tightening::SIGNIFICANT_DROP_TIGHTENING_INFO,
     crate::single_char_lifetime_names::SINGLE_CHAR_LIFETIME_NAMES_INFO,
     crate::single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS_INFO,
+    crate::single_range_in_vec_init::SINGLE_RANGE_IN_VEC_INIT_INFO,
     crate::size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT_INFO,
     crate::size_of_ref::SIZE_OF_REF_INFO,
     crate::slow_vector_initialization::SLOW_VECTOR_INITIALIZATION_INFO,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 243d1fd8606..cf6499b9616 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -288,6 +288,7 @@ mod shadow;
 mod significant_drop_tightening;
 mod single_char_lifetime_names;
 mod single_component_path_imports;
+mod single_range_in_vec_init;
 mod size_of_in_element_count;
 mod size_of_ref;
 mod slow_vector_initialization;
@@ -1045,6 +1046,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     });
     let stack_size_threshold = conf.stack_size_threshold;
     store.register_late_pass(move |_| Box::new(large_stack_frames::LargeStackFrames::new(stack_size_threshold)));
+    store.register_late_pass(|_| Box::new(single_range_in_vec_init::SingleRangeInVecInit));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 
diff --git a/clippy_lints/src/single_range_in_vec_init.rs b/clippy_lints/src/single_range_in_vec_init.rs
new file mode 100644
index 00000000000..dfe8be7a6a6
--- /dev/null
+++ b/clippy_lints/src/single_range_in_vec_init.rs
@@ -0,0 +1,147 @@
+use clippy_utils::{
+    diagnostics::span_lint_and_then, get_trait_def_id, higher::VecArgs, macros::root_macro_call_first_node,
+    source::snippet_opt, ty::implements_trait,
+};
+use rustc_ast::{LitIntType, LitKind, UintTy};
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, LangItem, QPath};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use std::fmt::{self, Display, Formatter};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for `Vec` or array initializations that contain only one range.
+    ///
+    /// ### Why is this bad?
+    /// This is almost always incorrect, as it will result in a `Vec` that has only one element.
+    /// Almost always, the programmer intended for it to include all elements in the range or for
+    /// the end of the range to be the length instead.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let x = [0..200];
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// // If it was intended to include every element in the range...
+    /// let x = (0..200).collect::<Vec<i32>>();
+    /// // ...Or if 200 was meant to be the len
+    /// let x = [0; 200];
+    /// ```
+    #[clippy::version = "1.72.0"]
+    pub SINGLE_RANGE_IN_VEC_INIT,
+    suspicious,
+    "checks for initialization of `Vec` or arrays which consist of a single range"
+}
+declare_lint_pass!(SingleRangeInVecInit => [SINGLE_RANGE_IN_VEC_INIT]);
+
+enum SuggestedType {
+    Vec,
+    Array,
+}
+
+impl SuggestedType {
+    fn starts_with(&self) -> &'static str {
+        if matches!(self, SuggestedType::Vec) {
+            "vec!"
+        } else {
+            "["
+        }
+    }
+
+    fn ends_with(&self) -> &'static str {
+        if matches!(self, SuggestedType::Vec) { "" } else { "]" }
+    }
+}
+
+impl Display for SuggestedType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        if matches!(&self, SuggestedType::Vec) {
+            write!(f, "a `Vec`")
+        } else {
+            write!(f, "an array")
+        }
+    }
+}
+
+impl LateLintPass<'_> for SingleRangeInVecInit {
+    fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
+        // inner_expr: `vec![0..200]` or `[0..200]`
+        //                   ^^^^^^       ^^^^^^^
+        // span: `vec![0..200]` or `[0..200]`
+        //        ^^^^^^^^^^^^      ^^^^^^^^
+        // suggested_type: What to print, "an array" or "a `Vec`"
+        let (inner_expr, span, suggested_type) = if let ExprKind::Array([inner_expr]) = expr.kind
+            && !expr.span.from_expansion()
+        {
+            (inner_expr, expr.span, SuggestedType::Array)
+        } else if let Some(macro_call) = root_macro_call_first_node(cx, expr)
+            && let Some(VecArgs::Vec([expr])) = VecArgs::hir(cx, expr)
+        {
+            (expr, macro_call.span, SuggestedType::Vec)
+        } else {
+            return;
+        };
+
+        let ExprKind::Struct(QPath::LangItem(lang_item, ..), [start, end], None) = inner_expr.kind else {
+            return;
+        };
+
+        if matches!(lang_item, LangItem::Range)
+            && let ty = cx.typeck_results().expr_ty(start.expr)
+            && let Some(snippet) = snippet_opt(cx, span)
+            // `is_from_proc_macro` will skip any `vec![]`. Let's not!
