Fix bug in computing the count and reword message

Author: rspencer01

clippy_lints/src/methods/map_with_unused_argument_over_ranges.rs

@@ -18,7 +18,7 @@ fn extract_count_with_applicability(
     let start = range.start?;
     let end = range.end?;
     // TODO: This doens't handle if either the start or end are negative literals, or if the start is
-    // not a literal In the first case, we need to be careful about how we handle computing the
+    // not a literal. In the first case, we need to be careful about how we handle computing the
     // count to avoid overflows. In the second, we may need to add parenthesis to make the
     // suggestion correct.
     if let ExprKind::Lit(lit) = start.kind
@@ -41,10 +41,14 @@ fn extract_count_with_applicability(
                 } else {
                     return Some(end_snippet);
                 };
-            } else if range.limits == RangeLimits::Closed {
-                return Some(format!("{} + {}", end_snippet, lower_bound + 1));
+            }
+            if range.limits == RangeLimits::Closed {
+                if lower_bound > 0 {
+                    return Some(format!("{end_snippet} - {}", lower_bound - 1));
+                }
+                return Some(format!("{end_snippet} + 1"));
             } else {
-                return Some(format!("{} + {}", end_snippet, lower_bound));
+                return Some(format!("{end_snippet} - {lower_bound}"));
             };
         }
     }
@@ -71,7 +75,7 @@ pub(super) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, receiver: &Expr<'_>, ar
             cx,
             MAP_WITH_UNUSED_ARGUMENT_OVER_RANGES,
             ex.span,
-            "map of a trivial closure (not dependent on parameter) over a range",
+            "map of a closure that does not depend on its parameter over a range",
             "use",
             format!("std::iter::repeat_with({snippet}).take({count})"),
             applicability,

tests/ui/map_with_unused_argument_over_ranges.fixed

@@ -20,6 +20,7 @@ fn main() {
     std::iter::repeat_with(|| do_something()).take(10);
     std::iter::repeat_with(|| do_something()).take(11);
     std::iter::repeat_with(|| do_something()).take(7);
+    std::iter::repeat_with(|| do_something()).take(8);
     std::iter::repeat_with(|| 3).take(10);
     std::iter::repeat_with(|| {
         let x = 3;
@@ -31,14 +32,13 @@ fn main() {
     let upper_fn = || 4;
     std::iter::repeat_with(|| do_something()).take(upper_fn());
     std::iter::repeat_with(|| do_something()).take(upper_fn() + 1);
-    std::iter::repeat_with(|| do_something()).take(upper_fn() + 2);
-    std::iter::repeat_with(|| do_something()).take(upper_fn() + 3);
+    std::iter::repeat_with(|| do_something()).take(upper_fn() - 2);
+    std::iter::repeat_with(|| do_something()).take(upper_fn() - 1);
     (-3..9).map(|_| do_something());
     // These should not be raised
     gen!();
     let lower = 2;
     let lower_fn = || 2;
-    std::iter::repeat_with(|| do_something()).take(upper_fn() + 2); // Ranges not starting at zero not yet handled
     (lower..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
     (lower_fn()..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
     (lower_fn()..=upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled

tests/ui/map_with_unused_argument_over_ranges.rs

@@ -20,6 +20,7 @@ fn main() {
     (0..10).map(|_| do_something());
     (0..=10).map(|_| do_something());
     (3..10).map(|_| do_something());
+    (3..=10).map(|_| do_something());
     (0..10).map(|_| 3);
     (0..10).map(|_| {
         let x = 3;
@@ -38,7 +39,6 @@ fn main() {
     gen!();
     let lower = 2;
     let lower_fn = || 2;
-    (2..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
     (lower..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
     (lower_fn()..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
     (lower_fn()..=upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled

tests/ui/map_with_unused_argument_over_ranges.stderr

@@ -1,4 +1,4 @@
-error: map of a trivial closure (not dependent on parameter) over a range
+error: map of a closure that does not depend on its parameter over a range
   --> tests/ui/map_with_unused_argument_over_ranges.rs:20:5
    |
 LL |     (0..10).map(|_| do_something());
@@ -7,26 +7,32 @@ LL |     (0..10).map(|_| do_something());
    = note: `-D clippy::map-with-unused-argument-over-ranges` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::map_with_unused_argument_over_ranges)]`
 
-error: map of a trivial closure (not dependent on parameter) over a range
+error: map of a closure that does not depend on its parameter over a range
   --> tests/ui/map_with_unused_argument_over_ranges.rs:21:5
    |
 LL |     (0..=10).map(|_| do_something());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(11)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
+error: map of a closure that does not depend on its parameter over a range
   --> tests/ui/map_with_unused_argument_over_ranges.rs:22:5
    |
 LL |     (3..10).map(|_| do_something());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(7)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
+error: map of a closure that does not depend on its parameter over a range
   --> tests/ui/map_with_unused_argument_over_ranges.rs:23:5
    |
+LL |     (3..=10).map(|_| do_something());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(8)`
+
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:24:5
+   |
 LL |     (0..10).map(|_| 3);
    |     ^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| 3).take(10)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:24:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:25:5
    |
 LL | /     (0..10).map(|_| {
 LL | |         let x = 3;
@@ -42,49 +48,43 @@ LL +         x + 2
 LL ~     }).take(10);
    |
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:28:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:29:5
    |
 LL |     (0..10).map(|_| do_something()).collect::<Vec<_>>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(10)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:30:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:31:5
    |
 LL |     (0..upper).map(|_| do_something());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:32:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:33:5
    |
 LL |     (0..upper_fn()).map(|_| do_something());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn())`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:33:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:34:5
    |
 LL |     (0..=upper_fn()).map(|_| do_something());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() + 1)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:34:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:35:5
    |
 LL |     (2..upper_fn()).map(|_| do_something());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() + 2)`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() - 2)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:35:5
+error: map of a closure that does not depend on its parameter over a range
+  --> tests/ui/map_with_unused_argument_over_ranges.rs:36:5
    |
 LL |     (2..=upper_fn()).map(|_| do_something());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() + 3)`
-
-error: map of a trivial closure (not dependent on parameter) over a range
-  --> tests/ui/map_with_unused_argument_over_ranges.rs:41:5
-   |
-LL |     (2..upper_fn()).map(|_| do_something()); // Ranges not starting at zero not yet handled
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() + 2)`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `std::iter::repeat_with(|| do_something()).take(upper_fn() - 1)`
 
-error: map of a trivial closure (not dependent on parameter) over a range
+error: map of a closure that does not depend on its parameter over a range
   --> tests/ui/map_with_unused_argument_over_ranges.rs:58:5
    |
 LL |     (0..10).map(|_| do_something());