Add tests for direct iteration and for array coercing to slice reference

Author: rommeld

tests/ui/chunks_exact_with_const_size.fixed

@@ -0,0 +1,32 @@
+#![warn(clippy::chunks_exact_with_const_size)]
+#![allow(unused)]
+
+fn main() {
+    let slice = [1, 2, 3, 4, 5, 6, 7, 8];
+
+    // Should NOT trigger - runtime value
+    let size = 4;
+    let mut it = slice.chunks_exact(size);
+    for chunk in it {}
+
+    // Should trigger - direct iteration without binding (gets suggestion)
+    for chunk in slice.as_chunks::<4>().0.iter() {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
+
+    // Should trigger - direct iteration with const
+    const CHUNK_SIZE: usize = 4;
+    for chunk in slice.as_chunks::<CHUNK_SIZE>().0.iter() {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
+
+    // Should trigger - chunks_exact_mut with direct iteration (gets suggestion)
+    // Note: The suggestion uses .iter() but should use .iter_mut() - this is a known limitation
+    let mut arr = [1, 2, 3, 4, 5, 6, 7, 8];
+    for chunk in arr.as_chunks_mut::<4>().0.iter() {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
+}

tests/ui/chunks_exact_with_const_size.rs

@@ -1,39 +1,32 @@
 #![warn(clippy::chunks_exact_with_const_size)]
 #![allow(unused)]
-#![allow(clippy::iter_cloned_collect)]
 
 fn main() {
     let slice = [1, 2, 3, 4, 5, 6, 7, 8];
 
-    // Should trigger lint - literal constant
-    let result = slice.chunks_exact(4);
-    //~^ chunks_exact_with_const_size
-
-    // Should trigger lint - const value
-    const CHUNK_SIZE: usize = 4;
-    let result = slice.chunks_exact(CHUNK_SIZE);
-    //~^ chunks_exact_with_const_size
-
     // Should NOT trigger - runtime value
     let size = 4;
     let mut it = slice.chunks_exact(size);
     for chunk in it {}
 
-    // Should trigger lint - simple iteration
-    let result = slice.chunks_exact(3);
-    //~^ chunks_exact_with_const_size
+    // Should trigger - direct iteration without binding (gets suggestion)
+    for chunk in slice.chunks_exact(4) {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
 
-    // Should trigger - mutable variant
-    let mut arr = [1, 2, 3, 4, 5, 6, 7, 8];
-    let result = arr.chunks_exact_mut(4);
-    //~^ chunks_exact_with_const_size
+    // Should trigger - direct iteration with const
+    const CHUNK_SIZE: usize = 4;
+    for chunk in slice.chunks_exact(CHUNK_SIZE) {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
 
-    // Should trigger - multiline expression
-    #[rustfmt::skip]
-    let result = slice
-        .iter()
-        .copied()
-        .collect::<Vec<_>>()
-        .chunks_exact(2);
-    //~^ chunks_exact_with_const_size
+    // Should trigger - chunks_exact_mut with direct iteration (gets suggestion)
+    // Note: The suggestion uses .iter() but should use .iter_mut() - this is a known limitation
+    let mut arr = [1, 2, 3, 4, 5, 6, 7, 8];
+    for chunk in arr.chunks_exact_mut(4) {
+        //~^ chunks_exact_with_const_size
+        let _ = chunk;
+    }
 }

tests/ui/chunks_exact_with_const_size.stderr

@@ -1,69 +1,23 @@
 error: using `chunks_exact` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size.rs:9:24
+  --> tests/ui/chunks_exact_with_const_size.rs:13:24
    |
-LL |     let result = slice.chunks_exact(4);
-   |                        ^^^^^^^^^^^^^^^
+LL |     for chunk in slice.chunks_exact(4) {
+   |                        ^^^^^^^^^^^^^^^ help: consider using `as_chunks` instead: `as_chunks::<4>().0.iter()`
    |
-help: consider using `as_chunks::<4>()` instead
-  --> tests/ui/chunks_exact_with_const_size.rs:9:24
-   |
-LL |     let result = slice.chunks_exact(4);
-   |                        ^^^^^^^^^^^^^^^
-   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
    = note: `-D clippy::chunks-exact-with-const-size` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::chunks_exact_with_const_size)]`
 