+            && snippet.starts_with(suggested_type.starts_with())
+            && snippet.ends_with(suggested_type.ends_with())
+            && let Some(start_snippet) = snippet_opt(cx, start.span)
+            && let Some(end_snippet) = snippet_opt(cx, end.span)
+        {
+            let should_emit_every_value = if let Some(step_def_id) = get_trait_def_id(cx, &["core", "iter", "Step"])
+                && implements_trait(cx, ty, step_def_id, &[])
+            {
+                true
+            } else {
+                false
+            };
+            let should_emit_of_len = if let Some(copy_def_id) = cx.tcx.lang_items().copy_trait()
+                && implements_trait(cx, ty, copy_def_id, &[])
+                && let ExprKind::Lit(lit_kind) = end.expr.kind
+                && let LitKind::Int(.., suffix_type) = lit_kind.node
+                && let LitIntType::Unsigned(UintTy::Usize) | LitIntType::Unsuffixed = suffix_type
+            {
+                true
+            } else {
+                false
+            };
+
+            if should_emit_every_value || should_emit_of_len {
+                span_lint_and_then(
+                    cx,
+                    SINGLE_RANGE_IN_VEC_INIT,
+                    span,
+                    &format!("{suggested_type} of `Range` that is only one element"),
+                    |diag| {
+                        if should_emit_every_value {
+                            diag.span_suggestion(
+                                span,
+                                "if you wanted a `Vec` that contains the entire range, try",
+                                format!("({start_snippet}..{end_snippet}).collect::<std::vec::Vec<{ty}>>()"),
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+
+                        if should_emit_of_len {
+                            diag.span_suggestion(
+                                inner_expr.span,
+                                format!("if you wanted {suggested_type} of len {end_snippet}, try"),
+                                format!("{start_snippet}; {end_snippet}"),
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+                    },
+                );
+            }
+        }
+    }
+}
diff --git a/tests/ui/single_element_loop.fixed b/tests/ui/single_element_loop.fixed
index 1697a0cf29b..598f259415d 100644
--- a/tests/ui/single_element_loop.fixed
+++ b/tests/ui/single_element_loop.fixed
@@ -1,6 +1,8 @@
 //@run-rustfix
 // Tests from for_loop.rs that don't have suggestions
 
+#![allow(clippy::single_range_in_vec_init)]
+
 #[warn(clippy::single_element_loop)]
 fn main() {
     let item1 = 2;
diff --git a/tests/ui/single_element_loop.rs b/tests/ui/single_element_loop.rs
index 860424f42dd..3fc461735a4 100644
--- a/tests/ui/single_element_loop.rs
+++ b/tests/ui/single_element_loop.rs
@@ -1,6 +1,8 @@
 //@run-rustfix
 // Tests from for_loop.rs that don't have suggestions
 
+#![allow(clippy::single_range_in_vec_init)]
+
 #[warn(clippy::single_element_loop)]
 fn main() {
     let item1 = 2;
diff --git a/tests/ui/single_element_loop.stderr b/tests/ui/single_element_loop.stderr
index 14437a59745..c40c6198945 100644
--- a/tests/ui/single_element_loop.stderr
+++ b/tests/ui/single_element_loop.stderr
@@ -1,5 +1,5 @@
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:7:5
+  --> $DIR/single_element_loop.rs:9:5
    |
 LL | /     for item in &[item1] {
 LL | |         dbg!(item);
@@ -16,7 +16,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:11:5
+  --> $DIR/single_element_loop.rs:13:5
    |
 LL | /     for item in [item1].iter() {
 LL | |         dbg!(item);
@@ -32,7 +32,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:15:5
+  --> $DIR/single_element_loop.rs:17:5
    |
 LL | /     for item in &[0..5] {
 LL | |         dbg!(item);
@@ -48,7 +48,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:19:5