 error: using `chunks_exact` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size.rs:14:24
-   |
-LL |     let result = slice.chunks_exact(CHUNK_SIZE);
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: consider using `as_chunks::<CHUNK_SIZE>()` instead
-  --> tests/ui/chunks_exact_with_const_size.rs:14:24
-   |
-LL |     let result = slice.chunks_exact(CHUNK_SIZE);
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
-
-error: using `chunks_exact` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size.rs:23:24
-   |
-LL |     let result = slice.chunks_exact(3);
-   |                        ^^^^^^^^^^^^^^^
-   |
-help: consider using `as_chunks::<3>()` instead
-  --> tests/ui/chunks_exact_with_const_size.rs:23:24
+  --> tests/ui/chunks_exact_with_const_size.rs:20:24
    |
-LL |     let result = slice.chunks_exact(3);
-   |                        ^^^^^^^^^^^^^^^
-   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+LL |     for chunk in slice.chunks_exact(CHUNK_SIZE) {
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `as_chunks` instead: `as_chunks::<CHUNK_SIZE>().0.iter()`
 
 error: using `chunks_exact_mut` with a constant chunk size
   --> tests/ui/chunks_exact_with_const_size.rs:28:22
    |
-LL |     let result = arr.chunks_exact_mut(4);
-   |                      ^^^^^^^^^^^^^^^^^^^
-   |
-help: consider using `as_chunks_mut::<4>()` instead
-  --> tests/ui/chunks_exact_with_const_size.rs:28:22
-   |
-LL |     let result = arr.chunks_exact_mut(4);
-   |                      ^^^^^^^^^^^^^^^^^^^
-   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
-
-error: using `chunks_exact` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size.rs:37:10
-   |
-LL |         .chunks_exact(2);
-   |          ^^^^^^^^^^^^^^^
-   |
-help: consider using `as_chunks::<2>()` instead
-  --> tests/ui/chunks_exact_with_const_size.rs:37:10
-   |
-LL |         .chunks_exact(2);
-   |          ^^^^^^^^^^^^^^^
-   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+LL |     for chunk in arr.chunks_exact_mut(4) {
+   |                      ^^^^^^^^^^^^^^^^^^^ help: consider using `as_chunks` instead: `as_chunks_mut::<4>().0.iter()`
 
-error: aborting due to 5 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/chunks_exact_with_const_size_unfixable.rs

@@ -1,10 +1,42 @@
 #![warn(clippy::chunks_exact_with_const_size)]
 #![allow(unused)]
+#![allow(clippy::iter_cloned_collect)]
 
 fn main() {
     let slice = [1, 2, 3, 4, 5, 6, 7, 8];
     const CHUNK_SIZE: usize = 4;
 
+    // Should trigger lint - literal constant (stored in let binding, so help not suggestion)
+    let result = slice.chunks_exact(4);
+    //~^ chunks_exact_with_const_size
+
+    // Should trigger lint - const value
+    let result = slice.chunks_exact(CHUNK_SIZE);
+    //~^ chunks_exact_with_const_size
+
+    // Should trigger lint - simple iteration
+    let result = slice.chunks_exact(3);
+    //~^ chunks_exact_with_const_size
+
+    // Should trigger - mutable variant
+    let mut arr = [1, 2, 3, 4, 5, 6, 7, 8];
+    let result = arr.chunks_exact_mut(4);
+    //~^ chunks_exact_with_const_size
+
+    // Should trigger - multiline expression
+    #[rustfmt::skip]
+    let result = slice
+        .iter()
+        .copied()
+        .collect::<Vec<_>>()
+        .chunks_exact(2);
+    //~^ chunks_exact_with_const_size
+
+    // Should trigger - array coerces to slice reference
+    let array = [1, 2, 3, 4, 5, 6, 7, 8];
+    let result = array.chunks_exact(4);
+    //~^ chunks_exact_with_const_size
+
     // Should trigger lint with help message only (not suggestion) - stored in variable
     let mut chunk_iter = slice.chunks_exact(CHUNK_SIZE);
     //~^ chunks_exact_with_const_size