+  --> $DIR/single_element_loop.rs:21:5
    |
 LL | /     for item in [0..5].iter_mut() {
 LL | |         dbg!(item);
@@ -64,7 +64,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:23:5
+  --> $DIR/single_element_loop.rs:25:5
    |
 LL | /     for item in [0..5] {
 LL | |         dbg!(item);
@@ -80,7 +80,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:27:5
+  --> $DIR/single_element_loop.rs:29:5
    |
 LL | /     for item in [0..5].into_iter() {
 LL | |         dbg!(item);
@@ -96,7 +96,7 @@ LL +     }
    |
 
 error: for loop over a single element
-  --> $DIR/single_element_loop.rs:46:5
+  --> $DIR/single_element_loop.rs:48:5
    |
 LL | /     for _ in [42] {
 LL | |         let _f = |n: u32| {
diff --git a/tests/ui/single_range_in_vec_init.rs b/tests/ui/single_range_in_vec_init.rs
new file mode 100644
index 00000000000..abf784e0f0e
--- /dev/null
+++ b/tests/ui/single_range_in_vec_init.rs
@@ -0,0 +1,58 @@
+//@aux-build:proc_macros.rs
+#![allow(clippy::no_effect, clippy::useless_vec, unused)]
+#![warn(clippy::single_range_in_vec_init)]
+#![feature(generic_arg_infer)]
+
+#[macro_use]
+extern crate proc_macros;
+
+macro_rules! a {
+    () => {
+        vec![0..200];
+    };
+}
+
+fn awa<T: PartialOrd>(start: T, end: T) {
+    [start..end];
+}
+
+fn awa_vec<T: PartialOrd>(start: T, end: T) {
+    vec![start..end];
+}
+
+fn main() {
+    // Lint
+    [0..200];
+    vec![0..200];
+    [0u8..200];
+    [0usize..200];
+    [0..200usize];
+    vec![0u8..200];
+    vec![0usize..200];
+    vec![0..200usize];
+    // Only suggest collect
+    [0..200isize];
+    vec![0..200isize];
+    // Do not lint
+    [0..200, 0..100];
+    vec![0..200, 0..100];
+    [0.0..200.0];
+    vec![0.0..200.0];
+    // `Copy` is not implemented for `Range`, so this doesn't matter
+    // [0..200; 2];
+    // [vec!0..200; 2];
+
+    // Unfortunately skips any macros
+    a!();
+
+    // Skip external macros and procedural macros
+    external! {
+        [0..200];
+        vec![0..200];
+    }
+    with_span! {
+        span
+        [0..200];
+        vec![0..200];
+    }
+}
diff --git a/tests/ui/single_range_in_vec_init.stderr b/tests/ui/single_range_in_vec_init.stderr
new file mode 100644
index 00000000000..3e3d521f4a5
--- /dev/null
+++ b/tests/ui/single_range_in_vec_init.stderr
@@ -0,0 +1,145 @@
+error: an array of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:25:5
+   |
+LL |     [0..200];
+   |     ^^^^^^^^
+   |
+   = note: `-D clippy::single-range-in-vec-init` implied by `-D warnings`
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200).collect::<std::vec::Vec<i32>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted an array of len 200, try
+   |
+LL |     [0; 200];
+   |      ~~~~~~
+
+error: a `Vec` of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:26:5
+   |
+LL |     vec![0..200];
+   |     ^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200).collect::<std::vec::Vec<i32>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted a `Vec` of len 200, try
+   |
+LL |     vec![0; 200];
+   |          ~~~~~~
+
+error: an array of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:27:5
+   |
+LL |     [0u8..200];
+   |     ^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0u8..200).collect::<std::vec::Vec<u8>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted an array of len 200, try
+   |
+LL |     [0u8; 200];
+   |      ~~~~~~~~
+
+error: an array of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:28:5
+   |
+LL |     [0usize..200];
+   |     ^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0usize..200).collect::<std::vec::Vec<usize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted an array of len 200, try
+   |
+LL |     [0usize; 200];
+   |      ~~~~~~~~~~~
+
+error: an array of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:29:5
+   |
+LL |     [0..200usize];