tests/ui/chunks_exact_with_const_size_unfixable.stderr

@@ -1,30 +1,108 @@
 error: using `chunks_exact` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:9:32
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:10:24
+   |
+LL |     let result = slice.chunks_exact(4);
+   |                        ^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks::<4>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:10:24
+   |
+LL |     let result = slice.chunks_exact(4);
+   |                        ^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+   = note: `-D clippy::chunks-exact-with-const-size` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::chunks_exact_with_const_size)]`
+
+error: using `chunks_exact` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:14:24
+   |
+LL |     let result = slice.chunks_exact(CHUNK_SIZE);
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks::<CHUNK_SIZE>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:14:24
+   |
+LL |     let result = slice.chunks_exact(CHUNK_SIZE);
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+
+error: using `chunks_exact` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:18:24
+   |
+LL |     let result = slice.chunks_exact(3);
+   |                        ^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks::<3>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:18:24
+   |
+LL |     let result = slice.chunks_exact(3);
+   |                        ^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+
+error: using `chunks_exact_mut` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:23:22
+   |
+LL |     let result = arr.chunks_exact_mut(4);
+   |                      ^^^^^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks_mut::<4>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:23:22
+   |
+LL |     let result = arr.chunks_exact_mut(4);
+   |                      ^^^^^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+
+error: using `chunks_exact` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:32:10
+   |
+LL |         .chunks_exact(2);
+   |          ^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks::<2>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:32:10
+   |
+LL |         .chunks_exact(2);
+   |          ^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+
+error: using `chunks_exact` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:37:24
+   |
+LL |     let result = array.chunks_exact(4);
+   |                        ^^^^^^^^^^^^^^^
+   |
+help: consider using `as_chunks::<4>()` instead
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:37:24
+   |
+LL |     let result = array.chunks_exact(4);
+   |                        ^^^^^^^^^^^^^^^
+   = note: you can access the chunks using `result.0.iter()`, and the remainder using `result.1`
+
+error: using `chunks_exact` with a constant chunk size
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:41:32
    |
 LL |     let mut chunk_iter = slice.chunks_exact(CHUNK_SIZE);
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: consider using `as_chunks::<CHUNK_SIZE>()` instead
-  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:9:32
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:41:32
    |
 LL |     let mut chunk_iter = slice.chunks_exact(CHUNK_SIZE);
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^
    = note: you can access the chunks using `chunk_iter.0.iter()`, and the remainder using `chunk_iter.1`
-   = note: `-D clippy::chunks-exact-with-const-size` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::chunks_exact_with_const_size)]`
 
 error: using `chunks_exact_mut` with a constant chunk size
-  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:16:31
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:48:31
    |
 LL |     let mut chunk_iter = arr2.chunks_exact_mut(CHUNK_SIZE);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: consider using `as_chunks_mut::<CHUNK_SIZE>()` instead
-  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:16:31
+  --> tests/ui/chunks_exact_with_const_size_unfixable.rs:48:31
    |
 LL |     let mut chunk_iter = arr2.chunks_exact_mut(CHUNK_SIZE);
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: you can access the chunks using `chunk_iter.0.iter()`, and the remainder using `chunk_iter.1`
 
-error: aborting due to 2 previous errors
+error: aborting due to 8 previous errors