+   |     ^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200usize).collect::<std::vec::Vec<usize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted an array of len 200usize, try
+   |
+LL |     [0; 200usize];
+   |      ~~~~~~~~~~~
+
+error: a `Vec` of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:30:5
+   |
+LL |     vec![0u8..200];
+   |     ^^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0u8..200).collect::<std::vec::Vec<u8>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted a `Vec` of len 200, try
+   |
+LL |     vec![0u8; 200];
+   |          ~~~~~~~~
+
+error: a `Vec` of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:31:5
+   |
+LL |     vec![0usize..200];
+   |     ^^^^^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0usize..200).collect::<std::vec::Vec<usize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted a `Vec` of len 200, try
+   |
+LL |     vec![0usize; 200];
+   |          ~~~~~~~~~~~
+
+error: a `Vec` of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:32:5
+   |
+LL |     vec![0..200usize];
+   |     ^^^^^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200usize).collect::<std::vec::Vec<usize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: if you wanted a `Vec` of len 200usize, try
+   |
+LL |     vec![0; 200usize];
+   |          ~~~~~~~~~~~
+
+error: an array of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:34:5
+   |
+LL |     [0..200isize];
+   |     ^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200isize).collect::<std::vec::Vec<isize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: a `Vec` of `Range` that is only one element
+  --> $DIR/single_range_in_vec_init.rs:35:5
+   |
+LL |     vec![0..200isize];
+   |     ^^^^^^^^^^^^^^^^^
+   |
+help: if you wanted a `Vec` that contains the entire range, try
+   |
+LL |     (0..200isize).collect::<std::vec::Vec<isize>>();
+   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 10 previous errors
+
diff --git a/tests/ui/while_let_on_iterator.fixed b/tests/ui/while_let_on_iterator.fixed
index 11f0de07c62..41a380ab8f6 100644
--- a/tests/ui/while_let_on_iterator.fixed
+++ b/tests/ui/while_let_on_iterator.fixed
@@ -6,6 +6,7 @@
     clippy::manual_find,
     clippy::never_loop,
     clippy::redundant_closure_call,
+    clippy::single_range_in_vec_init,
     clippy::uninlined_format_args,
     clippy::useless_vec
 )]
diff --git a/tests/ui/while_let_on_iterator.rs b/tests/ui/while_let_on_iterator.rs
index e54575dd3b4..4c6433880b6 100644
--- a/tests/ui/while_let_on_iterator.rs
+++ b/tests/ui/while_let_on_iterator.rs
@@ -6,6 +6,7 @@
     clippy::manual_find,
     clippy::never_loop,
     clippy::redundant_closure_call,
+    clippy::single_range_in_vec_init,
     clippy::uninlined_format_args,
     clippy::useless_vec
 )]
diff --git a/tests/ui/while_let_on_iterator.stderr b/tests/ui/while_let_on_iterator.stderr
index f8a66f2ad3e..3236765e1db 100644
--- a/tests/ui/while_let_on_iterator.stderr
+++ b/tests/ui/while_let_on_iterator.stderr
@@ -1,5 +1,5 @@
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:15:5
+  --> $DIR/while_let_on_iterator.rs:16:5
    |
 LL |     while let Option::Some(x) = iter.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in iter`
@@ -7,151 +7,151 @@ LL |     while let Option::Some(x) = iter.next() {
    = note: `-D clippy::while-let-on-iterator` implied by `-D warnings`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:20:5
+  --> $DIR/while_let_on_iterator.rs:21:5
    |
 LL |     while let Some(x) = iter.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in iter`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:25:5
+  --> $DIR/while_let_on_iterator.rs:26:5
    |
 LL |     while let Some(_) = iter.next() {}
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in iter`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:101:9
+  --> $DIR/while_let_on_iterator.rs:102:9
    |
 LL |         while let Some([..]) = it.next() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for [..] in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:108:9
+  --> $DIR/while_let_on_iterator.rs:109:9
    |
 LL |         while let Some([_x]) = it.next() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for [_x] in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:121:9
+  --> $DIR/while_let_on_iterator.rs:122:9
    |
 LL |         while let Some(x @ [_]) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x @ [_] in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:141:9
+  --> $DIR/while_let_on_iterator.rs:142:9
    |
 LL |         while let Some(_) = y.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in y`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:198:9
+  --> $DIR/while_let_on_iterator.rs:199:9
    |
 LL |         while let Some(m) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:209:5
+  --> $DIR/while_let_on_iterator.rs:210:5
    |
 LL |     while let Some(n) = it.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:211:9
+  --> $DIR/while_let_on_iterator.rs:212:9
    |
 LL |         while let Some(m) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:220:9
+  --> $DIR/while_let_on_iterator.rs:221:9
    |
 LL |         while let Some(m) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:229:9
+  --> $DIR/while_let_on_iterator.rs:230:9
    |
 LL |         while let Some(m) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:246:9
+  --> $DIR/while_let_on_iterator.rs:247:9
    |
 LL |         while let Some(m) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:261:13
+  --> $DIR/while_let_on_iterator.rs:262:13
    |
 LL |             while let Some(i) = self.0.next() {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:293:13
+  --> $DIR/while_let_on_iterator.rs:294:13
    |
 LL |             while let Some(i) = self.0.0.0.next() {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.0.0.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:322:5
+  --> $DIR/while_let_on_iterator.rs:323:5
    |
 LL |     while let Some(n) = it.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:334:9
+  --> $DIR/while_let_on_iterator.rs:335:9
    |
 LL |         while let Some(x) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:348:5
+  --> $DIR/while_let_on_iterator.rs:349:5
    |
 LL |     while let Some(x) = it.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:359:5
+  --> $DIR/while_let_on_iterator.rs:360:5
    |
 LL |     while let Some(x) = it.0.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.0.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:394:5
+  --> $DIR/while_let_on_iterator.rs:395:5
    |
 LL |     while let Some(x) = s.x.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in s.x.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:401:5
+  --> $DIR/while_let_on_iterator.rs:402:5
    |
 LL |     while let Some(x) = x[0].next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in x[0].by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:409:9
+  --> $DIR/while_let_on_iterator.rs:410:9
    |
 LL |         while let Some(x) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:419:9
+  --> $DIR/while_let_on_iterator.rs:420:9
    |
 LL |         while let Some(x) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:429:9
+  --> $DIR/while_let_on_iterator.rs:430:9
    |
 LL |         while let Some(x) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:439:9
+  --> $DIR/while_let_on_iterator.rs:440:9
    |
 LL |         while let Some(x) = it.next() {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
 
 error: this loop could be written as a `for` loop
-  --> $DIR/while_let_on_iterator.rs:449:5
+  --> $DIR/while_let_on_iterator.rs:450:5
    |
 LL |     while let Some(..) = it.next() {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in it`